Commercial micro-CHP Field Trial Report
2011 Report
SEAI Commercial micro-CHP Field Trial Report
March 2011
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Prepared for The Sustainable Energy Authority of Ireland by:
Georgina Orr, GASTEC at CRE Ltd
Tim Dennish, GASTEC at CRE Ltd
Iain Summerfield, GASTEC at CRE Ltd
Fergal Purcell, Energy Solutions
© GASTEC at CRE Ltd 2010
Technical Editor: Patrick Scully, Redacteurs
SEAI Document Sign off : Pearse Buckley
HOD Approval : Declan Meally
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Executive Summary
Micro combined heat and power (micro-CHP) refers to a group of technologies that generate both usable
heat and electricity, on a small scale. As in a conventional boiler, the heat is used for space heating and hot
water, but unlike in a conventional boiler, electricity is produced that can be used on site or exported to the
national grid. The electricity generated in this way displaces electricity generated at a central power station,
and this leads to significant carbon savings.
In 2008, the Sustainable Energy Authority of Ireland commissioned a field trial to assess the operation,
performance and benefits of micro-CHP in commercial situations.
Thirteen sites were selected across Ireland and a micro-CHP appliance or multiple appliances were installed.
The sites included both existing buildings and new build developments. In existing buildings and boiler
house refurbishments, the micro-CHP appliances were installed alongside the current heating system; in the
new builds, they were integrated into the system design.
At each site, measurements were made of the gas and electricity consumed, and of the electricity generated
and the heat produced (both for space heating and for hot water). This data was then assessed with regard
to engine efficiency, primary energy savings, run hours and carbon emissions. Maintenance and system
integration was also considered, as these are very important determinants of the success of an installation.
Overall, the engines were found to operate at an average of 82% efficiency (Gross CV basis), taking into
account both electricity consumed by the appliance and electricity generated by it. When considering
thermal and electrical efficiencies independently, the average thermal efficiency for all sites is 58% and the
average electrical efficiency is 24%. There was little seasonal variation in the monthly overall efficiencies of
the engines, which implies that the micro-CHP units were correctly sized to meet the base-line heat demand
of each site. The annual overall efficiencies are shown in Figure 1 below.
Figure 1: Annual Efficiency
(Purple indicates annual efficiencies calculated from 10 months of data).
A carbon benefit ratio (CBR) assessment was also carried out for each site. All sites were shown to be saving
carbon, with CBR values of over 100%. Those engines with the longest operational hours displayed the
highest efficiency figures and carbon savings. Those sites where the engines had integration issues, or where
operation was limited by timers and/or demand, were less efficient and saved less carbon – see Figure 2,
below.
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Figure 2: Annual Carbon Benefit Ratio
(Purple indicates annual efficiencies calculated from 10 months of data).
The annual efficiency and carbon saving of an engine is directly affected by the amount of time it is
operational. While in standby mode, it imports electricity (with a high CO2 emission factor) without
generating any of its own.
Figure 3, below, shows the maximum, minimum and average monthly run hours for each site.
Figure 3: Monthly Run Hours
The trial focused on primary energy savings, particularly on the energy saved at a centralised power plant
because of cogeneration on site. Overall, the engines produced primary energy savings of between 15% and
20%, meaning that the centralised power plant uses 15% to 20% less carbon intensive fuel to satisfy the
site’s requirements. This is significant and should encourage the uptake of micro-CHP in sites that are
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suitable and in areas where the grid electricity is derived from high carbon fossil fuels, such as coal or peat.
Figure 4, below, shows the primary energy savings from each site within the trial.
Figure 4: Percentage of primary energy saved at each trial site
System integration also has an effect on the performance of a micro-CHP appliance, and control strategies
that ensure the optimum running of the appliance are very important. Most of the engines in the trial were
installed alongside buffer tanks, which helped to ensure steady and consistent operation of the appliance.
One engine was installed directly into a low-loss header which was also influenced by supplementary
boilers. The performance and efficiency of this site were very variable compared with those of the other
sites. The heat losses from buffer tanks were also considered: on average 11% of heat produced by the
micro-CHP is actually lost from the pipework and buffer tank before being delivered to the heating system.
To ensure maximum benefit from micro-CHP, the system must be controlled correctly, so that the micro-CHP
always acts as the lead appliance and is always available for operation when there is a demand for heat.
Several of the sites had initial control problems where the integration with other boilers was causing the
micro-CHP to cycle on and off frequently, thus limiting electricity generation and lowering the carbon
savings. Many of the sites were altered to accommodate the micro-CHP appliances and the data shows
improvements in performance after the alterations were made.
There was a serious installation problem at one of the sites, where incorrect plumbing prevented the microCHP unit from operating as effectively as possible. In future, any site installing a micro-CHP unit should be
offered support, both during installation and during on-going maintenance.
The operational cost savings associated with the use of micro-CHP are:
•
the value of the electricity generated, based either on the cost of electricity imported from the network
or on the price paid for electricity exported to the network
plus
•
the value of the heat in avoided boiler fuel costs
minus
•
the cost of the fuel used by the micro-CHP.
The capital costs and the operation and maintenance costs for commercial-scale micro-CHP vary according
to the size of the unit and the type of engine on which it is based. Payback is highly dependent on utilisation,
or annual run hours – a minimum utilisation of around 50% or 4,000 hours per annum is required to achieve
a reasonable return on investment in micro-CHP – see Figure 5,below.
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Figure 5: Engine utilisation and payback
The trial demonstrates that micro-CHP systems in commercial sites that are well designed and installed
deliver reasonable levels of efficiency and CO2 savings, and are at least as cost-effective as competing
alternative energy technologies, such as solar thermal, small-scale wind, and solar photo-voltaics. However,
the investment cost for end-users is significant, and, in the absence of financial supports, this presents a
barrier to the deployment and uptake of micro-CHP.
Grant schemes are effective in promoting the uptake of CHP, although poorly designed grant schemes, and
grant schemes without accompanying quality measures can lead to unintended outcomes. An export tariff is
not an effective support mechanism, since a well-designed commercial-scale micro-CHP system does not
export significant quantities of electricity. A generation tariff, however, could promote the technology, and a
ten-year, 5 c/kWh tariff would deliver similar curtailed payback periods as a 40% capital grant, at a similar
cost. A tariff-based incentive scheme that links payment to performance has the advantage of preferentially
supporting good quality micro-CHP.
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Contents
1. Introduction .................................................................................................. 1
2. Background ................................................................................................... 2
What is Micro-CHP? .................................................................................................................. 2
Policy Context ............................................................................................................................ 5
3. SEAI Field Trial ............................................................................................... 7
Commercial micro-CHP .......................................................................................................... 7
4. Field Trial Results ........................................................................................ 14
Technologies Installed .......................................................................................................... 14
Data Quality .............................................................................................................................. 15
Energy Efficiency ..................................................................................................................... 16
Primary Energy Savings and Consumption ................................................................... 19
Operating Hours...................................................................................................................... 21
Buffer Tanks and System Integration............................................................................... 26
Carbon Benefit Ratio (CBR) .................................................................................................. 32
5. Financial Evaluation ................................................................................... 34
Fuel Costs................................................................................................................................... 34
Capital, Operating and Maintenance Costs................................................................... 34
Financial Assessment ............................................................................................................ 36
Financial Supports .................................................................................................................. 37
6. Policy and Regulatory Implications ........................................................... 39
Network connection and permitting............................................................................... 39
Quality Measures..................................................................................................................... 39
Building regulations and BER ............................................................................................. 40
Support Mechanisms............................................................................................................. 45
7. Summary and Key Learning ....................................................................... 42
Trial Summary .......................................................................................................................... 42
Key Learning ............................................................................................................................. 43
8. Case Studies ................................................................................................ 45
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Annex 1: Data Processing Procedure ............................................................. 53
Annex 2: Monthly Valid Data and Operational Days .................................... 54
Annex 3: Quality Tracking Document ............................................................ 55
Annex 4: Example of the rolling action list – Site by Site Basis .................... 61
Annex 5: Site-by-Site Data Analysis ............................................................... 68
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1. Introduction
In 2008, the Sustainable Energy Authority of Ireland (SEAI) commissioned a nationwide micro combined heat
and power (micro-CHP) field trial to assess the potential for widescale deployment of this technology in the
future. The trial aimed to investigate the performance of micro-CHP in terms of primary energy savings, in
existing and new installations, and to identify the possible barriers to deployment, and the risks and benefits
of this technology.
Data was collected from 13 sites across Ireland, with initial data collection in September 2008. The sites
included residential apartments, care and nursing homes, a hotel, a crèche, offices and a fire station. The
micro-CHP engines were integrated with supplementary heating appliances; they were designed to provide
heating and hot water for use on site. The electricity generated was mainly used locally; as most of the sites
had significant load, very few of them exported to the national grid.
The data collected has been analysed in terms of energy consumption and savings, engine efficiency –
including thermal and electrical efficiencies – primary energy savings and carbon emissions. Engine
performance, maintenance and utilisation have also been discussed to analyse the extent of integration with
other appliances and the system design.
The project team consisted of the Sustainable Energy Authority of Ireland (SEAI), Energy Solutions,
PowerTherm Solutions Limited (PTH) and GASTEC at CRE Limited (GaC). SEAI provided funding for the
installation of the micro-CHP appliances and played an active role in project coordination and deliverables.
PTH was responsible for equipment, data monitoring and on-site troubleshooting and repairs. GaC was
responsible for data auditing and analysis. Energy Solutions provided project management services for the
field trial and related activities.
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2. Background
Micro-CHP has been available for several years for installation in commercial situations. Domestic scale
micro-CHP technologies are also available, although in Europe fully operational engines have so far primarily
been deployed only in field trials 1. This section details the types of technology available.
What is Micro-CHP?
Micro combined heat and power (micro-CHP) refers to a group of technologies that generate both usable
heat and electricity, on a relatively small scale. Like a conventional boiler, a micro-CHP appliance requires an
input fuel, and it consumes electricity to power associated pumps, fans and controls. The most common
input fuel is natural gas, although LPG and oil are also used. The heat produced can be used for space
heating and hot water. The electricity produced can be used on site or exported to the national grid.
The electricity generated in this way displaces electricity generated at a central power station, and this leads
to significant carbon savings. An important determinant of the effectiveness of micro-CHP is the carbon
intensity of the national electricity supply. In countries where most electricity is produced from nuclear
power or wind, micro-CHP would not produce significant carbon savings; in countries where most electricity
is derived from gas or coal, considerable carbon savings arise. In Ireland, the grid intensity is currently
0.58kgCO2/kWh 2. A gas-fired micro-CHP unit will effectively reduce overall carbon emissions down to a grid
intensity of about 0.26kgCO2/kWh; at grid intensities below this value, micro-CHP may actually be carbon
positive – that is, it could cause higher emissions of carbon.
Fuel prices have fluctuated widely in the past few years which makes it difficult to predict accurate cost
savings. However, if micro-CHP units are correctly sized, installed and operated, they have the potential to
yield significant savings, both economically and environmentally. If the price per kWh of centrally generated
electricity is assumed to be at least twice the price of gas per kWh, most commercial micro-CHP units should
at least cover their operating costs. (This will vary from site to site, but these numbers do include an
allowance for maintenance.) These benefits will be better realised on sites with a continuous heat load (for
example, residential homes operating 24 hours a day).
Micro-CHP appliances consume more fuel than condensing boilers; the benefit from micro-CHP comes from
the electricity generated. If the engines do not run for periods long enough to generate substantial
electricity, they can be more energy- and carbon-intensive than the condensing boilers they replace. It is
essential that the units are sized correctly and installed in the optimum location, with the correct control
system. In general, it is poor practice to artificially increase heat loads to increase operation of the microCHP, as this generally leads to an increase in carbon emissions.
1
There are over 50,000 Honda Ecowill micro-CHP units installed in dwellings in Japan. However their suitability for the European market
has yet to be demonstrated.
2
Energy in Ireland 1990 – 2008, 2009 Report, SEAI, December 2009
2
Figure 6: Comparison between energy flows in a micro-CHP and condensing boiler
micro-CHP
Boiler
Micro-CHP
There are five main categories of micro-CHP as shown below. With the exception of fuel cells, all of them use
an engine to drive a generator and thus produce electricity.
•
Internal combustion engine
•
Stirling engine
•
Fuel Cell
•
Organic Rankine Cycle
•
Gas Turbine
Each is described in more detail below.
Internal combustion (IC) engine micro-CHP
The engines in internal combustion engine micro-CHP units are loosely based on the automotive engine and
are the most established of all micro-CHP appliances. The majority of these engines are substantially
modified to improve their longevity.
Previous field trials have demonstrated that, in order to maximise economic benefit, commercial-scale
micro-CHP should operate for over 3,000 hours per year[1]. IC units operate most effectively when they run
for extended periods of time with very few start-up cycles, as most of the wear on the engine occurs during
start-up. Low and high water temperatures also affect the IC engine, so the system must be well designed
and controlled. As many car engines have a total operational life of only 5,000 hours, they need to be
upgraded before they are used in a micro-CHP applications.
There are two basic types of IC engines: those that use spark ignition and those that use diesel ignition.
Spark ignition engines run on natural gas (although any flammable gas can be used): a mixture of fuel and
air is introduced to the cylinders and a spark ignites this mixture. In diesel ignition engines, air is tightly
compressed, which raises its temperature. Fuel is then injected into the cylinder and ignites spontaneously.
Diesels are usually more robust, reliable and long-lived; in comparison to a spark ignition engine, the partload performance and thermal efficiency are higher. On the other hand, diesels are heavier and generally
cost more.
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IC engines are used primarily in the commercial sector. At an average of 20–25% electrical efficiency, with
some engines even producing 30% electrical efficiency, the electrical output of an IC micro-CHP is relatively
high and often three-phase. Most of these units produce a steady power output, such as a steady 5kW of
electricity, but more modern designs can now vary their output, based on the demand for heat and/or
electricity.
Stirling engine micro-CHP
Stirling engines are external combustion engines used in a much smaller proportion of micro-CHP units,
although they are gaining in popularity. They are currently being launched into the domestic market as a
replacement for gas boilers. Stirling engine micro-CHP units can run on oil, gas or even solid fuel, although
only gas is currently approaching a mass market position.
The engine has a high-temperature heat input zone and a low-temperature heat transfer zone. A ‘hot bulb’ is
heated by continuous combustion and at the other end of the cylinder the ‘cold bulb’ is cooled by water
from the central heating system (at between 40°C and 70°C). A piston moves the heat from the hot to the
cold bulb using a compressed carrier gas, thus releasing mechanical energy.
In theory, Stirling engines are very efficient; in practice, the lower-cost Stirling engines currently on the
market 3 have an electrical efficiency of about 10%. This, together with their small size and limited range of
outputs, tends to make them less attractive in the commercial market.
Fuel cell micro-CHP
Fuel cells operate on principles similar to those of a battery. Thus, the fuel cell micro-CHP is very different
from an IC or Stirling engine micro-CHP. Electrochemical cells consume fuel to produce a small DC voltage.
These cells are arranged in series and the DC voltage is converted into an AC voltage.
Fuel cells are promising in the micro-CHP field due to their potential for high electricity output. While the
electrical consumption (in standby mode) may be higher than that of IC or Stirling engines, the net electrical
production should ultimately be higher than either of these technologies.
Current fuel cell designs are complex and require careful control at start-up (when all components must be
raised to the correct operating temperature before generation can begin). Current prototypes also tend to
be large, but future models are expected to be smaller.
The requirement for careful start-up and shut-down has resulted in some manufacturers moving towards
mixed electricity/heat led units or units with large heat stores. The applicability of these must be carefully
assessed on a site-by-site basis. Although in the advanced stages of development, the regular installation of
fuel cell micro-CHP units is still likely to be some years in the future.
Organic Rankine Cycle micro-CHP
An Organic Rankine Cycle micro-CHP uses a working fluid which is first pumped through a boiler, then
evaporated and passed through a turbine, and finally condensed. The fluid is organic, and may have a higher
boiling point than that of water. Low-temperature heat (sometimes called low-grade heat) can be used in
the micro-CHP by converting it to work and thus electricity if required.
Some Organic Rankine Cycle (ORC) engines are quite small and light, with theoretical net electrical
efficiencies of up to 17%. Some units can also vary their output in response to the heating demand. In
3
2010
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continental Europe there are several large biomass ORC machines, but there are currently none installed in
the UK or Ireland, and in practice the technology is still at the field trial stage.
Gas turbine micro-CHP
A gas turbine micro-CHP unit works by mixing air and gas in the combustion chamber and igniting it. This
increases the velocity, temperature and volume of the gas which is then passed through a nozzle over the
turbine blades. This turns the turbine which powers a compressor and generator.
There are many theoretical advantages to gas turbine micro-CHP, including high efficiency, clean
combustion and low maintenance. Gas turbines with foil bearings and air cooling operate without needing
lubricating oil or coolant, thus lowering their maintenance requirements.
Despite these advantages, they have not yet been successfully brought to market on a fully commercial
basis, and in practice the units have suffered reliability issues.
Policy Context
European Directive 2004/8/EC – the Combined Heat and Power Directive – defines micro-CHP as CHP with
an output of under 50kWe. Under the Directive, small-scale or micro-CHP is considered as high-efficiency
cogeneration if it delivers primary energy savings.
The CHP Policy Group Report (2006) noted that CHP can contribute significantly to the achievement of
Ireland’s energy policy goals of:
•
Supporting sustainable economic growth;
•
Protecting security of supply; and
•
Ensuring that energy supply and use are environmentally sustainable.
The CHP Policy Group Report recommended that ‘a field trial should be conducted of the micro-scale new
CHP technologies with a view to gathering the information necessary to assess the potential for this market
for longer term commercial development’. SEAI’s micro-CHP field trial was initiated in 2007 in response to
this recommendation.
The 2007 Government White Paper Delivering a Sustainable Energy Future for Ireland lays out a framework for
Ireland’s energy policy up to 2020. It proposes two broad actions relating to CHP:
•
Achieve at least 400 MW from CHP by 2010 through continued support under the CHP Deployment
Programme and R&D supports, with particular emphasis on biomass-fuelled CHP, with the additional
aim of achieving at least 800 MW by 2020;
•
A further target for CHP to be considered for 2020 in light of further feasibility studies into CHP
applications, a review by the Commission for Energy Regulation of potential administrative and
regulatory barriers, and decisions on appropriate price-support mechanisms for electricity generated
from new high-efficiency, large-scale CHP.
These targets are reiterated in the National Climate Change Strategy 2007 to 2012, also published in 2007,
which states that 0.162 Mt CO2 equivalent will be saved by 2010, as a result of CHP. The National Energy
Efficiency Action Plan published in May 2009 also reflects the targets set out in the Government White Paper.
While micro-CHP is by definition small scale, and individual units contribute only a small amount to overall
installed capacity, there is the potential for widespread use of commercial-scale micro-CHP in the services
sector, making a significant overall contribution to national targets.
A CHP Market Study published by SEAI in 2009 cites a total installed CHP capacity of 298.7 MWe at the end of
2008. This represents an increase of 30 MWe over the installed capacity in 2006. It included 23 micro-CHP
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units with an installed capacity of 211 kW, compared with two units with a total capacity of 76 kW in 2006 –
an increase of 178% over the period. While micro-CHP currently accounts for a small share of total installed
capacity, it has had the highest recent growth, and has the potential to make a significant contribution to
national CHP targets.
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3. SEAI Field Trial
The SEAI micro-CHP field trial was commissioned in 2007, originally with the intention of monitoring both
commercial and domestic installations. The pilot was designed to monitor market-ready technologies, and
suitable domestic-scale technologies were not available at the time. Thus the data and comments in this
report are based only on commercial-scale micro-CHP in commercial buildings.
CHP units suitable for use in domestic environments have subsequently come on the market, and SEAI, in
conjunction with Bord Gais, is currently conducting a field trial of domestic micro-CHP.
Commercial micro-CHP
The sites monitored throughout this trial are occupied buildings where the micro-CHP has been integrated
into the existing heating system alongside supplementary boilers. All energy flows in and out of the microCHP appliance are monitored; this means metering the gas and electricity use of the appliance and the heat
and electricity generated and used on site. The majority of sites also have a heat meter on the buffer tank,
which enables the performance and losses of the buffer tank to be assessed.
A trial of very similar nature was carried out by the Carbon Trust in the UK between 2004 and 2008. The data
in this trial provided the initial data for the validation process designed by GaC, and this has since been used
in many subsequent trials. The data in this report and collected throughout the SEAI micro-CHP Field Trial
can thus be directly compared to the data collected in the Carbon Trust’s study.
Site Selection
The field trial for commercial-scale micro-CHP was launched in January 2007 by issuing an open call for
proposals seeking sites meeting defined eligibility and evaluation criteria. Financial support of 40% of the
eligible investment cost of the micro-CHP installation was offered to twelve qualifying sites.
The field trial was designed to assess proven and tested market-ready technologies; applications had to
include evidence of the development process, testing and deployment of the products. For the purposes of
the field trial, commercial-scale micro-CHP was defined as micro-CHP with three-phase output, as the
overwhelming majority of sites suitable for market-ready technologies would have a three-phase supply.
Applicants were required to provide details on the thermal load at their site and details of a feasibility study
showing that the micro-CHP would be required to operate at least 4,000 hours per year.
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Applications meeting the eligibility criteria were evaluated on their relevance to the aims of the project,
which were to:
•
Gain direct experience of the installation and operation of the products;
•
Increase the capability of the Irish micro-CHP equipment supply chain;
•
Appreciate the operating and maintenance cost for the units;
•
Monitor the performance of units;
•
Assess the energy and emissions savings from the units;
•
Understand any issues which may be associated with product use;
•
Assess the performance of units against design specifications, using metrics such as energy savings,
environmental emissions and operating costs;
•
Explore appropriate connection and network protection requirements and the appropriateness of
existing guidelines;
•
Explore the metering and charging options and consider which could be appropriate to micro-CHP;
•
Assess the results in relation to future market potential; and
•
Assess the trial results in relation to possible future policy options.
The rate of applications was slower than anticipated and the installation phase of the field trial consequently
ran for longer than envisaged. The first application was received shortly after the launch in February 2007
and the last application was received in June 2008. A small number of applications were withdrawn, due to a
decision by the site not to proceed. Additional information was requested from some applicants, but all
applications were eventually approved for funding and inclusion in the field trial.
The total number of applications received and installations completed is shown in Figure 7. Two micro-CHP
units that had been installed prior to the start of the trial were included. The final installation was completed
in May 2009.
On average, the micro-CHP units were commissioned over six months after grant approval. This lag may be
largely attributed to the fact that nine of the eleven micro-CHP installations were either in new-build sites or
were part of a major mechanical and electrical upgrade at existing sites and the installation schedule was
therefore driven by the larger project schedule.
Figure 7: Micro-CHP Projects Applications and Installations
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Data Monitoring
PowerTherm Solutions was appointed as the data monitoring contractor, responsible for providing robust,
good-quality data sets to SEAI to allow them the evaluate the performance of the micro-CHP installations.
This work included:
•
System design, including selection of instrumentation;
•
Preparation of instrumentation installation guidelines;
•
Collection of valid data;
•
Delivery of data to the Data Auditor; and
•
Fault resolution.
Installation and commissioning of all equipment and instrumentation was subcontracted by PowerTherm to
approved integrators.
The monitoring system was a robust, multi-channel, data-acquisition platform. The PowerTherm remote
monitoring unit collected data nightly from each micro-CHP site using GSM communications.
The field devices were all hard-wired, and logging/communications equipment was located in a durable
metal enclosure, which was typically located in the site’s boiler room.
The parameters measured are listed in Table 1.
Table 1: Measured parameters
Description
Units
Volume of gas used by the micro-CHP unit
Litres
Gas temperature at micro-CHP meter
ºC
*Volume of gas/oil used by site boiler
Litres
Gas temperature at meter
ºC
Electrical output from micro-CHP unit
Wh
Electrical input to micro-CHP unit
Wh
*Gross electrical import into site
Wh
*Gross electrical export from site
Wh
Heat output from micro-CHP unit to site
Wh
Return temperature of water to micro-CHP unit
ºC
Water temperature flowing from the micro-CHP unit
°C
Water flow through the micro-CHP unit
Litres
Heat output from buffer tank to site
kWh
Return temperature of water to buffer tank
ºC
Water temperature flowing from the buffer tank
°C
Water flow through the buffer tank
Litres
Internal air temperature
°C
External air temperature
°C
Flue temperature of the micro-CHP unit
ºC
*Due to the nature of certain sites, boiler/electricity downtime to fit fuel/site electricity
meters was not possible.
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Critical metering devices, such as heat integrators and import/export meters were interrogated using
protocols such as Mbus and Modbus 485. These devices have internal accumulation registers for energy. This
allowed manual readings to be taken at the beginning and end of the trial.
Data acquisition was at five-minute intervals (to facilitate five-minute energy balance closure); this equates
to 288 data acquisitions per channel per site per day. There were approximately 20 data acquisition channels
for each site, so that 74,880 acquisitions of data were made each day across the thirteen sites. The data
logger has over three days data capacity.
Data was provided to SEAI and Gastec in CSV format, a simple and easily accessed data format. At the start of
the project, data was provided on a weekly basis, but once the data had been validated and any anomalies
and faults had been resolved, the frequency was reduced to monthly.
The acquisition system was designed to flag any failure of temperature sensors automatically. It allowed
remote dial-in to each site to test all instrumentation. Problems could be either resolved remotely or
escalated to a call-out for field service.
A full set of field device spares and metering software was maintained throughout the field trial. Issues that
did arise were most often the result of unintentional physical damage to devices by others. Other issues
related to water ingress following extreme weather conditions.
A diagram showing the key measured parameters is shown in Figure 8.
Figure 8: Measured Data Parameters
Temperature
Measurements
Calibration
Measurements
•
•
•
•
Gas CV
Other Optional
Measurements
External Temp
Atmospheric Pressure
Altitude
Flow
Temp
Gas into Property
Gas Used
•
•
Storage Tank Temp
•
Thermal store heat
Cold water feed
Temp
Return Flue
Temp Temp
Micro CHP
Heat Out
Unit
Electricity Imported
Electricity
Generated
Electricity Used
Unit-specific
Internal Data
Electricity Exported
Electricity used
in property
Electricity parameter definitions
•
Electricity Generated: the electricity out of the CHP system while generating. This is the total electricity
generated (minus that used internally) while generating.
•
Electricity Used: the electricity into the CHP system when not generating – such as on-going power for
controller and start-up/shut down (prior to/after generation).
•
Net Electricity Generated: [Electricity Generated – Electricity Used].
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Data Validation
The individual data channels are collated and processed to form monthly summaries based on the energy
consumed by the appliance (gas and electricity), the energy provided by the appliance (heat and electricity),
and the overall performance of the appliance within the property.
The project auditor performs a validation check on all data received to confirm the correct functioning of
the monitoring and recording equipment. The data is then processed and an energy balance calculated
across the appliance. This involves drawing an imaginary boundary around the micro-CHP unit and
accounting for all the energy going into the system and all the energy coming out of the system (including
losses) over a 24-hour period. This process is known as ‘closing the energy balance’; it provides a check on
the data which is critical to determining the performance of the CHP.
In order to confirm that the critical monitoring equipment is operating acceptably, the measured energy
leaving the system (plus calculated losses) must be between 93% and 103% of the measured energy
entering the system daily 4. If the energy closure is outside these limits, the day is said to be ’invalid‘ and the
possible cause investigated. Even if a day is declared invalid, the data itself may not be all invalid.
Sometimes unusual thermal conditions can cause significant errors in the heat balance, but overall the data
is valid. More commonly, just one parameter will be unreliable. The majority of the data from the monitored
sites has been very reliable, and it was decided to analyse the data without recourse to ‘data substitution’
procedures. There were some sites where data substitution might have been useful, but the sites in question
produced so little valid data that to do so could have produced unrealistic data; these have been excluded
from the analysis where appropriate.
As well as the term ‘valid energy balance’ GaC has also developed the concept of ‘operational days.’ These
are days when the engine uses more than 2.5% of its potential over the day – that is, an engine with a
potential input of 550kWh requires 14kWh of gas to be consumed to achieve a 2.5% utilisation. The reason
for this is that below 2.5% utilisation (representing only 36 minutes of operation) the errors in performing
the heat balance closure become significant – estimated losses become a very significant proportion of the
energy use accounted for. Thus days with very low or no usage are excluded from some analyses.
Run hours are also monitored – this is very useful when considering engine utilisation compared with other
appliances in the plant room.
To keep track of data quality and operational days throughout the trial, GaC formulated a quality tracking
document. This is included in Annex 2.
Performance Metrics
The data collected throughout the trial period has been analysed in terms of the following performance
metrics:
1.
Overall engine efficiency;
2.
Thermal efficiency;
3.
Electrical efficiency;
4.
Primary energy consumption and savings;
5.
Operating hours and cycling patterns of engine;
6.
Carbon benefit ratio; and
7.
Absolute CO2 savings.
4
A step-by-step guide to the data processing procedure is given in Annex 1.
11
These metrics are described in more detail below. All efficiency values (which are based on Gross Calorific
Value) take into account both the gas and the electricity consumed by the appliance.
Overall Efficiency
Overall efficiency is calculated as follows:
Overall Efficiency
=
Heat + Electricity Generated
Gas and Electricity Consumed
Thermal Efficiency
Thermal efficiency is calculated as follows:
Thermal Efficiency
=
_____Heat Generated________
Gas and Electricity Consumed
Electrical Efficiency
Electrical efficiency is calculated as follows:
Electrical Efficiency =
___Electricity Generated____
Gas and Electricity Consumed
Primary Energy Savings
Primary Energy Savings is a measure of the energy savings provided by cogeneration. They are calculated in
accordance with the EU Cogeneration Directive 5 as follows:
Primary Energy Savings =
1–
1
CHPHη
refHη
+
CHPEη
x 100
refEη
where:
CHPHη
Is the heat efficiency of the cogeneration product defined as annual useful heat output divided
by the fuel input used to produce the sum of useful heat and electricity from cogeneration.
refHη
Is the efficiency reference value for separate heat production.
CHPEη
Is the electrical efficiency of the cogeneration production defined as annual electricity from
cogeneration divided by the fuel input used to produce the sum of useful heat output and
electricity from cogeneration. Where a cogeneration unit generates mechanical energy the
annual electricity from cogeneration may be increased by an additional element representing
the amount of electricity which is equivalent to that of mechanical energy. This additional
element will not create a right to issue guarantees of origin in accordance with article 5.
refEη
Is the efficiency reference value for separate electricity production
Operating hours and cycling patterns
The duration of operation has a marked effect on the performance and benefit of micro-CHP. Engines that
run continuously for long periods are more efficient, generate more electricity and have fewer reliability
issues. The cycling pattern of an engine is also an excellent way of assessing the interaction between
supplementary appliances and the micro-CHP. Increased cycling also increases electrical consumption and
reduces efficiency.
5
Directive 2004/8/EC of the European Parliament and of the Council of 21 December 2006 on establishing harmonised
efficiency reference values for separate production of electricity and heat.
12
Carbon Benefits Ratio
Micro-CHP is designed to reduce carbon emissions by offsetting the electricity consumed from the grid.
Carbon Benefits Ratio (CBR) is one way of measuring this. It is similar to an efficiency figure, but takes into
account the carbon emission factor from the fuel used and electricity generated. It is calculated as follows:
CBR % =
(Heat Output x CEFgas + Electricity Generated x CEFelectricity) x100
(Gas Used x CEFgas + Electricity Used x CEFelectricity)
where:
Heat Output
Electricity Generated
Gas Used
Electricity Used
CEFgas
CEFelectricity
=
=
=
=
=
=
Total heat output from micro-CHP appliance
Gross electricity generated from the micro-CHP
Total gas used by the micro-CHP
Total electricity used by the system (pump, fans, controls etc)
Carbon emission factor for gas (kgCO2/kWh)
Carbon Emission factor for electricity (kgCO2/kWh)
Absolute CO2 savings
Another way to measure the net reduction in carbon emissions is to take the total CO2 emissions from the
fuel used and subtract the CO2 saved from the locally generated electricity. This measure enables a direct
comparison between boilers and micro-CHP, and to establish the savings achievable by replacing a
condensing boiler with a micro-CHP appliance. The absolute carbon emissions are calculated as follows:
Carbon Emissions
=
Gas Used x CEFgas + (Electricity Used – Electricity Generated) x CEFelectricity
(Obviously, when calculating carbon emissions for boilers, there is no electricity generated.)
13
4. Field Trial Results
Installations at thirteen sites were monitored in the field trial. The type of business/activity at each site is
shown below:
Site Ref
01
02
03
04
05
06
07
08
09
10
11
12
13
Type of business/activity
Nursing Home
Apartments
(district heating scheme with two micro-CHP units, each of which was monitored separately)
Nursing Home
Hospital
Crèche
Fire Station
Nursing Home
Nursing Home
Nursing Home
Nursing Home
Offices
Nursing Home
Hotel
Technologies Installed
Site Ref.
micro-CHP installed
Fuel
Thermal rating
Electrical rating
01
02
1 x Senertec Dachs
2 x Senertec Dachs
Natural Gas
Natural Gas
03
04
05
06
07
08
1 x Senertec Dachs
1 x Senertec Dachs
1 x Senertec Dachs
1 x Senertec Dachs
1 x Senertec Dachs
2 x Senertec Dachs
Natural Gas
Natural Gas
Natural Gas
Natural Gas
Natural Gas
Natural Gas
09
10
11
12
13
1 x EC Power
1 x Senertec Dachs
1 x Senertec Dachs
1 x Tedom Micro T30
3 x Senertec Dachs
LPG
LPG
Natural Gas
Natural Gas
Natural Gas
12.5kW
12.5kW
Total: 25kW
12.5kW
12.5kW
11.6–12.3kW
12.5kW
12.5kW
12.5kW
Total: 25kW
17–29kW
12.5kW
12.5kW
53kW
12.5kW
Total: 37.5
5.5kW
5.5kW
Total: 11kW
5.5kW
5.5kW
5kW
5.5kW
5.5kW
5.5kW
Total: 11kW
4–13kW
5.5kW
5.5kW
25kW
5.5kW
Total: 16.5kW
Note: All Senertec Dachs except site 01 have the condensing option fitted.
14
Data Quality
The validation process used throughout this trial is designed to ensure that the data used in the following
analysis is robust. Any data that falls outside the error band of 93 – 103% energy closure has been
discounted from the analysis.
Figure 9 shows the percentage of operational days in the trial period, as discussed in section 3, and the valid
data collected during operational days. This indicates the number of days on which the energy closure lies
within the 93%–103% range and engine utilisation is greater than 2.5%.
Figure 9: Percentage of operational days and valid data for each site during the trial period
Figure 10 shows the number of months each site was involved in the trial. A monthly breakdown of
operational days and valid data is included in Annex 2.
Figure 10: Number of months in trial
Issues with data validity during an operational day arise because of a number of factors, including
equipment failures and site-specific factors. Issues relating to monitoring equipment failures were identified
by PTH and GaC and were rectified by PTH and their subcontractors. An example of the fault-finding and
issue log is included in Annex 3.
15
There are some sites however, where issues on site limited the collection of valid data, in particular sites 09
and 13. Site 13 had integration issues and required extensive control alterations before valid data was
obtained. Data improved in October at this site and remained of good quality until the trial was completed.
In contrast, site 09 had considerable operational and integration problems which resulted in the micro-CHP
appliance performing unsuccessfully. Site personnel made the decision to leave the engine unused for
prolonged periods. When the engine was operational, the way in which it was integrated with the rest of the
system meant that the micro-CHP suffered from short cycles. Data collected from this site was inconsistent
and unreliable and is thus excluded from some of the analyses. Where data has been excluded, this is noted
in the text.
Energy Efficiency
Energy efficiency was calculated for three main parameters: the overall efficiency of the appliance, thermal
efficiency, and electrical efficiency.
Overall Energy Efficiency
Overall efficiency was calculated on a monthly basis. For sites where 12 months of data was collected, an
annual efficiency figure is also provided. The overall efficiency includes both electrical import and export,
and thus accounts for the efficiency of the engine while in standby mode as well as during periods of
operation. This varies from the full-load test efficiency stated by the manufacturer, as this relates to the
engine’s efficiency only during periods of operation.
Every micro-CHP uses electricity when in standby mode. The amount of time an engine is in standby has a
direct effect on the annual efficiency of the appliance due to the electricity consumed during these periods.
An engine that only operates for limited periods is in standby for considerable time and will have a reduced
efficiency compared with a similar engine that operates for long periods. This is because the engine in
standby is consuming imported (high CO2 emission factor) electricity, and not generating onsite electricity
for consumption.
Figure 11 shows the overall efficiency of all 13 sites within the field trial.
Figure 11: Overall Energy Efficiency
16
All the micro-CHP appliances in this trial seem to have been sized correctly to provide the base load of each
site. This means there is very little seasonal variations within the data and the engines operate at steady
efficiency values. If engine was over-sized or there was a high level of redundancy, a reduction in efficiency
would be expected during warmer months when there is a reduced demand for heat. Overall the engines in
the trial operated at between 70 and 90% efficiency, with the majority between 80 and 85% and an average
of 82%.
The engine at site 12 was connected to the electricity grid in August 2009. However the gas meter was found
to be faulty. This was replaced in October 2009 and efficiency values following this correction were good.
In contrast, there is an obvious decrease in efficiency at site 01 in August. At this time the original heat meter
was replaced and alterations were carried out on site to optimise data collection. This included the full
insulation of all pipework and re-positioning of the heat meter temperature sensor within the water flow.
Although these actions are unlikely to have changed the efficiency of the appliance by any significant
amount, the repositioning of the sensing equipment does appear to have had an effect on the recorded
system efficiency. While the collected data still meets the data validity criteria, the calculated thermal
efficiency is lower. It is possible that minor thermal effects caused the difference in readings.
Site 08 also shows a gradual decrease in efficiency after November 2009. The engine at this site required
maintenance during November and a slight alteration in the system set-up caused the supplementary
boilers on site to assume the position of lead appliance. In turn the micro-CHP started to cycle frequently
and thus not operate at its maximum potential. This was rectified in February 2010, where a step change can
be seen in the graph. This underlines the need to correctly integrate all the appliances to ensure optimum
performance of a micro-CHP.
The highest efficiencies were recorded at site 02, which also has the longest and most continual operation
(see Figure 16). As with many of the sites, the boiler house and heating system – specifically the water
storage options (the buffer tanks) – were altered to accommodate the micro-CHP.
The lowest efficiencies were recorded at sites 03, 05 and 06, all of which had limited operation due to
installation issues.
The annual efficiency has been calculated for those sites with 12 or more months of data. Site 09 did not
provide sufficient data or periods of operation for an annual efficiency figure to be calculated.
Table 2: Annual Efficiency
Site Reference
Annual Efficiency
01
82.1%
02 CHP1
86.6%
02 CHP2
87.1%
03
79.2%
04
83.9%
05
78.7%
06
78.1%
07
82%
08
80.4%
10
82.3%
11
79.4%
12
85.8%
13
78.9%
Note: Sites 11, 12 and 13 did not collect
twelve months of data. Table 2 indicates
their overall efficiency during the trial
period (10 months).
17
Thermal Efficiency
Figure 12 below shows the thermal efficiencies of all sites within the trial. As expected, the thermal efficiency
shows little seasonal variation. The engines are operating between 50% and 65% efficiency, with the
majority between 55% and 60%, and an average of 58%.
Month by month, thermal efficiency varies more than electrical efficiency, although the changes are not
significant (typically fluctuating by 1 to 2% a month). Electrical efficiency, however, remains almost constant.
The difference could be accounted for by variations in fuel supply, operating conditions or demand.
Figure 12: Thermal efficiency
As discussed above, a particular reduction in efficiency can be seen in sites 01and 08 in the latter period of
the trial.
Electrical Efficiency
Figure 13 shows the electrical efficiency throughout the trial period. Efficiencies range from 20% to 30%,
with the majority between 20% and 25% and an average of 24%.
The lowest electrical efficiency can be seen at site 05, which also has the shortest operating hours and has
suffered reliability issues.
18
Figure 13: Electrical efficiency
Primary Energy Savings and Consumption
The main focus of this study was to analyse the primary energy savings (PES) when operating a micro-CHP
appliance.
The extent of primary energy savings when operating a micro-CHP in place of a standard boiler depends on
the type of appliance the micro-CHP is replacing – for example, a condensing boiler operates at a higher
efficiency than a non-condensing boiler, and so its replacement by micro-CHP would potentially yield less
energy savings. A modern condensing boiler would operate with a gross efficiency of approximately 86%;
however condensing boilers are less common in commercial environments because of the generally higher
water temperatures, and it would thus be unrealistic to set the theoretical performance of a condensing
boiler as the standard for comparison. For consistency, the micro-CHP units in this trial have been compared
with a modern commercial boiler with a typical in-situ efficiency of 82%.
This is in line with the EU Cogeneration Directive, which specifies 90% efficiency (net) as the basis for
comparison; however this has to be adjusted for climatic conditions, and when these corrections are carried
out and the figure converted to a gross basis to allow comparison with the field trial data, the comparative
efficiency is approximately 82%.
Figure 14 shows the primary energy savings from each site within the trial. This is the saving in final energy
requirements due to cogeneration – that is, the reduction in primary energy requirements at a centralised
power plant (such as a reduction in the use of coal, gas or peat in electricity production).
19
Figure 14: Percentage of primary energy saved at each trial site
The majority of sites have a primary energy saving of between 15% and 25%. This means that, although each
site uses more fuel to generate its own electricity, the larger reduction in energy use in central power
generation leads to net savings of 15% to 25%. Site 09 had very limited operation, and there were therefore
no energy savings at this site.
As with efficiency and CBR, the primary energy savings are proportional to the length of time the engine is
operational. Figure 15 shows the run hours and primary energy savings for each site. In general, those with
low run hours have the lowest PES and those with high run hours have the greatest PES.
The orange triangular data point represents site 13, which has three engines. The total run hours at this site
have been divided by 3 to give an average figure for comparison with PES. (This assumes that each of the
engines is operational for the same amount of time.)
Figure 15: Annual run hours and PES for each trial site
20
To enable a direct comparison of a micro-CHP and a boiler in the same situation, the absolute carbon
emissions for each can be calculated as follows:
Carbon Emissions
=
Gas Used x CEFgas + (Electricity Used – Electricity Generated) x CEFelectricity
(In the case of boilers, there is no electricity generated.)
Table 3 shows the absolute carbon emissions of the micro-CHP appliances that provided valid data in the
field trial. The figures are in tonnes.
Note that these emissions are from the micro-CHP appliance only and do not take into account the other
supplementary appliances on site. The emissions from other boilers can be substantial, depending on how
frequently they are used and/or required. /
The total figure is the total CO2 emitted throughout the trial. For sites where 12 months of data was
collected, an annual figure is included. (This is the same 12-month period used for the annual CBR
calculation.)
Table 3: Carbon emissions (tonnes): micro-CHP appliances compared with boilers
Field Trial
Total
CO2 (tonnes)
Estimated CO2
emitted from
condensing
boiler (82%
efficiency)
CO2 saving with
micro-CHP
12 Month
Annual Total
Site
Reference
CO2 (tonnes)
Number of
months in
field trial
01
11.5
19
7.9
18.2
10.3
02 CHP1
13.2
19
8.1
45.6
29.1
02 CHP2
12.8
19
8.5
03
7.5
15
7.5
15.5
8
04
7.2
15
6.2
15
8.7
05
2.4
14
2.4
4.1
1.7
06
6.7
14
5.8
11
5.1
07
10.6
13
10.6
22.7
12.1
08
13.1
13
13.1
28.2
15.1
09
0.1
13
0.1
0
0
10
7.1
12
7.1
14.9
7.8
11
0.1
10
N/A
0.3
0.2
12
11.9
10
N/A
32.2
20.3
13
10.9
10
N/A
22.4
11.5
(where available)
Operating Hours
Commercial micro-CHP engines usually operate (run) for much longer periods than domestic installations,
some operating continually, 24 hours a day. Sites that run their CHP engines for longer periods derive
greater benefit from CHP than those where the supplementary boiler operates more. Table 4 shows the
potential and actual operational hours throughout the trial period for each site. For some engines, there is
over a year of potential operation, for others it is slightly less. The engines with the most data are sites 01
21
and 02 (engines 1 and 2), all of which have 19 months of potential operation. Those with the least amount of
data are sites 11, 12 and 13, all with 10 months of data collection.
The engine at site 09 was actually operational for four months at the start of the trial, and therefore shows
that 20% of the potential operation was achieved. However, due to installation issues the data from the site
is unreliable and has been removed from much of the analysis.
Table 4: Potential and actual operational hours at each site
Site Reference
Potential
Operational Hours
Actual
Operational Hours
% of potential
actually achieved
01
13,848
10,854
78
02 CHP1
13,848
12,420
90
02 CHP2
13,848
11,554
83
03
10,920
8,664
79
04
10,920
5,855
54
05
10,176
1,448
14
06
10,176
4,257
42
07
9,504
7,053
74
08
9,504
5,357
56
09
9,504
1,933
20
10
8,760
4,906
56
11
7,296
429
6
12
7,296
3,351
46
13
21,888
10,246
47
Note: Site 13 has three operational engines.
The percentage of potential run hours actually achieved at each site is shown more clearly in Figure 16.
Figure 16: Percentage of potential run hours achieved for each site
22
Some of the engines within the trial were on timers. The shortest operating period set by a timer is at site 05,
where the engine is only ‘on’ between 08:00 and 18:00, Monday to Friday. Sites 04 and 10 are timed to
operate 07:00 to 23:00 due to electricity tariffs, and both these sites show comparable operating hours. The
other engines operate as required to fulfil the heat demand of the site. The duration of operation, however,
depends on how the CHP is integrated with other appliances, on heat demand, and on interaction with the
buffer tank. (The effect of buffer tanks on the performance of micro-CHP appliances is discussed later in this
document.)
Run hours can also reflect periods of non-operation due to maintenance and service intervals. If service
requirements go unnoticed, the ‘down-time’ can be considerable. Run hours can also be an indicator of
faults and repairs – an example is site 01, where a cracked CHP heat meter casing was discovered in July
2009 and the engine remained off while this was replaced (August 2009).
Table 5 (next page) shows the significant site issues and the down-time due to service and maintenance for
each site.
A micro-CHP appliance requires different levels of servicing at different times, ranging from a minor service
every 3,500 operating hours to a major service every 35,000 operating hours. For an engine that is
operational continuously, this can mean two to three services a year, which can be very expensive.
The maintenance and service of a micro-CHP appliance is important, because micro-CHPs:
Are not as robust as conventional boilers;
•
Are sensitive to perturbations in the site gas and electricity supply;
•
Are complicated, with multifaceted mechanical and electrical components; and
•
Can be adversely affected by ill-considered adjustments to a building energy management system
(BEMS).
•
The success and optimisation of an installation depends upon the ability of the site, or a responsible
individual, to recognise the service requirements and know how to act in the event of a fault.
Figure 17 shows for each site the average hours of operation per month throughout the trial period, the
minimum run hours observed in a month, and the maximum run hours observed in a month. It also shows
the hypothetical average monthly operation if the engines were to operate for 24 hours, 16 hours or 8 hours
a day (8 hours would be an unusual operating pattern for commercial micro-CHPs). The total run hours for
site 13 are divided by three to account for the three engines operational on site to yield an average figure as
if all engines are operating to the same extent.
Figure 17: Average, Minimum and Maximum monthly run hours with average 24, 16 and 8 hour examples
23
Table 5: Site issues and associated down-time for service and maintenance
Down-time due to service intervals
and maintenance
Days
Hours
% of potential
operation
Cracked flow meter casing discovered during August
2009; engine was switched off while this was rectified
(16 days). Service and maintenance issues such as low
oil level caused periods of no operation.
101
2424
18%
02
CHP1
No significant engine issues on site.
44
1056
8%
02
CHP2
Engine suffered low oil levels during February and
March 2010 causing it to stop operating.
80
1920
14%
03
Initial installation issues due to lime build up.
38
912
8%
04
No significant engine issues on site.
51
1224
11%
05
Considerable site issues causing the micro-CHP to fail.
Engine required only one service during trial period (18
days of no operation); however other issues within the
system caused considerable loss of operation. This site
had a gas leak causing the safety valve to shut the
system down after periods of operation. In addition,
the site suffered flooding and weather damage
towards the end of the trial period.
149
3576
35%
06
Faulty gas slam valve caused the engine to fail
frequently from April to September 2009.
101
2424
24%
07
Ignition fault, due to either a faulty component or gas
pressure, caused erratic operation between December
2009 and March 2010.
87
2088
22%
08
Engine actually non-operational for 29 days. However
13 days were due to the fire alarms being set off and
causing the micro-CHP to automatically shut down.
16
384
4%
09
Engine had very limited operation and was never fully
utilised. Not possible to distinguish periods of
maintenance from those when the engine was
manually switched off.
N/A
N/A
N/A
10
No days lost due to service or maintenance.
0
0
0%
11
Engine had very limited operation and was never fully
utilised. Not possible to distinguish periods of
maintenance from those when the engine was
manually switched off.
N/A
N/A
N/A
12
During the initial months of the trial, the engine did not
operate due to ESB connection issues (67 days).
However, once operational very few days have been
lost due to service requirements.
6
144
2%
13
No days lost due to service or maintenance.
0
0
0%
Site Ref
01
Site Issues
24
Actual monthly run hours against 24-, 16- and 8-hour examples are shown for each site in Annex 5: Site-bySite Data Analysis.
As discussed previously, engine operating hours have an impact on the efficiency of the appliance, and
especially on electrical performance. Most of the micro-CHP engines in this trial operated between 12 and
24 hours a day; the average was approximately 16 hours a day. Figure 18 shows how run hours relate to the
efficiency of the engine at each site.
Figure 18: Efficiency and run hours for sites with valid data
There is an overall trend suggesting that the greater the monthly run hours, the higher the monthly
efficiencies. It can be seen, for example, that the engines at site 02, with high run hours, show high efficiency,
and the engines at sites 05 and 11, with the lowest run hours, also show the lowest efficiency.
Site 05 probably has the lowest heat load and shortest operational time of all the sites; thus low run hours
are not unexpected.
The engine at site 11 suffered considerable operational issues and was never fully used during the trial.
Similarly the engine at site 09 had considerable integration problems and was actually turned off during
August 2009, after which it had very limited operation until January 2010 (a total of less than 1 hour), and
was then turned off and not re-started.
Figure 18 also shows the continuity of operation at each site, with each engine showing relatively consistent
efficiency values, which do not appear to be related to the run hours observed.
The engines at sites 04 and 12, for example, show moderate run hours but consistently high efficiencies,
whereas the engine at site 06 shows comparable run hours but much lower efficiency. The engine at site 06
suffered fuel supply issues due to a faulty gas slam valve, so that operation was inconsistent. The engine at
site 12 is larger than the others (53kW thermal and 25kW electrical output).
The engine at site 03 shows monthly run hours comparable to site 02, but the efficiency figures are
comparable to site 05. This suggests the influence of the site- and installation-specific parameters, such as
interaction with the buffer tank and control strategies.
The engine at site 01 might be expected to operate at a lower efficiency than other installations because it is
the only non-condensing unit in the trial. However this is not evident, despite the fact that this site also
25
shows the most sporadic run-hour and efficiency values, probably because it is the only site in which the
micro-CHP feeds the low loss header directly (rather than a buffer tank) and is thus prone to influence from
supplementary boilers.
Buffer Tanks and System Integration
Buffer tanks
Many commercial micro-CHP appliances are installed with a buffer tank, to reduce cycling and increase the
likelihood of long periods of operation. This maximises the electricity produced and reduces wear on the
engine due to less frequent stop/start cycles.
The majority of engines in the SEAI trial are installed alongside a 750l buffer tank. The exceptions to this are:
•
Site 02, where the micro-CHPs are installed with 7500l buffer tank capacity (two custom made tanks);
•
Site 01, where the engine feeds the low-loss header directly; and
•
Site 12, where the micro-CHP feeds the return water directly to the boilers.
A storage vessel (buffer tank) with a capacity of 1,000 litre (1m3) can buffer 23kWh between 80°C and 60°C.
However, 23kWh is only slightly less than two hours’ operation for a 12kW thermal micro-CHP unit – buffer
tanks to take 4 to 5 hours of heat output are thus quite large. Some micro-CHP units can be modulated down
in output, but as the speed of the engine must remain constant (so that the electricity stays in phase with
the grid), such turn-down tends to reduce overall performance. If buffer tanks are oversized, standing heat
losses can grow disproportionately, especially if the vessel is located in a plant room or outside the heated
part of the building. If the outside surface of the heat store loses more energy than is provided in the form of
electricity, energy is wasted.
Heat transferred from the buffer tank was monitored on all sites equipped with a buffer tank, and all sites
except site 05 provided useful information. (The data from site 05 was very erratic, partly because of the
intermittent nature of the operation, but also because of problems with the monitoring instrumentation.)
See Figure 19.
Figure 19: Total monthly heat from buffer tank
26
With most sites, the monthly buffer load, after allowing for periods of non-operation, appeared to be very
consistent.
One of the most striking changes in buffer tank heat flows is for site 13, where the load on the buffer tank
increased dramatically as the operation of the system was improved. This site could potentially supply
approximately 27,000 kWh a month if all three machines at the site operated continuously; the site achieved
approximately 85% of this maximum in January 2010, delivering 23,000 kWh of heat. The heat delivered
from the buffer at the other sites also tends to reflect the run hours operated.
The consistency of heat output in the monthly charts is not apparent when the data is viewed on a more
detailed basis, with some sites exhibiting much more variable operation – see Figures 20 and 21.
Figure 20: Buffer Flow – Site 02 31 Oct 2009
27
Figure 21: Buffer Flow – Site 02 31 Dec 2009
It can be seen from Figure 20 and Figure 21 that even within a single site there can be considerable flow
variations at the buffer tank outlet. At site 02, the pumps are variable speed units under the control of the
building energy management system (BEMS). Despite the lower average flow rate on the 31 October, the
temperature difference was much higher (22.2ºC compared with 14.3ºC) resulting in a larger amount of heat
being transferred from the buffer tank on 31 October than on 31 December.
An example of flow rates through the buffer tank meters is presented in Table 6; the months were selected
as representing a load during the times of highest heat demand.
Table 6: Buffer flows at various sites
02
03
04
06
07
08
10
13
Average Buffer Flow (l/min)
Oct-09
15
4
17
22
12
24
9
Nov-09
16
4
11
16
15
22
9
33
Dec-09
20
5
9
13
15
24
9
32
Maximum Buffer Flow (l/min)
Oct-09
28
5
36
38
18
34
18
Nov-09
30
5
30
32
28
34
22
72
Dec-09
34
7
16
26
34
33
20
74
Minimum Buffer Flow (l/min)
Oct-09
0
3
0
4
6
6
2
Nov-09
0
3
6
2
8
6
2
6
Dec-09
0
3
6
0
6
6
2
8
28
All the systems in Table 6 are based on the Senertec Dachs CHP engine. In the units with a single CHP
engine, there is a wide range of average flow rates from the buffer tank to the heating system, ranging from
4 to 5 l/min for site 03 to 13 to 22 l/min for site 06. The two twin-engine systems have average flows ranging
from 15 l/min (site 02) to 24 l/min (site 08). Site 13 shows the largest flows at 32 to 33 l/min. Note, however,
that most of these systems use variable speed pumps (not electrically connected to the micro-CHP directly),
and the flow is therefore highly dependent on the configuration of the building energy management
system, or whatever is controlling the heating system.
On average, 89% of the heat output from the micro-CHP appliances is drawn from the buffer tanks,
indicating that losses in the pipework and tank are not excessive (only 11% of micro-CHP heat output). This
shows that the buffer tanks are in general operating efficiently. For some sites, the efficiency is slightly less,
in others slightly more, depending on system characteristics and level of insulation. There is considerable
variation at some sites, with some values greater than 100%, but this is most probably the result of
peculiarities in the operation of the plant, in particular heat being drawn off while the engine is nonoperational or heat being delivered to the buffer tank by other heating systems, or non-CHP parts of the
same system. The buffer heat meters did not record any negative energy (that is, heat from the heating
system being transferred back into the tank), but it is possible that some indirect heating of the buffer tanks
may take place, as some sites have very complicated piping arrangements.
Figure 22: Fraction of buffer heat output over CHP heat input
The losses recorded here (approximately 11%) were much lower than had been thought likely at the outset
of the programme. One of the reasons for the low levels of heat loss is the fact that the units are delivering
heat to the system as fast as they are receiving it. So the thermal store is effectively acting as a large low-loss
header. This suggests that the buffer tank may not be strictly necessary in some of these installations. The
system which appeared to use its own buffering system significantly was the EC Power micro-CHP at site 09.
However, the integration of the micro-CHP with the rest of the system at this site led to sub-optimal
performance and very restricted running time, which prevented the collection of conclusive data.
29
The effects of buffering on engine efficiency
The data presented previously shows that the majority of engines seem to operate at similar levels of
efficiency at high run hours, regardless of whether they are condensing or non-condensing. This could be a
result of the interaction between the micro-CHP and the buffer tank. A possible explanation is that the
return temperatures to the micro-CHP from the buffer tank are actually higher than the point of flue gas
condensation (approximately 57ºC when combusting natural gas). This would reduce the possibility of
condensation taking place, and thus lower efficiency. This has been investigated over a number of sites
while the engines are operating close to the maximum duration for that site.
Of those analysed, the efficiency ranged from 77% to 87% (based on gas input only), with the majority
between 77% and 84%. The non-condensing site efficiency was 79.7%, which is well within the range
observed for the other sites.
There was a clear difference in flue temperatures; the non-condensing unit had an average flue temperature
(during firing) of 90.1ºC, while that of the condensing boilers was between 60.6ºC and 80.9ºC. This indicates
a small efficiency improvement, but other unmonitored factors (such as Carbon Dioxide concentration) may
also have an effect. If the data from site 02 (exceptionally high efficiency) and site 01 (non-condensing) are
eliminated there appears to be a loose relationship between efficiency and flue gas temperature – see
Figure 23.
Figure 23: CHP Efficiency against Flue Temperature
Water temperatures from the system to the buffer tank were close to the temperatures of the water
returning from the buffer tank to the CHPs (while firing). These ranged from 49ºC to 68ºC with the buffer
flow being at most 3ºC higher than the CHP return temperature. This confirms that some sites are indeed
below the condensation temperature. Of the eight sites studied here, half showed conditions suitable for
condensation with return water temperatures of 49.1 to 50.4ºC. However, the data in this sample showed
that the efficiency difference between these sites and those experiencing higher temperatures was 0.2
percentage points in the wrong direction.
30
System Integration
All of the sites studied had supplementary boilers. Most of these were gas fired, but one (site 04) was dual
fuel (capable of firing oil too) and one (site 10) had oil boilers. The gas boilers were a mix of conventional
package burner types and more modern (but smaller) wall-mounted units. Most were controlled by building
energy management systems of varying complexity, or combined with timers. Some installations, in
particular site 03, had very complex systems combining CHP, heat pumps, solar thermal, solar photo-voltaic
and conventional heating appliances. Several sites had solar thermal in addition to micro-CHP and
conventional boilers.
System integration and system control are very important to the success of a micro-CHP installation. A
successful micro-CHP installation must be sized to operate at the base-load requirement of the site, which
means that it will nearly always be installed with supplementary appliances to satisfy the heat load during
very cold periods. These elements must work together in such a way that the micro-CHP always acts as the
lead appliance. Heat should be taken from the micro-CHP before any other appliance; the boilers must be
able to operate if required, but must not operate when the micro-CHP can satisfy the demand. The simplest
way of ensuring this mode of operation is to lower the temperature set point of the auxiliary boilers to a
point below that of the micro-CHP unit. This ensures that the boilers operate only if the micro-CHP cannot
maintain the required temperature. It is also important to ensure that the micro-CHP is actually available for
use – for example, if it is on a timer, this must be set correctly to operate when required.
Site 13 was the second largest of the installations in the SEAI trial, with three Senertec Dachs operating in
sequence. When initially installed, considerable issues became apparent regarding the cycle frequency of
the engines. All engines were trying to operate at once -- this was quickly satisfying the buffer tank and
causing the engines to cycle on and off very frequently. In October 2009, for example, the engines had 980
stop/start cycles (by comparison, site 02 had only one). At site 13, the control system and temperature set
points were significantly altered to account for the micro-CHPs, and in February 2010 the number of starts
had reduced to 221. Although this is still a considerable number, it shows much better control of the microCHPs within the system. This shows the importance of careful configuration of the system, particularly where
a complex building energy management system is involved, as incorrect configuration can prevent the
engines from delivering their full potential.
Physical integration
Most of the sites in the field trial used a twin-header system for connecting the heating appliances with the
physical heating system. In these cases, the heating appliances are connected in parallel between the flow
and return headers. An alternative is to introduce the CHP between the return to the boiler(s) and the
boiler(s). This arrangement, which was used in site 12, has some advantages in ensuring that the CHP gets
the greatest opportunity to operate. A commonly used piping arrangement involves the use of a low-loss
header; this has some advantages in creating a fluidic separation between the primary and secondary
circuits and allowing the heating appliance to operate at its optimum flow rate, regardless of heating
demand. Figure 24 shows the alternative installation locations for a CHP appliance within a system. The ‘inseries’ option is often used where the CHP is retrofitted to a boiler house. However, the ‘in-parallel’
arrangement may have benefits if the CHP load is significant. Similar arrangements can be visualised with a
twin header arrangement.
31
Figure 24: Possible CHP installations with a low-loss header system
The SEAI publication Commercial Scale micro-CHP Design and Installation Guide deals with the selection and
installation of micro-CHP systems in more detail.
The site that appeared to have most issues with system integration was site 09. Unfortunately this system
did not run for long during the trial, partly because the micro-CHP engine was added to the system at a late
stage and it appeared to have a less-than-ideal installation, and partly because on-site staff had set timers
and valves that restricted the micro-CHP to operating only on hot water demand, which (from observations
on site) was generally satisfied quickly. With more optimisation and possibly some re-piping, it is likely that
the micro-CHP would have been able to contribute far more than it did.
Carbon Benefit Ratio (CBR)
The Carbon Benefit Ratio (CBR) is similar to an efficiency figure, but takes into account the carbon emissions
from the fuel used and electricity generated. CBR can be calculated on any time basis, but an annual figure
gives the best understanding of performance.
The higher the CBR is, the better the site is in terms of benefiting from the electricity generated. Any value
over 100% means that local generation at the site is successfully offsetting grid electricity. Figure 25 shows
the CBR for the sites in the trial. The CBRs for sites 1 to 8 and 10 are based on 12 months of data, and are thus
true annual figures; those for sites 11, 12 and 13 are based on the available 10 months’ data.
32
Figure 25: Annual CBR%
All sites have CBR values over 115%, with the majority operating between 120% and 130%. This means all
sites are benefiting from the micro-CHP appliance in terms of carbon emissions. The sites with the highest
CBRs are the two Dachs engines at site 02 and the Tedon engine at site 12. The former two had the longest
run hours (almost continual) and the highest efficiencies; the latter is a different make of engine with an
electrical output of 25kWe, which is substantially higher than the Dachs (5.5kWe), and could reasonably be
expected to deliver significant benefit from electricity generation.
The CBR does not take into consideration the efficiencies of alternative heat sources, such as boilers. It is
rather an absolute measure of carbon benefit that can be applied to any technology. The CBR for a gas boiler
is similar to, but slightly lower than, the seasonal efficiency of the boiler. It is the principal metric used by the
Carbon Trust in their interim report on the UK micro-CHP Field Trial.
33
5. Financial Evaluation
Fuel Costs
Unlike renewable generation technologies, micro-CHP uses fuel to generate heat and electricity. The
operational cost savings for micro-CHP are therefore determined by the efficiency of the micro-CHP and the
relationship between fuel and electricity prices, rather than by electricity costs alone.
When operating, a micro-CHP unit generates both heat, which would otherwise be generated by a boiler,
and electricity. The operational cost savings associated with the use of micro-CHP are:
•
•
•
the value of the electricity generated, based either on the cost of electricity imported from the network
or on the price paid for electricity exported to the network
plus
the value of the heat in avoided boiler fuel costs
minus
the cost of the fuel used by the micro-CHP.
The key metric is the cost of electricity produced by the micro-CHP. If the unit is not producing electricity at
rates significantly lower than either the import or the export tariff, then there is little advantage in having or
running a CHP unit.
The cost of fuel required to generate electricity from a micro-CHP is:
Where:
=
ηe
=
ηCHP
=
ηB
electrical efficiency of the CHP unit
thermal efficiency of the CHP unit
thermal efficiency of the boiler
The cost of electricity thus depends on the cost of fuel, on the thermal and electrical efficiencies of the
micro-CHP, and on the thermal efficiency of the boiler it replaces. On the basis of the average electrical and
thermal micro-CHP efficiency of field trial installations and an average boiler efficiency of 82%, the average
cost of gas per unit electricity was just under 6c (5.98c). This represents the electricity tariff at which it would
be viable to run a micro-CHP at a typical site, disregarding capital, operating and maintenance costs.
Capital, Operating and Maintenance Costs
The capital, operating and maintenance costs for commercial-scale micro-CHP vary according to the size of
the unit and the type of engine on which it is based.
Table 7 shows the capital cost and operating and maintenance cost ranges 6 for micro-CHP from 1kW to
100kW. The installed costs vary widely. This reflects the high capital cost of small, domestic scale micro-CHP
technologies.
6
Data from Energy Technology Perspectives, IEA, 2010
34
Table 7: Costs and key parameters for small scale and micro-CHP
Reciprocating engines
2006
2050
Size range (kWe)
1-100
1–100
Economic life (years)
15–25
20–25
Electrical efficiency
20–40%
26–40%
Total efficiency
80–85%
80–90%
Installed cost (USD/kWe)
1,500–12,000
900–7,000
Variable O&M (USD/kWh)
0.011–0.017
0.01–0.013
Size range (kWe)
1–100
1–100
Economic life (years)
8–10
10–15
Electrical efficiency
30–37%
35–45%
Total efficiency
70–75%
75–85%
Installed cost (USD/kWe)
8,000–28,000
3,000–7 000
Variable O&M (USD/kWh)
–
0.02–0.03
Fuel cells
Figure 26 shows the capital cost, on a per kW installed basis, for the micro-CHP installations in the field trial.
This shows that, in general, installed cost per kW reduces as installation size increases.
Figure 26: Capital Cost vs Installed Capacity
Operation and maintenance schedules and costs vary according to the type of engine installed. At present,
the majority of market-ready commercial-scale micro-CHP products – and all of the field trial installations –
are based on the internal combustion engine. Regular scheduled maintenance is required at specified runhour intervals – typical maintenance includes oil changes, air filter replacement, and spark plug
replacement, with more extensive overhauls required at longer intervals.
Applicants to the field trial were required to specify maintenance costs as part of their application; this
varied from 1.1c/kWh to 2.6c/kWh, with an average of 1.7c/kWh. Operation and maintenance costs generally
35
include a fixed component, and labour and travel can form a significant proportion of total costs, so the
longer the service intervals for a given micro-CHP, the less significant the operation and maintenance costs
for that unit will be.
Financial Assessment
Figure 27 shows the average component costs (capital, maintenance and fuel) per unit of electricity
generated for the micro-CHP field trial sites. Fuel costs are shown for natural gas, oil and LPG; maintenance
costs are based on an average cost per kWh; capital costs are based on the average capital cost over a 15year economic lifetime; and electricity output is based on the average plant size and the average utilisation
factor.
The relative significance of investment and fuel costs will vary depending on the actual investment cost,
utilisation factor and efficiency of a specific installation.
Figure 27: Average cost per unit electricity generated
The annual cost saving delivered by a micro-CHP unit is the difference between the cost of generating
electricity at the micro-CHP and the value of that electricity, less the operating and maintenance costs. The
value of the electricity generated is the price the customer would pay for electricity used on site (if it were
imported from the grid) and/or the price paid for electricity exported to the grid.
36
The simple payback period for the field trial installations is plotted against their utilisation factors in Figure
28 7. This clearly indicates that payback is highly dependent on utilisation, or annual run hours, and that a
minimum utilisation of around 50% or 4,000 hours per annum is required to achieve a reasonable return on
an investment in micro-CHP.
Figure 28: Payback time vs Utilisation
On sites with reasonable run hours, payback is influenced by other factors, including fuel cost, investment
cost per kW installed and operational efficiency, generally in that order of significance
Financial Supports
All installations in the field trial qualified for 40% funding of eligible investment costs, subject to a maximum.
This is one of a range of possible mechanisms that could be used to promote micro-CHP, such as grant
schemes and combinations of generation and feed-in tariffs.
Figure 29 illustrates the payback periods for the sites involved in the trial in four scenarios: no support, a 40%
grant; a 5c/kWh generation tariff; and a 10 c/kWh generation tariff. This shows that payback periods are
greatly influenced by the level of support, and in some sites it would not be feasible to install a CHP unit
without any support, as the payback period would far exceed normal expectations.
7
These are based on actual costs and operating data and the following electricity and fuel prices (€/kWh):
Electricity (GP) €0.1639; Natural Gas (Small Business) €0.0474; L.P.G. Bulk (0-3 tonne) €0.0992; Diesel €0.0817.
37
Figure 29: Payback periods for different levels of support
38
6. Policy and Regulatory Implications
Network connection and permitting
As micro-CHP installations are by definition limited to a maximum size of 50kW and are usually installed in
existing plant rooms on sites where the Maximum Import Capacity (MIC) exceeds the generator output, the
network connection and permitting arrangements are relatively straightforward.
In general, planning permission is not required for installing a micro-CHP unit and the erection of a structure
for housing CHP plant is an exempted development under the planning regulations 8.
The rules and arrangements for connection to the distribution network are defined in ESB Networks’ Network
Code. Within the size limit of 50 kW, there are two categories of generators for the purposes of network
connection:
•
Generators subject to the connection arrangements for micro-generators (up to 16A per phase or 25A
single phase), and
•
Generators subject to ESB Networks’ general connection process.
Quality Measures
The field trial demonstrates that commercial-scale micro-CHP delivers significant energy and carbon savings
on a reasonable economic basis, provided that it is operated efficiently and integrated effectively with other
plant in a site with a suitable heat load.
The trial also demonstrates that if micro-CHP is installed in inappropriate situations, or is badly installed or
badly operated, it will deliver only poor performance. The trial highlights the need for proper sizing, design
and installation of micro-CHP, and its careful integration with Building Energy Management Systems and
boiler controls.
This is perhaps the single most important aspect to consider and address in promoting the deployment of
micro-CHP. Good quality design and installation can be promoted through information and guidance for
specifiers and installers and through training targeted at these groups.
While operational problems with the field trial installations have almost all been associated with design and
installation issues rather than product quality, there is the potential for poor quality products to contribute
to adverse outcomes in micro-CHP installations. The development of a registered product list, with defined
criteria, is an effective measure to mitigate this risk. SEAI’s Triple E products list, which includes CHP
(including micro-CHP), is an example of such a list. The qualification criteria include:
•
All equipment and/or components must be CE marked, as required by relevant EU Directive(s);
•
Accredited test certificates must be available demonstrating a minimum overall efficiency of 80%;
•
Operation and maintenance manuals must be provided for the end-user; and
•
The CHP must record electricity and heat production.
8
SI 235 of 2008, Planning and Development Regulations 2008
39
Building regulations and BER
Building Regulations, which include minimum energy and carbon performance requirements and
mandatory contributions from renewable and alternative energy sources, are a driver towards the
deployment of micro-CHP in new buildings.
Non Dwellings
A requirement for a quantified amount of energy from renewable sources is not specified in the 2008
Building Regulations, Part L – Buildings Other than Dwellings. However they do state that consideration
should be given to the use of renewable and alternative energy sources.
In addition, as micro-CHP reduces energy use and CO2 emissions, the incorporation of micro-CHP will reduce
the Energy Performance Coefficient (EPC) and Carbon Performance Coefficient (CPC) and contribute to
meeting the maximum permissible EPC and CPC specified in the Regulations.
Dwellings
While this document is principally concerned with the use of micro-CHP in commercial-scale applications,
the same products and technologies can be usefully deployed in community heating schemes, in which a
number of dwellings are connected to a centralised heat source, to improve the energy performance of the
dwellings and to contribute to compliance with Part L of the Building Regulations. Site 02, an apartment
building with centralised boilers and micro-CHP, is an example of this.
Building Regulations specify that dwellings should have minimum of 10 kWh/m2/annum supplied from
renewable sources, but also provides that in high-density developments, such as apartments, where the
provision of 10 kWh/ m2/annum from renewable sources to each dwelling is not practicable, the provision of
space and water heating from a small-scale CHP system would be an acceptable alternative.
There is also a recommendation that the unit should be sized to provide 45% of all heat demand on site,
including both space heating and hot water heating, unless there are overriding practical or economic
constraints. Unfortunately, full compliance with this recommendation could lead to over-sizing of the microCHP unit, with consequential poor performance.
Support Mechanisms
The trial demonstrates that well designed and installed micro-CHP in commercial sites delivers efficiency
and CO2 savings on a reasonable economic basis, and is at least as cost-effective as competing alternative
energy technologies, such as solar thermal, small-scale wind and solar photo-voltaic.
However, in the absence of financial supports, there is a significant investment cost for end-users, which is a
barrier to the deployment and uptake of micro-CHP.
Grant Schemes
Grant schemes have been effective in promoting CHP and in helping to overcome the initial capital cost
barrier. However, poorly designed grant schemes, and grant schemes without accompanying quality
measures, can lead to unintended outcomes.
Tariffs
An attractive export/feed-in tariff could be seen as a way of encouraging the generation of electricity for
export. However, a well-designed commercial-scale micro-CHP doesn’t export significant quantities of
electricity, as sizing around the base heat load generally means that the electrical output is also below the
site’s base electricity load. An export tariff is not therefore an effective support mechanism for micro-CHP.
40
A generation tariff 9, on the other hand, could promote the uptake of the technology, and a 10-year 5 c/kWh
tariff would deliver similarly short payback periods to a 40% capital grant, at similar cost (as seen in Figure
29).
A tariff-based incentive has the advantage of preferentially supporting well designed, installed and operated
micro-CHP, as payment is linked to performance.
9
The UK green energy cashback generation tariff offers a 10p/kWh generation plus 3p/kWh export tariff
41
7. Summary and Key Learning
Trial Summary
Data was collected from thirteen commercial sites in Ireland operating at least one micro-CHP appliance.
•
Ten sites operating a Senertec Dachs with condenser unit;
•
One site operating a standard Senertec Dachs;
•
One site operating a Tedom micro-CHP; and
•
One site operating an EC Power unit.
Two sites use LPG as the fuel, the remainder use natural gas.
Throughout the trial, an energy closure calculation was made on these appliances; data was collected and
analysed in terms of operation, performance, efficiency, and potential energy and carbon savings.
When the engines are operational (utilisation greater than 2.5%), the majority of sites produce between 80%
and 100% valid data. There are some marginal data points where closure falls outside the 93–103% error
band – these are sometimes due to particular start and end conditions which are impossible to account for
in the closure calculation (for example, the buffer tank was cold at start of day and fully heated at the end of
the day). They can also be the result of minor changes in the performance of the engine over a 24-hour
period (for example, a slight change in CO2 production). Where values lie very close to the 93–103% band, it
would be acceptable to use these in further data analysis (only if the primary indicators are in the same
proportions as in valid data); however, they are excluded from the data analysed in this study.
Overall there were only minor issues causing operational problems on site.
Site 12 had initial grid connection problems, due to the size of the electrical output. However, once
operational, the engine was successful and well utilised.
Other sites, such as sites 06 and 05, had gas supply problems, where the gas slam valve was limiting the
micro-CHP operation. At site 06, this was a faulty valve; at site 05 there was a minor gas leak causing the gas
to be shut off. Once these were rectified, no further problems occurred due to gas supply.
Several of the sites – specifically sites 09 and 13 – had integration and control problems. These were never
rectified at site 09 and this engine was never fully utilised during the trial period. At site 13, considerable
effort was made to successfully integrate the micro-CHP into the existing system. This included changing
the temperature set points, altering the control strategy and ensuring maximum operation was achieved
from all engines on site.
As could be expected, some of the engines also suffered general maintenance issues, such as low oil levels.
If successfully integrated and installed, a micro-CHP appliance can offer considerable savings for a site with a
consistent heat demand. The trial data has shown engines operating at an average of 83% efficiency, with
the majority of the engines running between 12 and 24 hours a day. All the appliances in the trial operated
almost independently of the external temperature; this suggests that they were sized correctly for the base
load of the site. Sizing the unit correctly ensures optimum performance and energy savings, and promotes
the use of micro-CHP in preference to the supplementary boilers. This could only be confirmed by further
metering of the other appliances on site. All sites derived benefit from the micro-CHP in terms of carbon
emissions, with all sites achieving a CBR of over 100%; this means they are successfully offsetting grid
electricity by local generation.
In the case of condensing versions of the micro-CHP engines, efficiency improvements were expected when
the engine return water temperature was below the condensation temperature (about 57ºC with natural
gas). However, the study did not produce solid evidence that the condensing engines operated any more
42
efficiently than the non-condensing site. Even when the conditions were favourable for condensation, there
was no significant improvement in overall engine performance. However, with only one non-condensing
engine in the study of the same type as the condensing ones, this could be a reflection on the type and
quality of installation rather than on the engine performance.
Overall, the sites have shown primary energy savings of 15% to 25%, meaning that co-generation reduces
the requirement for carbon–intensive fossil fuels at the centralised power plant by up to 25% to satisfy the
needs of the site. This is significant and should encourage the uptake of micro-CHP at sites that are suitable
for installation and where grid electricity is generated from high-carbon fuels, such as coal or peat. As with
efficiency and CBR, primary energy savings are directly related to the run hours. The longer the engine
operates for and the consistency of this operation, the better the efficiency, energy savings and carbon
savings.
The majority of the sites within the trial are installed alongside buffer tanks. There are some concerns about
heat losses from buffer tanks as these can be considerable, especially when the tanks are not in the heated
parts of the site. However, the losses from buffer tanks in this trial were not excessive. The load at most sites
appears to be sufficiently high to occupy the micro-CHP almost continuously. This means that the
throughput of the buffer tanks is high and, as a result, the heat losses from buffer tanks were only of the
order of 11%. This was much lower than had been thought likely at the outset of the programme. It would
be better if the buffer heat loss could be usefully employed within the site, but such integration would be
difficult at many commercial sites. The high throughput suggests that the buffer tank may not be strictly
necessary in all of these installations, but it does allow a degree of flexibility in operation. The system that
appeared to use its buffering system significantly was the EC Power micro-CHP at site 09, partly because it
was only used for water heating (intermittently). This meant short runs and significant cycling; however, as
this site had only a short operational period, it was not possible to improve the operational strategy.
Key Learning
For a micro-CHP installation to be environmentally and financially viable, it must generate electricity. It is this
generation which offsets the need for grid electricity and provides the carbon savings required to meet
political and environmental needs.
This study has clearly demonstrated that, in installing a micro-CHP appliance, very careful consideration
needs to be given to correct sizing of the appliance, its integration into the overall system at the site, its
control systems and the storage of water.
Sizing
At the outset, the heat demand of the site must be assessed. To optimise the performance of a micro-CHP
appliance and ensure that the maximum amount of electricity is generated, the micro-CHP appliance must
run continuously or regularly for prolonged periods. When a building is constructed, a design heat load is
specified; this is the maximum heat requirement of the building during the coldest weather. For a micro-CHP
appliance to be economically viable, it should not be sized to fulfil this requirement, but should be specified
to meet the base or background load, and supplementary boilers should be installed to satisfy the additional
requirements during those periods when the micro-CHP appliance cannot meet the heat demand. This
ensures that the micro-CHP has the potential to run almost continuously, and thus generates electricity to its
maximum potential. In turn, this ensures significant financial and carbon savings. If the micro-CHP is
oversized, it suffers periods of redundancy and frequent on/off cycling; this severely limits the generation
potential of the appliance, and also increases maintenance costs and the likelihood of engine breakdown.
Integration
The overall heating system at the site must integrate the operation of the micro-CHP appliance and the
supplementary boilers in a way that optimises performance. Many of the heating systems in the trial were
43
altered or designed to accommodate the micro-CHP appliance and to ensure it always acted as lead engine.
For example, at site 02 the buffer tanks and system were re-plumbed to ensure that the two micro-CHP
appliances were the lead engines and the boilers operated only when the micro-CHPs could not fulfil the
demand.
The control strategies and system set points should also be carefully considered; the micro-CHP should
always be available to run when heating is required, and any other appliance in the heating system should
have lower temperature set points, so that it operates only if the micro-CHP cannot fulfil the demand. By
ensuring the micro-CHP is optimised as the lead appliance, on/off cycling (which was noted at some sites)
can be substantially reduced.
Many sites require ongoing adjustments to ensure optimal operation; for example, at site 13 the whole
heating system control was altered to accommodate the operation of three micro-CHPs on site. This
included changing temperature set points, altering timer controls and sequencing of the micro-CHPs to
ensure that they operate in order (for example, engine 2 operates only if engine 1 cannot satisfy the heat
demand).
Installation
The micro-CHP appliance must be installed correctly within the heating system. This can significantly affect
the operation of the engine – incorrect installation can lead to substantial operating problems. For example,
the micro-CHP appliance at site 09 was not plumbed into the system correctly and was only available to
supply intermittent hot water demand. This limited its operation significantly, reduced electricity generation
and severely reduced the carbon benefit. The micro-CHP was thus very uneconomical to run and was turned
off rather than altering the installation. It is very important, therefore, that any site installing a micro-CHP
appliance is offered support to optimise the installation and ensure any problems with system integration or
engine failures are rectified. Without such support, sites may lose confidence in the technology and resort to
isolating the appliance or continuing to use it in an undesirable and uneconomical fashion, with regular
breakdowns and system faults.
Maintenance
It is also important that the maintenance team on site is aware of the requirements of the micro-CHP
appliance with regards to service and fault rectification. This may require external support from the microCHP supplier (for example, for an engine service), but in the first instance, there must be an individual or
team of people available to recognise any requests by the system (such as fault codes). Service intervals, if
ignored, can lead to the appliance being out of operation for a significant time, thus limiting operation and
electrical generation. Any service and maintenance requirements must be easily and readily identified, and
the associated down-time minimised. The majority of appliances monitored in this trial were maintained by
on-site personnel with support from Kinviro, who are the sole Irish partner of SenerTec and a provider of
micro-CHP systems. This meant that any problems encountered with the appliances or their integration into
the heating system could be effectively rectified.
44
8. Case Studies
The following four case studies are examples from the SEAI field trial. The sites vary in construction,
utilisation and engine performance.
Charlotte Quay Apartments
The Charlotte Quay Apartments are part of the new docklands development in central Dublin. The building
consists of 78 apartments and a number of offices and retail areas. It was developed with considerable
attention to energy efficiency and environmental impact. The building has been built to high thermal
standards; each apartment is fitted with a highly insulated glazing system and is mechanically ventilated to
minimise heat loss. During the design stage, it was decided that the heating system should incorporate
micro-CHP to supply the background electrical load, such as car park lighting 10. Footnote hidden by graph
The main focus of this study was the system used to provide heating and hot water to all the apartments in
the building. This is a centralised plant consisting of two condensing Senetec Dachs micro-CHP (12.5kW
thermal, 5.5kW electric) and two supplementary Viessman Vitoplex 200 (440kW) gas boilers. The micro-CHPs
were sized to cater for the background electrical load, estimated to be a constant 11kWe, and to ensure that
this was maintained, the appliances were installed alongside a 7,500 litre buffer tank to ensure maximum
operation and consistent electricity production. The installation is shown in Figure 30 below.
Figure 30: Charlotte Quay Schematic (from www.kinviro.ie)
Modulating 7.4kW pumps are used to distribute the heat to the apartments from a main header. In each
apartment, the demand is met by individual Danfoss Heat Stations, ensuring instantaneous hot water and
reducing losses from individual cylinders. This heat station acts as the interface between the district heating
system and each individual apartment7.
Performance and Savings
The engines at Charlotte Quay had the longest operational hours of all appliances in the field trial, and also
exhibited the highest efficiencies. Figure 31 shows the actual operational hours compared with the potential
operational hours in the trial. These engines were monitored for 19 months and thus had 13,848 potential
operating hours. Engine one achieved 90% operation and engine two 83%.
10
New Connections Micro CHP & Central Plant; South Dock, Charlotte Quay, Dublin 4; http://www.kinviro.ie/wp-
content/uploads/2009/07/Charlotte-Quay-DHS.pdf, accessed 19/05/2010
45
Figure 31: Operational hours of engines at Charlotte Quay
The consistent operation led to consistently high efficiency, with the two engines achieving annual
efficiencies of 86.6% and 87.1% respectively.
The boiler room was substantially altered to optimise the operation of the micro-CHPs at this site. The large
capacity of the buffer vessel ensured that the engines achieved maximum run hours and considerable
electrical generation. Over the trial period, the site generated 131,640 kWh of electricity for on-site
consumption. Overall, the carbon benefit of these engines has been considerable, with a primary energy
saving of 24% for each engine.
Table 8 shows the estimated CO2 savings at Charlotte Quay from using a micro-CHP plant in place of a boiler
operating at 82% efficiency. These estimates are based on hours of use and heat provided to the property.
Total heat provided by the micro-CHPs was used as a baseline to work out the energy requirements from a
boiler in the same situation. The electrical consumption is measured for the micro-CHPs and estimated for
the boiler based on hours of operation of the micro-CHPs. The data covers the period January to December
2009 and includes both micro-CHP engines.
Overall, approximately 29 tonnes of CO2 was saved at this site during the trial period by using micro-CHP,
primarily due to the protracted periods of operation of the micro-CHP appliances. This site provides
evidence that when micro-CHP appliances are correctly utilised within a heating system (such that they
operate almost continuously) the potential CO2 savings are significant. However, if the micro-CHPs were to
fail to generate electricity due to a fault, the energy consumption just to provide heat would be
considerably more than for a condensing boiler. For sites where the engines are running for much shorter
periods or that have frequent start/stop cycles, the savings could be significantly less. Note that the figures
are estimates, and further monitoring of the supplementary boilers would be required to accurately
measure the CO2 savings.
46
Table 8: Estimated carbon savings at Charlotte Quay – JAN-DEC 2009
CHP 1
kWh
CHP 2
CO2 (kg)
kWh
CO2 (kg)
91,882
TOTAL
TOTAL
kWh for
CO2 for
both CHP
both CHP
Boiler
CO2
engines
engines
kWh
(kg)
Heat Supplied
89,970
181,852
181,852
Gas Used kWh
148,157
30,328
149,030
30,506
297,187
60,834
221,771
45,396
Electric Used kWh
3.3
1.9
3.1
1.8
6.4
3.7
335.8
195.1
Total Energy Used
148,161
30,330
149,033
30,508
297,193
60,838
222,107
45,592
38,347
22,279
37,922
22,033
76,269
44,312
0
0
Electric Generated
kWh
Total CO2 emitted
taking in to account
electricity generated
(tonnes)
8
8
17
46
Saving in CO2 with
micro-CHP (tonnes)
29
Elm Green Nursing Home
Elm Green Nursing Home was constructed in 2007; it uses a range of technologies to provide heating, hot
water and electricity. They have a solar thermal system, six heat pumps, condensing boilers, and a micro-CHP
appliance operational on site. The building is a three-storey, 100-bed facility, with 15 staff apartments and 27
independent living units linked to the main building by a glazed corridor 11. The building is of conventional
construction, with attention to energy saving and environmental factors. Most of the heating is underfloor
and a high level of insulation is present throughout. Lighting has also been carefully considered, with low
energy fittings and movement sensors.
As in Charlotte Quay, the study focused on the heating system, and specifically on the operation of the
micro-CHP appliance. The plant room is an independent building feeding 4,700m2 of underfloor heating and
additional radiators, all of which are independently zone controlled. The site thus has a considerable heat
demand. The primary heating technology is the air source heat pumps, which are supported by the microCHP and if necessary by condensing boilers. The micro-CHP is a condensing SenerTec Dachs (12.5kW
thermal and 5.5kW electric), with three supplementary Heatmaster HM85TC units (modulating between 16.5
and 85kW). The electricity generated by the micro-CHP is consumed on site, predominantly in the boiler
house. The domestic hot water is supplied primarily by a 40m2 solar thermal installation, which is then
supported by the micro-CHP and condensing boilers if required.
The entire installation has an elaborate control system which ensures that the appliances operate in the
correct sequence and as required. This ensures correct operating temperatures and reduces excess
consumption. There are plans for further energy-saving measures at the site, including the installation of
heat recovery in the laundry and plant rooms.
11
Nursing Homes Innovates by Combining Sustainable Heating Systems; http://www.kinviro.ie/wp-content/uploads/2009/07/Elm-
Green-Nursing-Home-ver2.pdf (accessed 20/05/2010)
47
Performance and Savings
Figure 32 shows the run hours achieved at Elm Green. The micro-CHP appliance at this site was installed
during construction and was operational before the trial commenced. The engine suffered lime build-up at
the start of the trial period, and as a result the figure shows limited operation during the first months of the
trial. After April 2009, full operation was resumed. The site achieved 79% of the potential operational hours
during the trial period.
Figure 32: Operational hours of micro-CHP at Elm Green
The engine at Elm Green achieved 79% efficiency and a 17% primary energy saving over the trial period. An
estimated 8 tonnes of CO2 were saved over the trial period at Elm Green by using a micro-CHP plant in place
of a boiler operating at 82% efficiency – see Table 9.
Table 9: Estimated carbon savings at Elm Green Jan –Dec 2009
CHP kWh
CHP CO2 (kg)
Boiler kWh
Boiler CO2 (kg)
Heat Supplied
61,292
61,292
Gas Used kWh
110,106
22,539
74,746
15,301
Electric Used kWh
43.1
25.0
324.3
188.4
Total Energy Used
110,149
22,564
75,071
15,489
Electric Generated kWh
26,000
15,106
0
0
Total CO2 taking in to account the
electricity generated
7,458
15,489
7.5
15.5
Total CO2 emitted taking in to account
electricity generated (tonnes)
Saving in CO2 with a mCHP (tonnes)
8.0
As with the majority of micro-CHP appliances the gas consumption compared to a boiler in the same
situation is actually higher. The energy and thus carbon saving comes directly from the electricity generated,
thus if the engine is to fail to generate due to faults or maintenance issues then the micro-CHP will actually
consume more energy, thus emit more CO2 than a condensing boiler.
48
Dublin Central Mission
Dublin Central Mission operates several care and residential premises, including Mount Tabor care centre
and nursing home. Mount Tabor was opened in 1998 and offers general and specialised nursing care to the
elderly. The building is purpose-built, with individual and communal areas, including a library and a chapel.
Due to the activities on site, there is a continuous thermal demand and micro-CHP appliance was installed in
the heating system to satisfy the heat load. The micro-CHP at Mount Tabor is a much larger appliance than
those at the other sites in the field trial, with a maximum thermal rating of 53kW and electrical output of
25kWe. The micro-CHP is installed alongside two Beeston Bisley boilers (260kWt each) and directly feeds the
boiler return.
Performance and Savings
The micro-CHP appliance at Mount Tabor care home is operational for approximately 12 hours a day and has
an average efficiency of 86%. Figure 33 shows operational hours as a percentage of the potential operation.
Figure 33: Operational hours of micro-CHP at Mount Tabor
This site was monitored for only ten months during the trial; however, the following figures are indicative of
annual performance. The site achieved primary energy savings of 23%, meaning 23% less high-carbon fuel is
required at the central power plant to satisfy its needs. An estimated 20 tonnes of CO2 were saved over the
trial period at Mount Tabor by using a micro-CHP plant in place of a boiler operating at 82% efficiency (see
Table 10). This is considerable and is due to the high electrical output of the micro-CHP appliance. However,
due to the size of the engine, the gas and electrical requirements are much greater for the micro-CHP than
the estimated requirement of a boiler. The CHP uses 57,076kWh (73%) more gas and 504kWh (27%) more
electricity than a boiler. The site saves CO2 by offsetting the electricity required from the electricity network,
so if the engine were to fail to generate, the additional energy required would be considerable.
As with all micro-CHP appliances, the engine at this site needs to run for prolonged periods to be effective in
saving CO2.
49
Table 10: Estimated carbon savings at Mount Tabor Nursing Home Jan – Dec 2009
CHP kWh
CHP CO2 (kg)
Boiler kWh
Boiler CO2 (kg)
Heat Supplied
128,500
128,500
Gas Used kWh
213,783
43,761
156,707
32,078
Electric Used kWh
688.5
400.0
184.7
107.3
Total Energy Used
214,471
44,161
156,892
32,185
Electric Generated kWh
55,595
32,301
0
0
Total CO2 taking in to account the
electricity generated
11,861
32,185
11.9
32.2
Total CO2 emitted taking in to
account electricity generated (tonnes)
Saving in CO2 with a mCHP (tonnes)
20.3
Pery Square Hotel
The No. 1 Pery Square Hotel is a luxury Georgian townhouse hotel and spa with 20 bedrooms and an
extensive restaurant. The building has been fully restored and it was decided at the design stage to
incorporate micro-CHP to satisfy the thermal demands of the spa and hotel building. Due to the very large
thermal demand of the spa, three condensing 12.5kW (thermal) micro-CHP units were installed, supported
by two ProCon 75 (16 – 75kW output) condensing gas boilers. Both the hotel and spa benefit from the
electricity generated by the micro-CHPs (each rated 5.5kWe).
There are four heating circuits, including underfloor and radiator circuits, fed from the micro-CHPs and boiler
system. The micro-CHPs feed a 750l buffer tank which then delivers water to the heating system; these are
controlled by the onboard control system of the Dachs units – see Figure 34 12:
Figure 34: Pery Square heating system schematic9
1.
2.
3.
4.
12
Water from the return header conveyed to the bottom of the 750l buffer tank.
Water from bottom of the buffer tank conveyed to the micro-CHP installation through the condensing
units via a common return header.
Water from the CHPs (now at 83˚C) pumped from CHPs to the top of the buffer tank.
From the top of the buffer tank, a thermostatic pump delivers water back to the flow header of the
boilers.
SEAI Micro-CHP Field Trial Application Form Ver 2.0, December 2007.
50
Performance and Savings
Pery Square Hotel was one of the largest sites in the field trial, with a total thermal output of 37.5kW and a
total electrical output of 16.5kWe. When first installed, the integration of the micro-CHP appliances was
problematic, with the supplementary boilers operating as the lead appliances and the micro-CHPs largely
redundant. Substantial effort was made by personnel on site and the installers of the micro-CHP units to
adjust the control settings in order to optimise performance. Following this, the engines’ operation
improved – the frequency of stop/start cycles was reduced and the run hours increased. This can be seen
clearly in Figure 35.
Figure 35: Number of engine starts and run hours per month at Pery Square
Pery Square was monitored for only ten months during the trial. The data collected has been used to
estimate an annual performance. The site achieved a primary energy saving of 16% and the engines were
operating at 79% efficiency. Although three engines were operational, the whole installation was monitored
as a single appliance – for example, the total fuel input, and the total heat and electrical output of all three
engines was measured. As a result, it is not possible to assess whether the timing of the appliances was
optimised and it is possible that all three engines may have been competing to fulfil any heat requirement.
The site is still adjusting the heating system and it is recommended that each appliance operates in
sequence – engine one operates until it cannot fulfil the demand, then engine two starts and so on. This
would further reduce the on/off cycles and ensure longer periods of operation, thus maximising electrical
generation and carbon savings.
An estimated 12 tonnes of CO2 were saved over the trial period at Pery Square by using a micro-CHP plant in
place of a boiler operating at 82% efficiency – see Table 11. As with the other sites in the trial, the saving is
due to the electrical output of the micro-CHP engines, as the gas consumption to provide the required heat
is greater for the micro-CHPs than for a condensing boiler (68% more gas is required for the operation of the
micro-CHPs).
51
Table 11: Estimated carbon savings at Pery Square Hotel
CHP kWh
CHP CO2 (kg)
Boiler kWh
Boiler CO2 (kg)
Heat Supplied
88,374
88,374
Gas Used kWh
159,361
32,621
107,774
22,061
Electric Used kWh
56.8
33.0
560.5
325.7
Total Energy Used
159,418
32,654
108,334
22,387
Electric Generated kWh
37,476
21,774
0
0
Total CO2 taking in to account the
electricity generated
10,881
22,387
10.9
22.4
Total CO2 emitted taking in to account
electricity generated (tonnes)
Saving in CO2 with a mCHP (tonnes)
11.5
52
Annex 1: Data Processing Procedure
Raw Data
Pressure Data
(Met Office)
CO2 from Gas use
Flue Temperature
Fire Time Flue
Loss
CV (Bord Gais)
Site Info (Altitude, Unit
Location, Gas Temperature,
Flue Temperature)
Flow/Return
Temperatures
Cooling Flue Loss
Estimated Case
Temperatures
Estimated Case
Loss (Radiative/
Convective)
Heat Input
Heat Output
(Heatmeter)
Power (input)
Heat Balance (24
hr basis)
Power (Output)
Balance
between 93
and 103%
No
Bad Day
53
Yes
Good Day
Annex 2: Monthly Valid Data and Operational Days
Monthly breakdown of operational days and valid data on operational days.
Figure 36: Operational days (days in month with an engine utilisation of over 2.5%)
Figure 37: Valid data over operational days (% of days that are operational (greater than 2.5% utilisation) and
have valid closure (93–103%))
When operational, the majority of engines produce between 80 and 100% valid data in a month. This means
that the monitoring equipment is operating within the expected parameters and good quality robust data is
being collected.
54
Annex 3: Quality Tracking Document
Property
Site 01
Mar-10
Feb-10
Jan-10
Dec-09
Nov-09
Oct-09
Sep-09
Aug-09
Jul-09
Jun-09
May-09
Operating
Validity
100.00%
100.00%
100.00%
100.00%
100.00%
100.00%
100.00%
68.75%
0.00%
84.00%
83.87%
Operating
days
100.00%
85.71%
45.16%
100.00%
100.00%
100.00%
90.00%
51.61%
0.00%
83.33%
100.00%
Engine
resumes
operation
04/09/09.
Engine
serviced. Crack
found in heat
meter – engine
switched off
until replaced.
No engine
operation
Comments
Site 02
Engine not
operational
after 15/01/10
Operating
Validity
96.77%
89.29%
100.00%
100.00%
80.00%
96.77%
100.00%
70.97%
83.87%
85.19%
90.32%
Operating
days
100.00%
100.00%
100.00%
100.00%
33.33%
100.00%
100.00%
100.00%
100.00%
90.00%
100.00%
Comments
Site 03
Site 04
Engines not
operational for
2 weeks.
Operating
Validity
42.86%
3.70%
3.57%
92.31%
100.00%
100.00%
90.00%
100.00%
100.00%
100.00%
73.33%
Operating
days
90.32%
96.43%
90.32%
83.87%
93.33%
100.00%
100.00%
100.00%
100.00%
86.67%
96.77%
Comments
Flue sensor
replaced
18/03/10
Flue sensor
faulty
Flue sensor
faulty
Operating
Validity
90.32%
100.00%
100.00%
100.00%
100.00%
93.55%
93.33%
79.31%
100.00%
93.33%
100.00%
Operating
days
100.00%
60.71%
6.45%
100.00%
100.00%
100.00%
100.00%
93.55%
96.77%
100.00%
64.52%
Comments
Heat meter
data from
07/05/09.
Only 2 days of
operation in
Jan.
Engine
serviced
55
Site 05
Site 06
Operating
Validity
0.00%
100.00%
100.00%
91.30%
30.77%
90.91%
100.00%
84.21%
93.33%
100.00%
100.00%
Operating
days
0.00%
3.57%
45.16%
74.19%
43.33%
70.97%
63.33%
61.29%
48.39%
50.00%
29.03%
Comments
No operation
Very limited
operation
Sporadic
operation.
Various issues
on site
Operating
Validity
90.32%
96.43%
100.00%
100.00%
100.00%
83.87%
55.56%
0.00%
93.33%
33.33%
100.00%
Operating
days
100.00%
100.00%
100.00%
87.10%
100.00%
100.00%
90.00%
0.00%
48.39%
10.00%
19.35%
Engine
resumes
operation
04/09/09.
No engine
operation –
switched off
Problem with
gas slam valve
on site causing
engine to fail.
No operation
after 15/07/09
Problem with
gas slam valve
on site causing
engine to fail.
Engine
operational
from 28/06/09.
Problem with
gas slam valve
on site causing
engine to fail.
Connection
issues and
incorrect
external
temperature
readings.
Data collection
failure due to
vandalism.
Engine not
operational for
period due to
gas supply
issues.
Comments
Site 07
Site 08
Operating
Validity
0.00%
100.00%
100.00%
100.00%
100.00%
100.00%
100.00%
92.86%
100.00%
100.00%
100.00%
Operating
days
0.00%
57.14%
6.45%
93.55%
100.00%
100.00%
100.00%
90.32%
67.74%
100.00%
100.00%
Comments
No operation
Operating
Validity
61.29%
75.00%
87.10%
93.10%
100.00%
100.00%
100.00%
100.00%
100.00%
90.00%
100.00%
Operating
days
100.00%
100.00%
100.00%
93.55%
80.00%
67.74%
96.67%
93.55%
100.00%
100.00%
67.74%
Comments
Heat meter
faulty 1–
12/03/10
Only 2 days of
operation in
Jan.
56
Property
Site 09
Site 10
Mar-10
Feb-10
Jan-10
Dec-09
Nov-09
Oct-09
Sep-09
Aug-09
Jul-09
Jun-09
May-09
Operating
Validity
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
13.64%
0.00%
0.00%
Operating
days
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
70.97%
93.33%
87.10%
Comments
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
No engine
operation –
switched off
Closure
improves after
site visit by
GaC when
heat meter
pockets
inserted
further.
Heat out too
high. Further
detailed
investigation
required.
Heat out too
high. Further
detailed
investigation
required.
Operating
Validity
93.55%
67.86%
41.94%
80.00%
81.48%
100.00%
96.67%
96.77%
100.00%
100.00%
100.00%
Operating
days
100.00%
100.00%
100.00%
96.77%
90.00%
96.77%
100.00%
100.00%
96.77%
86.67%
100.00%
Operating
Validity
31.25%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
12.50%
4.17%
0.00%
Operating
days
51.61%
7.14%
0.00%
25.81%
0.00%
0.00%
0.00%
0.00%
25.81%
80.00%
0.00%
Comments
Engine
utilisation
increased
although
closure low
from 16/03/10
Very limited
engine
operation
Very limited
engine
operation
Very limited
engine
operation
No engine
operation
No engine
operation
No engine
operation
No engine
operation
Heat output
low, closures
are marginal
on some days.
Very little
engine use.
Heat output
low, closures
are marginal
on some days.
Operating
Validity
100.00%
100.00%
100.00%
100.00%
100.00%
40.00%
0.00%
0.00%
0.00%
0.00%
Operating
days
100.00%
100.00%
100.00%
100.00%
100.00%
80.65%
100.00%
64.52%
0.00%
0.00%
Gas meter
replaced
16/10/09.
Good data
follows.
High closure.
Gas meter to
be replaced.
Engine
operational
from 12/08/09.
High closure.
Very high heat
output
Engine not
operational
Engine not
operational
Comments
Site 11
Site 12
Comments
57
Property
Site 13
Mar-10
Feb-10
Jan-10
Dec-09
Nov-09
Oct-09
Sep-09
Aug-09
Jul-09
Jun-09
Operating
Validity
93.55%
100.00%
100.00%
89.29%
36.67%
0.00%
0.00%
0.00%
0.00%
0.00%
Operating
days
100.00%
96.43%
96.77%
90.32%
100.00%
100.00%
93.33%
96.77%
90.32%
56.67%
Temp sensor
and heat
integrator
changed. Valid
data from
20/11/09.
Heat output
low.
Heat output
low.
Heat output
low.
Heat output
low.
Heat output
low.
Comments
Property
Site 01
Apr-09
Mar-09
Feb-09
Jan-09
Dec-08
Nov-08
Oct-08
Sep-08
Operating
Validity
86.67%
22.58%
21.43%
0.00%
100.00%
0.00%
22.58%
83.33%
Operating
days
100.00%
100.00%
100.00%
6.45%
70.97%
86.67%
100.00%
100.00%
All data
present,
closures are
marginal,
data ok.
All data
present,
closures are
marginal, data
ok.
Engine does
not seem to be
operating until
30/01/09.
Engine
doesn’t
seem to be
operating
after
29/12/08.
Heat meter
replaced
27/11/08.
Engine not
operational
Heat meter
data
missing
Comments
Site 02
Operating
Validity
100.00%
100.00%
100.00%
23.08%
100.00%
86.67%
100.00%
86.67%
Operating
days
100.00%
96.77%
100.00%
83.87%
51.61%
100.00%
77.42%
100.00%
CHP1 flue
temperature
missing until
26/01/08.
No engine
operation
after
21/12/08
Comments
58
May-09
Property
Site 03
Site 04
Apr-09
Mar-09
Feb-09
Jan-09
Operating
Validity
0.00%
0.00%
0.00%
0.00%
Operating
days
93.33%
22.58%
100.00%
48.39%
Comments
No heat meter
data.
No heat
meter data.
No heat meter
data.
No heat meter
data.
Operating
Validity
96.67%
93.33%
100.00%
0.00%
Operating
days
100.00%
96.77%
100.00%
45.16%
Comments
Site 05
No electricity
data.
Operating
Validity
100.00%
0.00%
0.00%
Operating
days
73.33%
6.45%
10.71%
Engine not
running.
Only
preliminary
data. Engine
not running.
Comments
Site 06
Dec-08
Operating
Validity
100.00%
100.00%
100.00%
Operating
days
93.33%
96.77%
14.29%
Comments
59
Nov-08
Oct-08
Sep-08
Property
Site 07
Apr-09
Mar-09
Operating
Validity
100.00%
15.79%
Operating
days
100.00%
61.29%
Comments
Site 08
Site 10
Jan-09
Dec-08
Heat
missing
until 26/03,
electric
missing
until
29/03/09
Operating
Validity
100.00%
0.00%
Operating
days
90.00%
3.23%
Comments
Site 09
Feb-09
No engine
operation
until
31/03/09.
Operating
Validity
0.00%
0.00%
Operating
days
90.00%
9.68%
Comments
Heat out too
high. Further
detailed
investigation
required.
No heat
meter data
Operating
Validity
100.00%
Operating
days
23.33%
Comments
60
Nov-08
Oct-08
Sep-08
Annex 4: Example of the rolling action list – Site by Site Basis
The following is an example of the rolling action lists used each month to record any changes, issues or problems encountered at each site. The action would be raised and then
corrective actions carried out on site and reported in the action list. The list was then returned to GaC to complete for the next set of data received. This enabled a history of all sites to be
maintained.
(PTH = Powertherm, GaC = GASTEC at CRE, SEAI = Sustainable Energy Authority Ireland)
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
PTH
Confirm why the engine was not
running for July. Provide GaC with a site
update.
Service interval for this engine was reached during July;
this was carried out at the beginning of August.
However, flow meter on site has been found to be
leaking due to a crack in the casing. This is to be
replaced along with the heat meter probe pockets.
Until this replacement has been carried out the CHP is
turned off. Flow meter re-instated 04/09/09. Next set of
data should show this.
Monitor next set of data. Data resumes
04/09/09. Quality good.
PTH
Confirm why engine has stopped
operating. Service interval?
Low oil level , this has been topped up
None
PTH
Ensure engines are serviced.
Both units shut down due to service interval. This was
carried out and both units were re-instated Monday 8th
June. Data after this date was of good quality.
None
PTH
Check gas data for 24th Feb. Update GaC
as to changes on site.
Site visited 18/03/10 and flue probe replaced.
None
PTH
Re-instate heat meter in to heating
circuit as soon as possible
PTH state heat meter was re-instated 07/05/09 at
~6pm. GaC to check next set of data received.
Heat meter data received from 07/05/09.
Data that follows is good. No further action
required.
GaC
GaC to retrospectively process data
Retrospective analysis complete
None
01NPLH
Site 01
No outstanding issues however engine was not
operational throughout July and only resumed
operation on 04/08/09. Was there a fault or had the
engine reached a service interval?
Site 02
Ongoing:
04CHAR
No operation from engine 2 since 26/02/10
Site 02
Missing data at Charlotte Quay for 4th, 5th and 6th
June. Unit 2 shut down on Friday 5th (requiring a
service).
05ELMG
Site 03
Gas data missing on 24th Feb, all other data channels
present.
Closure remains low on this site. Flue sensor to be
replaced again.
Site 03
ONGOING:
No heat meter data – URGENT
Site 03
Scaling for gas has been corrected on site. GaC to
retrospectively analyse data with incorrect scaling
factor.
61
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
Site 04
No engine operation until 12/02/10.
PTH
Confirm why engine was not
operational. Service interval?
Several channels missing data in March. No information
as to why engine was not operational.
Ongoing
Site 04
Ongoing:
PTH
Check downloaded data and correct
channels. Re-send corrected data.
PTH has checked data and cannot retrieve missing files.
None
06STBR
Engine electrical consumption and heat output are
the same data on 03 & 04/10/09 then again on the 10
& 11/10/09.
Gas data has also been saved as flow temperature
data on 10 & 11/10/09.
Site 04
Engine has stopped running due to service interval.
Site to be visited 07/05/09 to re-set engine.
PTH
Confirm service has taken place and
engine is now operational.
CHP has been serviced and re-started (12/05/09). Good
data follows.
None
Site 04
Electricity meter scaling incorrect
PTH
Check and rectify
Data from 5th April seems ok. Data to be monitored.
Monitor
Site 04
No electricity data provided (used or generated).
PTH
Check electricity data is being
collected/recorded properly.
The scaling of the electricity output is incorrect and
was rectified on site. Additional channels were added
to monitor the total electricity meter readings in kWh.
This is to be used as a cross check to ensure the sums to
calculate the 5 minute values are correct.
Monitor data
Scaling on gas meter had been corrected before site
visit and data check on site showed sensible values.
Check gas meter scaling
Scaling on the gas meter seems incorrect, very low
figures compared to heat produced. This is causing
poor closure, which if re-scaled would probably
improve
Monitor data
08BARN
Site 05
Ongoing:
PTH
Rectify temperature issue.
Ambient temperature sensor is reading very high
values in the range 40–60C. It seems to have started
in the middle of September with temperatures
around 20C but has noticeably increased in October
and continued in November. PTH state sensor must
have failed or been tampered with.
62
PTH state there has been problems connecting to site
since 13th Nov causing loss of data. The site is to be
visited to resolve all outstanding issues. Problems are
currently ongoing.
Data from 9th December is valid and
connection problems seem to have been
resolved. External temperature sensor
rectified 02/12/09. Data to be monitored.
(Note (01/2010) – temp sensor is currently
being corrected, a new sensor to be fitted
when weather and access conditions
improve).
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
Site 05
Data collection and download errors have been
rectified; however data now suggests engine is not
operational, possibly due to a service interval. Site to
be investigated.
PTH
Investigate engine status, check if
service is required. Rectify issues asap.
Data resumes 19/05/09. PTH to update GaC as to what
the problem was.
Monitor
Gas scaling out by a factor of 10 until 7th April, then
seems to be ok.
PTH &
GaC
PTH to check scaling and data to be
monitored.
Data has correct scaling from 8th April. GaC to
retrospectively process the data. Retrospective analysis
complete
GaC to retrospectively process data with
correct scaling factor. – complete
Site 05
PTH informed GaC that unit was not running due to a
gas supply problem. The problem was resolved
however the CHP was not re-set. The CHP supplier
contacted the client and provided instruction on how
to re-set the engine (18/05/09) Data resumed after this
date.
09DROG
Site 06
Gas connection problems still on site. No move has
been made to re-instate. Engine is completely
switched off. Data resumes 04/09/09.
PTH
Update GaC as to site status and
problems.
Engine resumes operation 04/09/09. Good data
follows.
Monitor
Site 06
ONGOING:
PTH
Chase site to ensure problem has been
rectified. Update GaC as to site status.
Engine became operational 28/06/09. Data for July
continues and is of good quality. Note from PTH that
CHP stops again on 20th July, however GaC are yet to
receive this data.
Monitor
Provide an update as to engine and site
status.
Ignition fault error – this may relate to gas pressure, not
necessarily a CHP component fault.
Fault with on site gas slam valve causing the CHP to
cut out. Site is trying to resolve.
10NPUH
Site 07
Ongoing:
No engine operation since 20/02/10.
The unit was restarted but appears to have stopped
again.
Site 07
No engine operation from 22/07/09 until the
04/08/09. Why did the engines at Newton Park stop
working?
PTH
Confirm why the engine stopped
running and update GaC as to site
status.
PTH
Update GaC on problem with heat
meter.
11BLOO
Site 08
No heat meter data until 12th March.
Note from SEAI: ‘The DHW temperature was too low
with a risk of legionella so they increased the boiler
set point to increase the water temperature which
was tripping out the CHP so they switched off the
CHP’, (08/04/10).
63
Service interval for this engine was reached during July;
this was carried out at the beginning of August. Data
for August is complete and valid.
None
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
Site 08
CHP is not operational after 21/10/09. Some data
collected on 31/10/09 but not operating as it should
be.
PTH
Check status of engine at site.
CHP required maintenance and was restarted 10/11/09
Monitor
Site 08
PTH have been unable to collect data from site for
last 2 days (12 +13th May 2009), and now suspect that
something may have happened to panel on site–
PTH to investigate this.
PTH
Check data collection and
communication equipment. Rectify
issue
Data collection issues rectified and missing data
retrieved. Data processed 15/05/09 and quality is good.
Data continues to be good. No further
action required.
Site 08
Resident of the care home has been setting off fire
alarms and causing the system to cut out
(interrupting slam valve). Staff are taking measures to
stop this and are re-setting the boilers but not the
CHP. Caretaker is on site (07/05/09) to re-start engine
and ensure problem does not continue.
PTH &
GaC
Confirm engine is operational and
monitor data to ensure CHP remains
switched on.
PTH have been unable to collect data from site for last
2 days (12 +13th May 2009), and now suspect that
something may have happened to panel on site– PTH
to investigate this.
Re-assign
Site 09
Ongoing:
ALL
Monitor engine status
FP provided an update to situation: There have been
complications regarding funding meaning the client
will no longer operate the micro-CHP. Data will still be
collected and GaC are to process as normal however
the engine will remain off for the foreseeable future.
None
Ongoing
Ongoing
12HAVE
Engine non-operational and unlikely to start again.
Site to be monitored.
Very limited data in January and February due to
connection problems and difficulty contacting site.
Site 09
Ongoing:
PTH to rectify communication
problems.
SEAI
No engine operation during September – personnel
on site have decided they no longer want to use the
CHP. Uncertainty as to what will happen at this site.
SEAI to provide an update as to issues and future
here. PN– Client at site is not keen to carry out any
works.
Site 09
ONGOING:
SEAI to provide a site and status update.
PTH
Check and rectify. Is the correct Modbus
channel being read here?
PTH
Provide GaC with as much information
as possible regarding heat and water
flows. We need to understand where
the additional heat is coming from in
order to account for it.
Check ‘CHP total export’ is reading the correct value
as it doesn’t match the sum of instantaneous export
direct from CHP.
Site 09
ONGOING:
High closure. Heat is being recorded while CHP is not
operational, similar to problem at NPLH. However
when discounting this heat, closures are still too
high. Too much heat is being recorded compared to
gas going in. Is there a flow around the CHP when
the system is off? Do you have any further
information on the operation of the mixing unit as
this may be causing the problem?
64
Ongoing
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
Site 09
Site uses LPG. CV required.
SEAI
Provide LPG CV data.
Ongoing
SEAI to provide LPG CVs ASAP.
PTH
PTH state site to be visited.
Site visited 18/03/10 flue probe cleaned as some
carbon build up. Heat meter giving sensible readings
while on site and all other kit operating as expected.
Data to be monitored. Note from PTH that site had
been suffering voltage issues during very cold weather.
This was causing the CHP to switch off, but was restarted without problems.
Data in March is valid
PTH &
SEAI
Chase site for status update. Encourage
personnel to utilise engine more
effectively.
Valid data collected until 16/03/10. Following this
closure becomes low.
Ongoing
PTH
Discuss engine operation with site
personnel; including when the microCHP is expected to be turned on.
Four days of operation so far in December. Closure is
marginally low but cannot be sure of cause due to lack
of data. Site to be monitored.
Ongoing
Ongoing
Ongoing
13MIDD
Site 10
Some days with low closure. Heat out seems low
compared to gas in.
14GSTA
Site 11
Ongoing:
Engine is running for very limited periods despite
cold conditions. Site to be chased regarding
operation.
Site 11
Ongoing:
No engine operation on site as engine is only used
for the heating system.
Note from PTH: Boiler temperature probes were
moved from header to boiler flow and return. CHP
still off.
Due to time of year micro–CHP should now be
operational.
Site 11
Ongoing:
Awaiting unit re-start.
No engine operation on site as engine is only used
for the heating system.
Site 11
CHP does not seem to be operational from 07/07/09.
Are there issues with the engine?
PTH
Check and confirm engine status.
Limited engine operation due to summer period. CHP
is only used for central heating.
None
Site 11
Heat meter is under-reading, comment from PTH ‘We
have investigated this and suspect the bypass is
leaking we tried to open and close all by passes
today and it improved things slightly. I think the
hand valves will need to be changed. When we
arrived on site we noted that the CHP was off due to
a gas slam valve fault.’
PTH
PTH to ensure site issues are rectified.
Data received after the bypass was
altered shows an improvement.
Have contact client and provided photos etc to advise
of the issue. Client to change faulty gate valve with ¼
turn ball valve.
Ongoing
65
Site Ref
Data quality issues and site problems
Action
for
Action Required
Outcome
Ongoing action required/Reassign
15DUCM
Site 12
PTH panel powered down causing one day of data to
be lost (26/10/09). The CHP was not operational
between 17 – 21/10/09.
PTH &
GaC
Monitor data collection
Data for November is complete and valid.
None
Site 12
Ongoing:
GaC
Gas meter changed 12/10/09 and phase
sequence resolved of CHP electricity
meter.
Data from 16/10/09 is complete and valid. The engine
was not operational 17 – 21/10/09 but resumes
operation on 22/10/09 and good data follows. Site to
be monitored.
Monitor
PTH
Check data logging equipment and
scaling factors.
PN – Electricity meter Phase 1 appear s to be underreading Field Trial meter reads 20.2kW. Internal meter
in Tedum unit reports 25kW. Suspect the phases may
not be in sequence on field trial meter.
Low Carbon Solutions to resolve wiring.
Engine providing ~50% its potential heat; however
the gas seems lower than expected for this value.
Investigation by PTH suggests CHP gas meter is
indicating ~300litres gas in 5 mins. Site gas meter
indicates CHP gas meter may be under-reading by
~50%.
Site 12
Ongoing:
Further investigation on more operational data
suggest the gas meter is under reading compared to
heat generated..
CHP gas meter is indicating ~300litres gas in 5 mins.
Site gas meter indicates CHP gas meter may be underreading by ~50%
Site 12
CHP is not running. Awaiting ESB connection
approval. GaC to carry out a commissioning visit.
PowerTherm to arrange for gas meter to be
replaced
PTH &
GaC
Keep GaC updated as to site status. GaC
to carry out site visit.
Engine not operational during July. Connection
approved in Aug. Data to be monitored.
Monitor data
PTH
Check CHP heat meter and temperature
sensors. The heat measurement from
the CHP is definitely wrong.
PTH visited site to carry out corrective works Week
commencing 16/11/09. Temperature sensor was
replaced and heat integrator reprogrammed. Data
from the 20/11/09 is valid and providing good closure.
The engines seem to be operating more continually
with fewer starts from the 24/11/09. Changes have
greatly improved the data.
Monitor
16PERS
Site 13
Ongoing:
CHP heat meter is reading lower than buffer heat
meter.
The CHP heat meter is reading lower than the buffer
heat meter which is not thermodynamically possible.
PTH to investigate:
PTH state they have a flow meter for replacement if
required.
Flow meter, heat integrator setting, turbulence,
bypass valve passing. PTH plan send engineer to site
to (a) check and pulse hand valves (b) new heat
integrator to compare instantaneous values. This
should help identify if it is the flow meter or heat
integrator.
66
Site Ref
Data quality issues and site problems
Action
for
Site 13
Ongoing:
PTH
CHP heat meter probe was replaced early
September. Data still shows low heat output. Buffer
heat is also reading higher than CHP heat. Data also
suggests some filtering or averaging taking place.
Action Required
Check data logging equipment and
data collection. Ensure data is not being
averaged. Check scaling factors.
Outcome
Ongoing action required/Reassign
PTH state no averaging or filtering is taking place
within the data. Heat output is still lower than
expected. Possibly just a result of the very frequent
on/off cycles from all engines. Site needs to be
optimised so the CHPs work for longer periods.
Ongoing
Email sent 15/09/09 provides more detail.
Site 13
Low closure and low heat output. PTH to carry out
minor adjustment of heat integrator setting. GaC to
carry out a commissioning visit.
PTH &
GaC
Carry out site visit.
GaC visited site. Engines found to be cycling frequently
and boiler acting as lead appliance. CHP heat meter
probe not correctly inserted into pipe. Sensor pocket
blocked and probe bent. Pocket to be changed. Data
after site visit and pocket investigation shows slight
improvement. Data to be monitored.
Monitor data
GaC
Arrange commissioning visits to all new
trial sites.
All sites were visited between 30th March and 2nd April
2009. The outstanding actions were discussed and a
new set of actions produced.
Monitor all sites
All sites
All
Site visits to all sites to be scheduled.
67
Annex 5: Site-by-Site Data Analysis
This Annex shows the data collected from each site on a site-by-site basis. The aspects presented have all
been discussed in the main report however this allows the reader to view the data for each site individually.
For each site the operational days and valid data recorded on these operational days are displayed. This is
where the engine has been operational for longer than 2.5% of its potential and the energy closure across
the appliance (gas and electricity in and heat and electricity out) is within 93-103%. Run hours, engine
performance and engine efficiency are discussed, as well as the estimated carbon savings when compared
to a condensing boiler operating at 82% efficiency in the same situation.
Sites 01 and 07
Data Validity and Operational Days
The engines at site 01 and 07 are installed in two separate boiler houses at the same nursing home and are
thus analysed together in the following section.
Figure 38: Operational days and % of data valid on operational days, Site 01 and 07
The service interval for both engines was reached in July 2009 thus both engines show a reduced level of
operation at this time. The engine at site 07 also suffered an ignition fault in January 2010 which was not
resolved by the completion of the trial, this limited the engine operation at this time.
Run Hours
The run hours at sites 01 and 07 are shown in Figure 39 and demonstrate the service intervals and engine
issues as discussed above. It can be seen that both engines operate between 16 and 24 hours per day for the
majority of the trial period.
68
Figure 39: Total Monthly Run Hours Site 01 and 07
Performance
Engine efficiency is shown below separated for site 01 and 07.
Figure 40: Site 01 Efficiency Figures
69
Figure 41: Site 07 Efficiency Figures
Site 02
Data Validity and Operational Days
Figure 42: Operational days and % of data valid on operational days, Site 02
Both engines at site 02 required a service during June 2009 and again in November 2009 to this end the
operational data is reduced during these periods.
70
Run Hours
Figure 43: Total Monthly Run Hours Site 02
The boiler house at Site 02 houses two equally sized Baxi Dachs units, both of which run almost
continuously. These are connected to a pair of very large buffer tanks. As with operational days shown
above, there is a slight drop in run hours during June and November 2009 due to boiler service intervals,
however once serviced they return to continuous operation. The installation at this site was optimised
following the onset of this trial with the boiler and system set-up being altered to successfully accommodate
the micro-CHPs. This has ensured the optimum performance of the engines thus greater benefit to the site.
Performance
The following figures show the performance of the engines at Charlotte Quay with regards to efficiency.
Figure 44: Efficiency Site 02 CHP1
71
Figure 45: Efficiency Site 02 CHP2
Site 03
Data Validity and Operational Days
Figure 13: Operational days and % of data valid on operational days, Site 03
The heat meter was not operational between January and April 2009 because of a plumbing issue on site.
72
Run Hours
Site 03 operates one micro-CHP within a complex heating system including various renewables technologies
such as solar thermal and heat pumps. The micro-CHP runs successfully for prolonged periods as can be
seen in the figure below.
Figure 14: Total Monthly Run Hours Site 03
Performance
The following figure shows the performance of the engine at site 03 with regards to efficiency.
Figure 15: Engine efficiency, Site 03
Since replacement of the heat meter in April 2009 the efficiency of the engine at Site 03 has averaged 80%,
this has remained very consistent with values ranging from 79% to 80%.
73
Site 04
Data Validity and Operational Days
Figure 16: Operational days and % of data valid on operational days, site 04
Run Hours
Figure 17: Total Monthly Run Hours site 04
74
Performance
Figure 18: Engine efficiency, site 04
Engine efficiency at site 04 has averaged 84% ranging from 83 to 86%. The engine operates between 14 and
16 hours a day in most months.
75
Site 05
Data Validity and Operational Days
Figure 19: Operational days and % of data valid on operational days, site 05
Run Hours
Figure 20: Total Monthly Run Hours site 05
76
Performance
Figure 21: Engine efficiency, site 05
Average engine efficiency at site 05 is 79% remaining very consistent between 79 and 80% efficient. The
engine at this site has the shortest operational hours of all the field trial sites and also has one of the lowest
average efficiencies.
77
Site 06
Data Validity and Operational Days
Figure 22: Operational days and % of data valid on operational days, site 06
Run Hours
Figure 23: Total Monthly Run Hours site 06
78
Performance
Figure 24: Engine efficiency, site 06
Average engine efficiency at site 06 is 79% ranging between 78 and 82% efficient. There were on-going
operational issues at this site regarding a faulty gas slam valve thus the engine had limited and fluctuating
operational hours. The interrupted operation means the engine at this site also had one of the lower
efficiency values, similar to those seen at site 05.
79
Site 08
Data Validity and Operational Days
Figure 25: Operational days and % of data valid on operational days, site 08
Run Hours
Figure 26: Total Monthly Run Hours site 08
80
Performance
Figure 27: Engine efficiency, site 08
Average engine efficiency at site 08 is 81% and remains very constant around this value. Since
commissioning this site has been very successful with long running hours and consistently valid data.
81
Site 09
Data Validity and Operational Days
Figure 28: Operational days and % of data valid on operational days, site 09
Run Hours
Figure 29: Total Monthly Run Hours site 09
82
Site 09 had ongoing issues with poor data closure and CHP integration within the heating system. Following
a second visit by GaC it was identified that the heat meter pockets were not inserted correctly within the
water flow and were thus reading incorrect values. GaC inserted the probes further and advised PTH to
replace the current pockets with longer versions to ensure good contact with the water. Data following
GaC’s visit did show a marked improvement in the closure with data becoming valid for the last few days in
July. However, following this there was no engine operation as on site personnel decided they no longer
wanted to use the CHP. The electricity data at Haven Bay was also suspect and the initial site visit suggested
the wiring was incorrect, this was confirmed on the second site visit and an electrical contractor was
required to rectify the problem, this was never resolved.
Performance
Due to the issues on site, no valid data was collected from the micro-CHP appliance. However, using all the
data collected, average efficiency is 70% ranging from 24 to 104%. These figures should not be used in any
form of product evaluation and are only included as a summary of the available data.
83
Site 10
Data Validity and Operational Days
Figure 30: Operational days and % of data valid on operational days, site 10
Run Hours
Figure 31: Total Monthly Run Hours site 10
84
Performance
Figure 32: Engine efficiency, site 10
Average engine efficiency at 13MIDD was 82%, ranging from 81 to 84%. Since commissioning this site was
very successful with long running hours and consistently valid data. Voltage issued became apparent on site
during January and February seemingly due to the very cold winter. This was causing the CHP to switch off,
but the unit was restarting without issues.
85
Site 11
The micro-CHP at site 11 is only used for space heating and was very rarely utilised during the trial period.
The very limited data collected during equipment commissioning and the occasional usage has been used
in the following figures. Overall the engine averaged 78% efficiency, this is low compared to other sites but
is very likely due to the very limited operation and low run hours.
Data Validity and Operational Days
Figure 33: Operational days and % of data valid on operational days, site 11
Run Hours
Figure 34: Total Monthly Run Hours site 11
86
Performance
Figure 35: Engine efficiency, site 11
87
Site 12
Data Validity and Operational Days
Figure 36: Operational days and % of data valid on operational days, site 12
Run Hours
Figure 37: Total Monthly Run Hours site 12
88
Performance
Figure 38: Engine efficiency, site 12
Due to electricity connection issues, the micro-CHP at 15DUCM was not operational until August 2009 and
since commissioning several issues became apparent. The gas meter at this site was found to be
considerably under reading (~50%) and was replaced in October 2009. The phase voltages were also out of
sequence causing low electricity values to be recorded; this was also rectified in October. Data following
these changes showed 100% operational days and 100% valid data. The engine displayed prolonged periods
of operation and very respectable efficiency.
89
Site 13
Data Validity and Operational Days
Figure 39: Operational days and % of data valid on operational days, site 13
Run Hours
Figure 40: Total Monthly Run Hours site 13
90
Performance
Figure 41: Engine efficiency, site 13
There are 3 micro-CHP appliances at this site, integrated in a complex heating system with 2 supplementary
boilers. From the onset of the trial there were numerous issues with engine integration and sequencing
meaning the boilers were acting as the lead appliance and the micro-CHPs were acting as support
appliances. Several suggestions were given during the first few months to improve to micro-CHP control and
reduce the frequent cycling, these included:

Reducing the boiler temperature thermostat so the boilers only fire if the micro-CHP cannot satisfy the
heating load,

Increasing the pump power from the buffer tank to the heating system, thus increasing the heat
supplied to the system and providing more load for the micro-CHPs

Altering the pipework so the micro-CHP flow enters the system before the water returns to the boilers.
This increases the temperature of the return water to the boilers and this combined with a lower water
set point in the boilers should prevent them from firing unless the micro-CHPs cannot maintain the
required temperature.
These options were considered and further site visit carried out to improve the control strategy. This led to
considerable improvements, with reduce cycling, longer periods of consistent operation and high efficiency.
The initial data processing also identified errors in the micro-CHP heat meter readings (heat from the microCHP appliances) which were lower than the buffer tank output. This is not thermodynamically possible and
the heat meter integrator was re-programmed and probes replaced to rectify the issue.
Data became valid at the end of November and remained so throughout the rest of the trial.
91
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