Renewable Solar and Wood Pellet Heating in
a Large Building
Location: Coillte Headquarters,
Newtownmountkennedy,
Co. Wicklow
Project Start:
Commission date:
Modern wood fuelled heating
Modern wood heating is fuelled by wood chips or wood pellets. Heating systems with fully
automatic fuel feed and cleaning are available so that little manual handling is necessary to
operate the boiler.
Wood pellets
Wood chips
Wood pellets are a clean, compact and easy to store smokeless fuel. Wood pellets are made
from wood shavings and sawdust and are used in highly efficient and convenient
automatic wood boilers. They can be delivered in bags or in bulk. Because they have a low
moisture (less than 10%) and ash content (less than 1%) wood pellets burn very
efficiently.
Background to the project
Coillte Teoranta (The Irish Forestry Board) is a leading Irish company, which operates in
forestry and related businesses.
Coillte Headquarters is located at a large new premises at Newtownmountkennedy, Co.
Wicklow. The building is an all-timber office complex produced by sister company,
Griffner Coillte. It covers 25,000 square feet of floor space and houses 100 staff. Wood,
a renewable resource, was for the forestry company, the obvious and natural choice for
the building construction. It was also the preferred option for heating in combination with
solar.
Coillte Headquarters
Brief summary of the project proposal
Conscious of Ireland’s potential for biomass energy production, Coillte are in an
excellent position to use this potential and start an Irish timber biomass industry through
the harvesting of wood residue from saw mills and forestry.
To learn at first hand how wood heating operates in a large building, Coillte decided to
install a wood fuelled boiler as part of the heating system of its new headquarters.
A combined wood pellet/wood chip fuelled boiler is used as the second stage heat
generator for the building. Two arrays of solar thermal panels, which are made up of a
flat plate array and an evacuated heat tube array, are the primary heat source. A large
buffer vessel is used to store this heat, which is topped up from the wood boiler when
necessary. Both these systems are located in a purpose built Energy Centre, which also
contains full monitoring and feedback facilities. Designed by Stewart & Sinnott Studio
Architects, the Energy Centre generates heat entirely from renewable sources and is
carbon neutral in terms of CO2 emissions. The building is fully sustainable with the
primary building material being timber from sustainable sources, insulation by recycled
paper product to levels better than current building regulations, passive solar design
incorporating brise soleil, external fixed and retractable solar shading and very high
quality glazing.
The building is open to the public for education and demonstration purposes and a
meeting room has also been designed with full audiovisual facilities for lectures and
discussion purposes.
Coillte Energy Centre
Benefits of Renewable Heating
-
High-level comfort and convenience-always on hot water-fully controlled and
automatic heating system
Local wood fuel supply (long-term contracts are recommended)-wood pellets are
now produced on the island of Ireland
-
Highly efficient systems (up to 90%)
Sustainable and renewable heating source
Competitively priced wood fuels
Zero carbon emissions
Low energy consumption
The walls meet the new energy efficiency standards soon to be introduced as part of
Ireland’s greenhouse gas reduction strategy:
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The U-value of the walls are 0.23 W/m²K
The U-value of the roof is 0.16W/m²K
The U-value of the floor is 0.25 W/m²K
Timber-aluminum windows have argon filled double-glazing with low emission glass
The U-value of the windows are typically 1.4W/m²K, depending on size
Wood Chip/Pellet Boiler
The boiler is a KWB USV 100, which has an output capacity of 95kW. It has an
efficiency of 85.4%. Physical Size: 2035x855x2028mm
KWB 95kW Boiler
Features of the boiler and conveyor system include:
- KWB Biomass Boiler USV100 including intermediate container, agitator in the
storage and conveyor system, maximum heating power range between 32 – 95 kW.
- Motor for the conveyor system.
- 4 Meter conveyor systems with canal.
- Agitator with diameter 5,5m.
- Modem and software for remote control and maintenance.
The boiler can be fuelled with either wood chips and wood pellets. It is currently fuelled
from a 20m2 adjacent pellet store via an automatic feed system including an agitator
within the store and an automatic feed conveyor system.
The boiler will deliver approximately 152,000kWh of renewable heat a year, reducing
CO2 by 27.4tonnes per annum. compared with natural gas.
Installed Cost = €283 per kW
Conveyor
Evacuated Tube Solar Collectors
The vacuum in the glass tube, being the best possible insulation for a solar collector,
suppresses heat losses and also protects the absorber plate and the ‘heat-pipe’ from
external adverse conditions. This results in exceptional performance far superior to any
other type of solar collector.
The system from manufacturer, Thermomax, consists of a stainless steel manifold and
stainless steel support with solar collector tubes. The manifold, which has a minimal
liquid capacity, is made from a high grade of ‘marine quality’ stainless steel and sealed
in a weather resistant metal cover. The condenser of the solar tube fits inside the
manifold, which carries the heating fluid. There is a thick polyurethane CFC free foam
insulation between the manifold and its cover. The system is secured to the roof by
means of stainless steel fixing brackets.
Thermomax patented temperature-limiting tubes are unique. The maximum working
temperature is controlled by means of a memory metal spring, which is positioned inside
the heat-pipe’s condenser. The memory metal is programmed to change its shape at a
pre-set temperature. This allows for the condensed fluid to be retained inside the
condenser. When the programmed temperature has been reached, the memory metal
spring expands and pushes a plug against the neck of the ‘heat-pipe’ blocking the return
of the condensed fluid and stopping heat transfer. At temperatures below the maximum
programmed limit, the spring contracts allowing the condensed fluid to return to the
lower section of the ‘heat-pipe’. The fluid, due to the heat from the absorber plate, is
evaporated, transferring thermal energy to the condenser. Thermomax’s patented
Memotron tube provides complete safety through effective temperature control.
10m2 of panels were installed with the inclusion of 5 x MS20 Manifold.
Net Absorber Area
Overall Dimension
Manifold Capacity
Weight
Absorption
Vacuum Efficiency
Cost (excl. VAT)
2m2
1960x1420mm
3.4Litres
45kg
96%
81%
€950 per m2
Features of the solar collector system
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High Performance even in adverse weather conditions due to vacuum insulation.
Self-Limitation of maximum working temperature, achieved by the innovative use of
a memory metal spring inside the condenser.
The ‘Heat Pipe’ Technology ensures high heat transfer and low heat capacity.
Ease of Installation – each tube can be installed individually.
Minimum maintenance requirement – a single tube can be replaced at a time.
High durability and reliability due to the high quality of the material used in the
manufacturing process.
Flat Plate Solar Collectors
For Comparative purposes 10m2 of flat plate solar water collectors were also installed:
This included an array of 5x IDM-GSE 200 type panels:
Net Absorber Area
Weight
Cost (excl. VAT)
1985x1985mm
36kg
€805 per m2
Using Solar Collectors at Coillte reduces CO2 output by 4.3 tonnes per annum.
Automatic Temperature & Ventilation Controls for Coillte Headquarters
All heating and ventilation plant equipment is controlled from a dedicated motor control
centre and can be operated via a Building Management System (BMS). The BMS also
logs all energy requirements via heat meters installed on the wood boiler and on each
set of solar panels.
This information can be logged and scrutinized to investigate the efficiency of the each
of the sustainable approaches.
Replication Potential
Large buildings with a year round space heating requirement are highly suitable for solar
and wood-fuelled heating. Commercial and industrial buildings such as factories, offices,
hotels and hospitals could reduce their energy costs considerably by installing
renewable heating. For retrofitting existing buildings with wood heating, easily to install
‘plug and play’ pre-assembled units housing both fuel storage and the boiler can be a
solution. Existing oil and coal boilers can be adapted to wood by fitting a wood burner.
Further Information
Contact SEI REIO for an information pack on renewable heating including presentations,
case studies and publications or to discuss your individual project.
Tel 023 29146
Email biomass@reio.ie
Web www.sei.ie/reio.htm
Replication Potential
Suppliers
Solar collectors
Thermomax www.thermomax-group.com
Wood boiler
KWB
www.kwb.at
Project Partners
Buro Happold
Consulting Engineers