This paper has been published on the journal Energy and Buildings, Vol. 55, December
2012: 361-368
A domestic CHP system with hybrid electrical energy storage
X.P. Chen, Y.D. Wang, H.D. Yu, D.W. Wu, Yapeng Li, A.P. Roskilly
Newcastle Institute for Research on Sustainability, Newcastle University
Abstract
CHP (Combined Heat and Power) is widely regarded as one of the most promising
technologies to resolve energy-related problems, such as primary energy saving,
emission reducing etc. Domestic CHP is the energy system applied to the household
sector to supply both electric and heat energy to users. Due to the dissimilar
characteristics between household electricity and heat demands, conventional
off-grid CHP systems may not satisfy both of the demands simultaneously. This study
developed a domestic CHP system in which an engine-based CHP fuelled by biofuels
was integrated with a hybrid electric energy storage system and operated under FEL
(following electric load) energy management strategy. Experimental tests validate
the feasibility of this application and the results show that the system can satisfy the
fluctuant energy demands in a domestic dwelling. The overall energy efficiency has
been improved by 47.86% compared to conventional CHP.
Key words: Domestic CHP, Hybrid electric energy storage, Energy management,
Energy efficiency
Nomenclature
AC
CHP
DC
EES
FEL
FTL
HEES
PER
RC
SC
Alternating Current
Combined Heat and Power
Direct Current
Electric Energy Storage
Following Electrical Load
Following Thermal Load
Hybrid Energy Storage System
Primary Energy Ratio
Resistance and Capacitance
Super Capacitors
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2012: 361-368
Symbols
Storage system charging efficiency at time
output
with electric power
(%)
Electric transmission efficiency of the storage system over
charge/discharge at time point of
(%)
with electric power output
Electric efficiency of the engine at the time t (s) with electric power
output
(%)
The times of engine starting
Heat power recovered from coolant system at time
output power
with electric
(kW)
Nominal electric power of the engine (kW)
Heat power recovered from exhaust gas at time
output power
with electric
(kW)
Maximum Power (kW)
Total heat power recovered at time
with electric output power
(kW)
Electric output power of the energy storage system (kW)
Discharge power at discharge efficiency
(kW)
Total heat energy recovered (kWh)
Total heat energy recovered from coolant system (kWh)
Total heat energy recovered from exhaust gas (kWh)
Resistance (Ω)
Engine Operational Duration (s)
Storage System Discharging Duration (s)
Engine operation time during the duration i (s)
Peak Hour (s)
Open-circuit Voltage (V)
Efficiency (%)
Average charge efficiency of the storage system over
(%)
Average electric efficiency of the engine operation (%)
Electric efficiency of the storage system (%)
Overall efficiency of the system (%)
2
duration
This paper has been published on the journal Energy and Buildings, Vol. 55, December
2012: 361-368
1. Introduction
The Climate Change Act 2008 launched a trading scheme targeting on 80% reduction
in greenhouse gas emissions by 2050 compared to 1990 level in the UK[1]. As the
report from the Department for Environment Food and Rural Affairs (DEFRA, UK)
pointed out, domestic energy consumption contributed to half share of UK
greenhouse gas emissions [2]. Therefore, energy consumption and emission
reduction from homes and communities is one of the main sectors to decrease UK
emissions[3]. Therefore, development of energy efficient domestic energy supplying
systems is one effective way to achieve the target. Distributed domestic CHP is one
of the technologies for energy supply on the brink of wide application in Europe,
which is regarded as the most appropriate solution. Undoubtedly, domestic CHP
should satisfy both electricity consumption and heat demands. However, heat and
power consumptions are very different from each other in practice. Domestic heat
demands have apparently seasonal difference but the variation over one single day
is relatively slow compared to the electricity demands which fluctuate dramatically
within each day but have repeatability over the year. Lawson[4] investigated the
energy consumption in a three-bedroom house over 24 hours. The result from his
study shows that the daily electricity demands fluctuated over a wide range from
several-hundred watts for a majority of time to around 7kW for a very short period.
In comparison, the heating profile changed rather slowly. Therefore, following
electric load (FEL) strategy may be used for the distributed domestic CHP systems
preferably due to the complexity of electric demands profile in household dwellings.
On the other hand, the electric and heat output of the engine-based CHP system
performed differently. Generally, electric efficiency is much more sensitive when
load requirement increased. According to the study of engine performance which
will be discussed later, electric efficiency increased by a factor of four when engine
output varied from 10% to 100%. As a result, engine will be most efficient providing
it works on the highest load demands. By contrast, heat recovery efficiency has
relatively small variation in which there is only 4% difference as loads rise from 10%
up to 100%. Huangfu, Y [5] pointed out the electricity efficiency is the highest
influence factor concerning improving primary energy ratio (PER) in CHP systems. He
further advised that prime mover should be operated with the electricity output
higher than half of the full load. Therefore the engine/generator should work at a
relatively high output in order to achieve both higher electric efficiency and lower
fuel consumption. However, if an engine/generator is operated with high output,
there would be more electricity generated which may be excessive for a household
user due to the electricity needed in a household is quite low over the majority of
duration in one day, as shown in Figure 1. As a result, the system efficiency for an
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engine-based CHP system will be very low providing the engine is operated to match
the electricity demands. Therefore, it is difficult to find a satisfactory solution to
balance the outputs and consumptions of both electricity and heat at high efficiency
for a distributed CHP system. A considerable amount of investigations proposed
miscellaneous design and solutions for domestic CHP applications [6-10].
Furthermore, researchers, such as Mago, P.J. [11, 12], Piacentino, A[13] and Wang,
J.-J[14], did studies theoretically and it seemed that they had found solutions for the
problems. So far, however, most of investigations concentrated on the CHP systems
themselves statically rather than taking into account for the dynamic consumption of
energy in households. Aiming to develop an efficient distributed domestic CHP, this
work will design an improved domestic CHP system with electric energy storage (EES)
in which dynamic energy consumption in household will be taken into account. The
CHP coupled with an EES system comprises of a bio-fuel engine and a hybrid electric
energy storage system which is consisting of batteries and super-capacitors.
Improved FEL energy management strategy will be used and evaluated for primary
energy saving and efficiency improvement in this study.
2. The system of domestic CHP with hybrid electrical energy storage
2.1. Electricity and heat demand profiles of a selected household
A typical household in the UK was selected for this study. Figure 1 [4] shows the
electricity and heat consumption/demand profile over 24 hours for the selected
house. From the figure, it can be seen that the minimum demand of electrical power
was around 100W and the maximum demand reached to 6.544 kW. From Figure 1
(a), it can also be seen that the electricity consumption was lower than 1 kW during
the majority of 24 hours’ time while the peak demands happened at relatively short
periods. For instance, at 1.18pm, the demand was as high as 6.544 kW before it
plunged to 400 W 5 minutes later. The peak demands over 2.500 kW appeared 3
times, starting from 5.36am, 1.18pm, and 9.37pm. Electricity consumption for this
household over 24 hours is 9.85 kWh in total.
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Figure 1 (b) demonstrates the heat demand profile for the same house in the same
day. Heat energy was used for space heating and hot water. According to the profile
in the Figure 1 (b), the maximum heat demand was 1.375 kW while the minimum
was 205W. The overall amount of heat requirement was 18.5 kWh for the day.
Compared to the electricity profile, heat profile had a slow and moderate variation
during the 24 hours where there was no sudden great change from time to time.
Fig. 1 (a) Electricity demands
Fig. 1 (b) Space heating and hot water demands
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Gas Walve
Biodiesel pipe
Exhaust gas heat exchanger
AC generator
Biodiesel engine set
Jacket water
pump
Exhaust gas
Radiator
Water Walve
Water heating
exchanger (tank)
Jacket water
heat exchanger
Space heating
Water pump
Space
heating
Hot water loop
Tap
water
Hot water pump
Domestic hot
water pump Water Tank
AC
DC
Domestic
hot water
DC
Electrical Energy
Storage Hybrid
System
AC
Electricity
Inverter
Converter
Fig. 2 Schematic layout of CHP-HEES system
2.2. The design and implementation of the CHP-EES system for the household
Based on the heat and power demand profiles of the household, a domestic CHP
with hybrid electrical energy storage (CHP-HEES) system was designed and
implemented, as shown in Figure 2. The system included an engine/generator with a
heat recovery system (CHP) and a hybrid energy storage system (HEES). The system
was a distributed/isolated system and allowed different types of energy (electricity
and heat) to be generated locally. The engine was fuelled with bio-diesel and was
used to satisfy basic electricity demand; the waste heat from the engine cooling
system and the exhaust gas was recovered and stored in the form of hot water in a
tank; and the hot water was utilised to supply heating and hot water for the house.
The HEES consisted of battery bank and super capacitor module. It was connected to
the diesel generator. The electric energy generated from the generator but not used
at off-peak hours was stored in HEES system and then released along with electricity
generated from the generator to satisfy the electricity demands at peak time.
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2.3. The engine generator and the heat recovery system
One engine/generator, which provided a nominal power output
= 2.5 kW, was
selected as the primary mover of the CHP system; along with engine operation to
supply electricity demand, waste heat from both engine cooling system as well as
exhaust gas was recovered and stored in a hot water tank to supply heating and hot
water.
2.4. The hybrid electric energy storage system
The HEES system consisted of batteries and super-capacitors. Batteries are regarded
as common energy storage devices which can store and supply large amounts of
energy in a relatively small volume. Super-capacitors are used as auxiliary power
devices to store electricity. Compared to batteries, they have much lower energy
density and may store only limited energy inside. However, their advantages, such as
superior power density, long cycle lives and fast charge and discharge duration
enable them to become essential components to shave peak and response the
fluctuating load rapidly in storage application.
Andrew et al [15] discussed in detail the reason why super-capacitors are better than
batteries in high power application. Accounting for both batteries and
super-capacitors with similar weight, super capacitor module Superfarad 50V/250F
with 16kg weight, its energy density is 5.4Wh/kg only but it has 219W/Kg power
density. For Varta NiHD battery with weight of 17kg, it has 70Wh/kg energy densities
and 46 W/kg power densities only. Furthermore, Equation 1 describes maximum
power calculation for batteries and equation 2 represents the practical power value
by means of high power pulse.
(1)
(2)
Assuming
=95%, the practical discharge power
maximum power
is equal to 0.19 times nominal
. If discharge power is over this limit, the battery performance
would get worse. This is due to the unavoidably slow mass transport processes in the
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battery during charging and discharging. As a result, there may be half of discharge
energy being transformed into heat when batteries discharge with maximum power.
On the other hand, for super capacitors (SC), the specific energy stored in it is not
high because of the limitations in the accessible specific surface area of the electrode
in the SC, but the specific power is relatively high because of the short time constant
of double layer charging. A small RC time constant (0.1-2s) decides they can
response to rapid fluctuation of electric load transiently along with imperceptive
heat generated.
Therefore, super-capacitors can be used as supplementary power sources to assist
the batteries in hybrid applications. Combination of these two different types of
electric storage devices can achieve both power and energy advantages which can
satisfy both large alternation within short term and great amount of electric energy
demands over long period.
In this application, the energy storage system consisted of the batteries and
super-capacitors as shown in Figure 3. The batteries and super-capacitors were
linked together in parallel via DC link box and then DC current released from them
was transformed into AC current by the inverter. On the other hand, AC current
derived from the engine/generator was converted into DC current to charge the
HEES system through the charger. The HEES system consisted of 6 units of AGM
12V/200Ah batteries and a 30V/160F super capacitor module.
Circuit break 1
Engine/generator
Power meter 1
Batteries
current meter 1
DC link box
Charger
Super-capacitor
module
Circuit break 2
Load
Bank
Inverter
current meter 2
voltage meter 2
Shunt
voltage meter 1
Communication
and controller
Fig. 3 The layout of the HEES system
8
Power meter 2
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2.5. Energy management strategy
The most popular energy management strategies used in CHP application are FEL
(following electric load) and FTL (following the thermal load) [11-13]. Taking into
account electric demand varying much more quickly and more complicated than
heating demand in this application, as shown in section 2.1 above, FEL strategy was
selected as the energy management strategy. The CHP-EES system here adopts FEL
strategy targeting to optimize the overall system energy efficiency where all
efficiency calculated by energy gained against fuel consumed. Therefore, the system
aimed primarily to satisfy the electricity demand; and secondly to meet the heat
demand.
Figure 4 illustrates the system operation transmission chart and Table 1 summarizes
the variables applied to control procedure in Figure 4. There are three main states
and two sub states applied to the system operational procedures. State 1 represents
the operational mode in the following way: engine as the main source coordinate
with electric storage system to satisfy peak electricity demands. In operation state 2,
engine as the main source supply both electric load and HEES charging over a
Fig. 4 Operational state transferring diagram
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number of certain off-peak hours. In operation state 3, electric storage system
provides electricity to domestic demand alone in the period of low electricity
requirement. Sub-state 2-1 and 2-2 stand for two different charging approaches.
Both of them belong to state 2. In sub-state 2-2, EES is charged by default charging
curves. Otherwise, it would be charged by the amount calculated by engine power
subtracting loads power. The optimization energy management strategies are
implanted in control system for governing energy demands analysis as well as energy
generation.
Table 1 Variables summary
Variable name
Explanation
Note
flagEnd
State variable (true or false) represents
=True
Charge end
charge state
=False
In charging
Pcharge
Default charge power for storage system
Default setting charge curve
Pgen
The maximum value of output power from generator
Constant
pload
Load power demands
--
Pstorage
Maximum discharge power from storage system
Constant
2.6. System operational plan
The HEES system supplied the electric power to meet the demand when the load
was lower than 4000 W (refer to Figure 1 (a)). The engine/generator ran along with
the EES to satisfy peak demands. In order to obtain higher overall efficiency for the
CHP-EES system, the engine generator was started and operated 3 times, namely, 6
– 7 am, 13 – 16 pm and 22 – 24 pm. During the running periods, the EES was charged
with the extra electricity from the engine/generator, making sure it had enough
energy stored and supply electric power as required.
2.7. Waste heat recovery
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Heat obtained was recovered from the cooling system and the exhaust gas of the
engine/generator. Therefore, heat energy recovered was equal to the sum of them
over the whole engine operation which was calculated by the series of equations
below,
Fig. 5 Household electricity demands and supplying profile
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(3)
(4)
So,
(5)
With
(6)
2.8. System efficiency
Several important efficiency-related indicators can be produced. The calculation is
described in the following sections.
2.8.1 Engine electric efficiency
The electric efficiency of the engine is the mean efficiency over the engine operation
as follows:
2.8.2 The electric efficiency of the storage system
The electric efficiency of the storage system is equal to its charge efficiency
multiplied by its charge/discharge transferring efficiency. Therefore, electric
efficiency can be expressed as equation (8) below:
(8)
2.8.3 Overall electric efficiency of the system
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System overall electric efficiency
can be calculated by equation (10),
(10)
3. Results and discussions
According to the system operational plan and the energy management strategy
designed from the electricity and heat demand profiles of the selected house,
experimental tests were carried out and the results are shown in Figure 5 and Figure
6. The engine/generator generated all of electric power required by the house
including electric energy stored in the HEES system. When the test started, the HEES
system was fully charged.
Fig. 6 (a) Energy contribution
Fig. 6 (b) Operation duration (Hours)
3.1. The efficiency of the engine generator
Table 2 shows the test results of the electric and heat recovery efficiency of the
engine generator when it runs at different loads. It can be seen that the electric
efficiency altered from 7.8% to 28.1% as the loads increased. However, heat
recovery efficiency fluctuated within a small range between 34.5% and 41.1% when
the load changed widely.
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Table 2 Efficiency of the engine/generator
Engine load (%)
Electric efficiency (%)
Heat recovery (%)
10
7.8
38.4
25
16.3
34.5
50
24.2
36.4
75
27.3
41.1
100
28.1
41.0
3.2. Dynamic performance of the engine
In the tests, the engine started and ran three times when the electric load demands
were over 4.000 kW or the remaining energy stored in the EES system was
inadequate. Figure 5 (a) showed the electricity consumption profile. The
performance of the engine/generator was shown in Figure 5 (b). When the
engine/generator was running, it supplied electric power with the assistance from
the HEES system during peak time; otherwise, the engine/generator charged the
HEES system at off-peak time until the HEES was fully charged. From Figure 5 (b), it
can be seen that the engine/generator was always running above half load.
Therefore, high efficiency of the CHP-HEES was achieved.
3.3. Dynamic performance of the energy storage system
The test results of the HEES system when it was run in the CHP-HEES system are
shown in Figure 5 (c) and (d). The negative parts of the batteries in Figure 5 (c) and
the super-capacitor power profiles in Figure 5 (d) represent the amount of electric
power charged, while the positive ones stand for the amount of electric power
discharged. The batteries were charged as the engine/generator started at off-peak
hours to make sure there was enough energy stored in the HEES system. From Figure
5 (d), it can be seen that the super-capacitors responded to the load fluctuation
speedily. When electric demands varied, it released electricity with maximum
capability promptly.
For the engine/generator, the transition time during operation represents how
quickly the engine responds to load variation, which is normally around 3 to 10
seconds depending on engine types. From the test results, it can be seen that the
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HEES responded swiftly to the sudden change of loads, which has positive effect to
engine operation. Consequently, engine has enough time to alter its output properly.
3.4. Heat recovered
The total heat energy recovered from the engine during the 24 hours’ test is
21.07kWh, while the heat consumption for the day is 18.5 kWh [4]. The heat
recovered is 14% more that the demand. Furthermore, due to the engine being
operated at high loads, heat at higher temperature can be obtained for use.
Therefore, the practical heat recovered in the test can fully satisfy the requirement
for the house in the 24 hours. The heat recovered is 40.1% of the fuel input.
3.5. Electric efficiency and overall efficiency of the system
In the CHP-HEES system, an engine/generator rated 2.5 kW is used and coupled with
the HEES system. All of the test results are listed in Table 3. Discharge efficiency of
the storage system, engine efficiency and overall electric efficiency are 24.01%,
26.45% and 23.59% respectively, as seen in Table 3.
For comparison, a CHP system without EES is calculated. The CHP is assumed to have
a maximum power output 6.5 kW, to meet the maximum electricity demand; and it
has similar electric efficiencies at different loads as the engine/generator in the
CHP-HEES system. The simulated results of this CHP system are also listed in Table 3.
From the results, it can be seen that the average efficiency of the CHP system
without EES is only 4.95%. This is because the engine always runs at very low loads (<
1.000 kW). The heat may be recovered from the CHP is 75.01 kW. It is 4 times that of
the overall amount of heat requirement (18.5 kWh) for the day. That means there is
56.51 kW of heat wasted.
Compared to the CHP without EES system with 4.95% electric efficiency, the CHP-EES
system has a much higher electric efficiency, that is 23.59% overall, which is 4 times
more than that of CHP without EES. Furthermore, the overall CHP system efficiency
increased from 43.06% to 63.67% where the improvement of the overall system
efficiency is 47.86%, as shown in Table 3.
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Table 3 Performance comparison between two CHP systems
CHP without EES
CHP-EES
Improvement (%)
Engine nominal Power (kW)
6.500
2.500
--
0 – 6.500
0 – 2.507
--
24.00
6.89
--
(hours)
--
6.48
--
Storage system discharge duration
--
17.52
--
Storage system charge efficiency (%)
--
26.10
--
Storage system discharge efficiency (%)
--
24.01
--
Average engine generator efficiency
4.95
26.45
434.34
4.95
23.59
376.47
75.01
20.07
--
38.11
40.08
5.17
43.06
63.67
47.86
Operation range (W)
Engine operation duration (hours)
Storage system charge duration
(%)
Overall electric efficiency (%)
Heat recovered (kWh)
Average heat recovery (%)
Overall CHP system efficiency (%)
From the results, it is found that the engine generator supplied 36% of the electric
energy in 24 hours; the HEES system contributed 64% electricity needed. Figure 6 (a)
shows the percentage of electricity supplied from the engine/generator and the
HEES system. Figure 6 (b) shows the allocation of the operational duration of the
engine/generator, the HEES and both of them. The HEES system supplied power for
17.11hours at low load demand period; while the engine/generator worked for 6.48
hours and supplied power and recharged the HEES system; only within 0.41 peak
hour, the engine was running together with the HEES system to supply the peak
demands.
3.6. System economic analysis
The capital of CHP-EES system costs around £6800. According to daily electricity
demands, the engine will be operated for 6.89 hours with total fuel consumption of
4.88Kg to satisfy energy requirement, including both 9.85 kWh electricity and 20.07
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kWh heating energy in this case study. Therefore, fuel costs will be around £2.44 for
sunflower oil or rapeseed oil (50p per kg) as estimated.
In the UK, there are 1.5 million homes without access to the natural gas grid where
the most popular option for home heating is heating oil fired boilers. According to
relevant investigations, the overall fuel efficiency by using heating oil is only 48% on
average[16] and the price of heating oil is around 53 to 65p (VAT exclude) per kg[17].
Therefore, the cost for satisfaction of heating demands 20.07 kWh will cost £2.22 to
£2.72 where they have to pay extra to purchase electricity from power grid or
alternative way.
Another popular option for energy supplying system in the UK is solar energy system,
the capital of a domestic solar energy system with size of 4-10kW capacity in the UK
costs between £10,500 and £46,000. Additionally, the maintenance cost is around
£3000 over 20 years’ operation[18]. Furthermore, the solar energy system strongly
relies on seasons and needs to be connected with power grid. And it is not suitable
for stand-alone energy supplying application without the power grid connection.
Compare to the solar energy system, CHP-EES has obvious advantages including:



Much cheaper capital cost
Free of season-dependence
Free of the power grid connection.
4. Conclusions
The detailed study of a domestic CHP-HEES system shows that:

A CHP system integrated with a hybrid electric energy storage (HEES) system, a
smaller engine/generator can be used to satisfy the same energy demands of the
conventional off-grid/distributed CHP system. The smaller engine/generator is
able to work at much higher electric efficiency due to the effect of peak shaving
and valley filling from the HEES unit.

The integrated CHP-HEES system can satisfy both electric and heat demands
required by the house at high efficiency.

Overall energy efficiency increases to 63.10% with improvement by 46.89%,
compared to the conventional CHP only system.

CHP-EES system has much cheaper capital cost comparing to solar energy system
and more suitable to install in domestic applications.
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Obviously, biofuel CHP-EES is an ideal option for stand-alone energy supplying
system without grid connection and/or gas grid in rural area. CHP-EES features with
benefits including rational capital and operational costs. Free of season-dependence,
environmentally friendly etc.
Acknowledgement
This research outcome is from a joint UK–China research project of Bio-fuel Micro-Tri
generation with Cryogenic Energy Storage System (BMT-CES) funded by the
Engineering and Physical Sciences Research Council of the UK.
References
[1] O. o. P. S. I. (OPSI), "Climate Change Act 2008," O. o. P. S. I. (OPSI), Ed., ed, 2008.
[2] J. Fisher, "Reducing Household Energy Use and Carbon Emissions: the potential for
promoting significant and durable changes through group participation," presented at
the Proceedings of Conference: IESD PhD Conference: Energy and Sustainable
Development, Leicester, UK, 2010.
[3] DEFRA, "CLIMATE CHANGE: Taking Action," ed: Department for Environment Food and
Rural Affairs, 2010.
[4] R. Lawson, "A study of the energy usage in domestic UK dwellings to aid the
development of domestic combined heat and power(CHP) and micro renewable
technologies," Master Dissertation, Renewable energy, Newcastle university, 2010.
[5] Y. Huangfu, J. Y. Wu, R. Z. Wang, X. Q. Kong, and B. H. Wei, "Evaluation and analysis of
novel micro-scale combined cooling, heating and power (MCCHP) system," Energy
Conversion and Management, vol. 48, pp. 1703-1709, 2007.
[6] S. B. Riffat and X. Zhao, "A novel hybrid heat pipe solar collector/CHP system—Part 1:
System design and construction," Renewable Energy, vol. 29, pp. 2217-2233, 2004.
[7]
e
ri o
orteiro an
pe
easi i ity o a ne
o estic
trigeneration with heat pump: I. Design and development," Applied Thermal
Engineering, vol. 24, pp. 1409-1419, 2004.
[8]
De aepe
D’ er t an D
ertens, "Micro-CHP systems for residential
applications," Energy Conversion and Management, vol. 47, pp. 3435-3446, 2006.
[9] G. Gigliucci, L. Petruzzi, E. Cerelli, A. Garzisi, and A. La Mendola, "Demonstration of a
residential CHP system based on PEM fuel cells," Journal of Power Sources, vol. 131, pp.
62-68, 2004.
[10] G. Qiu, Y. Shao, J. Li, H. Liu, and S. B. Riffat, "Experimental investigation of a
biomass-fired ORC-based micro-CHP for domestic applications," Fuel, vol. 96, pp.
374-382, 2012.
18
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2012: 361-368
[11] P. J. Mago and L. M. Chamra, "Analysis and optimization of CCHP systems based on
energy, economical, and environmental considerations," Energy and Buildings, vol. 41,
pp. 1099-1106, 2009.
[12] P. J. Mago, N. Fumo, and L. M. Chamra, "Performance analysis of CCHP and CHP
systems operating following the thermal and electric load," International Journal of
Energy Research, vol. 33, pp. 852-864, 2009.
[13] A. Piacentino and F. Cardona, "An original multi-objective criterion for the design of
small-scale polygeneration systems based on realistic operating conditions," Applied
Thermal Engineering, vol. 28, pp. 2391-2404, 2008.
[14] J.-J. Wang, Y.-Y. Jing, and C.-F. Zhang, "Optimization of capacity and operation for CCHP
system by genetic algorithm," Applied Energy, vol. 87, pp. 1325-1335, 2010.
[15] B. Andrew, "Ultracapacitors: why, how, and where is the technology," Journal of Power
Sources, vol. 91, pp. 37-50, 2000.
[16] E. P. Johnson, "Carbon footprints of heating oil and LPG heating systems,"
Environmental Impact Assessment Review, vol. 35, pp. 11-22, 2012.
[17] B. Juice. (2012). Home Heating Oil Prices
[Website]. Available:
http://www.boilerjuice.com/heatingOilPrices.php
[18] P. Brinckerhoff, "Solar PV cost update," DECC, Ed., ed, 2012.
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