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Actual versus ideal performance of a SOFC mCHP unit
operating in a domestic building
Hydrogen & Fuel Cell SUPERGEN Researcher Conference
15 – 17th December 2014
Birmingham, UK
Theo Elmer1, 2, Mark Worall1, Shenyi Wu1 and Saffa B Riffat1
1Architecture, Climate and Environment Research Group, The University of Nottingham 2CDT Hydrogen, Fuel Cells and their Applications, University of Birmingham
*corresponding author email: [email protected]
Presentation outline
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 2
1. Introduction
2. Aims and objectives
3. mCHP and fuel cell technology
4. The scenarios studies
5. Assessment method
6. Actual assessment data
7. Emission assessment results
8. Economic assessment results
9. Combined efficiency results
10. Conclusions
11. Acknowledgements and references
1. Introduction Future energy supply must be secure, clean and economic
EU committed to reduce CO2 emissions by 20% by 2020 compared to 1990 levels [1]
European buildings account for 40% of energy demand [2] and 50% of CO2 emissions [3]
Built environment identified as holding the largest economic potential for the reduction of
CO2 emissions – IPCC [4]
Wednesday, 21 January 2015 3
CLEAN ECONOMIC
SECURE
FUTURE
ENERGY
SUPPLY
Fuel cell mCHP is a possible option for decentralised low carbon energy generation
H2FC SUPERGEN Researcher Conference
Wednesday, 21 January 2015 4
2. Aims and objectives
The aim of this work is to assess the emission and economic performance of a SOFC
mCHP system (BlueGEN) operating in a domestic home.
The assessment will compare three scenarios:
1. Base case – boiler and grid electricity
2. Ideal case – BlueGEN operating at quoted manufacture performance
3. Actual case – BlueGEN real operational data i.e. fluctuating electrical power output and
efficiency
In each scenario, the following assessments will be made:
i. Emission assessment – the difference in kg CO2 per scenario investigated
ii. Economic assessment – the cost difference (£) per scenario investigated
H2FC SUPERGEN Researcher Conference
3. mCHP and FC technology
Wednesday, 21 January 2015 5 H2FC SUPERGEN Researcher Conference
mCHP advantages [5]
1. Improved system efficiency 2. Reduction in NRPE demand
3. Transmission loss reduction 4. Environmental / economic benefit
5. Utility scale decarbonisation
FC advantages [5]
1. High electrical efficiency 2. Low H:P
3. Low / no harmful emissions 4. Near silent operation
5. Flexibility of fuel use
Wednesday, 21 January 2015 6
(1) Base case scenario (2) SOFC mCHP ideal case
(3) SOFC mCHP actual case
4. The scenarios studied
Grid
electricity
Natural
gas
Natural
gas
Grid
electricity
SOFC
Boiler
Boiler
H2FC SUPERGEN Researcher Conference
The SOFC used in this study is the commercially available
BlueGEN 1.5kWe SOFC mCHP unit
Assessment location - David Wilson House, CEH ,UoN
No WHR
With WHR
With TES
5. Assessment method
Wednesday, 21 January 2015 7
0 50 100 150 200 250 300 3500
10
20
30
40
50
60
70
Day number
Ener
gy
dem
and
(k
Wh
)
Electrical demand (kWh)Electrical demand (kWh)
Space heating demand (kWh)Space heating demand (kWh)
DHW demand (kWh)DHW demand (kWh)
David Wilson House energy load profile BlueGEN SOFC mCHP system
Auxiliary gas
boiler
Heat recovery
circuit
SOFC unit
Annual thermal demand 7814 kWh
Annual electrical power demand 4525 kWh
Annual H:P demand ratio ~ 1.75
Operates on natural gas
Runs continuously at 1.5kWe Import / export of electricity Supplemented with auxiliary gas boiler
Qualifies for UK export and feed in tariffs
H2FC SUPERGEN Researcher Conference
Hourly power and thermal demand data is known for the house
Hourly electrical power and thermal output data for BlueGEN is known
Energy balances completed at each hour for the three scenarios studied
SOFC performance summary Ideal Actual
Electrical power 1.5 kW Variable
Electrical efficiency 60 % Variable
CHP efficiency 85 % Variable
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 8
1. Burner ignited
2. Power export begins 3. Issue with water leak and PRV 4. Gas supply turned off
5. Stack failure
0 500 1000 1500 2000 2500 3000 3500 4000
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
Time [Hours]
Ou
tpu
t p
ow
er
[kW
]
BlueGEN electrical output - whole periodBlueGEN electrical output - whole period
90.5 % availability for power generation (3967 hours)
88.4 % availability for power generation at ηe ≥ 50% (3877 hours)
BlueGEN SOFC operational from 25th March 2014
Ran for six months, until stack failure on 12th September 2014
Six months’ worth of operational data for the unit in this period (4386 hours)
The assessment presented is for this six month period
March 2014 September 2014
6. Actual assessment data
0 500 1000 1500 2000 2500 3000 3500 4000-10
0
10
20
30
40
50
60
70
80
Time [Hours]
Ele
ctr
ica
l e
ffic
ien
cy [%
]
BlueGEN electrical efficiency - whole periodBlueGEN electrical efficiency - whole period
1
34
5
2
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 9
7. Emission assessment results Emissions analysis constants Value (kg CO2 / kWh)
Grid electricity 0.555
CCGT electricity (offset export) 0.36
Natural gas emission factor 0.184
For the TES scenario:
(a) An average 55 % reduction over the
6 month period (base & actual)
(b) An average 24 % difference over the
6 month period (ideal and actual)
(c) An average 66 % reduction over the
6 month period (base & ideal)
0 500 1000 1500 2000 2500 3000 3500 4000-0.25
-0.125
0
0.125
0.25
0.375
0.5
Time [Hours]
CO
2 e
mis
sio
ns [kg
]
Base case CO2
Real CO2 -TESReal CO2 -TES
Ideal CO2 - TESIdeal CO2 - TES
(a)
(b) (c)
Actual case
Added value of the FC (no WHR & TES)
35 % reduction with base case
Added value of WHR (no TES)
29 % reduction with FC no WHR & TES
Added value of TES
2 % reduction with FC with WHR no TES
No grid connection with WHR & TES
41 % increase with base case
Actual case Ideal case % difference
Base case (kg CO2) 1456.79 --- ---
FC with no WHR (kg CO2) 941.02 784.54 16
FC with WHR no TES (kg CO2) 667.65 533.36 20
FC with WHR & TES (kg CO2) 653.31 497.61 24
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 10
0 500 1000 1500 2000 2500 3000 3500 4000-0.25
-0.125
0
0.125
0.25
Time [Hours]
Co
st [£
]
Base case cost
Real cost -TESReal cost -TES
Ideal cost - TESIdeal cost - TES
Economic analysis constants Value (£/kWh)
Grid electricity 0.172
Natural gas 0.0421
mCHP FiT (OFGEM) 0.125
Export tariff (OFGEM) 0.045
8. Economic assessment results
Base
case
Ideal
case
Actual
case
% difference
(base & ideal)
% difference
(base & actual)
Cost (£) – EXT & FIT 427.14 - 476.99 - 441.37 212 % reduction 203 % reduction
Cost (£) – just EXT --- 262.38 298.01 39% reduction 30 % reduction
Cost (£) – no tariffs --- 437.70 473.33 2 % increase 11 % increase
(a)
(b)
(c)
For the TES scenario (all tariffs):
(a) An average 203 % reduction over
the 6 month period (base & actual)
(b) An average 8 % difference over the
6 month period (ideal and actual)
(c) An average 212 % reduction over
the 6 month period (base & ideal)
Actual case – ALL tariffs
Added value of the FC (no WHR & TES)
188 % reduction with base case
Added value of WHR (no TES)
17 % reduction with FC no WHR & TES
Added value of TES
1 % reduction with FC with WHR no TES
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 11
9. Combined efficiency results
Grid connection provides greater added value to CHP efficiency than TES
does, shown in the difference between the red and green lines
0 500 1000 1500 2000 2500 3000 3500 40000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Time [Hours]
CH
P e
ffic
ien
cy
Grid & TES
Grid & no TESGrid & no TES
No grid & TESNo grid & TES
No grid no TESNo grid no TES
Ideal 85% CHP efficiency with TES and grid
15% drop from ideal 85% CHP efficiency
42% drop from ideal 85% CHP efficiency
58% drop from ideal 85% CHP efficiency
~ 27 % difference
10. Conclusions
Wednesday, 21 January 2015 12
The aim of this work has been to assess the emission and economic performance of a
SOFC mCHP (BlueGEN) system operating in a domestic home, under three scenarios:
1. Base case – boiler and grid electricity
2. Ideal case – operating at quoted manufacture performance
3. Actual case – real operational data
H2FC SUPERGEN Researcher Conference
Specific conclusions from the work presented: 1. The BlueGEN system can provide considerable emission reductions and economic benefit compared
to the base case scenario – for both the actual and ideal cases
2. Grid interaction is essential for significant emission and cost reductions compared to the base case 3. Government incubator support significantly improves the economic performance (EXT / FIT) 4. For the six month assessment period there is reasonable difference between the real and ideal
performance of the system ~ 24 % for emission and 8 % for economic analysis. Differences attributed to issues of accelerated electrical efficiency degradation (components, gas shut off etc.)
5. WHR and TES do provide added benefit to the system performance, however it is not as significant as grid interaction
General conclusions from the work presented: 1. The increased reliance on natural gas in the case of the BlueGEN SOFC mCHP system needs
consideration, as this could have serious implications for the development of a more robust and secure energy system, less reliant on foreign imports of energy
2. The use of natural gas fed fuel cell technology today will provide an essential stepping stone to a future
low carbon economy based upon hydrogen
Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 13
0 500 1000 1500 2000 2500 3000 3500 4000 4500-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Time [Hours]
Ou
tpu
t p
ow
er
[kW
]
1
3
4 52
6
7
1. Burner ignited
2. Power export begins 3. Issue with water leak and PRV 4. Gas supply turned off
5. Stack failure 6. Stack replacement – 13.11.2014
7. Power export – 22.11.2014
Post stack replacement
11. Acknowledgements and references
Wednesday, 21 January 2015 14
ACKNOWLEDGEMENTS
The authors would like to acknowledge the support from European Commission under the Fuel Cell and Hydrogen Joint Undertaking Initiative (FCH-JU) for the “Durable low temperature solid oxide fuel cell Tri-generation system for low carbon buildings” project, agreement No. 303454. The authors would also like
to thank the EPSRC and CDT in Hydrogen, Fuel cells and their Applications for their continued financial and academic support.
REFERENCES [1] Böhringer, C., T.F. Rutherford, and R.S.J. Tol, THE EU 20/20/2020 targets: An overview of the EMF22
assessment. Energy Economics, 2009. 31, Supplement 2(0): p. S268-S273. [2] Ekins, P. and E. Lees, The impact of EU policies on energy use in and the evolution of the UK built
environment. Energy Policy, 2008. 36(12): p. 4580-4583. [3] Clarke, J.A., Johnstone, Cameron M., Kelly, Nicolas J., Strachan, Paul A., Tuohy, Paul, The role of built environment energy efficiency in a sustainable UK energy economy. Energy Policy, 2008. 36(12): p. 4605-
4609. [4] Hawkes, A., et al., Fuel cells for micro-combined heat and power generation. Energy & Environmental
Science, 2009. 2(7). [5] Elmer, T., Worall, M., Wu, S., Riffat, S., "Fuel cell technology for domestic built environment applications: State of-the-art review," Renewable and Sustainable Energy Reviews, vol. 42, pp. 913-931,
2015. [6] Conroy, G., A. Duffy, and L.M. Ayompe, Economic, energy and GHG emissions performance
evaluation of a WhisperGen Mk IV Stirling engine μ-CHP unit in a domestic dwelling. Energy Conversion and Management, 2014. 81(0): p. 465-474.
H2FC SUPERGEN Researcher Conference
Thank you
Questions welcome
www.trisofc.com
Hydrogen & Fuel Cell SUPERGEN Researcher Conference
15 – 17th December 2014
Birmingham, UK