Among the various fuel cell (FC) systems, molten carbonate fuel cells (MCFC) are nowadays one of the most promising technologies, thanks to the lower specific costs and a very high electrical efficiency (net low heating value (LHV) electric efficiency in the range 45%–50% at MWel scale using natural gas as fuel). Despite this high performance, MCFC rejects to the ambient almost half of the fuel energy at about 350–400 °C. Waste heat can be exploited in a recovery Rankine cycle unit, thereby enhancing the electric efficiency of the overall system. Due to the temperature of the heat source and the relatively small power capacity of MCFC plants (from few hundred kWel to 10 MWel), steam Rankine cycle technology is uneconomical and less efficient compared to that of the organic Rankine cycle (ORC). The objective of this work is to verify the practical feasibility of the integration between a MCFC system (topping unit) and an ORC turbogenerator (bottoming unit). The potential benefits of the combined plant are assessed in relation to a commercial MCFC stack. In order to identify the most suitable working fluids for the ORC system, organic substances are considered and compared. The figure of merit is the maximum net power of the overall system. Finally, the economical benefits of the integration are determined by evaluating the levelized cost of electricity (LCOE) of the combined plant, with respect to the standalone MCFC system. In order to assess the economic viability of the bottoming power unit, two cases are considered. In the first one, the ORC power output is approximately 500 kWel; in the latter, about 1 MWel. Results show that the proposed solution can increase the electrical power output and efficiency of the plant by more than 10%, well exceeding 50% overall electrical efficiency. In addition, the LCOE of the combined power plant is 8% lower than the standalone MCFC system.

References

References
1.
Angelino
,
G.
, and
Colonna di Paliano
,
P.
,
2000
, “
Organic Rankine Cycles (ORCs) for Energy Recovery From Molten Carbonate Fuel Cells
,”
Proceedings of the 35th Intersociety Energy Conversion Engineering Conference
,
Las Vegas, NV
, July 24–28.
2.
Angelino
,
G.
, and
Colonna di Paliano
,
P.
,
2000
, “
Air Cooled Siloxane Bottoming Cycle for Molten Carbonate Fuel Cells
,” Fuel Cell Seminar, Portland, OR, October 30–November 2.
3.
Remick
,
R. J.
,
Wheeler
,
D.
, and
Singh
,
P.
, “
MCFC and PAFC R&D Workshop Summary Report
,” U. S. DOE, January 2010, http://www1.eere. energy.gov/
4.
Campanari
,
S.
,
Iora
,
P.
,
Macchi
,
E.
, and
Silva
,
P.
,
2007
, “
Thermodynamic Analysis of Integrated MCFC/Gas Turbine Cycles for Sub-MW and Multi-MW Scale Power Generation
,”
ASME J. Fuel Cell Sci. and Technol.
,
4
, pp.
308
316
.10.1115/1.2744051
5.
Di Pippo
,
R.
,
2005
,
Geothermal Power Plants: Principles, Applications and Case Studies
,
Elsevier
,
New York
.
6.
Aspen Technology Inc.
,
2011
, Aspen Plus v. 7.3, Burlington, MA.
7.
The MathWorks Inc.
,
2011
, MATLAB 7.12, Natick, MA.
8.
Moreno
,
A.
,
McPhail
,
S.
, and
Bove
,
R.
,
2008
, “
International Status of Molten Carbonate Fuel Cell (MCFC) Technology
,” Joint Research Centre–Institute for Energy, JRC Scientific and Technical Report EUR 23373 EN, European Commission, Luxembourg.
9.
FuelCell Energy
,
2011
, private communication.
10.
FuelCell Energy
,
2010
,
DFC3000: Direct FuelCell Power Plant Applications Guide
,
FuelCell Energy
, Danbury, CT.
11.
Lai
,
N. A.
,
Wendland
,
M.
, and
Fischer
,
J.
,
2011
, “
Working Fluids for High-Temperature Organic Rankine Cycles
,”
Energy
,
36
, pp.
199
211
.10.1016/j.energy.2010.10.051
12.
Angelino
,
G.
, and
Invernizzi
,
C. M.
,
1993
, “
Cyclic Methylsiloxanes as Working Fluids for Space Power Cycles
,”
ASME J. Sol. Energy Eng.
,
115
, pp.
130
137
.10.1115/1.2930039
13.
Drescher
,
U.
, and
Brüggemann
,
D.
,
2007
, “
Fluid Selection for the Organic Rankine Cycle (ORC) in Biomass Power and Heat Plants
,”
Appl. Therm. Eng.
,
27
, pp.
223
228
.10.1016/j.applthermaleng.2006.04.024
14.
Angelino
,
G.
, and
Invernizzi
,
C.
,
2003
, “
Experimental Investigation on the Thermal Stability of Some New Zero ODP Refrigerants
,”
Int. J. Refrig.
,
26
(
1
), pp.
51
58
.10.1016/S0140-7007(02)00023-3
15.
Zyhowski
,
G. J.
, “
Honeywell Refrigerants Improving the Uptake of Heat Recovery Technologies
,” http://www.honeywell-orc.com/wp-content/uploads/2011/09/Honeywell-Refrigerants-Improve-Uptake-Heat-Recovery-Technologies.pdf
16.
Schroeder
,
D. J.
, and
Leslie
,
N.
,
2010
, “
Organic Rankine Cycle Working Fluid Considerations for Waste Heat to Power Applications
,”
ASHRAE Trans.
,
116
(
Part 1
), pp.
525
533
.
17.
Andersen
,
A.
, and
Bruno
,
T.
,
2005
, “
Rapid Screening of Fluids for Chemical Stability in Organic Rankine Cycle Applications
,”
Ind. Eng. Chem. Res.
,
44
, pp.
5560
5566
.10.1021/ie050351s
18.
Havens
,
V. N.
,
Ragaller
,
D. R.
,
Silbert
,
L.
, and
Miller
,
D.
,
1987
, “
Toluene Stability Space Station Rankine Power Systems
,”
Proceedings of the 22nd Intersociety Energy Conversion Engineering Conference (IECEC)
, Philadelphia, PA, August 10–14.
19.
van Buijtenen
,
J. P.
,
2009
, “
The Tri-O-Gen Organic Rankine Cycle: Development and Perspectives
,”
Power Eng.
,
13
(
1
), pp.
4
12
.
20.
Ginosar
,
D. M.
,
Petkovic
,
L. M.
, and
Guillen
,
D. P.
,
2011
, “
Thermal Stability of Cyclopentane as an Organic Rankine Cycle Working Fluid
,”
Energy Fuels
,
25
(
9
), pp.
4138
4144
.10.1021/ef200639r
21.
Calderazzi
,
L.
, and
Colonna
,
P.
,
1997
, “
Thermal Stability of R-134a, R-13I1, R-7146, R-125 Associated With Stainless Steel as a Containing Material
,”
Int. J. Refrig.
,
20
, pp.
381
389
.10.1016/S0140-7007(97)00043-1
22.
Colonna
,
P.
,
Nannan
,
N. R.
,
Gurdone
,
A.
, and
Lemmon
,
E. W.
,
2006
, “
Multiparameter Equations of State for Selected Siloxanes
,”
Fluid Phase Equilib.
,
244
, pp.
193
211
.10.1016/j.fluid.2006.04.015
23.
Colonna
,
P.
,
Nannan
,
N. R.
, and
Gurdone
,
A.
,
2008
, “
Multiparameter Equations of State for Siloxanes: [(CH3)3-Si-O1/2]2-[O-Si-(CH3)2]i=1,…,3, and [O-Si-(CH3)2]6
,”
Fluid Phase Equilib.
,
263
(
2
), pp.
115
130
.10.1016/j.fluid.2007.10.001
24.
Prabhu
,
E.
,
2006
, “
Solar Trough Organic Rankine Electricity System. Stage 1: Power Plant Optimization and Economics
,” Subcontract Report No. NREL/SR-550-39433.
25.
Angelino
,
G.
,
Invernizzi
,
C.
, and
Macchi
,
E.
,
1991
, “
Organic Working Fluid Optimization for Space Power Cycles
,”
Modern Research Topics in Aerospace Propulsion
,
Springer-Verlag
,
New York
.
26.
Colonna di Paliano
,
P.
,
1996
, “
Fluidi di Lavoro Multi Componenti Per Cicli Termodinamici di Potenza (Multicomponent Working Fluids for Power Cycles)
,” Ph.D. thesis, Politecnico di Milano, Milano, Italy.
27.
Leslie
,
N. P.
,
Zimron
,
O.
,
Sweetser
,
R. S.
, and
Stovall
,
T. K.
,
2009
, “
Recovered Energy Generation Using an Organic Rankine Cycle System
,”
ASHRAE Trans.
,
115
(
Part I
), pp.
220
230
.
28.
Lemmon
,
E. W.
,
Huber
,
M. L.
, and
McLinden
,
M. O.
,
2010
, “
NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.0
”,
National Institute of Standards and Technology, Standard Reference Data Program
,
Gaithersburg, MD
.
29.
“NIST Chemistry WebBook,”
NIST, http://webbook.nist.gov/chemistry/
30.
Calm
,
J. M.
, and
Hourahan
,
G. C.
,
2011
, “
Physical, Safety and Environmental Data for Current and Alternative Refrigerants
,”
Proceedings of 23rd International Congress of Refrigeration (ICR2011)
, Prague, Czech Republic, August 21–26.
31.
Papadopoulos
,
A. I.
,
Stijepovic
,
M.
, and
Linke
,
P.
,
2010
, “
On the Systematic Design and Selection of Optimal Working Fluids for Organic Rankine Cycles
,”
Appl. Therm. Eng.
,
30
, pp.
760
769
.10.1016/j.applthermaleng.2009.12.006
32.
Maizza
,
V.
, and
Maizza
,
A.
,
1996
, “
Working Fluids in Non-Steady Flows for Waste Energy Recovery Systems
,”
Appl. Therm. Eng.
,
16
(
7
), pp.
579
590
.10.1016/1359-4311(95)00044-5
33.
Chen
,
H.
,
Goswami
,
D. Y.
, and
Stefanakos
,
E. K.
,
2010
, “
A Review of Thermodynamic Cycles and Working Fluids for the Conversion of Low-Grade Heat
,”
Renewable Sustainable Energy Rev.
,
14
, pp.
3059
3067
.10.1016/j.rser.2010.07.006
34.
Marciniak
,
T. J.
,
Krazinski
,
J. L.
,
Bratis
,
J. C.
,
Bushby
,
H. M.
, and
Buyco
,
E. H.
, “
Comparison of Rankine-Cycle Power Systems: Effects of Seven Working Fluids
,” Argonne National Laboratory Report No. ANL/CNSV-TM—87.
35.
Turboden s.r.l.
, http://www.turboden.eu
36.
Martelli
,
E.
,
Nord
,
L. O.
, and
Bolland
,
O.
,
2012
, “
Design Criteria and Optimization of Heat Recovery Steam Cycles for Integrated Reforming Combined Cycles With CO2 Capture
,”
Appl. Energy
,
92
, pp.
255
268
.10.1016/j.apenergy.2011.10.043
37.
Box
,
M. J.
,
1965
, “
A New Method for Constraint Optimization and a Comparison With Other Methods
,”
Comput. J.
,
8
, pp.
42
52
.10.1093/comjnl/8.1.42
38.
Stijepovic
,
M. Z.
,
Linke
,
P.
,
Papadopoulos
,
A. I.
, and
Grujic
A. S.
,
2012
, “
On the Role of Working Fluid Properties in Organic Rankine Cycle Performance
,”
Appl. Therm. Eng.
,
36
, pp.
406
413
.10.1016/j.applthermaleng.2011.10.057
39.
Macchi
,
E.
,
1977
, “
Design Criteria for Turbines Operating With Fluids Having a Low Speed of Sound in Closed Cycle Gas Turbines
,”
Lecture Series 100 on Closed Cycle Gas Tubines
,
Von Karman Institute for Fluid-Dynamics
,
Bruxelles
.
40.
Lozza
,
G.
,
Macchi
,
E.
, and
Perdichizzi
,
A.
,
1982
,“
On the Influence of the Number of Stages on the Efficiency of Axial-Flow Turbines
,”
27th International Gas Turbine Conference and Exhibition
,
London
, April 18–22.
41.
Craig
,
H. R. M.
, and
Cox
,
H. J. A.
,
1970
, “
Performance Estimation of Axial Flow Turbines
,”
Proc. Inst. Mech. Eng.
,
185
, pp.
407
424
.10.1243/PIME_PROC_1970_185_048_02
42.
Bronicki
,
L. Y.
,
1999
, “
Organic Rankine Cycle Power Plant, for Waste Heat Recovery
,”
13th Symposium on Industrial Applications of Gas Turbines
,
Banff, Alberta, Canada
, October.
43.
“Costi di Produzione di Energia Elettrica da Fonti Rinnovabili,”
Rapporto Commissionato da AEEG al Politecnico di Milano - Dipartimento di Energia, Dicembre
2010
, http://www.autorita.energia.it/allegati/docs/11/103-11arg_rtalla.pdf
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