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Research Papers

# Energy System and Thermoeconomic Analysis of Combined Heat and Power High Temperature Proton Exchange Membrane Fuel Cell Systems for Light Commercial Buildings

[+] Author and Article Information
Whitney G. Colella

Pacific Northwest National Laboratory,
P.O. Box 999,
Richland, WA 99352
e-mail: wcolella@alumni.princeton.edu

Siva P. Pilli

Pacific Northwest National Laboratory,
P.O. Box 999,
Richland, WA 99352

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL SCIENCE AND TECHNOLOGY. Manuscript received April 28, 2012; final manuscript received May 23, 2012; published online March 16, 2015. Editor: Nigel M. Sammes.

J. Fuel Cell Sci. Technol 12(3), 031008 (Jun 01, 2015) (12 pages) Paper No: FC-12-1032; doi: 10.1115/1.4007273 History: Received April 28, 2012; Revised May 23, 2012; Online March 16, 2015

## Abstract

The United States Department of Energy’s Pacific Northwest National Laboratory is teaming with industry to deploy and independently monitor 5-kilowatt-electric (kWe) combined heat and power (CHP) fuel cell systems (FCSs) in light commercial buildings. Results of an independent evaluation of manufacturer-stated engineering, economic, and environmental performance of these CHP FCSs are presented here. An important contribution of this paper is the precise definition and development of these essential terms for quantifying distributed CHP generator energy use within buildings: (1) electricity and heat utilization, (2) electrical and heat recovery efficiencies, (3) in-use electrical and heat recovery efficiencies, (4) percentage usage of electricity, and (5) percent usage of recoverable heat. Key additional parameters evaluated include the average cost of the CHP FCSs per unit of power and per unit of energy, the change in greenhouse gas (GHG) and air pollution emissions with a switch from conventional power plants and furnaces to CHP FCSs, the change in GHG mitigation costs from the switch, and the change in human health costs from air pollution. CHP FCS heat utilization is expected to be under 100% at several installation sites; for six sites, during periods of minimum heating demand, the in-use CHP FCS heat recovery (HR) efficiency based on the higher heating value of natural gas is expected to be only 24.4%. From the power perspective, the average per-unit cost (PUC) of electrical power is estimated to span $15–19,000/kWe (depending on site-specific installation, fuel, and other costs), while the average PUC of electrical and HR power is$7,000–9,000/kW. Regarding energy, the average PUC of electrical energy is $0.38–$0.46/kilowatt-hour-electric, while the average PUC of electrical and HR energy is $0.18–$0.23/kWh. GHG emissions were estimated to decrease by one-third after replacing a conventional system with a CHP FCS. GHG mitigation costs were also proportional to changes in GHG emissions. Estimated human health costs from air pollution emissions decreased by a factor of 1000 with changing to CHP FCS. Reported for the first time here is the derivation of the PUCs of power and energy for a CHP device from both standard and management accounting (MA) perspectives. Results show that the average PUC of combined electrical and HR power is equal to the average PUC of electric power applying an MA approach, and also equal to the average PUC of HR power applying an MA approach. Similar relations hold for the average PUC of energy. Results presented here demonstrate the value of using the equations herein for economic analyses of CHP systems to represent the average PUC of electrical power, HR power, or both, and for energy.

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## Figures

Fig. 1

Percentage of building electricity demand supplied by the fuel cell systems

Fig. 2

Expected electricity utilization of fuel cell system electricity by building sites

Fig. 3

Percentage of building heat demand supplied by the fuel cell systems

Fig. 4

Expected heat utilization of fuel cell system recoverable heat by building sites

Fig. 5

Manufacturer-stated cost distribution for an average CHP FCS in deployed fleet

Fig. 6

Combined capital and installation costs of CHP FCSS compared with gas turbines

Fig. 7

Breakdown of cost per unit of installed electrical power capacity

Fig. 8

Breakdown of cost per unit of installed electrical and heat recovery power capacity

Fig. 9

Breakdown of the cost per unit of installed electrical energy capacity

Fig. 10

Breakdown of cost per unit of electrical and heat recovery energy capacity [41,42,43]

Fig. 11

Capital and installations costs versus installed capacity of various CHP FCS

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