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SPECIAL SECTION ON THE 2ND EUROPEAN FUEL CELL TECHNOLOGY AND APPLICATIONS CONFERENCE

# Basic Electrochemical Thermodynamic Studies of Fuel Cells and Fuel Cell Hybrids

[+] Author and Article Information
M. Williams

University of Utah, Salt Lake City, UT 84112

T. Horita, K. Yamagi, N. Sakai, H. Yokokawa

National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8565, Japan

J. Fuel Cell Sci. Technol 6(2), 021303 (Feb 27, 2009) (4 pages) doi:10.1115/1.3080546 History: Received November 15, 2007; Revised December 07, 2007; Published February 27, 2009

## Abstract

It is important to understand the maximum possible thermal efficiency a device is capable of obtaining and then what of this it actually achieves. In this paper it is shown that the thermal efficiency is a product of the voltage efficiency and the maximum possible thermal efficiency. One can mathematically demonstrate that for any elemental direct anodic oxidation reaction for a simple hybrid system, any fuel cell, and any operating temperature, any pressure, the maximum reversible work is equal to the free energy of reaction at the standard state. This is useful in defining an intrinsic fuel cell exergetic efficiency. An equation for thermal efficiency as a product of exergetic efficiency and maximum possible thermal efficiency is developed and presented for loosely integrated fuel cell turbine hybrids. From these simple studies alone one would conclude that the efficiency potential of fuel cells is expanded through simple fuel cell turbine hybrids.

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## Figures

Figure 1

Maximum efficiencies

Figure 2

Maximum exergetic efficiency

Figure 3

Simple hybrid system

Figure 4

Maximum efficiencies—high case

Figure 5

Maximum efficiencies—medium case

Figure 6

Maximum efficiencies—low case

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