Page 74 - Introduction to Transfer Phenomena in PEM Fuel Cells

Charge Transfer Phenomena 63
2.2.7. Theoretical efficiency
The efficiency of any energy system is defined as the ratio of the energy
collected (useful) to the energy supplied. In the case of the fuel cell (see
Figure 2.1), the energy received is the electrical energy produced by the cell
and the energy supplied to the system is the enthalpy of hydrogen, more
specifically the HCV of hydrogen [BAR 05, OHA 09, SPI 07].

Figure 2.1. Energy balance for a fuel cell

The efficiency of the fuel cell is written as:

 Electrical Energy Produced  Δ G
η %100×   = 100× [2.42]
=
 Energy released by the reaction  Δ H
The efficiency can also be written in the form:

  Δ  S 
η= 100× 1 T     [2.43]
−
%
  Δ H  
The relationship defining the efficiency of a fuel cell in the case where
the produced water is in the liquid state, the HCV value is used, it is written
as:

237.34
=
η % 100× ≈ 83% [2.44]
286.2