FUEL CELLS - Desktop Study

 4. INFLUENCES ON FUEL CELL EFFICIENCY

As with any energy conversion device, fuel cell efficiency is affected by different factors.

Temperature
The fuel cell operates at a specific operating temperature. Operating above it can destroy the cell and operating below it can reduce the reaction rate and also the efficiency. High temperature fuel cells need to use some fuel to be warmed up before operation starts. Also high temperature fuel cells are usually more efficient than low temperature ones.

Nature of electrolyte
The efficiency of the fuel cell will be affected depending of the type of electrolyte and catalysts used. Platinum electrodes give the best efficiency but are also the most expensive. Research is active at the moment to improve efficiency without using expensive material.

Voltage
The fuel cells deliver a typical voltage around 1.2V. The voltage is also dependent of the temperature of the fuel cell. Operating at a voltage below this reduces the reaction rate and also the efficiency.

Fuel side
On the fuel side, operating current is a factor influencing the efficiency of the fuel cell. Also the flow rate of reactance (H2) has an influence on the reaction rate and fuel cell efficiency.

Air side
On the air side, the operating pressure and flow rate of oxidant (O2) influences the fuel cell efficiency. Therefore it is suggested to use twice the stochiometric flow rate of oxidant (air) to be sure to complete the reaction (10.5% instead of 21%)

Also the following factors do not influence the fuel cell efficiency

- Size of the plant
- Load change (above 40% of rated load)

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