Other Factors Affecting Choice of Pressure

Although it is the simplest to quantify, the voltage boost is not the only benefit from operating at higher pressure. Similarly, loss of power to the compressor is not the only loss. 

On the negative side there are the issues of size, weight, and cost. However, it must be borne in mind that some sort of air blower for the reactant air would be needed anyway, so it is the extra size, weight, and cost of higher pressure compressors compared to lower pressure blowers that is the issue. The practical issue of product availability means that this difference will often be quite small for fuel cells of power in the region of tens of kilowatts. 

In practice, most small systems ( 1 kW) operate at approximately ambient air pressure. It is the larger systems ( 5 kW) that usually operate at higher pressure. 

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