Efficiency Calculations and Fuel Consumption

As we have seen in Section 6.6, Chapter 6, the efficiency of fuel cells depends on a number of factors, not least the power output. In the case of electric road vehicles driven by PEMFCs, the reasons generally advanced for this form of transportation are  

The first two arguments constitute a powerful case for electric vehicles. The third point is of questionable benefit since it might lead to an increase in the number of accidents involving pedestrians. The final two points merit deeper consideration they are closely inter-related. 

When comparing different transportation fuels, different motive-power units and different vehicles, it is essential to speak of well-to-wheels efficiency. This concept embraces  

It is well known that ICEVs have rather low on-the-road efficiencies (currently 20-25%, at best), but their overall performance is in fact even lower when account is taken of the energy used in the extraction, transport and refining of the oil and then in the delivery of the petrol. Together, these extra losses typically amount to around 13% i.e., a net efficiency of 87%). On multiplying the two values, the overall well-to-wheels efficiency is reduced to 17—22%. 

Electrochemical generators, such as fuel cells, are certainly more efficient than internal combustion engines, but there is considerable confusion over the 

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