The Need for Zero-Emission Transport
EU and G8 leaders declared in 2009 that CO2 emissions must be cut by at least 80% (from 1990 levels) by 2050 in order for atmospheric CO2 to stabilise at 450 parts per million (ppm) and keep global warming below 2°C.1 This level of decarbonisation could require up to 95% decarbonisation of the road transport sector2 – a daunting target. The internal combustion engine (ICE) is not expected to improve more than 30% in efficiency during that timescale3 and the availability and compatibility of alternative biofuels is uncertain; as such it is unlikely that conventional vehicles can meet this target alone. There is an evident need for zero-emission solutions across the full range of car types, from small cars for local use to larger, high-mileage vehicles.

Fuel Cells as a Technology
A fuel cell is similar to a battery in that it generates electricity from an electrochemical reaction. Both batteries and fuel cells convert chemical energy into electrical energy and also, as a by-product of this process, into heat. However, a battery holds a closed store of energy within it and once this is depleted the battery must be discarded, or recharged by using an external supply of electricity to drive the electrochemical reaction in the reverse direction.

A fuel cell, on the other hand, can run indefinitely as long as it is supplied with a source of hydrogen fuel (hence the name) and is similar to an ICE in that it oxidises fuel to create energy; but rather than using combustion, a fuel cell oxidises hydrogen electrochemically in a very efficient way. During the reaction, hydrogen ions react with oxygen atoms to form water; in the process electrons are released and flow through an external circuit as an electric current. The only exhaust is water vapour. The fuel cell type used in the automotive industry is the proton exchange membrane fuel cell (PEMFC), a low-temperature, hydrogen-fuelled cell containing a platinum catalyst; it is the most common type of fuel cell and allows for variable electrical output, ideal for vehicle use.
 

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