Powering transport with fuel cells

Hydrogen is currently being piloted in the public transport sector on bus fleets in various locations worldwide

Photo by Tom Page

There is no doubt that fuel cells will eventually be a key technology in the hydrogen economy. Hydrogen could represent a useful energy storage medium in the future for transportation, and is currently being piloted in the public transport sector on bus fleets in various locations worldwide. Vancouver is aiming to have the world’s first hydrogen-fuelled bus fleet and a number of UK cities are considering introducing fuel cell powered buses to existing fleets. London is introducing them this year.

Unfortunately hydrogen currently has to be provided from a hydrocarbon source or by using electricity to electrolyse water to provide free oxygen and hydrogen (using hydrogen as an electricity storage and distribution method). When excess renewable electricity is available nationally, then hydrogen can be produced at times of low electricity demand, but until then fuel cells are unlikely to be a major technology for reducing CO2 emissions.

A fuel cell is an electrochemical energy conversion device in which, as a result of the chemical reaction, electricity is produced. The reactants are hydrogen and oxygen and a potentially useful reaction by-product is water. Heat is another potentially useful by-product of the process that can be used in other systems.

Fuel cells have very high efficiencies in converting chemical energy in hydrogen into electrical energy, from 40 per cent to 60 per cent, nearly double that of a typical modern internal combustion engine.

They can be used in large static systems, providing electricity and heat, transport applications, military and portable applications. However, they are still in development as a power source for cars and are not a viable commercial technology at the moment.

In the future, fuel cells could be appropriate at the block, neighbourhood or city scale. However, they should not be seriously considered at the moment except in exceptional circumstances since they require anchor heat loads and a supply of renewably sourced hydrogen as a fuel. This is unlikely to be available until later this century unless produced via an advanced waste treatment or biomass conversion process such as plasma torch pyrolysis with suitable gas reformation plant to produce hydrogen.

Opportunities exist for transport in cities to progressively switch to alternative fuel sources. The use of electric motors which are cheaper to run and emit virtually no local air pollution or noise is an attractive option in the medium and longer term. Sourcing a low carbon or renewable source for the electricity for this option will be central to maximising its positive impact.

Priority: develop a low carbon and renewable energy portfolio
Tags: energy, transport, cities and towns