The choice of methanol as the energy source for fuel cell engines has brought developer DBB a step closer to its aim of commercially launching a vehicle by 2004.
The company – a joint venture between Daimler-Chrysler, Ballard Power Systems and Ford – has been in talks with oil companies about the possibility of converting petrol stations to methanol.
Fuel cells work by mixing hydrogen with oxygen to produce electricity and water. But safety concerns about pressurised hydrogen and the cost of developing distribution networks have prompted engine makers to look for other sources of the fuel.
Hydrogen can be extracted from methanol using extraction equipment called a reformer. However, DBBand its development partner, German chemical firm BASF, have struggled to reduce the reformer to a practical size. The total weight of the fuel cell system in the 1997 prototype Necar3 was 760kg, taking up 960 litres of space and weighing the equivalent of ten people. A conventional petrol engine weighs in at about 100kg.
The reformer DBB and BASF are working on uses a catalyst consisting of copper, zinc and aluminium to convert a mixture of water and methanol into hydrogen, carbon monoxide and carbon dioxide. Carbon monoxide from the reformer is further oxidised to carbon dioxide. The reaction takes place at temperatures of 200-350 degrees C.
The challenge in designing a reformer for a fuel cell vehicle is to make it capable of coping with variable loads. The reformation reaction is endothermic, needing heat, which is supplied by a catalytic burner. If the load changes suddenly, heat must be distributed evenly and rapidly to remove a lag between the accelerator pedal being pressed and the engine’s response. This called for the catalyst to be developed to precisely match the reformer.
Fuel cell engines are seen as the key to developing low-emission, clean vehicles as they are quiet and emit no particulates or nitrogen oxides. BASF argues that while methanol still emits the greenhouse gas carbon dioxide, it is environmentally neutral as it can be produced in a cleaner process than other fuels by using vegetable sources. But the most common industrial sources of methanol are natural gas, petroleum residues and coal.