Ultra Light Rail – the Fast Track to Fuel Cells
Introducing Fuel Cells to the Commercial Public Transport Market
Fuel cells are now recognised as a key technology in the process of weaning the modern world from its dependence on fossil fuels and leading it into a new age of alternative energy. The principal obstacle still to be overcome is the high cost of fuel cells. In transport, for example, one kilowatt from a fuel cell costs around $3,000, compared with $30 per kilowatt for an internal combustion engine. Somehow a reduction of two orders of magnitude has to be achieved if fuel cells are to compete with alternatives in the commercial market for transport.
There are two complementary approaches to achieving this reduction. The first and most obvious is to increase the efficiency of the fuel cell in producing electricity from hydrogen. But producing electricity is not an end in itself. It is rather a means to enable us to achieve the end objective, which is to provide people with useful services such as heat, light and mobility. The cost of mobility can therefore be reduced just as much by increasing the energy efficiency of the system in which the fuel cell is used, as by increasing the efficiency of the fuel cell itself.
Ultra Light Rail is a transport system designed to eliminate the two orders of magnitude gap between the fuel cell and the internal combustion engine. The first step is to increase the efficiency of the vehicle system in which the fuel cell is used. This can be done in a number of ways but the most dramatic “step change” in energy efficiency can be achieved by using a vehicle running with steel wheels on steel rails. This immediately reduces the energy requirement by a factor of three, since the lower rolling resistance allows a tram to use only one third of the energy required by a similar sized bus.
Further cost reductions in the vehicle system can be achieved by introducing an on-board energy storage system in a hybrid electric drive train, similar, in principle, to that used in the Toyota Prius and other cars and even in some buses. This makes possible a lower rating for the prime on-board power source which is required only to run at its optimum level, in order to keep the energy storage system topped up. It also allows for the energy from braking to be recaptured and used, rather than dissipated in heat vented to the atmosphere. Still more efficiency can be introduced by integrating the electric motors into the wheels. The overall weight of the vehicle can be reduced by each of these innovations whilst the body itself can be manufactured from carbon fibre composite materials in a monocoque form. The whole process, using standard proven technology, creates a spiralling cost reduction, resulting from each innovative feature.
Using only some of these features, practical test work carried out by Sustraco Ltd, with support from a Carbon Trust grant, has shown that a 25 kilowatt fuel cell would be sufficient to power a light tram with similar capacity to the fuel cell buses tested in London under the EU’s CUTE programme. These buses have done an invaluable job in demonstrating to the public that fuel cells are no different to internal combustion engines in performance and safety. However the buses themselves are grossly inefficient in commercial terms, costing, as they do, some five times as much as a similar diesel bus and requiring 250 kilowatts fuel cell to operate them. The next logical step in commercialising the operation of fuel cell powered public transport vehicles must therefore be to integrate the fuel cell into an energy efficient tram.