In a move tying in with mayor Ken Livingstone's draft Transport and Air Quality Strategies, Transport for London (TfL) recently announced plans to introduce zero emission buses to the capital. London is one of nine European cities taking part in a two-year practical trial in which three hydrogen fuel cell powered Mercedes-Benz Citaro city buses will be implemented into the public transportation system.
The Proton Exchange Membrane fuel cells to be used in the buses rely upon a proton-conducting plastic membrane. This is only tenths of a millimetre thick and has an extremely thin layer of platinum on both sides. It breaks the hydrogen into protons and electrons with the former migrating through the membrane to the oxygen to form water. The excess of electrons on the hydrogen side and the shortage on the oxygen side creates a plus and minus pole. If the two sides of the membrane are connected, an electrical current flows as a result of the voltage difference and this can be used to provide drive energy for the vehicle.
The partners in the London HFC bus project are: TfL; Evobus, the bus division of DaimlerChrysler, which is to manufacture the buses; FirstGroup plc, which will operate the HFC buses and BP - developer and supplier of the hydrogen fuel. The Department for Transport, Environment and the Regions is supporting the project.
40 per cent of the hydrogen for these buses will be produced using renewable energy sources, 40 per cent from natural gas and only 20 per cent from crude oil. "In England it will be solely from natural gas to begin with", says Michael Jones, hydrogen technology manager at BP. "In Barcelona where it's far sunnier, we're looking at introducing photovoltaic solar panels to produce the hydrogen."
The electrochemical reaction of hydrogen and oxygen creates electrical energy, water and heat. The only emission is therefore water vapour. This, coupled with quieter running, will help to reduce environmental problems such as summer smog, disturbance through traffic noise and damage to buildings through emissions. Fuel cells also utilise the energy of the fuel significantly more effectively than spark-ignition engines and therefore achieve higher efficiency levels. Darren Johnson of TfL says: "In order to make a real difference, I hope this is the first of many schemes employing fuel cells, not just in transport, but to power and heat buildings too."
The total cost of the hydrogen fuel cell bus project is estimated at around [euro symbol]90 million. Costs are mainly dominated by fuel cells themselves today and are expected to fall with development and larger production scales.
Around 25kg of hydrogen can be stored on the buses' roofs making distances of up to 250km possible. The maximum speed is approximately 50 miles per hour. It is not yet decided which routes the buses will run but they are expected to be ready to carry passengers by early 2003.