1. Purpose of the development
Fuel cell systems are becoming the focus of worldwide attention as they are considered to be a most promising alternative drive concept in the future. They will effectively reduce CO2 emission as a post- fossil fuel. They feature extremely low emission. Additionally fuel cells can work on a variety of renewable, alternative fuel sources. For example, it has already been applied to generators including those on space shuttles. In the technical field of automobiles in particular, fuel cells are expected as an energy supply system of the next generation in place of conventional internal combustion engines. The possibility of practical application of fuel cells to motorcars has risen recently with the progress of proton exchange membrane fuel cells (PEFC).
On the other hand, the railway is superior to other transportation facilities due to its less energy consumption. Moreover, it is required to strengthen the competitiveness of the railway by reducing maintenance costs, preserving the ground environment along railway lines and restricting emission from running vehicles or construction of railways. For example, diesel multiple units (DMUs) run on non-electrified lines to cause a noise problem, CO2 emission and exhausting particle pollutants. The advantageous properties of fuel cells could help to solve or reduce the impact of these problems.
2. Outline of R&D on fuel cell railway vehicles
Hereunder explained is a technical outline of the development of fuel cell railway vehicles. To preserve the environment on a global scale, the energy source for railway vehicles shall be converted into non-emission fuels.
First, the fuel cell vehicle will be a candidate to substitute diesel vehicles that are directly dependent on petroleum. Second, fuel cell vehicles may create a new low-cost railway system which doesn't need electrification unlike the present electric vehicles. A concrete development of fuel cell vehicles has never been seen yet, though there would have been an idea to use fuel cells on railway vehicles.
The feature of the traction system for electric railway vehicles is different from that of automobiles in terms of output power, expected equipment life and other factors. Therefore, on-board fuel cells must be developed for railways. Issues on development of fuel cell railway vehicles are shown below (Fig.1).
|1)||We have to select a fuel for fuel cells. There are three candidates, pure hydrogen, liquid natural gas and methanol. Special reformers are additionally needed to chemically generate hydrogen for fuels other than pure hydrogen.|
|2)||Since railway vehicles need a large amount of power, fuel cell units are required in quantities for propulsion when compared with automobiles. An appropriate control system is inevitable to generate high current and voltage and drive induction motors.|
|3)||As railway vehicles are generally used for 20 years or over, fuel cell systems are expected to operate approximately for the same time lengths. The durability of fuel cells in cyclic uses has to be confirmed for such a long period of time.|
|4)||To realize fuel cell vehicles, safety of the systems shall be ensured and manufacturing costs of fuel cells shall be reduced considerably.|