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Fuel Cell Vehicles (FCV)
The solid molecular type fuel cell is one of the next generation power sources that are estimated as the most promising. This effective power source generates electric energy through the reaction of hydrogen and oxygen (air).
This source is expected to attain a high efficiency of 50 to 60 % on the hydrogen basis in ultra low emission vehicles. Hydrogen is extracted from petroleum fuels or natural gas. For the storage and transportation of the hydrogen thus manufactured, there are three methods by:
- Storing hydrogen in high-pressure gas cylinders;
- Liquefying hydrogen at an ultra low temperature;
- Storing hydrogen inside absorbing materials.
All these three methods, however, have a common problem of difficult installation of the hydrogen storage and transportation equipment. Hence, other types of systems are under study where vehicle-mounted reforming equipment is used to extract hydrogen from liquid fuel such as methanol, or gasoline of high purity. Methanol needs a reforming temperature of 300 while hydrocarbon base fuels need a temperature of 700 to 800 which needs the secondary battery to cope with cold temperature start-up and responsiveness of the system, which will result in increase in the whole system complexity.
The direct methanol fuel system (DMFC), which directly reforms methanol internally, appears promising in concept for future performance improvement since the system can be more simplified.
Table 6.8 shows a comparison of efficiency of two cases: the case where hydrogen or methanol is generated from natural gas versus the case where gasoline is reformed. Some experts say that the gasoline reforming will provide more benefits in view of cost and supply systems, but this type is not always effective in curbing the petroleum consumption or reduction of CO2 emissions. In the future, solar energy, wind-generated electric power and regenerable energy such as biomass may be used to produce hydrogen.
However, it is necessary to ascertain how much hydrogen supplied from these resources can replace the natural resources fuels. The author believes that one of the yardsticks to assess future technological scenarios shall be well-to-wheel efficiency - the overall efficiency of an energy source, from the time it is extracted from the ground to when it actually runs the wheels of a vehicle. Another yardstick is the environmentally clean level. This is based on the Life Cycle Assessment (LCA) method for the analysis and evaluation of the environmental impacts of vehicles.
Currently, we have more difficult and important issues to solve such as:
- Much higher performance for each factor;
- Smaller size of the total system;
- Increased durability and reliability;
- Significant cost reduction;
- Selection of the best fuel;
- Establishment of hydrogen-supply facilities.
Expansion of the hydrogen supply infrastructure network is especially an important prerequisite for the success of fuel cell motor vehicles.
In search of practical issues of fuel cell vehicles, the State of California of the United States began, in November 2000, the California Fuel Cell Partnership (CaFCP) to perform test drives of passenger cars and buses in cooperation with automobile manufacturers. Daimler Chrysler AG announced to start a limited sale of its gNECAR 5h using methanol fuels in 2004. Although several companies, both Japanese and foreign, have announced to launch their FCVs into the market. But a real spread of such vehicles in the market will take another ten to twenty years, depending on the supply - demand balance of oil.
Reference
Book title: EV Handbook
Written by: EV Handbook Publisher's Group
Published by: Maruzen Co., Ltd. (URL http://www.maruzen.co.jp)
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