However, they are now beginning to be used in more ordinary applications, though they are still not in widespread use. They are expensive, and most current applications are for research or where a subsidy has been secured because of their particularly benign environmental properties. Nevertheless, in recent years encouraging progress has been made, and the environmental benefits of fuel cells should soon be much more widely available without the need for massive subsidy.
The principle of the fuel cell is extremely simple. The electricity is produced without rotating machines, and at efficiencies considerably better than those obtained in even the largest fuel-burning engines and power stations. Fuel cells are silent and efficient, even at part loads, and so their advantages are particularly strong when issues of pollution and energy conservation are to the fore. One area where Fuel Cells are set to make a big impact is in Combined Heat and Power systems.
In a combined heat and power (CHP) system a small power station is used to generate electric power AND heat in places like a block of flats or a factory. The heat can be used, unlike in the large power stations where the heat energy is just wasted. This can be done with a diesel generator or a gas turbine, but they have two major disadvantages:-
1) They are noisy
2) They produce a lot of heat, and not enough electricity.
Fuel cells are completely silent, and much more of the energy is converted into electricity. Looking at the figures, the reason for using CHP systems, and fuel cells in particular are clear! Many people simply do not realise how much or our precious energy is being wasted right now!
Large coal, oil or gas power station.
35 % energy to electricity - 65% to heat and thrown away!
Diesel or Gas Turbine CHP system
30% energy to electricity - 50% to heat, some of it used - 20% used to run the system(i.e. lost)
Fuel Cell CHP system
40-45% energy to electricity - 35-40% to useful heat used at the site - 20% used to run the system (i.e. lost)
Fuel cells, with their very high efficiency even at low powers, their silent operation, their simplicity and inherent reliability, are the best type of energy converter for CHP systems - the only trouble is that at the moment they still cost more.
Another very important boost to fuel cell use has been given by recent decisions of some US state governments. A key decision has been that of the State of California, and some other North American states, to require that an ever increasing percentage of new car sales must be "zero emission" - which in practice means electric. Rechargeable batteries are very heavy and take a long time to charge. whcih means that the fuel cell is much to be preferred.
Buses are in many ways even better candidates for fuel cell power than cars, and they have been used very successfully in Canada and the USA. The fact that fuel cells need hydrogen fuel is a problem for the motorist, as it is not readily available, but this problem is more easily solved for buses, since only one point of supply is needed, the bus garage.
The third important area is for mobile equipment. We all like to use mobile phones and portable computers, but for most flexible use we would like very long lasting batteries that can be recharged instantly. The energy density of hydrogen stored in metal hydrides, or in methanol, far exceeds any of the rechargeable battery technologies. Furthermore, hydrogen and methanol "refills" can be virtually instant. This is why there so much research develoment directed at methanol fuel cells.
These then are the main likely uses of fuel cells - in mobile equipment such as phones and "laptop" computers, combined heat and power systems and for electric vehicles.
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