Concern over the effects of pollution caused by the burning of fossil fuels has led to increased interest in alternative forms of energy, and one of the main areas of research is in developing automobile engines that produce low levels of pollution. Lowering levels of pollution can be done in a variety of ways; two of the most promising sources of clean energy are electric and hydrogen power.
Electric vehicles
Vehicles powered by electricity are often thought of as a new development, but as long ago as 1837, Robert Davidson of Aberdeen, Scotland, built an electric carriage powered by a crude iron–zinc battery and driven by a very simple electric motor, which contained all the basic elements of the modern electric vehicle.
The advent of the lead–acid battery allowed the first commercial battery-operated vehicle to be introduced in 1881 by the Paris Omnibus Company. London had its first electric bus in 1888, and the world’s first mechanically propelled taxicabs, were built in 1897 by W. C. Bersey for the London Electric Cab Co. Ltd., and operated for two years.
The most commonly used fuel for vehicles is oil, in the form of gasoline, diesel fuel, or aviation fuel. Oil is a nonreplenishable resource, and oil-burning engines are complex, noisy, and pollution-creating. Electricity, however, is available from many sources and can provide quiet, vibration-free transport without creating pollution. Electric vehicles may be divided into two classes: those that are continuously fed electric power from an external source (such as electric trains, trams, trolley buses, and fairground dodgem cars) and those that carry their energy source internally. Externally powered electric vehicles normally pick up their power from either an electrified rail or an overhead conductor. Some London commuter trains use both—they pick up current from an electrified third rail as they run through the city subway network, but once they break the surface on the edge of town, a pantograph is raised to make contact with an overhead wire that provides the necessary power during the rural portion of their journey.
Internally powered electric vehicles present severe design problems in many applications. They stem from the amount of energy needed to accelerate the vehicle, allow it to climb hills, and overcome wind and frictional resistance. Using traditional lead–acid batteries, an automobile with performance comparable to its gasoline-driven equivalent would have a very limited range. The range cannot easily be extended by adding more batteries, since the extra weight will demand more power for acceleration and climbing and therefore result in only a small increase in range. Some automobile manufacturers have attempted to produce electrically powered versions of standard production vehicles, but these typically need to fill most of the trunk and/or rear passenger space with batteries. The weight of these batteries often results in poor ride and handling characteristics. Since electric traction motors tend to be more efficient than gasoline engines, they produce less waste heat and so cannot be used to supply interior heating requirements. If interior heating or air-conditioning is needed, a lot more battery power will be required.
There are some applications where poor acceleration, low top speed, and lack of range are unimportant. A number of specialized vehicles have been designed to exploit these areas, including local delivery vans, golf buggies, wheelchairs, and mobile industrial robots. A lot of research is being directed toward producing a small, electric-powered personal commuting vehicle. Gasoline-driven vehicles are at their most inefficient when used for short journeys through heavy traffic, and they bring problems of congestion both on roads and in parking lots. If a suitable electric vehicle could be produced, it would bring substantial environmental benefits but consumers cannot be expected to move to a vehicle that has a performance and convenience significantly worse than they get now.
