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Electric Traction

first electric vehicle

                 Battery-powered vehicle, 1842

Faraday built the first electric motor in 1831. It was purely experimental, but more practical ones followed rapidly, Thomas Davenport in the United States patented a small battery-powered electric motor in 1837 and apparently made many of them for experimental purposes. In 1842, Robert Davidson, a Scotsman, built the battery-powered rail vehicle shown above. It weighed five tons and had under one horse-power to move it, so although historically significant, it was far from being a commercial proposition.

Development continued during the 1840’s but could find no practical applications for many years since battery technology had not yet progressed sufficiently. The high cost of basic materials for batteries continued to slow progress for some time and their poor power-weight ratio discouraged their use in vehicles. The pressure to develop small electric motors for appliances may have been reduced during the second half of the century by small hot air motors operating on the Sterling Cycle and by rather larger water motors attached to the household tap. Small electric motors only came into their own following the installation of local power distribution systems towards the end of the century.

Electricity as an efficient form of motive power for public transport had to wait for the invention of the dynamo (1870) and the subsequent development of power distribution systems, whose first application, incidentally, was for tramways. In 1881, Siemens provided equipment for the first street tramway system near Berlin and in 1882 built a primitive trolley bus running on a 500m stretch of road (below).

trolleyfirst

Tramway systems followed during the late ’80’s in the US and some years later in Europe. By the turn of the century they dominated urban transport. Unfortunately, trams did take up a lot of street room and as traffic increased, were a major cause of congestion. As the motor car manufacturers and user lobbies gained power they began to be replaced by more flexible but of course more noisy and polluting motor buses.

The trolleybus was developed as a quite successful compromise well before the first world war to provide more flexibility and reduce congestion. Eventually, however, the lobbies triumphed and the petrol-engined bus became universal, pushing electricity completely off the scene during the ’50’s. Fortunately it never expired completely: many European countries retained a tramway network and others a sketchy trolleybus service while local deliveries continued using small electric vehicles until quite recently.

Around the turn of the last century battery development reached the point where it could at least provide power to move appreciably more than its own weight. Electric cars proliferated and around the turn of the century provided a very attractive alternative to the then noisy and unreliable motorcars for urban driving. Recharging centres were put in place in Paris, since in general, domestic wiring (when it existed) was not robust enough in the 1890’s.

electriccars1898 However, as the car became more reliable and considerably faster, and of course capable of going more or less anywhere there was a decent road, the electric car lost its competitive edge and with it, the investments that would have ensured its survival.

The use of the electric motor as an autonomous power source for buses was still hindered by the poor power-weight ratio compared to the ever-improving petrol engine, which of course limited payload. Hybrid buses were put into service before the first world war in London, apparently quite successfully. These were of course, nothing like today’s, no regenerative braking nor switching between the two power sources and so on. They were thus rather inefficient. Their advantage and of course that of the trolleybus over buses lay in smoothness and silence (no mean advantage with the savage clutches, whining gearboxes, and the absence of syncromesh, which made for slow and noisy gear changes). It was fun though to take a bus in those days and their drivers, crammed in their tiny cockpits and surrounded by levers and instruments (generally not working) were as gods to us schoolboys.

Electricity is now returning. Battery development, necessary for complete autonomy has been slow but has accelerated recently. Even today, to compete with conventional vehicles, electric motors are normally combined with a heat engine in the hybrid format to charge the battery and provide supplementary power. However, there is little doubt that continued battery development allied to a complete network of chargers will, perhaps in twenty-five years or so, see out the heat engine, at least in the countries able to provide reasonably low-cost electricity, preferably non-thermal) and a charging infrastructure. However, the poorer countries will continue to depend on it for the foreseeable future, hopefully in vehicles designed for their use.

. As cleaner and renewable sources of energy provide a greater share of electric power it will come again to dominate as a mobile power source in urban areas. Tramways are proliferating in the richer countries, providing more comfortable and faster urban transport when separated from traffic. Hybrid bus operation is ideal on less dense routes, requiring frequent stops, and needing smooth acceleration. Interest is growing in trolley buses, but their lack of system-wide flexibility and proliferation of overhead wires makes one wonder whether hybrid buses may not be more cost-effective. Hybrids for individual use, although promising, have been somewhat oversold and  are only cost-effective at the moment in large and expensive vehicles whose owners can afford to pay extra for driving comfort or for those who cover long distances annually.

Small electric motors with rechargeable batteries have enormous potential in poorer countries where light vehicles operating over short distances and cheap to buy and run and of above all non-polluting are needed for passenger and goods transport in the enormous cities. In Chinese cities electric scooters and light goods carriers are already numerous. Older vehicles are even been retrofitted, implying an interesting path for small enterprise development. The positive impact on air pollution and global warming will be considerable as their use spreads to other developing countries. The transition will be long and will need considerable help. We should now, at the very least, stop putting pressure on poor countries to reduce vehicle emissions. We caused the problem: why should they pay?