IN AMERICA, electric vehicles are on the threshold of mounting a major
challenge to the internal combustion engine. But just as electric cars are about
to become a commercial prospect, Britain鈥檚 lead in the battery technology needed
to power them has disappeared.
The developers of the sodium-sulphur battery, Silent Power of Runcorn in
Cheshire, closed this week. Although American tests show that the battery worked
as it was supposed to, Silent Power鈥檚 German owners, RWE, decided to pull the
plug on it鈥攁nd on 25 years of British research.
Guy Hitchcock, a researcher in alternative fuels at the government鈥檚 Energy
Technology Support Unit at Harwell鈥攖he site of some of the original
research on sodium-sulphur batteries, says: 鈥淚t certainly did not fail for
technological reasons.鈥�
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One of the key problems of electric vehicles is that the conventional
lead-acid batteries are very heavy. The sodium-sulphur battery was one of the
most promising alternatives because weight for weight, it packed three times the
power of a lead-acid battery.
It all began in the early 1970s, with three British teams separately trying
to develop a sodium-sulphur battery. British Rail鈥檚 efforts were being
backed by the Department of Transport, while research at the the UK Atomic
Energy Authority at Harwell was funded by the Department of Energy, and the
Department of Industry was supporting work by the battery-maker, Chloride.
At the government鈥檚 prompting, the researchers pooled their resources and set
up a new company to develop the battery called Chloride Silent Power. The
company was backed by Chloride and the Electricity Council, so the research was
effectively subsidised by the electricity generating and distribution
industry.
The company鈥檚 first attempts were not a success. Sodium-sulphur batteries
operate at about 350 掳C and preventing leaks of molten sodium has always
been a major problem. Initially, the company鈥檚 designers decided to opt for a
relatively small number of large cells in the battery to minimise the number of
seals.
But the design was not successful. If one cell in the battery
failed鈥攁nd they did regularly鈥攖he vehicle suffered a dramatic loss
of power. Trials of two parcel vans in a 拢500 000 research programme
funded by the Department of Industry were a fiasco. The research was very nearly
halted.
But in 1984 Chloride鈥檚 chief engineer, Peter Bindin, turned the design
philosophy on its head (鈥淏atteries for the van about town鈥�, New
快猫短视频, 17 July 1986, p 37). He developed a 2-volt sodium-sulphur cell
that was only slightly larger than a torch battery. When 250 small cells were
tied up together in a vehicle battery, the failure of the odd cell had only a
trivial effect on the battery鈥檚 power output.
The strategy paid off in September 1986 when the US Department of Energy
awarded Chloride a five-year $2.7 million contract to help develop the
sodium-sulphur battery. The battery was tested at the Argonne National
Laboratory, Illinois, as part of the US government鈥檚 backing for battery
research.
The test found that 鈥渢he battery satisfies all specifications of the
contract, including weight, volume, energy and power鈥�. In 1992, Kevin Myles,
director of Argonne鈥檚 electrochemical technology, said that the battery showed
promise.
The privatisation of Britain鈥檚 electricity industry in the late 1980s,
however, dampened these hopes. A spokesman for Silent Power says that the
electricity industry withdrew its support for the research and in 1992 the
company, renamed Silent Power, was sold to RWE.
Brian Roden, the director of the Electric Vehicle Association, says the
battery successfully passed all German safety tests, including being dropped
from 15 metres onto a tree trunk. The tree trunk test鈥攕imulating the
impact of a vehicle with a telegraph pole鈥攚as designed to find out whether
the battery caught fire. Not only did it not burn, says Roden, but it kept
working.
Late last year, RWE decided to close the company at the end of May, if a
buyer could not be found. Last month most of the company assets were sold at an
auction鈥攁nd with them went the last British hopes of a lead in advanced
battery technology.