A good briefing in The Economist of 5 September about developments in batteries for electric cars.  The lithium-ion battery is the leading technology, having entered the market in small devices like mobile phones and laptops, next into niche markets like the high priced Tesla sports car (0 to 60mph in 3.7 secs), and then?  Three possibilities:

o    Small thrifty city cars such as the Mitsubishi i-MIEV with a range of 160km and  the costs of a full charge of a few £.
o    Add a petrol-driven generator, a ‘range extender’, to ensure that you never get a flat battery.  The Chevrolet Volt has an all-battery range of 65km – enough for most daily usage -  before the extender kicks in.
o    Build a refuelling infrastructure to exchange depleted batteries in seconds.  To be  attempted by ‘Better Place’ in ‘islands’ like Israel, Denmark, Hawaii.

Electric cars are efficient, able to travel 6.5km on a kwh of energy, compared with 1.5-2.5 km for a conventional car, and night-time electricity for recharging is cheaper than petrol.  For electric cars to become generally popular, a three-fold increase in energy density and a two-thirds price reduction would be necessary.

Electric traction has the potential to be a ‘disruptive technology’. Michelin is developing a wheel with inbuilt power, braking and suspension, allowing much standard equipment to be dispensed with – gearbox, clutch, transmission, differential, suspension – thus reducing weight and permitting innovative vehicle designs.  The existing auto-makers could find themselves out of business.   As The Economist puts it: ‘…propelling modern transport by means of serial explosions in a series of tin-cans does seem an incredibly primitive way of doing things.  The time is ripe for a change.’

One big problem in judging the potential for electric vehicles is that the electrochemistry of batteries is hard to understand.  I say that as someone who has a first degree in chemistry and would be prepared to swot it up if that seemed fruitful. But there are a lot of R&D people hard at work.  A couple of pointers from the Technology Quarterly section of the same issue of The Economist. 

o     Researchers at the University of St Andrews have replaced the lithium cobalt oxide of the standard Li-ion battery with an electrode made from porous carbon and Li-oxide, using oxygen in the air.  This has the potential to reduce the size and weight by a factor of 8-10, and the cost also.  
o     Unmanned aerial vehicles (‘drones’) are the coming thing in warfare.  The smallest, equipped with electric motors, are quiet enough for low-altitude surveillance.  A new fuel cell design for this use is 25% lighter and provides eight times the power of the version three years previously.