Super-capacitor to add spark to national grid

Scientists at Cambridge University have designed a super-capacitor that could provide sufficient storage capacity to cope with peak demand on the national grid.

Scientists at Cambridge University have designed a super-capacitor that could provide sufficient storage capacity to cope with peak demand on the national grid, and on a smaller scale provide electric vehicles with better acceleration.

Dr George Chen, Professor Derek Fray and Dr Milo Shaffer coated carbon nanotubes with a conducting polymer to create a device with a million times the capacity of conventional capacitors.

The project is funded by a £200,000 grant from the Engineering and Physical Sciences Research Council, but the team is already approaching commercial partners to develop possible applications.

One use might be in electric cars, which need large amounts of energy to accelerate. The lithium ion batteries and fuel cells being developed for use in future vehicles cannot supply power quickly enough to enable a rapid increase in speed. But the super-capacitor could.

‘It is like a battery that can output energy like a capacitor,’ said Chen. ‘The device could be the size of a cigarette pack, a laptop computer, or much larger. A very large device could even be used to help with power needs in the national grid.’

Chen envisages power companies storing energy in a vast super-capacitor to cope with sudden surges in demand.

The super-capacitor could also prove useful in mobile phones and PCs which use conventional capacitors holding one microfaraday of energy. A super-capacitor could store two faradays – one million times more.

Capacitors have two electrodes sandwiching an insulator or dielectric. The surface area of the dielectric is key to the storage capacity and the rate of output.

Chen’s dielectric is made up of carbon nanotubes which have a very small mass in relation to their surface area. ‘Because our nanotubes are coated with a conducting polymer, we can combine the features of a battery and a capacitor,’ said Chen.