Scientists at the energy group's technology centre in Nottingham aim to build a large-scale prototype that would be able to store one megawatt of electricity for four hours - the equivalent to 10m AA batteries and the same size as four articulated lorry containers.

"Green power is only generated from wind farms when the wind blows and that might not be when the power's needed by customers," said Bob Taylor, managing director of energy wholesale and technology. "By researching and developing this battery we can store the power generated by wind farms any time and then use it when our customers need it the most.

Eon is already working with small-scale prototypes; it expects the large prototype to be operational by autumn 2009. The project is being supported by the Department for Business, Enterprise and Regulatory Reform.

The industry regulator, Ofgem, said the concept was increasingly attractive. "It looked a long way from being deployed but we are seeing good progress here and internationally," said a spokesman.