The largest rooftop solar power station in the world is being built in Spain, on the roof of a General Motors car factory. GM, who has taken a recent knock to their Hummer sales, also plans to install solar panels at another 11 plants across Europe.

The power station, with a capacity of 12 megawatts of power, is made up of 85 000 lightweight panels that cover an area of two million square feet. It should produce power by September, and will produce enough energy to power a third of the GM factory or the needs of 4600 households with an average of 3300kWh. The solar energy produced should cut CO2 emissions by 6,700 tonnes a year.

Solar panels on houses usually produce a few kilowatts of power. On large commercial buildings, installations of one or two megawatts are now common. A one-megawatt installation could run about 1,000 air-conditioners while the sun is shining. [guardian]