The UK's first commercial wind farm, at Delabole in Cornwall, has reopened following a multimillion-pound redevelopment.
The wind farm opened in 1991 with 10 turbines, which stand at 164ft (50m), at the remote site near Wadebridge.
Energy Secretary Chris Huhne unveiled four more 325ft (99m) turbines, which harness wind more effectively.
Potential electricity generated at the site will increase to 9.2 megawatts, enough to power 7,000 homes.
Mr Huhne said: "Delabole was the first commercial wind farm in the UK and, in its new form, it remains at the forefront of best practice.
"Wind is an abundant, clean, home-grown alternative to fossil fuels.
"It can't be blown off course by instability abroad and so it's vital we use it for our low-carbon, energy security."
Good Energy, which runs the site, has spent £11.8m on the redevelopment.