Britain's first commercial wind farm is set to reopen after a multimillion-pound redevelopment which will double potential output.
Energy Secretary Chris Huhne is to relaunch the Delabole wind farm 20 years after the blades first started turning on the site.
The wind farm opened in 1991 with 10 turbines, which stand at 164ft, at the remote site near Wadebridge in Cornwall.
Mr Huhne will unveil four more powerful turbines standing 325ft high, which harness wind more effectively.
The potential electricity generated will more than double 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.
Electricity supplier Good Energy has run Delabole since 2002 and spent £11.8 million on the revamp.
Chief executive Juliet Davenport said: "Delabole wind farm now accounts for 20% of the total 100% renewable electricity supplied by Good Energy and is the first in a pipeline of new wind energy projects we're working on."
