Greenpeace has released a report calling for the creation of an offshore wind-powered electricity grid in the North Sea.

The North Sea Electricity Grid [R]evolution report outlines the development of an integrated power network based on wind-generated electricity to be shared between seven different European countries.

According to Frauke Thies, Greenpeace EU renewables policy campaigner, the grid would get around the problem of variable production from isolated wind farms by networking multiple sites together to create a more uniform and predictable supply. "The grid would enable the efficient large-scale integration of renewable energy in the power system across the whole North Sea region," said Thies. "A dip in wind-power generation in one area could be 'balanced' by higher production in another area, even hundreds of kilometres away, providing clean power for millions of European homes."

Greenpeace estimates the cost of developing the grid to be between €15bn (£12.2bn) and €20bn, which would be shared between the UK, France, Germany, Belgium, the Netherlands, Denmark and Norway and overseen by the European Commission.

The project would allow the integration of renewable energy and provide opportunities for power trading and cost efficiency, the group claimed. A new 600 kilometre-long power line between Norway and the Netherlands which cost €600m to build, but is already generating €800,000 a day in cross-border trade, proves that the North Sea grid project is more than just a theory, the group claims.

"Building a North Sea grid is not just a pipe dream; it is common sense both environmentally and financially," said Thies. "Greenpeace calls on the Commission to deliver a strong EU Action Plan for offshore wind and to push for a co-ordinated approach to make this scenario a reality."

According to Greenpeace, about 8550MW of wind turbines were installed in the EU in 2007 alone, which is equivalent to 40 per cent of all newly installed capacity. By 2020–2030, offshore wind energy in the North Sea could grow to 68,000MW and supply 13 per cent of all current electricity production of seven North Sea countries, the group claims.

UK renewable energy trade association the BWEA claims that with sites such as the 1,000MW London Array in the Thames Estuary, the UK is set to overtake Denmark as the largest generator of offshore wind power in the world and could have 20,000MW of offshore wind capacity by 2020, the equivalent of 17 per cent of UK supply.

According to the Department for Business Enterprise and Regulatory Reform, wind has overtaken hydro power as the second largest renewable energy-generation source in the UK in output terms, with a 30 per cent growth (90MW) in offshore-generating capacity between 2006 and 2007. "Companies want to build here because we have made the UK one of the most attractive places to invest in wind power," said energy secretary John Hutton in a statement last month.

Interest in onshore wind farms is also on the rise. Last month Romania become the site of Europe's largest proposed wind farm. Formed from the sale of two adjacent sites owned by renewable power developer Continental Wind Partners (CWP) to Czech utility company CEZ, the combined site will generate about 354MW by the end of 2009, with the rest of the turbines expected to be in operation by the following year.