THE volcanoes of Iceland could soon be pumping low-carbon electricity into the UK under government-backed plans for thousands of miles of high-voltage cables across the ocean floor.

The British energy minister, Charles Hendry, is to visit Iceland in May to discuss connecting the UK to its abundant geothermal energy. “We are in active discussions with the Icelandic government and they are very keen,” said Hendry.

To reach Iceland, which sits over a mid-ocean split in the Earth’s crust, the cable would have to be 1,000 to 1,500km long and by far the longest in the world.

Hendry has already met the head of Iceland’s national grid about the plan. The web of sea-floor cables — called interconnectors — planned for the next decade would link the UK to a Europe-wide supergrid, which is backed by the prime minister.

The supergrid would combine the wind and wave power of northern Europe with solar projects such as Desertec in southern Europe and north Africa to deliver reliable, clean energy to meet climate change targets and reduce dependence on fossil fuel imports.

There are two existing international interconnectors, to France and the Netherlands, but nine more are either in construction, formal planning or undergoing feasibility studies. The next to open, in autumn 2012, will be a link between the Republic of Ireland and Wales, allowing green energy from the windswept Atlantic coast of Ireland to be delivered to British homes.

The UK has been energy independent for virtually its entire history. But with the North Sea’s oil and gas failing and coal banned as too polluting, Hendry was frank about the future: “We will be dependent on imported energy.” The cables were “an absolutely critical part of energy security and for low carbon energy”, he said.

The government’s legally binding targets to reduce carbon emissions are another key driver for the new interconnectors, which if all built could supply a third of the nation’s average electricity demand.

Renewable energy, such as the offshore wind power at the heart of the government’s renewable plans, is zero carbon once built but is also intermittent, meaning backup gas plants or energy storage are needed.

A 900km interconnector to Norway, due to open by 2019, would enable excess wind energy to pump water into storage lakes above the fjords. Then, when the electricity is needed, floodgates are opened and the water flows back down through turbines. Both the pump storage and the high-voltage direct-current interconnectors lose very little energy.

Another ambitious interconnector would link England to Alderney, where very strong tides could produce 4GW of electricity, and then on to France and the new 1.6GW nuclear power plant being built at Flamanville.

— The Guardian, London