United Kingdom

United Kingdom

Undersea cable for renewables -- An expensive transmission solution

An offshore electricity transmission line along Britain's west coast to connect power from renewables into the national grid has been proposed by the UK government. But experts are warning that the ambitious plan could double the cost of power from the wind.

The west coast of Britain is rich in renewable resources -- particularly wind energy, but if they are to be fully exploited to help meet government renewables targets, the existing electricity infrastructure needs upgrading. One option, says the government, is an underwater cable of some 400 miles linking the western seaboard of Scotland, northwest England, Northern Ireland, west Wales and, possibly, the southwest of England to the main grid.

A government funded initial feasibility study is to be carried out by consultants PB Power Ltd which will look at cost, geographic location, and the extent to which renewables would benefit from an interconnector. The study is expected to be completed by the end of 2001. If it shows that an interconnector is economically and technically viable, a second study will follow to examine the detailed cable route and points of connection with the electricity transmission network.

"The UK has huge untapped renewable resources, but much of this potential cannot be fully utilised at present because of weak or non existent electricity infrastructure in some places. The proposed interconnector is a possible means of capturing this power flow and transmitting it around the UK, without encountering many of the inevitable environmental concerns which land based transmission systems would attract," says energy minister Brian Wilson.

He adds that the western seaboard, from the Hebrides down to the west country, could contribute far more of the country's energy needs if the transmission deficiency could be overcome. "The economic implications of these proposals are enormous," he says.

According to Department of Trade and Industry (DTI) figures, the cable could cost around £400 million at £1 million per mile -- although it stresses this price would depend on the sub-sea terrain. But this would double the cost of offshore wind energy, warns energy consultant David Milborrow. A cable of that length needs to be direct current (DC), he explains. "For £1 million per mile you are unlikely to be able to afford a cable with a rating above about 400 MW." Four hundred megawatts of offshore wind would cost about £400 million, so the interconnector roughly doubles the cost of delivering the power, says Milborrow. "Although wind speeds in Scotland are good, the energy yields that could be achieved are nowhere near double those around the English coast. So you would end up with a hefty electricity price premium," he adds. "The sums still do not add up if you look at the possibility of exporting higher power levels; cable costs then go well above £1 million/mile and the electricity price premium is about the same."

The DTI stresses the cable will help the country meet its aim of 10% of electricity from renewables by 2010, and will prepare for the longer term when it anticipates setting tougher targets. Ten of the first round of offshore wind farms are already planned for the north Irish Sea and further offshore wind farms and extensions to the current round of offshore projects are likely to be built later.

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