Tidal energy could power half of Scotland

Tidal streams could bring large amounts of energy within a decade if government support is available, study says

The Pentland Firth has been described as the Saudi Arabia of tidal power – and boasting some of the fastest tides in the world (Pic: John Haslam)

By Damian Carrington, the Guardian

The world’s best site for tidal power, the Pentland firth, could provide half of Scotland‘s electricity, according to the first robust estimate of its potential.

The tidal streams, which surge through the firth at five metres per second, could bring large amounts of renewable energy in reach within a decade if enough government support is available, said the Oxford University engineer behind the new study.

From Anglesey to the Severn estuary to Portland Bill, the UK has the greatest potential for generating predictable, clean energy from tidal channels. Turbines are already operating at Strangford Loch in Northern Ireland and prototypes are being tested in the Menai Straits off Anglesey.

But the Pentland firth is the greatest resource. “It is almost certainly the best site for tidal stream power in the world,” said Thomas Adcock, at Oxford University, who led the new work published in the journal Proceedings of the Royal Society A. The water flow is rapid there because the tide shifting from the Atlantic into the North Sea is forced through a narrow eight-mile channel.

The engineers developed new models to find the technical and economic “sweet spot” between the extremes of bringing water in the firth to a standstill and having a free flow. They calculated that underwater turbines strung across the entire width of the firth could generate a maximum 1.9GW of energy, averaged across the fortnightly tidal cycle. That is equivalent to 16.5 terawatt hours of electricity a year, almost half Scotland’s entire annual electricity consumption in 2011. As Scotland already produces 14.6Twh a year of renewable energy, a fully exploited Pentland would bring Scotland close to meeting its aim of 100% renewable electricity by 2020.

However, Adcock’s estimate of 1.9GW is far lower than the Scottish government’s published estimate of 14GW, making suggestions of huge exports of electricity seem unlikely. Adcock said those behind the high estimate were “in a minority of one” in the academic community: “We are happy our number is very robust.”

Four licences have been issued by the crown estate to different companies to develop tidal power in the Pentland firth. But Adcock said the potential of the channel could be compromised by piecemeal development, because early projects could be affected by reduced flows when later projects come on stream. “We do have a really good resource but to get that out you have to plan it as one unit,” he said.

John Robertson, from the Crown Estate, welcomed the new work building understanding of the energy resource in the Pentland firth. He added: “We recognise the potential for interaction between projects and have had arrangements in place to manage those interactions since 2010.”

Adcock said it would take 10 years to develop tidal power in the firth to a scale that had a national impact. “But it depends on the level of government financial support given, which is a political decision,” he said. “As engineers we can make this happen – if the support is there.”

The Pentland firth is a busy shipping route and it may be decided to leave a clear channel for traffic, which would reduce the electricity output. A full string of turbines would reduce the tidal flow by 30%, and although more work must be done, experts expect the environmental impact to be low. “Marine mammals are intelligent enough to avoid these things,” said Adcock. “The turbine blades move pretty slowly compared to even a baby seal.”

This article first appeared at the Guardian

RTCC is part of the Guardian Environment Network

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