Scotland's Tide and Wave Plan

This article was written by Discover'sSmriti Rao.

About 750,000 Scottish homes expect to be powered by ocean technology by 2020, as the Scottish Government announced that 10 wave and tide power schemes capable of generating up to 1.2GW in total would be built around the Orkney islands and on the Pentland Firth on the northern coast of the Scottish mainland. The 10 projects will comprise the world's first commercial-scale wave and tidal power scheme. With this project, Scotland plans to produce the same amount of clean energy as a small nuclear power station, and hopes to start on a path to becoming the "Saudi Arabia of marine energy."

Some of the strongest tidal currents in the world race around UK shores and there's some of the highest energy in the waves that roll in from the Atlantic. And while wave power is, to an extent, dependent on the weather, tidal power has the tremendous advantage of being totally predictable.

It will cost about $7.6 billion in total to install and maintain the structures used to generate power from the strong waves and tides, and to transmit the energy back to land. The bulk of the work will be done by three major power firms: E.ON, Scottish and Southern Energy (SSE) Renewables, which already operates the UK's largest hydro schemes, and Scottish Power Renewables, a heavy investor in windfarms, in joint ventures with four of the UK's leading marine energy firms marine energy firms.

style="text-align: center;">The Sea Snake

One of the smaller companies involved in this project, Pelamis Wave Power, has pioneered marine energy with its "sea snake device," which is currently being tested off the coast of Portugal. The device is expected to be used in four of the new sites in Scotland. Each of the semi-submerged Pelamis snakes measures 466 feet in length and is made of 700 tons of carbon steel.

A series of four connected tubes bob up and down in the waters to convert wave motion cleanly into electricity. The energy of the undulating ocean is captured by the three "power modules" that are hinged between the four sections. There are large hydraulic rams sticking into the modules. As the long sections twist and turn in the waves they pull the rams in and out of the modules like pistons. The huge force of the rams is harnessed to run generators in the power modules. The electricity is then fed into an offshore grid via undersea cables. Each snake produces about 750 kilowatts of clean electricity.

Tidal Turbines

The OpenHydro tidal power machines will be used for a 200 megawatt site south of Scotland's Orkney Islands. The machines will lie beneath the waters and will not be visible from the surface. The first 14-foot test unit produced enough energy to supply 150 average European homes and saved the emission of over 450 tons of CO2 greenhouse gas each year.

OpenHydro's device is essentially a large underwater turbine with an open center, which the company says minimizes the risk to marine life. The slowly rotating turbine gathers the energy from the powerful surges of water pushed through the channel between the Orkney Islands and the north coast of Scotland with every turn of the tide.

Image: OpenHydro

Efficient Oysters

A newer iteration of the Oyster wave power machine is being developed for the current project in Scotland. Each Oyster, which is more technically known as a Oscillating Wave Surge Converter (OWSC), is an enormous lever mounted on the seabed, that sways back and forth in the waves. It operates near the shore in water as deep as 30 to 50 feet. The efficient machines can be arranged in clusters, and they can function in extreme weather. The Scottish project will use a cluster of 200 machines that produce 1 megawatt each; the Oysters are expected to start producing power by 2015.

Tidal Towers

The SeaGen tidal machines, which are due to be installed off the Orkney Islands in a 100 megawatt site, function as underwater windmills, except their rotors are driven by currents and not the wind. One of Sea Generation's first turbines, which is already fully functional near the mouth of Strangford Lough in Ireland, generates 1.2 megawatts, enough electricity to power 1,000 homes, the highest level of power produced by a tidal stream system anywhere in the world.

It is estimated that by using a combination of tidal and wind power, Scotland could produce enough energy to meet more than 80 percent of all its electricity requirements. That would be the equivalent of taking 4.5 million cars off the roads, and would reduce CO2 emissions by 30 percent.

By Smriti Rao
Reprinted with permission from Discover