Riding the waves
Wave and tide power ‘could contribute 20%’ to UK energy mixWatch out for the Wave Dragon. It should be seen strutting its stuff off the Welsh coast next spring - and, all being well, could have spawned an 11-dragon wavepower station about ten miles off Milford Haven by 2008/2009. Which would make it probably the first serious wave power contributor to the electricity grid, with a capacity of 77MW - equivalent to the needs of up to 60,000 homes.
Still just a drop in the ocean, perhaps, but the Wave Dragon is one of a raft of marine power technologies that are getting close to commercial viability, and which merit recognition as the potential source of 20% of the UK’s electricity. That’s the view taken by the Carbon Trust, whose January 2006 report urges increased public funding for both wave and tidal power technologies. Although the government’s current energy review is almost silent on the subject, the report estimates the potential of wave power at an annual 50 terawatt hours (one seventh of current UK consumption), plus a further 18 Twh from devices that harness the tides.
But it won’t happen overnight. John Griffiths, head of marine at the Renewable Energy Association, expects wave and tidal power to provide about 5-6% of our electricity by 2020. “As the Trust would agree,” he told Green Futures, “20% really is a topside figure for a longer period. Even though there are about 80 companies out there doing these things, only about a quarter of them will have any machines to deploy in the next couple of years. Over the next five years, it’s likely that a handful of wave and tidal technologies will be proven and can go on to commercial use between 2010 and 2020.”
Funding is another challenge, says Griffiths. “It takes a lot of work trailing round persuading venture capitalists to fund these technologies. The people behind these companies tend to be optimistic, and don’t necessarily see the pitfalls. But that’s the nature of inventors, I guess.” Accepting that the cost of electricity from marine power will be higher than that for other renewables for the first few hundred megawatts of capacity, the Carbon Trust nevertheless expects costs to come down appreciably thereafter. Britain has the opportunity, it says, to achieve a global lead in this field by timely investment now.
Creatures in contention
Wave dragon: basically a huge metal box floating in coastal water, with a ramp on the end facing out to sea. Waves hitting the ramp get catapulted up into the reservoir on the top of the metal box. The water then rushes back down into the sea, driving turbines as it passes through the outlet holes. It’s fanciful to liken it to a dragon spitting water, but there is real beauty in its low-tech simplicity. The only moving parts are the turbines, making it highly suitable for the harsh offshore environment. www.wavedragon.net, +45 3536 0219
Limpet: a shoreline power device, already operational - and grid connected - on the Scottish island of Islay, which uses the incoming waves to force air in and out of a specially constructed air chamber through a hole fitted with a turbine. www.wavegen.com, 01463 238094
Pelamis sea snake: The dragon’s closest technological rival, a Scottish-developed deep water device, which (like the dragon) can thus take advantage of the full power of the waves before they lose energy approaching the coast. It’s a long hinged tube which bobs up and down with the waves; as the hinges bend, they pump hydraulic fluid that drives generators [see GF51, p43]. Three of them should be floating off the Portuguese coast this spring and, depending on their performance, the same location could sport 30 sea snakes in a ‘wave farm’ with a capacity of 20MW by early 2007.www.oceanpd.com, 0131 554 8444
Wave energy converters: Devices of various designs [see ‘Trident tested’, GF56] which float on the waves and channel their motion into electrical generators.
Mighty whale: a floating metal construction being tested in prototype in Japan, using wave action to make the internal water level in each of three connected chambers rise and fall, creating a bi-directional airflow over an air turbine.
Tapchan: a shoreline device where incoming water is forced into a reservoir above sea level via a tapered channel, and is fed through a turbine back into the sea. One has been installed in Java, and interest is being shown by Chile, India and Sri Lanka.
Limpet: a shoreline power device, already operational - and grid connected - on the Scottish island of Islay, which uses the incoming waves to force air in and out of a specially constructed air chamber through a hole fitted with a turbine. www.wavegen.com, 01463 238094
Pelamis sea snake: The dragon’s closest technological rival, a Scottish-developed deep water device, which (like the dragon) can thus take advantage of the full power of the waves before they lose energy approaching the coast. It’s a long hinged tube which bobs up and down with the waves; as the hinges bend, they pump hydraulic fluid that drives generators [see GF51, p43]. Three of them should be floating off the Portuguese coast this spring and, depending on their performance, the same location could sport 30 sea snakes in a ‘wave farm’ with a capacity of 20MW by early 2007.www.oceanpd.com, 0131 554 8444
Wave energy converters: Devices of various designs [see ‘Trident tested’, GF56] which float on the waves and channel their motion into electrical generators.
Mighty whale: a floating metal construction being tested in prototype in Japan, using wave action to make the internal water level in each of three connected chambers rise and fall, creating a bi-directional airflow over an air turbine.
Tapchan: a shoreline device where incoming water is forced into a reservoir above sea level via a tapered channel, and is fed through a turbine back into the sea. One has been installed in Java, and interest is being shown by Chile, India and Sri Lanka.
Roger East and Saskia Walzel
8 March 2006
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