ENERGY producers and environmentalists from around the world will this month
turn their eyes towards the west coast of Scotland. On the Hebridean island of
Islay, a small power station called Limpet is poised to start generating
electricity from the waves rolling in from the Atlantic.
Limpet鈥檚 500-kilowatt output will only be enough to power around 300 homes.
But as the only commercial-scale wave power scheme operating anywhere in the
world, it鈥檚 make-or-break for wave energy. If it proves a success, it will give
the fledgling wave power industry a much-needed boost. Any hint of failure could
spell disaster.
鈥淚 think the success of this project is critical to wave power development
around the world because of the high profile it has,鈥� says Nicholas Goodman, a
consultant with Northern Renewables, a project management company in Anchorage,
Alaska. That high profile has a lot to do with the fate of Limpet鈥檚 predecessor,
an ambitious 2-megawatt offshore demonstration project called Osprey. It used
the same technology as the shore-based Limpet and was also made by
Wavegen鈥攖hen known as Applied Research and Technology. But in August 1995
Osprey was destroyed by bad weather before it had even been properly installed
(快猫短视频, 26 August 1995, p 11).
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鈥淲e need some success stories as an industry,鈥� says Richard Yemm of Ocean
Power Delivery in Edinburgh. 鈥淲e must show that wave power installations can
stay put, because there is still a perception that they will 鈥榙o an
翱蝉辫谤别测鈥�.鈥�
There are several very good reasons to be confident that Limpet will not
suffer the same fate. First, a smaller, 75-kilowatt version operated
successfully on Islay for some 10 years until it was decommissioned last year.
Secondly, the precarious business of installing offshore systems is not an issue
with Limpet, which is built into the shoreline and is only partially submerged.
鈥淚t鈥檚 a civil engineering project,鈥� says David Langston, business development
manager with Wavegen. 鈥淭here are no expensive or hazardous marine operations
involved.鈥� Finally, Limpet is built out of solid concrete. 鈥淚t鈥檚 not going
anywhere,鈥� says Langston.
Osprey (Ocean Swell Powered Renewable Energy) and Limpet (Land Installed
Marine Power Energy Transformer) share a technology called oscillating water
column (OWC). At its heart is a chamber that is open to the sea below the
waterline and to the air through a blowhole at the top
(see Diagram). As water
in the chamber rises and falls with the waves, it pumps air back and forth
through the blowhole, driving a turbine that generates electricity.
Another reason the Islay project must succeed is the decidedly shaky start
experienced by the European Commission鈥檚 OWC demonstration plant on the island
of Pico in the Azores. This experimental station was scheduled to start up two
summers ago, but has twice been delayed by bad weather. The first time, 10-tonne
boulders broke loose from the coffer dam that was supposed to be protecting the
plant and smashed it. The following year a storm pulled off the door to the
control room, flooding it and destroying the electrical equipment. The station
is now due to start operating early in 2001.
鈥淚鈥檓 convinced Pico will be a success in the end,鈥� says Gordon Senior, a
consulting engineer who advises the European Commission on energy from the sea.
鈥淏ut wave energy is desperate for a success story and it鈥檚 terribly important
that Wavegen gets it right.鈥�
Meanwhile, other companies are developing alternative systems. For example,
the Australian company Energetech plans to build a 500-kilowatt demonstrator at
Port Kembla, 80 kilometres south of Sydney, by next May. Energetech鈥檚 scheme is
a shoreline OWC plant with a difference. A parabolic breakwater juts into the
sea and focuses the energy of the waves, raising them to three times their
initial height by the time they reach the OWC chamber. The computer-controlled
turbine is also different, because the pitch of its blades is constantly
adjusted to take best advantage of each wave.
Another contender is the Dutch company Teamwork Techniek, which uses an
offshore technology called Archimedes Wave Swing (AWS). A 2-megawatt pilot plant
is being built in Romania, for installation next year at the Portuguese port of
Viana do Castelo. AWS machines use a cylindrical air-filled chamber fixed to the
sea bed. Electricity is generated by the compression and expansion of the air
inside in response to the changing water pressure as waves pass over the
chamber.
In spite of the problems that have beset Osprey and the Pico project, OWC is
the wave technology that is closest to success. 鈥淥ther technologies are still at
the proof of concept stage, while Wavegen has a commercial project,鈥� says Steve
Szewczuk, a project manager with the CSIR in South Africa, the country鈥檚
national research body.
It鈥檚 too early to say which approach will win out, but there will probably be
niches for several technologies. 鈥淵ou might want a frail but really efficient
system in the Mediterranean, but something rather different if you鈥檙e somewhere
like Islay where you鈥檙e head-butting the Atlantic,鈥� says Yemm.
Offshore schemes have a head start over shoreline installations, however.
Where the sea is 40 metres deep or more, waves can deliver around 70 kilowatts
per metre of wavefront. In shallower water, this falls to 30 kilowatts per
metre. By the time they reach the shore the waves can only muster around 20
kilowatts per metre. 鈥淏uilding at the shore is like deciding to build a wind
farm where there isn鈥檛 any wind,鈥� says Yemm.
But in addition to being much easier to install, shoreline devices don鈥檛 need
expensive undersea cabling and grid connections for the electricity they
produce. Access and maintenance are also far easier. 鈥淚t鈥檚 not a straightforward
issue,鈥� says Langston. 鈥淵ou have to look at all the economic factors over the
life of the plant.鈥�
Like other renewable energy sources, wave power will ultimately have to
compete economically with fossil fuels. Limpet will supply the grid under the
Department of Trade and Industry鈥檚 third Scottish Renewables Order at a price of
5.95 pence per kilowatt-hour. The average price paid by the grid is around the 2
to 2.5 pence mark鈥攕o wave power looks pricey in comparison.
But experience with other renewable energy sources shows costs can fall. A
decade ago, each kilowatt-hour of electricity produced by wind energy schemes in
Britain cost 10 pence. The average has now dropped to 2p, with some wind farms
managing 1.8p. 鈥淭here have been massive improvements in turbine technology, but
it鈥檚 also down to operating experience,鈥� says Alison Hill of the British Wind
Energy Association. There is no reason to suppose that the wave power industry
can鈥檛 repeat that success.
Consultant Tom Thorpe, who currently runs the European Thematic Network on
Wave Energy, says that the likely global contribution of wave power is over 2
terawatt hours per year if the development programmes of the different companies
go according to plan. That will require an investment of over 拢500
billion.
But for this ambitious goal to be reached, investors need to have confidence
in wave power. 鈥淭he priority is to demonstrate the survivability and reliability
of the first devices in order to overcome the credibility problems,鈥� says
Thorpe. All eyes will be on Islay to see if Wavegen can get its system up and
running before the winter weather closes in.