Four schemes in hand

Press, 30 December 1976, Page 11

Four schemes in hand

There are at present four proposals. The best known is an idea put forward by Stephen Salter and a ream from Edinburgh University, Mr Salter is probably the leading authority for wave power at the present time, and his efforts are responsible for a good deal of the interest in the idea that now exists. Yet he became involved in wave power only recently. He says: “In September. 1973, I caught flu. My wife said to me, with callous indifference to my misery: 'Stop lying there looking sorry for yourself. Why' don't you solve the energy crisis?’ It seemed a good idea at the time” The result was the “Salter Duck". This is an oscillating vane, mounted on a fixed spine, which would be moved back and forth by the oncoming waves. This movement, would provide energy that could be extracted and converted into electricity.

A string of “ducks” would be set up, about 500 m long, and fixed into position across the path of the oncoming waves. Mr Salter says that the waves reaching British waters would be powerful enough to provide energy for 80 per cent of the time, and for 90 per cent of the time in winter, when it is most needed. Another device that is based on somewhat similar principles has been suggested by Wavepower Etd, a company set up by Sir Christopher Cockerell, the inventor of the hovercraft, and partners. Known as the “contouring raft’’, the scheme would consist of a series of linked rafts floating on the surface of the sea. in line with the advancing waves. As the rafts rose and fell, hydraulic pumps between each one would convert the resulting energy into high pressure in a fluid.

The third scheme under consideration has been produced by the National Engineering' Laboratory at East Kilbride, in Scotland. Unlike the first two, which are mechanical in nature, this, one is hydraulic, and is based on work originally done by Commander Y. Masuda of Japan. While investigating floating breakwaters, Commander Masuda found that a structure in the form of an inverted can could be used to provide power: the advancing waves would impress the air inside the can. and this could be used to drive, a turbine mounted on top of the can.

This principle has been successfully used in Japan to power navigation buoys, but tests at the N.E.L. have shown that Masuda design only absorbs about 30 per cent of the potential wave power. The N.E.L. says: “Theoretical studies indicated that this could be improved and it has already been s h o w n experimentally that quite elementary modifications to -the design will inctease the maximum efficiency to approximately 75 per cent.

The fourth scheme has been evolved at the Hydraulics Research Station, Wallingford, and is known as the Russell rectifier. The scheme consists of a structure made up of a series of high level and' low level reservoirs. These would be separated from the sea by a series of nonreturn flaps. The waves would drive water into the high-level reservoir, and it would be extracted through the low level one. This extraction process would enable a turbine to be driven.

One of the team working on the scheme, Peter Rance, says: “Originally we thought the device would be rather like .the cross section ' of a super-

tanker, moored in deep water. We now think it might be better to moor it in about 100 ft—that is, roughly three to five miles offshore. We think we could go ahead with the scheme now, the only question is: how much will it cost? That's the only thing that matters.”

This is, indeed, the crux of the matter. The technology for most of these devices already exists—but does the money? That is one thing which the government is trying to find out. Each of the schemes outlined above has received a government grant, and ultimately, no doubt, further funds will go. to the scheme — or schemes — that seem worth while from an economic as well as a technical point of view r .

It will, inevitably, be many years before any of these schemes is actually in a position to contribute anything to Britain's power supplies. According to Dr Marshall, of the Department of Energy, government spending would increase as investigation revealed the most promising areas for research. In perhaps 10 years’ time large prototypes would be moored in the Atlantic —probably off northwest Scotland or the coast of Cornwall —but it would be another 10 years before a full-scale wave-power station went into operation.

No matter how successful wave power proves to be. therefore, it is unlikely that it will be in effective operation until the next century, but since that is about the time that Britain’s North Sea Oil and gas reserves are expected to be running out, there is clearly every reason for starting research now.

The fuel for wave power is free, but it does seem that the capital costs

of a wave-power station are likely to be high. If the power that results is competitive with power produced by other means, then presumably wave-

power stations will he built. If not, then it will remain an idea that is technically feasible but economically out of the question. This does not mean that all wave,power projects are likely to be priced out of existence. The Japanese have shown that it is already economic for limited purposes, and more than 20 years ago work began on a scheme to use wave power for generating power on the island of Mauritius, in the Indian Ocean. The idea was to build a concrete ramp on the reef surrounding the island, which would help waves to pass over the reef into the lagoon beyond. This lagoon would be dammed-up, and the resulting head of water be used to generate power. According to A. N. Walton Bott, speaking to Britain’s Royal Society of Arts last year, research into this project has continued. even though actual work was discontinued in 1966, mainly because of the difficulties of storing power. Apart from the power itself, such a scheme could have other benefits —for example, the enclosed lagoon might be used for fish farming, something which could become very important as the world’s population continues to rise

Mr Walton Bott said that even now the Mauritius scheme gives every promise of financial viability, and a big advantage is that: it does not require a massive capital outlay. This means that it could be used in areas that require relatively small amounts of energy—the developing nations, for example.