Power-starved world looking at waves to lighten the load

Press, 30 December 1976, Page 11

Power-starved world looking at waves to lighten the load

Ba,k in 1170. a miller j- Woodbridge. Suffolk, v. a < making flour in a rn :' that was powered bs the t de. A century age a m. <>i at Spring Creek. Ne.’ York State was doing the same thing. And f. hundreds of years tidal tn: - were relatively common—there are 32 sites m Dexon and Cornwall alone. A.though the tides were free they -were also inconvenient They had a habit of flowing at night when the miller wanted to sleep, and hey never worked at the same time each dav. Then came the age of steam. Coal was cheap, and gradually tidal power fed into disuse When oil was adopted as a power source the idea of using the sea for energy virtual!' disappeared. Today, neither oil nor coal is as cheap as it once was—and supplies of both a:e beginning to run out. The world is becoming mo<e and more concerned about >vhat will replace them in the not-very-distanr future. And as a re ul; scientists and gov-

ernments are now giving serious consideration to a number of schemes for tapping the energy that is known to exist in the world's oceans in virtually unlimited quantities. One of these ideas, not surprisingly, is to generate electricity by harnessing the power of the. tides—a somewhat more sophisticated system than was ised in 1170. but roughly the same in principal: as the tide goes in or out, it is used to drive a turbine (or waterwheel). There are. of course,

snags. Large-scale schemes to harness the tides are only practicable where the tidal range is abnormally high, and this automatic cally limits projects to a handful of areas in the world. They include Passamaquoddy Bay, which divides Canada from the United States, the Severn Estuary in Britain, the area around St. Malo in France, one or two sites in the Soviet Union, and places in east Asia, Australia, and South America. Schemes for harnessing

the tides in some of these regions have been around for at least half a century—a pilot project was actually started in Bristol in 1920—but the problems in the way are formidable. To date, only two tidal power schemes are in operation in the entire world. The first, and the best known, is at the mouth of the River Rance in Brittany. The Atlantic tides at this point are funnelled into the Rance by the Brittany and Cotentin peninsulas and produce a range from 37 ft. to 44 ft. A French engineer, Robert Gibrat, planned the project as long ago as 1942 and construction began in 1961. It was completed five years later. Now, a huge dam, into which a series of turbines have been built, runs across the estuary. One of the most important features of Rance is that the 24 turbines, or “bulb sets”, can operate when the water is flowing in either direction. When the tide has stopped coming in, power is drawn from the grid to pump still more water into the area behind the dam, raising its level by another 19in. As the tide falls, the turbines are reversed, more electricity is generated, and the extra 19in. give back 12 times as much power as it took to raise them. Another advantage of the Rance system is that power can be generated when it. is required, not only when the tide is right; the water is simply kept dammed up until power is needed.

This is also true of the Russian pilot scheme at

Kislaya Bay, near Murmansk. This plant has a 400-kilowatt capacity, and began producing power in 1970. It is essentially a prototype, and the Russians are said to be studying proposals for further, much larger schemes.

These successes have established the technical feasibility of tidal power schemes, but their economic viability is less sure. The Rance scheme was intended as the forerunner of a much larger plan T o enclose much of the Gulf of St Malo: but the scheme has been abandoned. largely on the grounds of the enormous expense involved. It was

also found that the sheer scale of the project would actually reduce the tidal flow, and hence the power generated. The same fate has so far met the suggestions for an ambitious scheme at Passamaquoddy Bay. Work actually started on a tidal power project there in the 19305, but was later abandoned. Although the scheme is still being considered by the United States and Canadian governments, no decisions have been ‘made. A favourite site, for the advocates of tidal power

it the Severn estuary, whose tidal range is the second highest m the world. It could, say some experts, provide up to 10 per cent of Britain’s total electricity requirements, and cost up to £5OO million. But others say it

would cost £2OOO million. The gap between the various estimates shows just how difficult it is to make accurate forecasts concerning such a project. That, perhaps, is one reason why official opinion seems to have turned against the Severn scheme, and those for other sites such as at Morecombe Bay and the Solway Firth.

The British Central Electricity Generating Board now believes that the tidal barrage power station would not be able to produce fuel .as cheaply as nuclear or fossil-fuel plants. Dr Walter Marshall, chief scientist of the

Department of Energy, wrote recently that, the Severn scheme would cost at least £lOOO million—and perhaps six times as much depending on its complexity—yet would produce barely 2 per cent of the nation’s energy requirements by 1985. This proportion would drop steadily by the end of the century, whicn is when the scheme might be expected to start producing energy—if work began now.

There would also be problems associated with, pollution—many towns discharge sewage into the Severn —and shipping, since special locks would have to be constructed Nevertheless, the British Government has no:: turned its back on tidal power completely, and -although it has decided not

to initiate a £500.000 feasibility study, it will back two’ smaller proje~t.-. Tidal power is attracting attention in Indit, where the Gulf of Kutcn and the Gulf of Cambay both have sufficient tidal range. The Coast Engine eering Research Unit <. f the Central Water and Power Commission has established that 6-7000 megawatts could be generated at Cambay, anti 1000 megawatts at Kurch. With the aid of a United Nations grant, the CERU is carrying out further research.' Another study into tidal power possibilities is io be carried out in Wes.ern

Australia. Walcott Bay and Secure Inlet both have the necessary tidal range, and the study is being funded by the Western Australian” Government. Despite this, interest in tidal power does seem to be waning slightly, and in Britain attention has switched to another target—energy from the waves. Thanks to Britain's geographical position, the waves that pummel its shores are more powerful than those found almost anywhere in the world, and over the years hopeful inventors have tried to

use that strength. In the last 100 years alone more than 350 devices have been patented in the United Kingdom — and promptly been forgotten.

Now there is a very real possibility that wave power will, within the

next decade or so. mase an mportant contribution to Britain's energy supplies. The Department of Energy believes that a 600-mile stretch of ocean might provide half of Britain’s present electricity requirements, and has announced that more than SI million will be spent oxer the next two years investigating the best ways of tapping it. The project is being run by the Department of Energy, which has set up a special Wave Energy' Steering Committee, headed by Dr L. E. J. Roberts. A working party, which includes Dr R. A. Goodman, principal surveyor of the Development unit of Lloyd's Register’s Hull Structures department; is evaluating the various designs that have been put forward so far.

Reprinted from the Magazine of Lloyd’s Register of Shipping