Tidal power station for UK

EFL Tech - France
a Site for Teachers of English ( as a Foreign Language) for Engineering

Back to CONTENTS Page [frameless version]

Tidal power station

By Rob Edwards

1 - A tidal power station that taps the surging power of strong underwater currents will be tested for the first time this summer. In Britain, there are about 40 key locations around the coastlines where, in theory, there's enough energy in tidal streams to generate up to a quarter of the nation's electricity.

2 - Wind creates waves on the sea surface, but as wind blows intermittently, wave power is quite unpredictable. But tides are regular, as they are caused by the gravitational pull of the Moon and Sun on large masses of water. If the local geography is right, ocean channels create fast-moving "tidal streams", where vast masses of rising or falling water are squeezed into a restricted space. But no one has proved that extracting energy from tidal streams is practical.

3 - That could soon change. The British government is now looking for new energy sources to help cut carbon emissions. And this month, British offshore equipment company Engineering Business was given a 1.1 million government grant to build a 150-kilowatt prototype tidal power station.

4 - Dubbed Stingray, the machine should be installed between May and September on the seabed to the south-east of the Sound of Yell, off mainland Shetland. A pair of 15-metre-long hydroplanes, mounted on a stand, will oscillate with the tide to drive a hydraulic motor that generates electricity (see animation on the Web at www.engb. com/Pages/animation.htm).

5 - Hydraulic pistons control the angle at which Stingray's hydroplanes face the tidal current to make the most of the onrushing water. Like an aircraft wing, their angle of attack (the angle at which it bites into the current) changes to create "lift", which pulls the hydroplane up and down. As they move, the hydroplanes yank on an attached arm that pumps high-pressure oil through a hydraulic motor, which turns an electric generator.

6 - Although the design is still being finalised, the structure is expected to weigh 35 tonnes, rise to 20 metres above the seabed and work in currents of between 2 and 3 metres per second (4 to 6 knots). Most of it will be made of steel, though the hydroplanes could be cast in glass-reinforced plastic.

7 - Stingray may only work with the tide flowing in one direction, but its successors will swivel round or flip over four times a day so they can catch the tidal stream in both directions. Depending on the site, this should mean they generate power at least three-quarters of the time.

8 - Engineering Business's managing director Tony Trapp told New Scientist he is "quietly confident" that Stingray will work, but stresses that its economics are less certain. He estimates that it will generate electricity for between 4.7 and 12 pence per kilowatt-hour. Although this is more expensive than wind and nuclear power, it is comparable to wave power and much more predictable.

9 - Another contender in the tidal-stream game is an underwater windmill developed by Marine Current Turbines of London. A prototype that generates power using the circular motion of propeller-like turbines was originally due for installation off the coast of south-west England in 2000. But according to MCT's Peter Fraenkel, it was postponed because of delays in getting almost 1 million in government funding.

10 - Now he has the money, Fraenkel is planning to install a 300-kilowatt underwater windmill north-east of Lynmouth, Devon, in September. But both Fraenkel and Trapp insist they are not racing to be the first to generate tidal power. It is likely to be a multibillion-pound industry, predicts Fraenkel. "There's room for both of us."

NEW SCIENTIST 26 January 2002

VOCABULARY

Read paragraphs 1 and 2. You probably do not understand "tidal" (§1). Find a word which sounds similar in l§ 2. What details do we get?

A power station that taps (§ 1) the power is : ¨a power station that hits ¨ that collects ¨ that produces the power.

Squeezed (§ 2) masses of water are ¨ projected ¨ compressed ¨ deviated into a restricted space.

A 1.1 million government grant (§ 3 is ¨a government which gives money ¨ a sum of money given by the government ¨ a sum given to the government.

The hydroplanes yank on an arm (§ 5) : ¨ pull on an arm ¨ rest on an arm ¨ look like an arm.

Its successors will swivel round (§ 7) : ¨tourner ¨pivoter ¨ basculer

flip over (§ 7) : ¨tourner ¨ pivoter ¨ basculer

It was postponed because of delays § 9) : ¨différé ¨annulé ¨abandonné.

RIGHT OR WRONG

1 - Say whether the following statements are RIGHT or WRONG and justify by quoting from the text.

40 power stations will be built.

R	W