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TWO concrete blocks on the bottom of the sea off the north coast of Scotland
are all that鈥檚 left of the world鈥檚 first attempt to build a commercial wave
power station. When Osprey, a large yellow 2-megawatt generator, was wrecked by
waves that were meant to power it, hope died. Before its steel ballast tanks
could be filled, heavy seas scoured the sand from beneath them and they ripped
open. The engineers who designed the machine were 鈥渁bsolutely gutted鈥� and Lloyds
insurers had to pick up a bill for more than 拢1 million.

Worst of all, says the company behind Osprey, Applied Research &
Technology in Inverness, was the cleanup. By a cruel twist of fate, radioactive
particles which had leaked from the nearby Dounreay nuclear plant contaminated
the seafloor around Osprey. Protecting divers from this marine menace made it
more costly to remove the generator than to install it. 鈥淭he whole thing ended
up being a nightmare,鈥� says ART鈥檚 managing director, Allan Thomson. 鈥淏ut we
learnt an awful lot.鈥�

Osprey鈥檚 spectacular failure three years ago seemed to confirm almost
everyone鈥檚 prejudices about wave power. Governments felt vindicated for having
refused to fund it, on the grounds that marine engineering is just too costly,
while conventional electricity producers, who have long ridiculed wave power,
looked smug. On the face of it, the dream of harnessing wave power to generate
endless 鈥渃lean鈥� electricity had faded.

But appearances can be deceptive. Wave power is not so easily scuppered. Even
as Osprey went down, researchers had a number of other devices ready to be
tested in the water. They learnt lessons from Osprey just as they had from other
disappointments. They revised their designs and created new ones. Today, the
prospects for wave power have never looked better. For the first time,
independent analysts reckon that the electricity it could produce will cost less
than that from new nuclear and coal-fired stations.

At least 15 wave power generators are planned across the globe: nine in
Europe, four in the Far East, one in the US and one in India. Eight of them
should be producing energy next year (see 鈥淪hort-term bets鈥�). All are robust,
realistic designs, shaped by years of trial and error. Five of
them鈥攊ncluding Thomson鈥檚 latest version of Osprey鈥攁re backed by
private investors. Public funds are also pouring in. The European Union (EU),
which has already put 2 million ecus (拢1.4 million) into a wave generator
in the Azores, is about to invest more鈥攑erhaps as much again. The Danish
government, which invested early in wind power and opened the way for Danish
companies to dominate what is now a fast-growing market, has committed
拢3.6 million to wave power over the next three years.

No wonder there鈥檚 an optimistic mood this week at the Third European Wave
Energy Conference in Patras, Greece. Tom Thorpe, an international expert on wave
power, thinks it could eventually supply more than 10 per cent of the world鈥檚
electricity and help to solve shortages of drinking water by desalinating
seawater. 鈥淭hese uses represent a potential market in excess of 拢100
billion,鈥� he says.

It is no accident that most of the impetus behind wave power research comes
from Western Europe, and particularly from Britain. The Atlantic waves that
pound the British Isles give them one of the largest wave power resources in the
world. Thorpe, the British government鈥檚 main adviser on wave power since 1989,
estimates that waves in British waters could be tapped for 10 000 megawatts of
electricity, more than 20 per cent of its needs. Waves in waters off the Irish
republic could generate nearly 75 per cent of its electricity, he says.

Enticed by this prospect, researchers in Britain have been in the vanguard of
wave power research since the oil crisis in 1973. For much of that time, they
have had to work without help from government. The British government withdrew
most of its funding in 1982. Nevertheless, teams in Edinburgh, Inverness and
Belfast scraped together enough money from universities, industry and the
European Union to continue their research. They are now trying to push the
technology to the point of commercial reality.

The teams鈥� progress has been such that the British government could now be
about to change its mind. Energy minister John Battle has hinted that his
forthcoming review of policy on renewable energy could offer support to wave power
(This Week, 16 May, p 15).
The Scottish Office has already taken the lead
by saying that it will consider wave power plants under its scheme for
encouraging renewable energy, the Scottish Renewables Obligation. This, says
Thomson, is 鈥渁 tremendous step forward鈥�.

Sea change

Much of the credit for this sea change must go to Thorpe, who is a consultant
with AEA Technology at Culham in Oxfordshire. He reviewed wave power devices in
1992 and discouraged the British government from investing in the technology. It
was, he calculated, too costly to compete. But earlier this year, in a second
review, he revised his analysis, advising the government that the average cost
of electricity from the best devices under development is now just one-tenth of
what it was in 1982. 鈥淲ave energy is already economically competitive in niche
markets,鈥� he concluded, 鈥渁nd has good prospects of being commercially
competitive with further research and development.鈥�

Thorpe himself has played an active role in this dramatic improvement.
Because wave power teams had criticised earlier government reviews as secretive
and unaccountable, he took an open approach. In his two reviews, he invited
research teams to respond to his criticisms. This concentrated minds on how best
to reduce costs.

Most wave power machines operate by trapping air in a chamber above the
surface of the sea. As wave crests and troughs arrive at the machine, the water
level in the chamber rises and falls, blowing and sucking air through a hole in
its ceiling. A turbine placed across this hole draws off power
(see Diagram).

This principle, called the oscillating water column (OWC), was the basis of
the only large wave machine to have operated in Britain, a 75-kilowatt prototype
installed in a rocky gully near Portnahaven on the Scottish island of Islay.
Unfortunately, its performance between 1988 and 1996 never matched the hopes of
its designer, Trevor Whittaker from Queen鈥檚 University of Belfast. Water
turbulence caused by the rough walls of the gully and the complex topography of
the seabed limited the efficiency of the device, so that it converted only 33
per cent of the power of incoming waves into electricity. 鈥淲e made mistakes,鈥�
confesses Whittaker. 鈥淲e were sufficiently naive in the 1980s to think that we
could build a commercial plant straight away.鈥�

With lessons learnt, he has now designed the Limpet, a 500-kilowatt OWC
device due to be installed next year 300 metres along the coast from its
predecessor. It will be built into an artificial 鈥渄esigner鈥� gully optimised to
harvest wave power, so it does not have to rely on the vagaries of a natural
gully. Large sections will be constructed on land, pushed down a slipway to the
site and quickly assembled during calm weather 鈥渓ike a flatpack kit鈥�, Whittaker
says. Together with ART, which is a partner in the project, Whittaker is now in
final negotiations with the EU over funding for the device.

Like most OWC machines, the Limpet depends on turbines invented by engineer
Alan Wells in 1977 while he was working at Queen鈥檚. Thanks to an innovative
blade design, the Wells turbine rotates in the same direction whichever way the
air flows. This reduces the need for valves, which are prone to failure, and
improves efficiency because the turbine does not have to keep stopping and
starting. The problem is that it converts only around 40 per cent of the power
from the moving air into electricity, so designers are searching for
enhancements. To capture at least some of the lost power, the Limpet will use
two Wells turbines in series, one turning clockwise and the other anticlockwise.
According to Whittaker, this could allow the Limpet to convert as much as 60 per
cent of the airflow鈥檚 power into electricity.

Another variation on the Wells turbine is expected to make its debut next
year, on a 500-kilowatt OWC generator on the shore of Pico Island in the Azores.
It is the brainchild of Stephen Salter, head of the wave power team at the
University of Edinburgh, and has blades that change their pitch up to 10 times a
minute in response to the velocity of the air flow. The turbine is due to be
installed next to a conventional Wells turbine so that comparisons can be made.
Salter says the variable pitch turbine could deliver twice as much energy as its
neighbour.

High energy

While shoreline machines are showing tremendous promise, most researchers
agree that the real potential of wave power will only be realised when wave
machines move offshore, where the wave energy is highest. Gordon Senior, a
consultant to the EU and chairman of a British government task force on wave
power, makes projections that are even more optimistic than Thorpe鈥檚. 鈥淲e could
generate half of Britain鈥檚 electricity requirements from waves by 2040,鈥� he
says. 鈥淚 am convinced we can do it.鈥�

There is no shortage of ideas for generating power offshore. The McCabe Wave
Pump, for example, which Thorpe regards as promising, uses the differential
movement of three rafts to produce power. Developed by Peter McCabe of Hydam
Technology in Killarney, Ireland, it consists of a stationary steel pontoon
attached to the seabed and linked on either side by hinges to two floating pontoons
(see Diagram). The pitching motion of the two floating pontoons
pumps hydraulic fluid back and forth鈥攎otion that is used to drive a
generator. Unfortunately, during tests two years ago on a 140-kilowatt prototype
off Kilbaha, southwest Ireland, hydraulic pipes burst under pressure from strong
waves. A strengthened version is due to be tested next year.

Another machine with good prospects, according to Thorpe, is the Shim Hybrid,
designed by Hyun Jin Shim of the Korean company Baek Jae Engineering. It
envisages an array of floating buoys each anchored by a rope to a central shaft.
The rope is wound onto a drum inside the buoy which behaves like an upside down
yoyo. As the buoy falls and rises, the drum turns and drives a generator.

One of the newest and most intriguing ideas for an offshore device comes from
Richard Yemm, a former student of Salter. His design, which he is unveiling at
the Patras conference this week, would generate power from the differential
motion of 10 floating tubes placed end to end. The tubes would form a spine some
120 metres long. Once again, hydraulic pumps driven by the difference in motion
between adjacent tubes would turn generators. He has applied under the Scottish
Renewables Obligation to install two 375-kilowatt spines in Machir Bay off the
west coast of Islay next year.

But of all the plans for offshore devices, Thorpe believes that the best
prospects lie with one of the oldest and most famous designs鈥擲alter鈥檚
鈥渄uck鈥�. This consists of a row of floats shaped like ducks鈥� bodies, and uses the
angular motion of the 鈥渘odding鈥� floats to drive a generator. In 1982, government
advisors reckoned that it would produce uneconomic electricity at more than 100
pence per kilowatt-hour. But in his review earlier this year, Thorpe suggests
that rows of ducks off South Uist in Scotland could generate power for as little
as 2.6 pence per kilowatt-hour, compared with 4 pence per kilowatt-hour or more
for new coal and nuclear stations. The proportion of a wave鈥檚 energy that ducks
can capture has risen from 42 per cent to 65 per cent, he says, making them
鈥減otentially one of the most efficient devices under consideration鈥�.

The reason for this improvement lies in fundamental changes to the duck, many
in response to Thorpe鈥檚 criticisms. Within each float is a cylinder about which
the float turns, and it鈥檚 the relative motion of these two components that
generates the machine鈥檚 power. In the original design, the power came from the
precession of pairs of huge gyroscopes housed in sealed tubes. But Salter has
now changed all this.

The gyros have been dispensed with entirely, because advances in antifouling
treatments and seals make it economical to operate power systems in the wet. The
power is generated by dozens of pistons fixed inside the cylinder which are
pushed in and out by a ring of cams fixed to the moving float
(see Diagram).
This arrangement works thanks to a piece of 鈥渄igital hydraulics鈥�
invented at Edinburgh called a wedding cake. This smart machine juggles the
pressures inside many hydraulic circuits, turning the slow, bidirectional
movement of the float into the constant, high-speed rotation of a generator.
鈥淭his makes as big a difference to wave power as the jet engine did to
aviation,鈥� says Salter. Though today鈥檚 duck is more efficient than ever, Salter
still reckons that it will be about eight years before one begins generating
power.

Salter is also developing an enhanced version of another offshore wave device
invented in Sweden. Called the IPS buoy, it consists of a float connected below
to a weighted, vertical tube. Inside the tube, which is open to the sea at both
ends, is a piston that extends upwards to the float. Out at sea, the float and
tube move up and down more vigorously than the piston and, again, this
difference in motion is converted into electricity. Salter has found that by
making the float and tube sit at an angle from the vertical he can increase the
machine鈥檚 efficiency.

Technocean, a Swedish company, is planning to test its own design of the IPS
buoy near the Greek island of Amorg贸s next year. The buoy is also being
refined by an American firm, Ocean Power Technologies, for testing in the Gulf
of Mexico, although few details have been released.

Back in Scotland, ART is developing a new offshore device known as the
Powerbuoy, although details of this are also still under wraps. But the
British-Borneo Petroleum Syndicate, an oil company with a track record of
innovative investment, was so impressed that in March it bought a 20 per cent
share of the company. ART has also designed a new version of the near-shore OWC
device, Osprey, in which the ballast tanks are made of concrete and are
subdivided into cells to strengthen them. The company has applied for 拢1
million, which the Irish government promised to wave power in 1996, to install a
2-megawatt generator in the sea off the west coast of Ireland next year. Thomson
is now waiting to hear whether it will be given the go-ahead.

Despite all this progress, it would be wrong to suggest that wave power has
reached technological maturity. Mistakes are bound to be made and fond hopes may
again founder. Thorpe points out that the plethora of devices being developed is
itself 鈥渁n indication that the best way forward has still to be identified鈥�.
Wave power鈥檚 inventors have seen too many false dawns to allow themselves to be
swept away by enthusiasm. But they know that their goal has never been closer.
鈥淚 am too battle-scarred to be overoptimistic about the future,鈥� says Salter.
鈥淏ut I am quietly hopeful.鈥�

• The Limpet, a 500-kilowatt oscillating water column (OWC) device from
  Queen鈥檚 University of Belfast and Applied Research & Technology in
  Inverness, is due to be installed on the shore of Islay, Scotland, next year
• A 500-kilowatt OWC device developed by the Technical Institute in Lisbon
  and the University of Edinburgh is due to be installed on the shore of Pico in
  the Azores later this month
• WPT-375, a 375-kilowatt 鈥渂ending spine鈥� generator developed by Richard
  Yemm, an Edinburgh engineer, is planned for Islay in Scotland next year
• The McCabe Wave Pump, a 140 kilowatt pontoon device developed by Peter
  McCabe of Hydam Technology in Killarney, Ireland, is due to be tested off the
  southwest coast of Ireland next year
• Ten, 30-kilowatt IPS buoys, built by Swedish firm Technocean are due to be
  moored off the Greek island of Amorg贸s next year
• Osprey is a 2-megawatt OWC device developed by Applied Research &
  Technology planned for the sea off Kilkee on the west coast of Ireland next
  year
• The Mighty Whale, a 110-kilowatt OWC device developed by the Japanese
  Marine Science and Technology Centre in Yokohama, is being tested in Goyasho
  Bay, south of Nagoya in central Japan
• A 100-kilowatt OWC generator, developed by the Chinese Academy of Sciences,
  is being installed on the south coast of China at Zhelang near Hong Kong