Your location: Home > Publications > New Ground > No. 63

Offshore gets On-message

New Ground 63
Summer 2002

The government is now paying more attention to renewable energy. But is it doing enough? Dave Elliott of SERA’s Energy Group looks at the potential of the UK’s neglected wave and tidal resources

The UK’s offshore energy resource is huge. At long last we are starting to develop it; 18 offshore wind farms are being considered. But there are also large wave and tidal energy sources to tap. In its recent Energy Review, the Cabinet Office claimed that the total wave and tidal resource, if fully developed, could meet about twice UK electricity demand. This is the theoretical total; what we could extract in practice at reasonable cost would be far less, but still significant.

In which case, it is surprising that wave and tidal energy have received so little support from government. Twenty years ago, the Tory government cut funding for the deep-sea wave energy programme, claiming wave power would be expensive. And in 1994 it cut the rest of the programme. Now there has been a rethink. In March 2001, the DTI admitted that the earlier decision to end government funding for wave energy research and development had been a mistake.

The emphasis is still on offshore wind, which in theory could generate most of our electricity. In practice, 30% is more likely at a realistic cost. Tapping economically viable tidal and wave resources could deliver at least another 30%, especially if we go further out to sea.

There are some novel ideas for building circular tidal basins offshore to capture high tides for barrage-type operations, but the main future for tidal power looks like being the use of tidal flows around the country. Tidal barrages across estuaries like the Severn were once considered an option, but the use of small, free-standing turbines mounted on the sea bed in tidal flows is now seen as better than building large, expensive, environmentally invasive barrages, and the total energy resource is about the same.

Although waves provide more energy than tidal flows, their energy is more geographically concentrated, most of it off the North Atlantic coast, which implies that it would have to be landed mostly in Scotland. Hence the interest in a proposed undersea power cable from Scotland to England and Wales (see opposite).

Wave and tidal energy resources are more predictable than wind power. Waves are in effect stored wind energy and the tides are driven by the lunar cycle. They would fit well with the other major offshore energy option of wind power. Indeed, there have been plans for combining offshore wave or tidal devices with wind turbines, although there are trade-offs because the best tidal and wave sites are not always the best wind sites. But they all share one big advantage; they are offshore, so there is far less visual intrusion, and the impact on marine ecosystems seems likely to be minimal. Some might provide a habitat for sea creatures, although environmental impact studies are needed to ensure there are no hidden problems. But it seems possible that marine renewables; wave and tidal, along with offshore wind, could between them meet much of our energy needs. If, that is, we fund R&D now to get the technology developed and the price down.

So what has emerged in the last year or so? There is no shortage of ideas. Several wave energy devices, along with newly developed tidal current devices, are under test, as government money at last flows into this key area. But funding is still low, and the new projects are being pursued by a handful of tiny companies. Wavegen was the pioneer, with its 500 kilowatt (kW) LIMPET shoreline device on Islay. Now it is going offshore with a new floating device, backed by a £1.67m DTI grant. Ocean Power Delivery is about to test its Pelamis wave snake device in Scottish waters and Marine Current Turbines to test its submerged 300kW tidal turbine off the coast of Devon – with an EU grant of 1m euros matched by the DTI. Other projects include the Stingray sea bed-mounted tidal system, which has just been given a £1.1m DTI grant, and the Rochester Venturi tidal device initially developed at Imperial College.

But at around £6m so far, including generic Research Council funding, total government R&D support for these new technologies is tiny compared with what nuclear power gets, which is about half the £50m total allocated to energy R&D. If we really think wave and tidal power could form the basis of a new renewable energy industry, alongside offshore wind, then we have to do better.

Most of the wave and tidal device teams expect their first prototypes to deliver power at about 7p/kWh, which is far better than on-land wind achieved at an equivalent stage of development. In 1991, on-land wind energy was getting 11p/kWh under the NFFO. Now it’s down to around 2p on good sites. The wave and tidal teams hope commercial devices will deliver energy costing about 4p/kWh, making them viable for take-up under the Renewables Obligation (three of the wave projects already have NFFO contracts). Offshore wind has already just about reached this key price point and looks like moving ahead, backed by reasonable grants from the DTI. But the DTI seems to see wave and tidal only contributing to energy needs after 2010.

The progress of on-land wind energy is being slowed by opposition from the likes of Country Guardian, a pressure group with Sir Bernard Ingham as vice president, so we must push ahead with wave and tidal power more rapidly if we want to reach the target of obtaining 10% of electricity from renewables by 2010.

You can, of course, go too fast with new technologies; that arguably was one reason why the ambitious, 2MW Osprey wave device came to grief in 1997. It was wrecked before it could be properly moored after an unexpected storm. But around the world, marine renewables are being taken seriously. In Europe, the Netherlands and Denmark have major wave energy programmes and Norway’s Norsk Hydro has taken interest in the Pelamis tidal device. If we are not careful, the UK could repeat the mistake it made with wind power, which, despite our early involvement, has all been developed by other countries, notably Denmark.

For a maritime nation like the UK, with its offshore engineering know how, the same thing happening with wave and tidal power would be disastrous. Adding to the sense of urgency, there’s nuclear power. The nuclear industry claims that the new AP1000 reactor will be able to deliver power at 3p/kWh. The race is on.

Dave Elliott is a member of SERA’s Energy Group