Go with the flow

Atkins | 04 Dec 2008 | Comments

The UK’s waves and tidal currents have the potential to generate up to 20 per cent of its total electricity. a simple and unique invention could help to harness it.

The UK Government has set a target of obtaining 15 per cent of its energy from clean sources by 2020, and the Scottish Nationalist Government an ambitious 50 per cent. With the creation of the Department of Energy and Climate Change in October 2008, it’s clear that they have every intention of meeting them.

With 11,072 miles of coastline, the UK has considerable potential to generate some of this energy from wave and tidal power, and Government funding should speed up the commercialisation of the technologies involved.

Furthermore, the UK has become an international trail-blazer in marine and tidal power technology, with around 50 per cent of the world’s marine power patents coming from the UK.

How much progress has been made so far in capturing that energy? “We’re about where the Wright brothers were,” says Neil Kermode, managing director of the Orkney-based European Marine Energy Centre (EMEC), the world’s first dedicated test site for wave and tidal power technology. “In other words, we have the research machines working, but have a huge way to go before we reach the equivalent of modern aviation. However, like the Wright brothers, we have demonstrated to the world that the principles are sound.”

Hotbed of innovation

“Much of the groundwork on the theoretical side of marine power was conducted back in the 1970s, when fears about rising oil prices first prompted interest in unlocking the power of the sea,” says Atkins’ Rod Rainey, who has played a key role in developing marine energy technology for three decades.

Two visionary and tenacious people were especially important in making this progress, adds Kermode: “Professor Stephen Salter at Edinburgh University and Peter Fraenkel, founder of Marine Current Turbines, established the concept of marine energy in the public consciousness.”

Salter designed a revolutionary wave power device in 1974, while Fraenkel began exploring ways to convert water currents into electricity at around the same time.

More recently, the Carbon Trust has been a key champion of marine power innovation in the UK. Throughout 2004 and 2005, the organisation ran the Marine Energy Challenge, a programme designed to improve understanding of marine power technologies. Under the scheme, eight wave power technology developers worked with leading offshore engineering and power generation consultants, including Atkins, to put their innovations to the test. This programme also provided the start-up firms taking part with valuable access to engineering expertise, essential in the successful deployment of reliable power generation installations.

Following the results of the Marine Energy Challenge, the Carbon Trust is confident that marine energy has the potential to become competitive with other generation forms in future. However, it also raised a major short-term challenge: cost.

“To turn this potential into a commercial reality, marine needs sustained additional funding to accelerate its breakthrough into the mainstream of energy generation sources,” says Tom Delay, chief executive of the Carbon Trust.

“Fast learning or a step change cost reduction is needed to make offshore wave energy converters cost competitive for reasonable amounts of investment,” stated the Carbon Trust in a recent report, Future Marine Energy.

In other words, current wave power technologies are simply too expensive.

Sea snake

To address this issue, Atkins’ Rainey is working to create cheaper, more reliable forms of marine power. He has already played a key role in the independent verification of the current trail-blazer in wave power technology, Pelamis – in particular, helping to overcome the challenge of metal fatigue.

Alongside his advisory role, Rainey teamed up with renowned British physicist Professor Francis Farley to create Anaconda, a radical new model for marine power generation that has the backing of the Carbon Trust. Whereas past devices tended to be heavily engineered and complicated, Anaconda is simplicity itself.

“I sought to design something that would be cheap and maintenance free,” Rainey explains. The outcome was a water-filled rubber tube, around 200 metres long, designed to surf the currents just beneath the ocean surface.

Large groups of the tubes would sit off the coastline, attached to the seabed by chains. As the passing ocean swell hits the front end of a tube, a bulge forms inside, which races down its length just ahead of the wave.

As the bulge reaches the far end of the tube, it hits a series of turbines that capture the energy and convert it to electricity.

The process, says Rainey, is similar to the way the pulse moves in your arm. “Your heart beats and the pressure pulse travels down to your wrist, but it does so much more slowly than the speed of a sound wave in blood,” he says.

“This is because the elasticity of the artery wall slows the pulse down. Similarly, Anaconda slows the speed of the sound wave in water right down to the speed of the water wave outside. This makes for a light, maintenance-free wave power machine.”

Put to the test

Rainey and co-inventor Professor Farley have teamed up with Avon Fabrications, a major rubber component manufacturer, to build prototypes of the machine.

Meanwhile, professors John Chapin and Grant Hearn at Southampton University have been awarded a three-year grant by the Engineering and Physical Sciences Research Council to test Anaconda’s theory and practice.

Early results are promising. The Carbon Trust has identified the Anaconda device as having the potential to provide a step change in the cost of wave energy.

As well as being cost-effective, Anaconda is durable enough to withstand the harsh maritime environment. “A rubber tube is much more likely to survive than other technologies,” says Professor Farley. “It’s totally flexible, so waves won’t break it.”

More testing with scaled up versions of the technology will now follow, he adds: “If that goes well, we’ll be able to build a full-scale prototype – possibly next year. We’re optimistic about the future.”

Conducting thorough trials is key, says Kermode at the EMEC. “We need to get equipment into the water to find out what works, what doesn’t and which technologies are the most effective.” Rather than focus on specific types of technology, these trials should directly compare prototypes. “We need multiple machines in the water, in multiple locations,” he says.

Following further trials, Kermode expects utility companies to commercially deploy the technology and start pumping wave and tidal power into the National Grid.

“Marine power generation in the UK should be at least comparable to what nuclear energy is currently delivering,” he says. As fossil fuels continue to deplete, global energy demands surge and pressure mounts from all quarters to reduce carbon emissions, the case for marine power can only get stronger in the future.

Back to its roots

With all of this potential, how likely is it that the UK will be ready, willing and able to take advantage? Quite good, according to the recent Carbon Trust report.

Future Marine Energy found that “the UK is well placed to leverage its skills and experience in offshore oil and gas, ship-building and power generation to accelerate progress in the marine renewables sector and capture the economic value for the UK.”

The Carbon Trust’s Delay adds, “We are leading the world in the development of marine energy and the UK is a hotbed of innovation for these key technologies. We have the potential to deliver up to 20 per cent of the UK’s electricity needs from marine energy and there are already a number of exciting technologies in development.”

“Were the UK to make full use of this potential, the economic returns could be considerable,” points out Professor Farley. “The UK’s Atlantic coastline, for example, including Ireland, could produce around 50GW of electricity at peak generation.”

Should that potential be realised, it could go a long way in helping to address the dual challenges of climate change and energy security in the future.

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