Flexible curved CCell device

Wave energy: Harnessing wave power

There is no lack of waves on our oceans. So will today’s innovations to harness their power make wave energy viable?

In 2012, an old portacabin was moved to Scotland’s National Museum of Mining to provide a space for teaching children about renewable energy. But this wasn’t any portacabin - it came from the University of Edinburgh and was ground zero for several wave power technology breakthroughs. Occupied by the team of Stephen Salter, pioneer of the ‘duck’ wave power converter, over a 30-year period, the portacabin spawned three companies. Together they contributed about £200m to the Scottish economy but have also shown the potential and pitfalls of a technology still looking to prove itself.

Like the waves it’s trying to harness, the industry has had its peaks and troughs. In the last 18 months, two big Scottish wave power companies have gone into administration - in November 2014 Pelamis Wave Power, which started in Salter’s portacabin, and in October 2015 Aquamarine Power, whose ‘Oyster’ device was being tested at the European Marine Energy Centre in Orkney. “It was a hugely gutting process. It was 17 years and 750 person years of engineering effort,” says Pelamis founder Richard Yemm of his company’s failure.

The Scottish government, however, has a plan to kick-start the industry and prevent it from becoming another technology lost to foreign competitors. In February 2015 it established a public innovation company, Wave Energy Scotland, investing £14.3m over a 13-month period including acquiring some Pelamis assets.

Sitting ducks

Scotland boasts a large wave resource, particularly on its western coast. According to Tim Hurst, managing director of Wave Energy Scotland, the industry could create much-wanted high-value jobs and exports. “We have a number of key things needed to develop the industry - we’ve got our oil and gas industry, which is already established... we’ve got a world-class research and development facility in the form of Edinburgh University and we’ve got small companies who are interested in developing the technology,” he says.

The story starts with Stephen Salter. He says he became interested in the area around the 1973 energy crisis while at home with flu: “My wife said instead of feeling miserable, why don’t you sort out the energy crisis - we need something that is clean, safe, lasts forever and works in the winter in Scotland, and that made me look at waves.” His ideas led to a revolutionary device, as well as the first portacabin spin-out, Edinburgh Designs. The company, created in 1987, commercialised the wave tanks that Salter’s team created to simulate ocean waves. Since then it has installed over 1,000 systems, including one at Disney’s California Adventure Park in the USA.

The Salter duck, as it became known, could pivot with the waves, reacting against an internal gyroscope and converting wave energy into electricity via a generator. The cleverness of the device was its ability to work with the waves. “What I wanted to do was have something where the water moved in the same circular motion when driving the machine that it would normally in the open sea - that gave this duck shape,” says Salter.

“We were getting 80 to 90 per cent efficiency really very quickly,” he adds, meaning that a very high proportion of the energy reaching the duck was extracted. Salter aimed to feed a string of huge, bus-sized floating ducks - connected via a central spine and generating 50 megawatts - into the national grid (a typical coal plant produces 600 megawatts).

One of the problems with wave power is the extremes in ocean wave conditions, varying by a factor of 1,000. “You’ve got to be able to build a device that can survive a 25m wave but also absorb energy from a 1m wave, and that leads to huge technical challenges,” says Hurst. This was particularly the case for power transfer. Win Rampen, another portacabin alumnus and now chairman of Artemis Intelligent Power, explains that “it is a very difficult power to harness. You are looking at motion ratios of hundreds to one and it’s changing all the time... so the transmission ratio has got to change”.

Conventional hydraulic systems designed to cope with varying outputs would have large inbuilt ‘parasitic’ energy losses. Rampen says that they “set out to completely redesign the hydraulics by essentially integrating the controls directly into the hydraulic pump”. This led to a unique digital hydraulics power transmission technology using high-speed valves controlled by electronic microprocessors. When wave power research slowed down, Rampen and colleagues concentrated on wider applications. A second spinout, Artemis Intelligent Power, emerged in 1994 and was eventually bought by Japanese engineering giant Mitsubishi Heavy Industries in 2010.

Scaling down the size

In the 1980s funders fell out of love with wave power, partly due to decreasing oil prices but it was also clear that wave power was not cheap. Will Bateman, currently developing the CCell device in Somerset, says the early designs were over-ambitious in size. “Salter's duck is one of the cleverest devices out there. Where he went wrong was scale - it was very difficult for him to scale it up and virtually impossible to make it economically,” he says.

Salter disagrees, explaining that “by 1981 the official costs were getting within a factor of two of coal and probably cheaper than the true costs of nuclear”. He says that UK research was largely discontinued for political reasons.

When funding returned in the 1990s there was a shift to smaller devices, forming wave power farms - analogous to wind turbine farms. Pelamis’s sea snake was one of these smaller second-generation devices.

Yemm started out in Salter’s portacabin on other projects, but says that “an engineer who is exposed to the wave energy challenge can’t help but try and come up with better ways of doing it”. His device ran at lower efficiencies, but would be cheaper to operate. Pelamis launched in 1998, introducing the line absorber concept, which Yemm says was a huge step forward: “If you distribute your volume into a long line pointing into the waves, quite the opposite of a terminator machine [like Salter’s duck] sitting across the wave crest, you actually have some very big advantages in terms of the system’s ability to absorb power, but also to survive”.

Pelamis developed a machine over 142m long and 3.5m in diameter, made from five hinged sections that bend as waves pass, causing hydraulic motors to drive electrical generators. The shape minimises wave inertia, drag and impact forces as it responds to the rotating force of the wave, rather than an up and down heave motion. In 2004, several 750-kilowatt Pelamis sea-snakes were tested at the European Marine Energy Centre, making it the world’s first grid-connected wave energy machine.

From the 1990s onwards, a myriad of international companies were developing different approaches. Other countries with wave resources funded devices, including Ireland, Portugal, France, Denmark, Australia and the USA. The sector became flooded with new designs, not all an improvement on older ideas. Rampen jokes that “if you could call it the name of a furry marine animal - the seal or the whale or the dolphin, then all the better - then you were liable to be able to find investors!”

Problems in the sector began with the 2007 financial crash and a collapse in investor confidence. The technology was not yet cost competitive with wind power and technical progress was slow. For Pelamis, a €9m (£7.14m) collaboration with Portuguese utility company Enersis disintegrated and they ultimately ran out of money.

Recognising the commercial difficulties of funding the sector, Hurst says the Scottish government is now hoping to move forwards to a third phase of development. “We needed to use a different model,” he says. In November 2015, Wave Energy Scotland awarded over £2.25m to eight consortia, not limited to Scottish companies. The hope is that the first proof-of-concept projects will be ready for private investment by 2020 and the first wave farms could be operational by 2025.

One of the companies being funded by Scotland is Will Bateman’s Zyba Renewables. Bateman thought a curved, rather than flat, pivoting paddle would improve performance and in 2012 tested his ideas at University College London. He found his curved design was 40 per cent more efficient and the CCell device was born. It has the shape of a boat hull, but the open side faces oncoming waves. His curved structure minimises the energy lost from the paddle’s own motion in the water and also provides structural support. “You can reduce the strength of your materials in your device by about 90 per cent technically, by putting an extra curvature in it,” says Bateman, who compares it to bending a piece of paper to keep it rigid.

Bateman thinks his device could be more efficient than Salter’s duck but says that they are still doing a lot of work on it. Unlike Salter’s duck, the machines are designed to work individually or in farms. They can capture wave energy that passes around them, by creating beneficial pressures on the shore-facing side of the paddle, which dramatically increase the net forces across the paddle. The company is testing its next four-metre device off the coast of Cumbria with a view to having at least five devices deployed by 2017.

Advances in wave power

Bateman’s strategy differs from others, he says, because he is “trying to make a design that is comparatively small and incredibly cheap”. His 20-60 kilowatt devices will cost in the order of £10,000 and are aimed at micro-grid markets that currently use diesel, such as small islands or military bases. “We need to gradually prove our technology and demonstrate that we can deploy and operate it safely,” argues Bateman, but adds that he’s not taking his eye off the grid - “our aspirations are very much in line with what Scotland and the UK wants, but it’s a longer-term goal”.

In the meantime, development continues elsewhere. In 2015, Australian company Carnegie Wave became the first to operate multiple connected units, off the Perth coast in Western Australia, and US engineering giant Lockheed Martin announced a joint venture to create a 62.5 megawatt installation, also in Australia. But the future for wave power in the UK is not clear. “If the industry can demonstrate big economic innovations by 2020, then I’m optimistic, if not, I fear it may go back to being a purely academic curiosity,” says Yemm.

Whether children visiting Salter’s portacabin in the future will hear about Scotland’s successful wave power industry is likely to depend on advances in the next five years.

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