The last weeks have seen some crucial developments in the commercialisation of wave power. Inverness-based AWS received major investment from Alstom, the French power generation company. Aquamarine Power of Edinburgh, backed by Scottish and Southern, started drilling the foundations for the second major trial of its Oyster wave energy collector in the Orkneys. The machine itself is being finished at Burntisland Fabrications and will be installed over the summer. The granddaddy of them all, Pelamis, took on a round of new money from investors and continued its plans for installing its huge red sea-snake-like devices for E.ON and Scottish Power. As well as having tidal currents that match anywhere in the world, the UK has excellent potential for using waves to generate electricity. Despite this, the National Grid’s seven year forecast sees no wave farms before at least 2018. Other commentators, such as the Committee on Climate Change are politely unenthusiastic.

Who is right, the hard-headed financial analysts or the committed companies pushing ahead to install wave collectors in the waters off western Scotland and the northern isles? My money would be on the bloody-minded enthusiasts pushing ahead with their huge steel structures in the face of mild scepticism from banks and governments. I spoke to Martin McAdam, the CEO of Aquamarine Power, to discuss the opportunities for wave power in the UK and understand what needs to happen to get rapid growth in wave power utilisation.

There is, of course, nothing new in observers being sceptical about a new technology while the inventors and engineers running the business developing the machines are mustard keen on the opportunities. Wave is no different to so many compelling opportunities in the past. It is currently four or five times too expensive to compete with gas for electricity generation, even on the west coast of the British Isles. The engineers still have major technical challenges to overcome.

The power of the waves

Waves a few hundred metres from the shore can contain huge densities of energy, often as much as tens of kilowatts per linear metre. The ordinary British house, using about half a kilowatt on average across the 24 hour day, could be powered by a device collecting the energy in a few centimetres of waves. There is a downside to the density of energy in a wave – most collectors that have been tried off the shores of the UK have failed within a few days, unable to deal with enormous forces being placed upon them. Since the Edinburgh-based engineer Stephen Salter developed his eponymous ‘Duck’ in the 1970’s, hundreds of companies have tried and failed to convert wave energy into commercially-priced electricity. It is only in the last few years that credible designs have been developed that are both efficient at capturing wave motion and which can hope to survive storm conditions.

Aquamarine Power's Oyster is one such device. A large scale prototype worked successfully at the Orkney Wave Centre for the best part of a year. A scaled-up device generating a maximum of 800 kilowatts is will be installed at Billia Croo in the Orkneys in late July with the first commercial machines put in place in 2014.

How does it work? ‘It has a design like a laptop’, says Martin McAdam, ‘with the lid, mostly submerged, moving back and forward with the waves’. This motion powers pumps which generate high pressure water. A pipe takes this water to the shore, where it drives conventional hydro-electric turbines, housed in containers. The crucial part of the design is that most of the critical equipment is on-shore, easily and conveniently maintained without having to get into a boat in rough seas. A relatively small number of moving parts are offshore. The design used by the Oyster is very different to the other contenders, with Pelamis capturing the energy from the flexing of the joints in its thin body and AWS getting power from the bobbing of the waves changing water pressure inside the twelve-sided floating structure.

McAdam says that the ideal location is in water about 15 metres deep. Around much of the UK, this depth can be found quite close to the shoreline, with the new site in the Orkneys about 500 metres from land. He says that the Oyster technology installed in large farms in appropriate locations around the British Isles has the potential to generate a maximum of about 8 gigawatts, with the other obvious European markets, such as Portugal, Ireland and France, offering another 8 gigawatts of potential. (For comparison, current total UK generating capacity is about 75 gigawatts, with average demand running at about 35 gigawatts). Oyster’s parent, Aquamarine Power, has its eyes on sites for a 200 megawatt farm in Orkney and 40 megawatt installation off Lewis in the Western Isles. What about expected rates of actual production, as opposed to peak power? McAdam mentions an expected annual output of about 35-40% of the maximum capacity, comparable to well-sited offshore wind turbines. In quiet years, such as 2010, this number would be lower.

The estimates from Aquamarine’s CEO are not inconsistent with the Committee on Climate Change’s figure of 40 terawatt hours for the potential for wave power, about 12% of current UK electricity usage. However McAdam stresses that other companies’ machines will work in locations not suitable for Oysters, implying that the total UK potential may be substantially greater than the CCC thinks.

Wave power is intermittent but marine energy has two advantages over wind. First, it is rarely, if ever, completely still on the western coastline of the UK. Unlike wind turbines, which require a reasonable breeze to start turning, wave collectors will almost always generate some power. Second, wave energy tends to be out of phase with wind power. If it is blowing a gale today, the waves, generated a long way away and only gradually reaching the shore, will arrive after the wind has blown itself out.

Martin McAdam gives some figures for the cost of his collectors. The first Oyster installed in the water cost about £35m per megawatt of peak capacity. The machine being attached to the seafloor over this summer costs about £10m per megawatt. McAdam sees the figure declining to about £3m once costs have been driven out by further R+D, ‘learning by doing’ in the fabrication process and from the benefits of installing many devices along the same piece of shoreline. At £3m, wave is competitive with today’s offshore wind costs, which are running at about £4m per megawatt in shallow locations. Since ‘capacity factors’ are similar at about 35-40%, the output per megawatt installed will be about the same as a wind turbine and the costs of megawatt hour very similar.

Wave farms face many of the same technical challenges as offshore wind. The brutal environment means wave collectors need to be made from huge quantities of corrosion resistant steel. Fabrication is not a simple matter – the leading UK constructor, Burntisland Fabrications or BiFab, is going to be very busy indeed. Wave farms will tend to be far away from easy connection to robust parts of the electricity distribution network. Maintenance work on wave collectors will be difficult, and the absence of electrical gear on the Oyster itself is a huge potential advantage compared to some other offshore technologies. Similarly, the relatively shallow depth in which the Oyster machines operate – 15 metres – implies that, according to the laws of wave physics, all waves greater than 15 metres will have broken by the time they pass over the device, improving survivability.

The crucial question facing the wave power industry is how to get from about £10m per megawatt to £3m as fast as possible. McAdam says while private money and the grants from government bodies such as the Carbon Trust have been very useful these funds are going to be enough to push wave to a point at which it is viable without subsidy. For rapid rollout of wave power, the industry needs a substantial injection of subsidy for further R+D and cheap equity to enable the construction of substantial farms of collectors. This will enable the industry to move down the learning curve far faster than would otherwise happen.

Sceptical commentators will note that unproven renewable technologies often demand large subsidies in order to reach commercial viability at some uncertain and always receding future date. And, indeed, much money on energy R+D will be wasted. Marine Current Turbines in Bristol is close to proving that tidal current power can overcome technical challenges but no company in the wave business can yet claim similar certainty. Real issues remain and waves may never produce power that is cost-competitive with other low-carbon technologies. Nevertheless, consider the following comment in a letter published by distinguished scientists in the Guardian on 13th October 2010, commenting on the £2bn a year spent on military research.

‘As an example of the current imbalance in resources, we note that the current MoD R&D budget is more than 20 times larger than public funding for R&D on renewable energy.’

McAdam says his company might only need to make a total of as few as 50 or 60 Oysters to get the costs down to the £3m/MW figure. If subsidy on all these first production machines was £7m a megawatt, the total public cost would be about £400m, a massive amount but neglible in terms of the amount spent on military research.

Wave power collectors could provide one of the UK’s most important manufacturing exports in twenty years time. The natural energy resources around Britain’s coast may eventually provide a substantial fraction of our energy needs at almost zero running cost. Does it not make sense to divert a larger fraction of the government’s R+D budget towards this increasingly plausible form of low-carbon, environmentally relatively benign, electric power?