Wave energy has had many false dawns. But now a company from Finland has a working 2MW prototype up and running in Portugal. Has wave power finally been cracked?
Wave energy is generated by using the power as a wave rolls towards shore to spin a turbine or pump hydraulic pistons. The energy is determined by wave speed, wave height, and the ‘fetch’ — the distance over which the wave has travelled. The larger the ocean, the greater the potential for speed and fetch — and given that Portugal has the entire Atlantic ocean between its coastline and the Americas, the fetch is pretty good.
“There are several different types of wave technology”, explains Chris Ridgewell, CEO of AW-Energy, the Finnish company behind the WaveRoller. He was a naval architect and marine engineer working in liquefied natural gas (LNG) before joining the company as chief technology officer in 2014, and taking over the CEO reins in 2018. “There’s floating ones that bob up and down, things on the shore that take water in and drain it out again. Instead, the WaveRoller is fixed and hinged to the seabed, only about 10 metres deep, using the back-and-forth motion of the wave swell. This surge phenomenon drives across the Atlantic ocean… as it starts to touch the seabed closer to shore, the wave length reduces and the wave speed increases.”
Whereas a typical solar panel can capture “about 150 watts per square metre on average”, says Ridgewell, “with wave energy, it is about 40,000 watts per metre. It’s a huge difference.”
He’s not the first to get excited about the potential for sea power. From 1855 to 1973 there were 340 patents for wave energy devices filed in the UK alone. Needless to say, none of them really worked — although there is some evidence that a M. Bochaux-Praceique of Royan, France, used a vertical bore hole in a cliff to drive a turbine, supplying power and lighting to his house, as early as 1910.
Since then, engineers have come back to the idea again and again. The 2000s saw the first real breakthroughs. The Islay LIMPET in Scotland was the world’s first commercial wave power device and was connected to the UK National Grid in November 2000. However, what was expected to be a 500kw unit was soon downgraded to 250kw, and eventually decommissioned in 2018. Next came the Aguçadoura Wave Farm in Portugal, designed to use three Pelamis Wave Energy Converters (see pic above) to convert the motion of the ocean surface waves into electricity, with a much more promising 2.25MW in total installed capacity. The farm opened on 23 September 2008… and was shut down only two months later. Pelamis, the company behind the machines, ceased operations in 2014.
What makes the Finnish WaveRoller different is arguably the scale of the units, the power output, and the steps taken towards commercialisation. When I ask Ridgewell about the previous wave energy failures, he tells me , “We haven’t been looking in that direction — we’ve been looking more towards offshore wind. The price reduction recently in offshore wind has happened because of the low cost financing achieved due to insurability, and the offshore wind industry applying codes and standards. In the early days of offshore wind… my sense is there wasn’t the same standardisation in place. So, insurance costs have now gone down and financing is cheaper. That’s the direction we have been following. As you say there have been some failures in the past, but that’s all part of the normal technology development cycle.”
Another advantage, he says, is that “we are just applying existing, known engineering. If you a picture rudder on a ship, but facing downwards, so our panel moves backwards and forwards in the wave swell… When you get to about 10 metres in depth, the wave height is limited by the seabed depth — if the wave height is more than 75% of the depth, then the wave breaks. That means in our operational depth there is a wave break limit of 7 metres… The 100-year storm won’t make much difference, we know what the maximum wave conditions are going to be, so the design variables are smaller.”
What isn’t small are the WaveRoller panels themselves. AW-Energy’s first working prototype off the Portugal coast, the Surge #1 project, which ran from 2012–2014, saw three 9x10 metre units each delivering 100KW of power. The latest iteration, Surge #2, sees a single mighty 18x10 metre panel, delivering 400kw of continuous power.
As the WaveRoller panel moves like a horizontal ship’s rudder attached to the sea floor, so hydraulic pistons inside the panel pump fluids inside a closed hydraulic circuit. These feed into a power storage and smoothing system, which connects to a hydraulic motor that drives an electricity generator. The electrical output from this renewable wave energy power plant is then connected to the electric grid via a sub-sea cable. Each wave can deliver 2MW every ten seconds or so, but digital smoothing feeds this out to the grid at a continuous, flat rate of 400kw.
The obvious advantage of flattened, continuous energy that runs all day and all night is that this is the opposite of most renewable energy technology. Wave energy doesn’t have an intermittency problem — arguably, it solves the intermittency problem. Fossil fuel and nuclear energy companies like to claim that they are indispensable, because we need flat, baseline energy as a constant; however, wave energy could provide the same, but cleanly, with zero emissions during operation.
“California is good example”, says Ridgewell. “In summer you’ve got peak solar and wind, which then dramatically drops off in winter when you’ve get less sun and wind. But that’s exactly when wave energy is at its highest, when the big storms come in. It’s an effective balance to wind and solar… If California gets up to 80% renewables, the [energy shortfall] in December is about 5TW/hours… That would need something like 40-times the world’s current production of lithium to store it in batteries.” He adds that the electricity from wave power can also be sold at a higher price because it can produce when wind and solar cannot.
The obvious concern for huge steel panels splashing about in large waves is the implications for marine wildlife. How do fish and marine mammals interact with the WaveRoller? Here Ridgewell gives a surprising answer — so far, they have actually attracted marine wildlife. “We have had an artificial reef effect — we operate on a sandy seabed that is usually pretty dead, but our [concrete] foundation and panel create a reef for seaweed and shellfish, and fish come to feed… In Portugal, the fishermen aren’t allowed too close, but they go fairly close and they tell us they catch more fish there!” The coastline in Peniche, Portugal, is also an EU Environment Protected Area, and so far they have met all the stipulations to operate. “It is part of our [insurance] certification with Lloyd’s Register, to ensure we don’t create any adverse environmental impact”, says Ridgewell. “That includes failure modes ensuring against any leak or release from the hydraulics… and noise measurements… If you compare our device moving backwards and forwards with a wave to a speedboat zipping by, ours has a much more benign impact.”
AW-Energy only have a small team of 10–15 or so people. They are a start-up with grand plans — of which there have been many that have come and gone in the renewable energy industry, especially in sea energy. But they have the backing of some big investors, including Aura Capital, Fortum, John Nurminen Oy, Sitra and the European Investment Bank.
Ridgewell can’t name the customers he is currently in negotiations with, but he says they include government departments and energy companies, both large and small. “Some countries don’t have the energy price right now that would support it — but even so, some of those see the benefit of producing energy as the sun goes down. Other countries already have a high energy price, which means we can develop a profitable project.” The only limitation, he says, is that not every coastline is suitable — it needs to be a large sea with a long ‘fetch’. “The Mediterranean is challenging — the wave conditions are much smaller, you’d need a different type of technology there. We’ve developed this technology to really take the battering of a big ocean… So west coast of Ireland, Cornwall in the UK, Portugal, Chile, South Africa, the Indian Ocean…” Basically, wherever the surfing is good, it’s also good for wave energy.
Ridgewell hopes to have a customer for a “small 15 unit array” to start with, and expand from there. He makes it sound modest, but 15 18x10 metre panels would be a large operation. Unlike an offshore wind farm, however, the running and maintenance of a wave farm a couple of hundred metres out to sea isn’t so complex — “we can use the beach”. And 15 panels delivering a constant 400kw would amount to 6MW of renewable power: that’s the same output as three large Vestas V90 wind turbines or 12 Vestas V39s in windy conditions, enough to power approximately 6000 homes. That would be incredibly good for a fledgling energy source. I’ve made this point in a previous article, but the world’s first wind farm was built in New Hampshire in 1980, with 30kw wind turbines — and they subsequently all broke down. But look at wind power now: 39 years later, the largest single wind turbines currently operating can achieve 8MW.
When I’ve written about Blue Energy before it seemed far off; not quite pipe dreams, but simply good ideas that are worth exploring. The wave power devices built by AW-Energy, however, look the real deal. They aren’t theoretical; they are solid, impressively engineered steel units the size of a bus and ready to deploy. But they will need an innovative, ambitious customer — one with a stormy coastline and a need for new energy resource — to make the first move. As Ridgewell says, wryly, “there is always a long line of people willing to buy your second device.” However, this is their second device. The #1, capable of 100kw, proved the concept for two years off the Portuguese coast; now the 400kw #2 is ready to go. The potential is too exciting to see it sink without a trace, like previous wave energy attempts. Hopefully, the tide of energy prices and renewable energy targets is now pulling in the right direction.
Tim’s book, Clearing the Air: the Beginning and the End of Air Pollution, is out now, published by Bloomsbury.