Combining wind and wave energy production in a single floating power plant holds potential for capturing the benefits of both, or so believes a company staking its future on the concept.
Wave power has a long history of failure and unfulfilled potential. Despite its considerable promise — in theory it could meet the world’s electricity demand at least twice over — the efforts of researchers and entrepreneurs over six decades have failed to produce a commercial result. A small Danish company, however, believes it has found a way, by marrying wave and wind power. After more than a decade of development and testing, Floating Power Plant says its technology is now ready for full scale commercialisation in two wavewind power stations, one off the coast of Wales and the other in Scottish waters. The combined power rating of each floating device, dubbed the P80, will range from 7 MW to 10.3 MW, using large commercially available wind turbines with rated capacities of 5 MW to 7 MW and wave power devices with capacities between 2 MW and 3.6 MW. The wind turbines will account for 70% of total production and wave power the remainder. “The two sources of energy complement each other and share the costs. After a storm, the waves will continue and wash into the device for some time and produce energy when there is no wind. At the same time, it is easier to forecast how much energy you can harvest from the waves at a certain time. These two conditions increase the value of the wave power,” says Floating Power Plant engineer Nils Ebsen. Jens Peter Kofoed, head of wave energy research at Denmark’s Aalborg University, says wave power development has suffered from lack of investment. “In developing new technologies, tests at sea are necessary but also expensive. It is not like wind power, which is possible to test at minor scale on land and in which the room for failure is bigger,” he says. “There are many different concepts for harvesting wave power and for investors it is difficult to decide which kind of technology to invest in,” adds Kofoed.

RADICALLY DIFFERENT

Marrying well established offshore wind power with unproved wave power may attract the venture capital needed, according to Ebsen. “What we have done that is radically different from others is that we are building hybrid devices. As wind is a more developed technology it is a safer business case to set up at sea,” he says. In water depths of 45 metres and more, wind turbines mounted on floating platforms anchored to the seabed are expected to be a commercial competitor to wind turbines in shallower water mounted on foundations that are piled into the seabed or held in place by gravity and suction forces. Installing wave power technology on the underside of floating platforms will absorb the energy from the waves and in the process, stabilise the platform, reducing its required weight and thus the cost of construction, explains Esben.

According to the International Renewable Energy Agency, the levelised cost of electricity from a 10 MW demonstration wave power device would lie between €330/MWh and €630/MWh, falling to an average of around €150-180/MWh in 2030. The agency’s projection for offshore wind in 2030 is €70/MWh, higher than bids accepted last year for projects now nearing construction

INTO THE MARKET

In November 2016, Floating Power Plant announced a partnership with DP Energy, an Irish firm, to proceed with development of two full scale projects with planned rated capacities of 200 MW each. Anders Køhler, CEO of the Danish company, describes the deal as a breakthrough for his business. “We are on the doorstep of commercialisation. We have spent more than ten years turning the idea into reality. It’s all about these two projects now. We have to show that the technology is functional and the prices are able to compete,” he says. Whether the first project will be off Wales or Scotland has yet to decided, but construction will begin in 2018 and the first device is to be up and running in 2019. “We must be able to compete with the prices of offshore wind. That is our goal and we know our technology is up to it,” says Køhler. The levelised cost of energy (LCOE) from commercial offshore wind in Europe today lies between €90/MWh and €140/MWh. The lowest bid accepted for the next round of offshore wind construction is €49.9/MWh for a project in the Baltic Sea, excluding the cost of the transmission infrastructure for sending the power to shore. For projects further out to sea, an LCOE of €71/MWh by 2022 is predicted in a recent report on offshore wind financing by FTI Consulting, a global business advisory firm. Køhler is certain that Floating Power Plant will be able to deliver at competitive prices in the long run. Initially, however, LCOE will be around €200/MWh for the first units built. “That is the deal when you set up prototypes. But the price is still significantly lower than it was for the pioneering solar and wind power projects,” Køhler claims. He expects the next generation of offshore wind will see turbines on floating platforms, citing the deep waters off the UK, France, Japan and Portugal as the most likely venues. Kofoed at Aalborg University believes that wave power is part of the energy future. “The consumption of energy varies a lot. At a coal fired power plant you can increase or decrease the amount of energy produced depending on demand,” he says. “As long as it is not possible to store the power produced from renewable energy, you need to have complementary sources. A combination of sun, wind and wave power is all in all better for the system.” •

Text Eskil Meinhardt Hansen