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14 November 2019

Wave power too expensive to stand alone, looks to pair with wind

Wave energy could provide up to 64% of the US’s current electricity generation, according the US Energy Information Administration. Devices are being established, but developers will struggle to justify adopting expensive wave power technology instead of offshore wind. Hybrid solutions with wind could provide a last gasp chance of survival for wave energy.

Technologies currently under development, including those by Ocean Energy and Blackfish, have yet to converge on the most efficient method of harnessing the power of wave oscillation, with some capturing power from displaced air movement and some from the motion of the wave itself. Ocean Energy is currently one of the most promising players in the sector, developing a variety of “OE Buoys” as wave energy convertors. With a floating hull, large volumes of air are displaced by passing waves, inducing an increased pressure to rotate a turbine and generate electricity.

Waves are essentially a derivative of wind power because they are made by the wind, although water has a greater density, meaning some argue that the wave energy sector could potentially equal and even exceed the offshore wind sector, taking into account that waves are a concentrated form of wind energy capable of travelling large distances with minimal losses.

Despite this, the technology is still immature compared to its alternatives and still the preserve of individual inventors rather than engineering combines. Unlike some forms of renewable energy however, this cannot be blamed on a lack of historic effort. The first patent for a wave power device was filed in 1799, nearly 50 years before any movement in solar power, with devices like the Bristol Cylinder and Salters Duck appearing promising to scale for electricity production. The first commercial-scale project was however only commissioned at the turn of the millennium, with the UK receiving power from the Islay LIMPET project, which to this day has a capacity of 250 kW. Since then, the industry has struggled to gain momentum, with a measly 25 MW installed globally as of 2017.

Similar stagnation has been seen on a company level. Ocean Energy claims that in-situ testing has been successful since 2011, but currently no large-scale orders or projects have been reported.

This is largely due to the rapid development of offshore wind, following the extended success in onshore technology. With high intensity waves often seen in conjunction with high intensity wind, developers have not looked kindly upon using an unproven technology, with the same intermittency issues and greater exposure to high loads from the sea and have stuck with offshore wind.

Innovation is still ongoing, with the market dominated by university spin-offs and start-ups. Near-shore projects have been suggested for use in remote locations, where electricity demand is low, but with countries rushing towards renewables in lieu of a ‘climate crisis’, large-scale projects have and are likely continue favoring offshore wind or in some cases floating solar.

However, as wave power technology matures, potential will arise for hybrid projects to come into play. With grid infrastructure established to accommodate offshore wind projects, the high LCOE of wave power can be offset if farms can be retrofitted with wave energy technology.

Ocean Energy’s OE50 buoy projects has a stated capacity of 2.5 MW, meaning that if deployed to a maximum extent alongside 8 MW offshore wind turbines, hybrid farm capacity theoretically increases by over 20%.

A pairing such as this would be comparable to the recent uptake in hydro and floating solar, increasing the capacity of renewables projects, without the necessity to develop new infrastructure to accommodate new technology, although the need to address storage issues would remain.

A review from IRENA indicates that the foundation and mooring of wave energy platforms accounts for 6% of lifetime expenditure, with grid connection responsible for another 5%. Up to 41% of project costs would be offset through retrofitting to an offshore wind project.

In 2014, the study by IRENA indicated the LCOE of wave power to sit between €330 and €630 per MWh, and far too high to be considered competitive within the current renewables market. With economies of scale, the report suggests that this is likely to fall to between €113 and €226 MWh by 2030, if more than 2 GW of capacity is installed.

If costs can squeeze below this, then it may be feasible for wave power to become a contributor in the renewable energy mix, but this will rely on significant investment in the immediate future for prices to fall. At present this is not happening, and despite this hybrid potential, all indicators suggest that if wave energy was ever going to take off, it would have done so already.