Photo: InfinityWEC design with upgraded PTO (Courtesy of Ocean Harvesting)

Swedish company upgrades wave energy system

Ocean Harvesting Technologies has upgraded its InfinityWEC wave energy converter with innovative power take-off (PTO) solution, which is expected to contribute to the reduction of electricity production costs.

InfinityWEC design with upgraded PTO (Courtesy of Ocean Harvesting)
Ocean Harvesting’s InfinityWEC device (Courtesy of Ocean Harvesting)

The technology innovation uses hydrostatic pressure to provide a constant pre-tension force in the PTO, reducing size, weight, complexity, and ultimately cost of electricity production (LCoE), according to Ocean Harvesting.

In the upgraded InfinityWEC design, the PTO hull is split into two halves, with the top half moving up and down with the buoy, while the bottom half is fixed to the anchor.

Similar solutions have been used by pressure-modulating wave energy converters, to extract energy from the variation in pressure below waves, close to the surface.

InfinityWEC however, is a point-absorbing wave energy converter, with a buoy on the surface driving the PTO positioned close to the seabed.

At 70-meter depth, the high pressure of the water provides a 100-ton pre-tension force with only a 1.6-meter diameter PTO hull, Ocean Harvesting explained, adding that a patent application has also been filed for the innovation.

Mikael Sidenmark, Ocean Harvesting’s CEO, said: “The new pre-tension solution is a further improvement of the InfinityWEC wave energy converter, reducing the weight of the PTO by approximately 40%.

“We take advantage of the water pressure outside the PTO to generate the constant pre-tension force, which in combination with ball screw actuators provides instant force control with very high efficiency.

“This enables wave-by-wave tuned force control, improving the annual energy production by up to 30% compared to sea-state tuned control.”

InfinityWEC design with upgraded PTO (Courtesy of Ocean Harvesting)
InfinityWEC design with upgraded PTO (Courtesy of Ocean Harvesting)

Ocean Harvesting is preparing for sea trials of InfinityWEC at scale 1:3, to be performed off the west coast of Sweden. The sea trial project, to validate the performance in a real sea environment, will be conducted between February 2023 and June 2025. Results will be used to further develop and improve the full-scale system with regards to energy yield, efficiency, and affordability.

To remind, Ocean Harvesting was awarded a €2 million grant earlier in November for the project. To complete the project financing, the company is now raising €3 million in equity investment.

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