By Prof. Tony Lewis, Chief Technology Officer, OceanEnergy.
A partnership project with potential global impact
It is really exciting to be starting work on the WEDUSEA project, after years in the planning. We are setting out to prove that wave energy can be commercialized and so the potential global impact of this partnership project is huge.
Wave energy is the last remaining untapped renewable energy resource.
The prime sites for wave energy conversion are on the Western coastlines of land masses adjacent to the world’s oceans. The waves are generated by the wind, accumulating the energy and carrying it, with very little loss, across the ocean. This means that the waves are concentrating the wind energy from the whole ocean surface and transporting it to the downwind coast as swell. Consequently, there are many occurrences where wave energy is available at the coastline during times of low wind locally, thus making a combined system of wind and wave energy converters less variable.
Typical areas of high wave energy resource are along the Western coastlines of the Atlantic Ocean in Europe and Africa, in the Pacific Ocean along the North and South American coasts as well as a large number of offshore islands distributed throughout all of the oceans.
A highly reliable and robust construction
The OceanEnergy wave energy convertor (OEBuoy) has the OWC as a floating system supported by a large, sealed buoyancy chamber. The OWC has an L-shaped configuration to house the oscillating water in a tunnel length compatible with the expected wave conditions at the deployment site and this shape reduces the necessary draft of the device.
The OEBuoy is a highly reliable system as there is only one moving part, which is the air turbine runner, located above the waterline, with all of the required electrical and ancillary equipment, housed within the watertight buoyancy chambers. The construction of the OEBuoy uses steel and conventional shipbuilding technology making it ideally suited for mass production.
Demonstrating the world’s largest grid-connected wave energy converter
The WEDUSEA Project is the natural progression of the OEBuoy development on the path towards commercialisation. This project is an exciting development and will provide scale-up to a 1MW device to be deployed at a more exposed site typical of future wave farm sites. The basic layout of the WEC structure will build on the experience of the previous OE35 deployment at the WETS site. The design will incorporate a number of innovations related to the power conversion system, the mooring system and the operations and maintenance strategy.
The Consortium involved in the delivery of this project comprises some of the most experienced companies, research institutions and universities in the wave energy space.
How our wave energy technology works
There are many concepts for wave energy converters (WEC) but the one being developed by OceanEnergy is the Oscillating Water Column (OWC). The OWC system consists of a large enclosure semi-submerged with an underwater opening to the sea and a large trapped-air volume above the waterline. The rising wave pressure at the underwater opening causes the water surface in the enclosure to move and compress the air inside. This compressed air is then directed through an air turbine located in the outlet ducting to the atmosphere. The falling wave pressure results in the air being inhaled back into the air chamber through the air turbine.
This type of turbine is called self-rectifying and a number of designs exist. The one being used in the WEDUSEA project is a Wells Aerofoil Turbine which is highly efficient during the reversing air flows. The diameter of the air turbine outlet is significantly smaller than the surface of the enclosed water column and this results in a gearbox effect by speeding up the air flows through the turbine to be more compatible with electrical generator rotational speeds. As a result, no mechanical gearbox is required.
How the OEBuoy was developed
OceanEnergy has been developing the OEBuoy for a number of years progressively following the OES Testing protocols and conforming to the Evaluation and Guidance Framework requirements. The device has been tested at small scale in laboratory wave tanks and then a one third scale device, rated at 40kW, was tested at the Irish Scale Test Site in Galway Bay for over three years, co-funded by the European Commission.
This step-wise development through the Technology Readiness Levels (TRL) has reduced the risks for future deployments. The present demonstration device is 35m long, was constructed using steel at the Vigor Industries shipyard in Portland, Oregon, with a rated capacity of 500kW. This OE35 device will be tested at the US Navy Test Site (WETS) in Hawaii during 2023.
The deployment will be for two years at the world renowned European Marine Energy Centre (EMEC) in Orkney, Scotland commencing in Summer 2024. The WEC will be moored in 60m water depth and located about 5km from the shore and connected, via a submarine cable, to the onshore electrical grid at Orkney.
This will be the largest grid-connected WEC of its type worldwide when in operation.
The successful demonstration of the OE35 in the WEDUSEA project will pave the way for future deployment of multiple devices in an array to form a wave energy farm. This will be the stepping stone to full commercial roll out for significant power station developments to be in line with the future targets of the European Commission’s Offshore Strategy of 1GW of ocean energy by 2030.
WEDUSEA is the project that can finally unlock the enormous potential of wave energy.