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Sean Hegarty
Sean Hegarty, Moneypoint Station Manager. Photograph by John Kelly

Sea giants to power the future

Turbines up to 300 metres high on massive floating platforms will be developed by ESB with experienced partners, reports Dan Danaher

A NEW floating offshore windfarm of 1,400 megawatts will be developed off the coast of Clare and Kerry in two phases by ESB and joint venture partners, Equinor, a world leader in floating offshore wind technology. Once complete, the windfarm will be capable of powering more than 1.6 million homes in Ireland. Subject to the appropriate consents being granted, it is expected to be in production within the next decade.

In an interview with the Clare Champion, Moneypoint station manager, Sean Hegarty said it is envisaged the new turbines will be constructed on an enormous floating concrete base weighing up to 15,000 tonnes, with the turbine built on a corner of the triangular structure.

While the turbines in Peterhead off the UK coast, developed by ESB’s partners Equinor have a different base structure, he confirmed that, above the water, they will look very similar to the ones envisaged for Green Atlantic. Asked about the expected height of the new turbines, he said these new turbines range between 200 and 300 metres high, before adding the precise height will be subject to the planning process.

While the wind turbines will be constructed on a massive floating concrete platform, he confirmed they will be tethered to the sea bed. He said offshore turbines tend to provide between 15 and 20 megawatts of electricity. He expects that in the region of 20 giant offshore turbines may be built as part of the first phase, depending on how much technology has advanced over the last four years.

The ESB has stated the cost of providing renewable energy through offshore wind continues to decline in recent years. Mr Hegarty believes this has been achieved through economies of scale and the emergence of new technology that has been used in different countries.

Asked if the location of the offshore windfarm off the Clare coast would ensure that it doesn’t interfere with shipping lanes, Mr Hegarty outlined a consultation process will start once new legislation is put in place later this year involving all the necessary stakeholders to ensure they can be accommodated for all their on-shore and offshore requirements.

Asked if any Environmental Impact Statement has been completed as part of the pre-planning process, he said offshore windfarm technology isn’t new and outlined the whole planning and consent process will take environmental concerns into account to allow the company provide the infrastructure. He confirmed a foreshore licence application to facilitate this proposed development was lodged recently and the next phase would involve an environmental impact assessment.

Equinor, which is going into a 50/50 partnership with the ESB to develop the offshore windfarm off the Clare coast, was involved in the world’s first full-scale floating windfarm off Peterhead, which was recorded as having the UK’s best results for capturing potential output offshore for the third year.

Five giant wind turbines make up the Hywind Scotland development, about 25 kilometres off Aberdeenshire. The project – run by Equinor – started generating electricity in 2017. Thick mooring lines tether the towers to the sea base. During its first two years of operation, the windfarm achieved an average capacity factor of 54%.

Sebastian Bringsværd, head of floating wind development at Equinor, said access to deeper waters meant higher and more consistent wind speeds and an efficient way to generate electricity. It allows turbines to be installed in much deeper waters than conventional offshore installations. There is a third more under the water weighted heavily at the bottom with iron ore to keep the structure floating stable in the water.

Statoil assembly site manager, Monica Petterson said floating windfarms give the company much more flexibility when locating them around the world. The tower, including the blades, stretches to 175 metres or 575 feet, would dwarf Big Ben.

Each turbine weighs 11,500 tonnes. Each blade is 75 metres long. This windfarm can power 20,000 homes. The box behind the blades – the nacelle – could hold two double-decker buses
Statoil says the blades harness breakthrough software – which holds the tower upright by twisting the blades to dampen motions from wind, waves and currents.

This floating windfarm is positioned in water depths of up to 129 metres whereas those fixed to the seabed are generally at depths of up to 50 metres. Statoil believes the new technology has the potential to work in water depths of up to 700 metres. Average wind speeds at the site are around 22mph.

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