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Offshore wind farm technology is not particularly green when its ‘whole of life’ is considered

Decommissioned turbine blades are usually disposed of in a landfill or incinerated

Last week, the Government announced the provisional results of its first offshore wind auction. Four projects were successful, two off the coast of Dublin, one off Wicklow and one off Galway. Together they would implement 60 per cent of the Governments target of five gigawatts (GW) of offshore wind power for the national grid by the end of 2030, and equivalent by then to about 20 per cent of national capacity.

The Government’s 2021 climate action plan (gov.ie/en/publication/6223e-climate-action-plan-2021/) envisages a longer-term goal of up to 30GW of offshore wind power off our Atlantic coasts. This enormous capability could in part be exported, and also be used to generate liquid hydrogen as a fossil fuel replacement.

There is considerable work before the projects are operational. None of the successful auction bidders have yet been able to apply for planning permission. Delays in An Bord Pleanála, the National Parks & Wildlife Service and in the establishment of the Maritime Area Regulatory Authority are causing concern for the industry. A Government taskforce for offshore wind delivery (gov.ie/en/publication/c8749-offshore-wind-delivery-taskforce/) was established a year ago and chaired by the Department of the Environment with six other Government departments, the Commission for Regulation of Utilities, EirGrid and Enterprise Ireland.

Norman Crowley on the business of decarbonisation

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Offshore wind generation faces considerable engineering challenges compared to onshore plants for initial installation, subsequent servicing and eventual end-of-life decommissioning. Nearshore wind farms can be built using pylon towers anchored deep into the sea bed. Pylons on floating platforms can be used further offshore, benefiting from steadier wind conditions and less visual impact. In both cases, periodic inspection and maintenance not just of the generators, but also of the turbine blades, must be feasible offshore. Larger turbines generally have higher operating efficiencies, and so some offshore towers now have gearboxes at least 100m above the sea surface. Some suppliers are manufacturing blades for offshore, which are themselves more than 100m in length, and so require even higher pylon towers.

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The design and engineering of such massive structures is highly specialised. The blades on a single turbine must be delicately balanced, due to the immense strains induced on the structure. Damage to a blade and erosion of the leading edge — whether by ageing and delamination, physical strikes from birds, or ice accretion in winter conditions — can cause excessive vibration, leading to failure of the drive train. While blades and gearboxes are typically designed for lifetimes of 20 to 25 years, it is not at all unusual for a gearbox to be changed or replaced in as little as 10 years.

Paradoxically, climate change may affect our national plans for offshore wind. Over the next 20 to 25 years we may well see stronger storms and possibly even hurricane conditions, especially off our Atlantic coasts. Also, as the Marine Institute recently emphasised, the Gulf Stream may change leading to cooler conditions for Ireland and our waters. Both stronger wind conditions and heavier icing have consequences for offshore wind generation.

Decommissioned turbine blades are usually disposed of in a landfill or incinerated. However, there are a few alternatives

Ironically, wind farm technology is not yet particularly green when the whole of life is considered. While pylon towers, gear trains and generating equipment can usually be dismantled and recycled at the end of life, the turbine blades themselves are a very different story. Large offshore blades are typically cast from fibreglass-reinforced epoxy resins. Carbon fibre technology is also being introduced, although its manufacturing releases much greater carbon emissions than for epoxy or glass fibre blades.

The scale of the decommissioning challenge is growing. A 2020 study (sciencedirect.com/science/article/abs/pii/S0956053X20301306) forecasts 325 thousand tonnes of annual blade waste in Europe by 2050, to which the Irish offshore farms will contribute.

Decommissioned turbine blades are usually disposed of in a landfill or incinerated. However, there are a few alternatives. The Dutch firm Superuse Studios has proposed architectural applications, using decommissioned blades to make bus shelters or city benches. There have also been proposals to reuse blades in the construction of affordable housing for roof frames. The US company Global Fibreglass Solutions crushes old blades into pellets for fibre boards for walls and flooring. Danish company Refiber recovers the glass fibres in blades under high temperatures in a rotary kiln, for insulation materials.

There are several EU directives relating to the control of composite waste, including hazardous waste directive, incineration and landfill. However, there are no standards for the decommissioning of wind turbine blades across the industry. Furthermore, the costs of decommissioning are sometimes ignored in considering the total lifetime costs of a wind energy project, potentially with downstream implications for the public purse. I hope the Government is carefully considering the full costs and responsibilities over the lifetimes of each Irish offshore wind project.