Seabed Issue Could Relocate Danish Offshore Wind Farm

An issue with soft seabed conditions at the Hesselø offshore wind farm site is currently being investigated in relation to the framework set for the project and the planned (and currently paused) tender process, with one of the solutions now mentioned being the development of the second of Denmark’s three new large-scale offshore wind farms at a different location.

On 8 October, the Danish Energy Agency (DEA) and Energinet invited potential developers to a technical dialogue on the soft seabed found at the Hesselø offshore wind farm site. The developers are asked to dive into the seabed data and to contribute with their assessment of whether the project is still attractive to be developed and built within its current framework.

Denmark paused the tendering procedure for the Hesselø offshore wind farm this June after preliminary seabed surveys identified soft clay bottoms in large parts of the designated area, especially in the upper 20-30 metres below the seabed.

The Danish Energy Agency had originally planned to publish the preliminary tender conditions and open applications for pre-qualification to the tender in autumn 2021 and to conclude the process at the end of 2022.

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Now, the DEA published a report and associated data from the preliminary geophysical investigations, with a draft report and data from the preliminary geotechnical investigations expected to be published at the end of October.

The Agency also said that processing of data from the preliminary investigations now reached a point where the DEA and Energinet could invite potential developers to a technical dialogue to discuss whether the seabed conditions challenges the establishment of Hesselø offshore wind farm within the politically agreed framework, e.g. in relation to subsidy scheme, the target capacity of 800-1,200 MW, the planned time of completion, etc.

The technical dialogue will be held online and will be taking place from late October to late November 2021.

Based on the input provided by the potential developers as well as further analyses, the DEA will assess whether the tender for the Hesselø offshore wind farm can continue under the current framework.

If new political decisions are required in order to move ahead with the project, the parties behind the 2020 Climate Agreement for energy and industry must re-assess whether the Hesselø wind farm site is still the preferred solution, or whether this second offshore wind farm mentioned in the 2018 Energy Agreement should instead be established at an alternative site, according to the DEA.

Hesselø is planned to become the second offshore wind projects from the 2018 Energy Agreement, in which it was decided to establish three new large-scale offshore wind farms of at least 800 MW by 2030, with Thor being the first of the three.

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With the Climate Agreement from 2020, it was decided to place the second offshore wind farm in the Kattegat, 30 kilometres north of Zealand and some 20 kilometres offshore the island of Hesselø, and for the third wind farm to be built as part of Denmark’s energy island project.

The Agreement also advanced the time schedule for the Hesselø project with completion in 2027, at the same time as Thor.

Photo: Danish Energy Agency