HOFOR Orders Offshore Wind Foundations with Nature-Inclusive Design at Aarsleff

Wind Farm Update

July 4, 2023, by Adrijana Buljan

Copenhagen’s power supply company HOFOR has contracted Per Aarsleff A/S (Aarsleff) for the supply of foundations for the Aflandshage offshore wind farm that will be built in the Øresund Strait. The contract includes Nature-Inclusive Design, which will see artificial reefs being built at Aflandshage to house cod, crabs and other small marine wildlife.

The artificial reefs will consist of large rocks deployed at some of the 26 concrete gravity-based foundations to form crevices that will help improve conditions for fish and other marine animals, and especially cod, which has been in sharp decline in Danish waters in recent years, according to HOFOR.

Furthermore, the contract for the foundations, which will be between 17 and 25 metres tall and weigh up to 4,000 tonnes, includes minimising CO2 footprint by choosing a material with lower emissions. For Aflandshage’s foundations, Aarsleff will be using CEM III cement for the concrete as this type of cement uses blast furnace slag, a by-product of iron- and steel-making, to reduce the amount of regular Portland cement, which has a higher carbon content.

“We have designed a sustainability strategy specifically for this project with various initiatives spanning greenhouse gas emissions, circularity and workforce engagement with sustainability. The rebar in the foundations, for example, is almost exclusively made from recycled iron, and the foundations will be recycled as far as possible when the life of the turbines is over”, said Jesper Kristian Jacobsen, Managing Director at Per Aarsleff A/S.

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The design and planning for the foundations will begin now, while the fabrication of concrete, excavation and deployment of rock pads will start in 2024.

The first foundations will be installed in the first half of 2025 and the work is expected to be completed in autumn 2025.

The condition of the foundations at Aflandshage’s offshore wind turbines will be monitored during the lifetime of the wind farm.

“It is a strategic goal for us to help strengthen Denmark’s green transformation, and the turbines will provide the Øresund region with plenty of renewable energy, but it is not CO2-free to build wind farms, and we have therefore chosen to set requirements about sustainability to all our suppliers. In the tender material for the foundations, we have demanded that as far as possible we consider and strengthen the marine environment and also reduce the CO2 footprint where possible”, said Henrik Plougmann Olsen, Director at HOFOR.

Earlier this year, HOFOR signed a contract with Siemens Gamesa for the supply of 26 of its SG 11.0-200 DD wind turbines for the Aflandshage project, which will be installed by Cadeler.

The Danish Energy Agency (DEA) granted an establishment permit to the Aflandshage offshore wind farm in November 2022.

HOFOR applied for the wind farm through the open-door scheme which was suspended by the Danish Energy Agency this February as it was concluded that the permitting scheme was potentially in breach of EU law.

The DEA resumed the processing of the Aflandshage wind project in March, after the Ministry of Climate, Energy and Utilities assessed that the establishment permit was not in violation of the EU regulations. The project was granted a feasibility study permit in 2019.

The Agency has now resumed with a total of 13 projects whose applications were being processed through the open-door scheme, including the three offshore wind farms that were laid out in the Marine Plan, issued in June, and four demonstration projects.