Middelgrunden has ’30 years of life left’

Hofor has applied to keep the Danish offshore project running after its current licence runs out in 2026 [Image: Kim Hansen/Wikimedia Commons]

Danish company Hofor said initial analysis of the 10 turbines it owns at the 40MW Middelgrunden offshore wind farm off Denmark has found that there are at least 30 years operating life left in the towers and foundations.

The project, which has been operational since 2001, is now awaiting the authorities’ approval to ensure that the turbines can continue to produce electricity, the company said.

The current operating licence runs out in 2026.

If successful, Hofor expects to be able to start extending the life of the turbines at Middelgrunden next year.

Analysis of the wind farm was carried out by R&D Engineering, it added.

The analysis was carried out as part of an EUDP-supported project that aims to find a model for how it is possible – through restoration and recycling – to add up to several decades to the life of offshore wind turbines approaching retirement age.

R&D Engineering key account manager Peter Winther said: “We have inspected the turbines and thoroughly analysed how the stand is on all the individual parts and elements of the tower and foundations.

“As expected, the structural integrity is generally good here after approximately 20 years of operation.

“Some parts of the foundations can last for several hundred more years, and we conservatively estimate that the entire foundation can last at least about 35 years of continued operation.

“While the tower can last at least about 30 years of continued operation – if the technical parts of the turbines, which are more prone to wear, are renovated or replaced.

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“This applies to moving parts such as gearboxes and wings.

“With some minor measures, such as periodic inspection of critical details, it will be possible to extend the operating period further by at least 10 years for the tower and 20 years for the foundation.”

Hofor director of finance and business Jan Kauffmann said: “Our project is dependent on the Danish Energy Agency extending the turbines’ operating license for a sufficiently long number of years.

“If we can only get permission to extend the operation for, for example, five-10 years, it will be difficult to make the finances of the project cohesive.

“Our current operating license is valid for 25 years, and it expires in about five years.

“We therefore hope that we can soon get a clarification on how long the turbines can continue to be in operation. We are the first to try to extend the life of offshore wind turbines in Denmark.

“The legislation provides for the possibility of extending the operating license, but the rules are unclear.

“There is no current practice for this type of project and therefore we are in close dialogue with the authorities.

“We naturally hope that it ends up with a decision that makes it attractive to extend the life of older offshore wind turbines instead of building new ones.

“This ensures optimal resource utilisation – and ultimately the lowest CO2 footprint.”

Hofor bought 10 of the project’s 20 2MW Bonus 76 turbines from Orsted in 2018.

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