HOFOR seeks to extend Middelgrunden's lifetime

4C Offshore | Tom Russell
By: 05/07/2021 HOFOR

HOFOR is awaiting approval for the lifetime extension to its 20 year-old
Middelgrunden offshore wind farm off Copenhagen. According to analysis that R&D Engineering has done for HOFOR, the turbines are suitable for at least a further 30 years of generation.

Located in the Øresund, 3.5 km outside Copenhagen, Denmark, the 40 MW
Middelgrunden project features 20 2 MW B76/2000 (Bonus) turbines and has been operational since 2001. The wind farm is a collaboration between Middelgrundens Vindmøllelaug and HOFOR, with each party responsible for the ownership and operation of 10 turbines. The 20 offshore wind turbines produce around 90 million kWh annually, which corresponds to the electricity consumption of 30,000 Copenhagen households.

“We have inspected the turbines and thoroughly analyzed 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,” explains Peter Winther, Key Account Manager at R&D Engineering, and continues: “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. 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.”

The analysis were carried out as part of an EUDP-supported pilot project, which 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.

HOFOR stated it is now ready to carry out the work that can ensure that the turbines at Middelgrunden can continue to produce green electricity after the year 2026, when the current operating license expires. HOFOR is, however, awaiting the authorities' approval of the project, which is necessary for the turbines to continue operation.

“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, 5-10 years, it will be difficult to make the finances of the project cohesive,” said Jan Kauffmann, director of Finance and Business at HOFOR, and concludes: “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 utilization - and ultimately the lowest CO2 footprint.”