HOFOR seeks company to give Middelgrunden turbines new life

4C Offshore | Bridget Randall-Smith
By: 24/06/2022 HOFOR
Danish utility HOFOR, is looking for companies to help extend the life of turbines at the Middelgrunden offshore wind farm by 25 years.
The 40 MW wind farm features 20 2 MW Bonus 76 offshore wind turbines and produces about 90 million kWh annually since commissioned in 2001.

HOFOR owns the 10 northernmost of the turbines on Middelgrunden, which were bought by Ørsted in 2018. The last 10 are owned by Middelgrundens Vindmøllelaug who are also weighing up future options.

The foundations of the turbines consist of approximately 1800 tonnes of iron and concrete per turbine, while each turbine itself consists of approximately 250 tonnes of materials. By reusing all the heaviest parts, HOFOR can save several thousand tons of materials and thus CO2.

The life extension of the ten turbines on Middelgrunden is conditional on HOFOR receiving the necessary regulatory permits. HOFOR has applied to the Danish Energy Agency for permission to upgrade the turbines and extend the operation of the turbines by 25 years. Case processing is still in process and HOFOR expects to get the last permits in place before the summer holidays.

HOFOR has settled on the technical solution and launched a tender for upgrading and renovation of the turbines as well as service and maintenance until 2025, when the turbines' current operating license expires.

Due to distance and height requirements, larger turbines cannot be installed. Analyzes have shown that the existing turbines are in a very good condition, and that certain measures can be deployed to extend project lifetime. In connection with the service life extension, HOFOR will carry out a repair of turbine blades, upgrade of control system and SCADA, installation of new systems for monitoring displacement and temperature on main bearings and installation of a new lubrication system.

HOFOR has been in dialogue with a number of suppliers over the past eight months and has identified several interested bidders. HOFOR therefore expects that a contract can be signed with a supplier in the autumn of 2022.

By extending the service life and continuing the operation for many more years, HOFOR hopes that the turbines can also become a good example to the outside world of circular economy and efficient utilization of resources.


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