Lifetime extension of Bockstigen offshore wind farm on Gotland
The offshore wind farm is located in Bockstigen on Gotland, Sweden, and is notable for being the third offshore wind farm to be established in the world. Bockstigen was built in 1998. The project consisted of five 20-year-old Wind World 550 kW wind turbines, which have been generating electricity since their installation.
The offshore wind farm is located in Bockstigen on Gotland, Sweden, and is the third offshore wind farm established in the world. Bockstigen was built in 1998. The project consists of five 20-year-old Wind World 550 kW wind turbines, which have been generating electricity since their installation. When we made the decision, 4 out of the 5 wind turbines were still working, but all were close to the end of their technical lifespan. The low electricity prices and lack of government subsidies meant that the future of the project was uncertain and some important decisions had to be made.
Momentum laid out a plan to replace existing wind turbines with refurbished or new wind turbines. It was eventually decided that the nacelles, rotors and transformers from the old wind turbines would be replaced with refurbished Vestas V47 nacelles and new DEIF transformers and monitoring systems.
The repowering process was financed by various banks and the owners’ equity. Momentum was responsible for purchasing used Vestas V47 wind turbines (rotors and nacelles) in Germany and refurbishing them in Denmark. The old wind turbines were replaced with the refurbished wind turbines, after which the old ones were dismantled and dismantled. All five turbines have been back in full operation since November 2018. Less than a year passed between the planning phase and the operational phase.
A sustainable approach to repowering
Technical lifetime extension of the wind farm by at least 15 years. Used existing tower, lattice and foundations, saving the owners a fortune. The use of refurbished main components such as gearboxes, blades, generators, etc. was the first example of its kind in the area, opening up new possibilities for similar projects. From end-of-life to an expected long-term double-digit IRR on gross investments at market conditions (no subsidies).
The result exceeded all expectations
After the first year of successful operation, we have realized an availability of over 99% and more than a 100% increase in production compared to before. As a result of the strong development, the wind farm was sold to a Danish investor in December 2019.