Bockstigen

Bockstigen is a small, historically important offshore wind farm located off southern Gotland, Sweden, originally commissioned in the late 1990s. The site comprises five early-generation machines and was one of the world’s first commercial offshore wind installations. Rather than pursue a full redevelopment, the owner-operator executed a pioneering partial repowering in 2018: nacelles, rotors and control systems from used Vestas V47 (660 kW) units were installed on the existing towers, increasing nameplate capacity modestly and more than doubling annual energy output while re-using foundations and electrical infrastructure. The work—completed in under a year and reported to have cost under €5m—focused on life-extension and resource-efficient reuse of components, delivering roughly 15 extra years of service and demonstrating a pragmatic alternative to full replacement. The repowering also reflected local grid and market constraints; a planned larger redevelopment was aborted after a proposed 400 kV mainland-Gotland link was cancelled, removing the export capacity needed for a bigger project. Installation faced challenging Baltic Sea conditions and required specialist marine lifting from a jack-up platform. The project is owned/operated by Momentum (Momentum Gruppen / Momentum Energy Group) and is widely cited as the world’s first commercial offshore wind repowering, making it a reference case for end-of-life options and multibrand component reuse in offshore fleets.