As wind turbine technology has evolved, wind turbines have become both larger and more efficient at capturing energy from the wind. As a consequence early wind farms, based on relatively large numbers of small wind turbines, are starting to appear significantly less economical than modern wind farms with smaller numbers of larger wind turbines. Aesthetically the modern wind farms are often more attractive too.
This change is creating a market for the repowering of existing wind farms with new wind turbines. Repowering can be economically viable and it has the attraction of allowing a new, potentially more financially attractive, wind farm to be built at a site where a wind facility already exists, avoiding the need to acquire the various permits that might be needed at a new site.
The earliest repowering took place in California when large numbers of small wind turbines were scrapped during the late 1980s and early 1990s. Repowering has also taken place in Denmark where, before 2002, around 1800 wind turbines were taken down. Meanwhile, Germany began to encourage repowering in 2004 with financial incentives after most of the best onshore sites had already been used.
Typically, repowering of a wind farm with new turbines aims to double the output of the farm while reducing the number of wind turbines by 50%. Repowering also creates a market for secondhand wind turbines that can be refurbished and then sold on. This has led to older turbines from western European countries being re-erected in countries of the Balkans and eastern Europe. Older turbines can also be exported to developing countries for reuse, potentially cutting the cost of introducing the technology to these nations.