Key challenges and prospects for large wind turbines

The so-called 20-20-20 targets for the European Union include a reduction in greenhouse gas emissions by 20% compared to 1990, 20% of primary energy from renewables, and a 20% reduction in primary energy demand through energy efficiency by 2020. Wind energy has played and will continue to play a significant role in progress towards meeting these goals; in 2012 it accounted for around 7% of total European electricity consumption. Against the background of the recent trend towards ever larger wind turbines at higher hub heights, this contribution explores the challenges to and prospects for a continued up-sizing of wind turbines in the future. Based on a literature review and interviews with experts in the European wind industry, the key challenges for large onshore wind turbines are identified and qualitatively analyzed in a European context. Further developments of large wind turbines depend on several components and related challenges rather than just one. The main challenges are thought to be related to social acceptance, the logistics of transport and erection, and the medium term sustainability of the political and economic support for wind energy. It seems likely that social acceptance will center around the issue of aerodynamic noise and the allowed distance from the turbine, although further research is required to fully understand the public perception of especially large wind power plants. In addition, the sheer size of larger wind turbines in the future presents significant challenges in terms of the materials and structures employed. There is little consensus on the likely development of drive train technologies, though a slight tendency towards direct drive systems with permanent magnet generators as well as multi-stage gearboxes was encountered, which could also serve to improve reliability. For the rotor blades, a trend towards fully carbon fiber blades is expected, and towers will continue to be constructed from steel and/or concrete, albeit both of these components increasingly in the form a modular construction.