Foundations for o® shore wind turbines

An important engineering challenge of today, and a vital one for the future, is to develop and harvest alternative sources of energy. This is arm priority in the UK, with the government setting a target of 10% of electricity from renewable sources by 2010. A component central to this commitment will be to harvest electrical power from the vast energy reserves o® shore, through wind turbines or current or wave power generators. The most mature of these technologies is that of wind, as much technology transfer can be gained from onshore experience. Onshore wind farms, although supplyinggreen energy', tend to provoke some objections on aesthetic grounds. These objections can be countered by locating the turbines o® shore, where it will also be possible to install larger capacity turbines, thus maximizing the potential of each wind farm location. This paper explores some civil-engineering problems encountered for o® shore wind turbines. A critical component is the connection of the structure to the ground, and in particular how the load applied to the structure is transferred safely to the sur- rounding soil. We review previous work on the design of o® shore foundations, and then present some simple design calculations for sizing foundations and structures appropriate to the wind-turbine problem. We examine the deciencies in the current design approaches, and the research currently under way to overcome these decien- cies. Designs must be improved so that these alternative energy sources can compete economically with traditional energy suppliers.