BOTTOM SUPPORTED TENSION LEG TOWER FOR OFFSHORE WIND TURBINES

Power production from the high energy density offshore wind has now emerged as a potential source of renewable energy for the future of mankind. While the installed global cumulative offshore wind capacity in 2014 was around 8 GW [1], almost all of this came from the shallow water sites (water depths equal to 25m or less) where typical bottom founded structures (such as: monopole, jacket, concrete gravity type, etc) are used to support the turbines. Today, most of the shallow water sites are exhausted, and the industry is looking for setting up turbines at the deeper water sites, where the existing bottom founded structures tend to become massive and expensive. On the other hand, the floating wind turbine concept, apart from being expensive, is more suitable for water depth of 100 m or more. It is expected that in the near future, the industry will primarily focus on concepts that may extend the application range of the existing bottom founded structures towards the deeper waters. In this paper, a novel support structure concept termed "Bottom supported tension leg tower" is presented, and its preliminary technical feasibility is checked for a monopile type structure for 50 m water depth. The concept can also be used with a jacket or a gravity type support structure. The potential of using the monopile based structure at 100m water depth is also briefly addressed