Feasibility Study of Adaptive Inflatable Structures for Protecting Wind Turbines Cezary Graczykowski, Jaakko Heinonen VTT Technical Research Centre of Finland IPPT Institute of Fundamental Technological Research, Poland Abstract Collisions with small ships are one of the main dangers for offshore wind turbines. Installing torus-shaped inflatable structures that surround a wind turbine tower at water level is one method of effective protection. Such structures contain several separate air chambers equipped with devices for fast inflation and pressure release. The system can be adapted to various impact scenarios by adjusting the level of internal pressure in each chamber and by controlling the release of compressed air during collision. This paper presents simulations of ship collisions with wind turbine towers protected by pneumatic structure. The numerical analysis is conducted using ABAQUS/Standard and ABAQUS/Explicit. Several methods of precise pressure adjustment are introduced. The performed feasibility study proves that inflatable structures can protect the wind turbine tower and the ship against serious damage. INTRODUCTION Wind turbines are the main source of renewable energy. Moreover, the contribution of wind energy to global energy production is still increasing. The European Commission priorities assume that the present wind energy production of 40 GW will have grown to 150 GW by 2020. The largest wind generators currently operating provide up to 3.6 MW power. An increase of their effectiveness is still required, which can be achieved by locating wind turbines in regions where the wind conditions are more beneficial, for instance in offshore regions where the wind flows smoothly and briskly. Additional advantages of locating wind turbines offshore include the availability of large open spaces and the lack of noise and aesthetics-related inconveniences for inhabitants. Wind turbines are usually situated in shallow continental shelves in the vicinity of large ports (for example near Copenhagen). Such locations incur a relatively low cost for wind turbine installation and energy transportation, cf.[1]. In offshore regions, wind turbines are exposed to harsher environmental conditions. The main threats for offshore wind generators are very strong winds and ice loading in winter. Additional dangers are collisions involving small ships which have to dock to wind turbine towers for the purpose of maintenance and monitoring. Such collisions occur especially often during rough sea conditions and can lead to serious damage to both the wind generator tower and the ship. Therefore, an additional structure providing safety for docking operations is required. In this paper, an Adaptive Inflatable Structure (AIS) attached to the wind turbine tower is proposed and its feasibility verified. MODEL OF THE WIND TURBINE Let us commence with the finite-element model of a typical wind turbine, as shown in Fig. 1, which was introduced in [2]. The tower consists of beam elements with