Analysis and Design of Guyed 120 m-Long Offshore Met Mast Supported on Suction Piles

Abstract

Development of modern technology has increased thrust for renewable energy. The land-based resources were used to its maximum potential. India with a coastline of 7,517 km is seeking to meet its demand from offshore resources like offshore wind energy through installation of offshore wind turbines. Ministry of New and Renewable Energy (MNRE) has identified the coasts of Gujarat and Tamil Nadu as potential sites. The wind potential was assessed either using satellite winds or extrapolated onshore winds, which include considerable uncertainties. Before setting up an offshore wind farm, it is mandatory to collect bankable wind data for a couple of years at potential location. In the present study, an initiative has been taken to come up with a low-cost and feasible structure for the collection of wind data considering financial constraints in prefeasibility stages. Feasibility of using conventional onshore-based-guyed met mast in offshore environment by replacing the anchorage with suction pile foundation was studied. The structure was modeled using beam elements and analyzed for environmental loads using finite element method. The deflected profiles of the structure were arrived and are in acceptable limits. Free vibration analysis was performed to study the resonance of the structure due to wave loads. Earthquake analysis was performed using spectral and time history methods and the utilization factors are in acceptable limits. A nonlinear static pushover analysis was carried out and results indicate reserve strength ratio of 2.2. An installation methodology was developed for the proposed structure considering available marine spread in Indian waters. Preliminary cost estimates indicated the cost of proposed structure to be less than conventional offshore self-standing mast and LiDAR-based platform.