Offshore Wind Turbine Support Structures along Indian Coast - Multi Criteria Analysis

The selection of a feasible support structure for the site-specific environmental conditions helps in reducing the capital cost of the offshore wind turbines. As the study location falls under shallow water depth, the bottom fixed structures such as monopile, tripile and jacket have been considered as alternatives. The analysis of the alternatives has been carried out using API and DNVGL codal provisions in a finite element based framework, accounting for hydrodynamic and soil structure interaction effects. OWTs are simultaneously subjected to aerodynamic loads from the turbine blade rotations, estimated using blade element momentum theory based software and are coupled analysis is carried out. Multi criteria decision analysis (MCDA) is adopted to aid in the decision making regarding the choice of the feasible support structure. Multi- criteria evaluation problem consists of a viable set of alternatives for a given problem. MCDA explicitly evaluates the conflicting criteria involved in the decision making. It helps analyzing a complex problem using a predefined set of variables/criteria to derive at a logical solution. Among the various methods of MCDA for evaluating the alternatives against the criteria, the Analytical Hierarchy Process (AHP) has been adopted. In this, the pairwise comparison is made for the given alternatives using predefined criterion. The criteria considered for the study are structural configuration, fabrication, transportation and installation of the structure. The criterion again are classified into different sub criteria in order to sort out the priority of all the alternatives. The support structure with the highest priority has been identified as the optimal and feasible structure for the location under study.