Optimal Placement of FloatingTwo-Turbine Foundations in Offshore Wind Farms

Abstract: This project is conducted in cooperation with Hexicon AB, which is a Swedish design and engineering company developing floating two-turbine platforms for offshore wind power.The study aims to investigate the optimal placement of Hexicon AB’s platforms in an offshore wind farm with respect to the Annual Energy Production (AEP). Wind farm layout optimization is a complex problem and it has been approached by the development of calculation and optimization programs in Matlab. The analytical Jensen wake model has been utilized for calculation of AEP and important inputs to the program have been turbine parameters and site specific conditions. The optimization strategy used is a multi-stage algorithm where the gradient-based local search algorithm Fmincon has been used in combination with a version of the heuristic genetic algorithm. The developed programs have been tested and evaluated through a case study. Included in the case study is also a brief financial evaluation regarding how different scenarios in electricity export price and costs for cabling could affect the feasibility of the optimized layouts. Concluded from the project is that the developed programs can be used to investigate the optimal placement of floating two-turbine platforms with respect to AEP. In the case study it was found that the optimized layout obtained a wind farm efficiency of around 4% more than for the conventional staggered layout that was tested. What is also emphasized is that the feasibility of the optimized layouts obtained from the program is quite sensitive toward changes in future electricity export price and costs for cabling and installation. Hence, it is important to perform a careful financial analysis in order to draw conclusions regarding what layout is the better option for a specific situation.