Design and assessment of vertical axis wind turbine farms

Wind energy is the fastest growing of all renewable energy resources. Most of the existing wind turbine farms consist of Horizontal Axis Wind Turbines because the efficiency of an isolated Horizontal Axis Wind Turbines is the highest of all other wind turbines. This thesis is interested in Vertical Axis Wind Turbines farms, we developed Savonius and Darrieus Vertical Axis Wind Turbine efficient and patterned farms for energy generation. The developed farms consist of multiples of triangular three Vertical Axis Wind Turbine clusters. The three turbines in the cluster are arranged in a close proximity in order to enhance their average power output and power density. The geometry of the cluster is optimized using numerical solutions of two co-rotating and counter-rotating turbines in parallel and oblique configurations. The gap distances and oblique angles between upstream and downstream turbines of the cluster are carefully chosen to achieve a maximum average power coefficient by the clusters. The numerical method is validated by simulation of the flow field around a single Savonius and Darrieus turbines, the numerical results for the power coefficients of the single turbines are compared with the available experimental data at different tip speed ratios. The unsteady Reynolds averaged Navier-Stokes equations are solved using Fluent 14.5 solver. The results for the single turbines show a good agreement with the experimental data. The numerical solutions of two parallel and oblique co-rotating and counter-rotating Savonius and Darrieus turbines show a mutual enhancement in the power coefficient of individual turbines in particular configurations. Efficient triangular three turbine clusters are developed based on the results of the two parallel and oblique co-rotating and counter-rotating turbines. The efficiencies of the developed three Savonius and Darrieus turbine clusters are 26% and 30% higher than their isolated counterparts respectively. We used these findings in developing patterned efficient farms with the triangular cluster as a building unit and having the same geometric topology of the cluster, for example, a triangular nine turbine farm consists of a three turbine cluster at each vertex and a triangular twenty-seven turbine farm consists of a nine turbine farm at each vertex, etc. The developed farms performance parameters are assessed numerically in terms of moment and power coefficients against Vertical Axis Wind Turbine farms having the same number, type and size of isolated turbines. The pattern of the developed farms and power coefficient enhancement are confirmed by numerical solutions of Savonius nine and twenty-seven turbine farms, and a Darrieus nine turbine farm. The results show that the developed Vertical Axis Wind Turbine farms have the same power ratios achieved by the three turbine clusters. Also, the power densities of the Savonius nine and twenty-seven turbine farms are seven and four times that of the isolated turbine farms respectively. On the other hand, the power density of the Darrieus nine turbine farm is about thirteen times that of the isolated counterpart. These patterned efficient farm designs make the Vertical Axis Wind Turbine farms more efficient than the Horizontal Axis Wind Turbines farms.