Assessing the effectiveness of a global optimum strategy within a tidal farm for power maximization

Abstract

In the next years, tidal farm will increase in size and density of devices to obtain an economically significant amount of energy. Because of the high density of the devices within the farm, the turbines will be hydrodynamically coupled. The negative effects of this coupling could be reduced by optimizing the tidal farm layout or by optimizing the operating point of each turbine within the farm. In this paper, we investigate the second strategy. The objective is to maximize the overall production of the farm. The power of the upstream tidal turbines is then reduced, allowing the increase of power of the downstream turbines. The Binary Particle Swarm Optimization (BPSO) Algorithm is used in order to find the rotational speed for each device such that the net energy yield is optimized over a tidal cycle.The proposed methodology is firstly applied to an ideal case (i.e. tidal flow constant in magnitude and direction) to assess the influence of the machines density, the ambient turbulence rate and the speed magnitude on the power improvement rate. Secondly, the method is applied to a hypothetical tidal farm located in the Alderney Race (Raz Blanchard in French), situated between the Alderney Island and La Hague Cape (France). The results of these scenarios indicate that the proposed strategy is interesting mainly when the density of devices is high and/or when the ambient turbulence rate is lower than 10%. In this cases, it is possible to improve the rate by 2.5%.