Optimal control for power generating kites

In this paper we present optimization studies for kites that produce wind energy by periodically pulling a generator on the ground while flying fast in a crosswind direction. We derive a model for a single kite and formulate an optimal control problem with periodic boundary conditions and free cycle duration. The objective function is the average power at the generator. We solve this nonlinear and unstable optimal control problem numerically with a direct multiple shooting method. Here, the main result is that we can attain about 5MW with a 500m²-kite at equation wind speed. Finally, we consider a system of two kites and show that such systems can further increase the efficiency.