As instrumentation and processing power increase, so does the power consumption of the platform. Since drifters powered only by batteries have a limited lifetime, long-term applications rely on means of energy harvesting. One common solution is to use solar power, but this can only be used on buoys with sufficient space and may be completely useless in polar regions. In this case, the use of wave energy with its high availability becomes particularly interesting. Within the scope of this project, investigations are being carried out on the implementation of a wave energy converter for ocean drifters. The working principle is based on a non moored self-reacting point absorber (SRPA), which uses relative motion between the buoy and the drogue. Since SRPAs are usually studied for large power plants, IMEK has focused on optimizing this operating principle for small-scale energy harvesting. The power take-off is realized by an electrical generator in the buoy. Since the motion of a SRPA is linear, a direct-drive linear generator has the great advantage of simple design and implementation.
In a cooperation between the Institute for Mechatronics in Mechanics (IMEK) and the Institute of Mechanics and Ocean Engineering, a small scale wave energy converter is developed and optimized, which can be integrated into a small, free-floating sensor drifter. The development of the mechanical part is based on mechanical simulations and experiments in the TUHH Wave-Flume. The generator design uses electromagnetic FEM simulations and a generator testbench implementation to optimize the power output for the low wave frequencies. The developed prototype currently achieves an output power of up to 400mW and we still have promising ideas for improvement.
