Development of an Angularly Oscillating Wave Energy Converter

The averaged power density of ocean waves is about 25 times as high as that of solar or winds. Yet, energy harvesting from ocean waves is far less competitive than that from solar and winds nowadays. The primary hurdle is the high installation/maintenance cost associated with wave energy harvesting devices. The present research focuses on the development of a wave energy converter (WEC) that is expected to have negligibly low cost on installation and maintenance. To achieve this goal, a new working mechanism is applied. The enabled WEC is a surface-floating device. It can be loosely anchored to the seabed through single-point slack mooring; that makes the installation as easy as anchoring a boat. The WEC uses wave-enabled angular oscillation to harvest energy. Such angular oscillation directly turns into nearly the same angular oscillation between the rotor and stator of a specially designed electric generator. The whole system is encapsulated in a rigid and watertight buoy — the hull of the WEC, thus the WEC is corrosion free. Furthermore, the only parts that subject to wear in the entire system are a couple of high-endurance bearings, which may make the WEC maintenance free in its designed lifespan (e.g., 5 years). In this paper, we present and discuss the design and testing of our first prototype WEC. Experimental exploration from hydrodynamic perspective was conducted in a wave tank to improve the shape design of the buoy, which plays a critical role on exciting large angular oscillation of the WEC in waves. Numerical simulation from electromagnetic perspective was carried out to guide the design of the electric generator; the resulted generator is capable of working efficiently in slow angular oscillation mode (e.g., at 1 Hz or lower).