Small-Scale Wave Energy Convertor System for Effective Extraction and Storage of Energy from Sea Waves for Power Generation Applications.

Abstract

The sea wave energy is a potential sustainable solution for the global energy crisis in generations to come. However, particularly in Sri Lanka, there is very limited research carried out on wave energy convertors (WEC). Furthermore, most of the international level WEC systems developed so far are just limited to harness either kinetic or potential energy of the sea waves and are not optimised to Sri Lankan sea conditions. In addition, the energy storage has become a critical requirement in next era power generation systems. In this background, this research developed a small- scale wave energy convertor (WEC) and storage setup having a theoretical capacity of 20 W, which was tested in a near-shoe sea area located near to Ginthota, Galle, Sri Lanka having 1.5 m of mean wave height and 0.1 Hz of mean wave frequency. The system consists of a 20 1 floater to extract potential energy and a two-dimensional tilting flap to extract kinetic energy of the incident waves. As the waves interact with the WEC, a set of four pneumatic cylinders were used in series to compress air in to a 12 1 storage tank. During three trials in the sea, it was observed that within a 30 min time interval, the tank was pressurised at an average to 0.8 bar, which equal to 960 J, having enough capacity of delivering 16 W for1 min as pneumatics. However, it was observed that the average continuous power delivering capacity was about 0.5 W than the designed capacity of 20 W, leading to a continuous overall efficiency of 2.5% in energy conversion from waves to pneumatics. Frictional losses, leaks in the pneumatic cylinders and slow response of the floater to the waves were observed. The main reasons for this lower performance may he that the WEC was developed using non-optimal materials and components under a limited budget of LKR 50,000. Corrosion was also clearly observed in the device after few days of trials, which leads to lower performance of the WEC, highlighting the criticality of using non-corrosive materials for the WEC. Future works of this research will focus more on the improvement of the efficiency, reliability and durability of the WEC while increasing the generation capacity. The insights drawn from this research will be highly useful in developing much larger scale WEC capable of generating electricity out of waves around Sri Lanka providing a sustainable solution to the energy crisis.