Development of Floating Tidal Current Energy Systems to Support Energy Independence in Island Areas

Abstract

Some of the optimum sites for the tidal current energy system in Korea are suggested to be in island regions with a deep-water depth. It is known that floating systems are more advantageous than fixed systems for a water depth of 20 m or deeper. In this study, a floating tidal current energy system development, thus, considered for sites deeper than 20 m such as Incheon, Gyeonggi, or Chungnam province. Floating systems with a total power rating of 100 kW were developed combining two 50 kW vertical axis turbines. The systems have a hybrid mooring configuration with catenary and taut mooring. Two different types of steel hull systems were sized and configured considering the turbine operating loads and sea states. The first one, the “base platform” is consisted of a circular pontoon barge, four cylinders, a damping plate, and turbine supporting structures. The other one, the “pontoon platform” is consisted of a circular pontoon barge and turbine supporting structures. Both platform displacements and weights are similar, but platform dimensions differ greatly. Platform motions and mooring line strength analysis were carried out for the site operating and extreme conditions. Results demonstrate that the design requirements are met so that the platform and mooring systems are technically feasible. The pontoon platform has shown somewhat better than the base platform in the performances of the motions, tensions, and costs. A single unit, excluding turbine cost, is estimated to be around $4.7 to $5.0 million depending upon the platform configurations and anchor options. Due to the slight cost difference, further analysis is recommended in the next phase, to identify the most viable option. Results suggest that drilled and grouted anchors may be a more cost-effective solution. However, further seabed study will be required to confirm an optimum anchor type.