Power Generation Potential of a VLFS Equipped With OWC Type WECs and Damper Effects on Elastic Motion

Abstract

This paper describes potential of PTO (Power Take-Off) and the damper effect of motion in a large scale pontoon type floating structure on which lots of oscillating water column (OWC) type wave energy convertors (WEC) are installed. It is enable to use upper space for utilizing marine renewable energy such as wind power, tidal power, wave power generation farm using large pontoon structure. Due to the concept, it should reduce cost of maintenance as well. For investigation of PTO and elastic motion behaviours of large floating structures, we calculated three types of models on which OWC devices were installed differently. We examined how much reduction was possible when including elastic motion effects and the fixed type which radiation wave was not taken into account. In this paper, a boundary condition in order to give effect of a free water surface with air pressure is theoretically modeled. We can directly consider influence of wave energy absorption to hydrodynamic forces and wave exciting forces on the floating structure with the Green’s function method based on the linear potential theory. In the modeling, a boundary condition on a free water surface and an equation of state within an air-chamber above OWC are mathematically and linearly formulated. Air-pressures and vertical displacement within OWC areas can be simultaneously and directly solved by setting both the variables and by solving the simultaneously equations of the air-pressure and the vertical displacement. As a result, performance of PTO and hydroelastic motion of the floating structure increased when including elastic motion effect. In addition, expected value of annual PTO was about 4.4MW with 146 OWCs.