Drag-type cross-flow water turbine for capturing energy from the orbital fluid motion in ocean wave

Since the energy of ocean wave exists mostly near the water surface and decreases exponentially with depth, the resource of wave energy is measured in the line density unit (kW/m). Therefore, in the scaling up of a wave energy converter, the captured wave energy increases slowly in proportion to the wave front width of the device while its cost tends to increase in a pace faster than the square of device size. To overcome the problem, the authors propose a drag type cross-flow water turbine with its rotational axis lying horizontally and parallel to the wave front. Since the device will be light-weight and linearly extendable in the wave front direction, the larger (longer) converter can obtain the merits of scale for higher economic performance. The shape of proposed turbine is not axisymmetric for directly utilizing the orbital fluid particle motion in wave. The basic unit of the device is compact and the diameter of turbine is in the order of wave height. Two-dimensional flow simulation of the device in regular wave demonstrates the mechanism of the turbine and provides its preliminary performance prediction.