Haigui Kang

Analytical Study on an Oscillating Buoy Wave Energy Converter Integrated into a Fixed Box-Type Breakwater

An oscillating buoy wave energy converter (WEC) integrated to an existing box-type breakwater is introduced in this study. The buoy is installed on the existing breakwater and designed to be much smaller than the breakwater in scale, aiming to reduce the construction cost of the WEC. The oscillating buoy works as a heave-type WEC in front of the breakwater towards the incident waves. A power take-off (PTO) system is installed on the topside of the breakwater to harvest the kinetic energy (in heave mode) of the floating buoy. The hydrodynamic performance of this system is studied analytically based on linear potential-flow theory. Effects of the geometrical parameters on the reflection and transmission coefficients and the capture width ratio (CWR) of the system are investigated. Results show that the maximum efficiency of the energy extraction can reach 80% or even higher. Compared with the isolated box-type breakwater, the reflection coefficient can be effectively decreased by using this oscillating buoy WEC, with unchanged transmission coefficient. Thus, the possibility of capturing the wave energy with the oscillating buoy WEC integrated into breakwaters is shown.

Effect of the PTO damping force on the wave pressures on a 2-D wave energy converter

The information of the wave loads on a wave energy device in operational waves is required for designing an efficient wave energy system with high survivability. It is also required as a reference for numerical modeling. In this paper, a novel system, which integrates an oscillating wave energy converter with a pile-restrained floating breakwater, is experimentally investigated in a 2-D wave flume. The measurements of the wave pressure on the wet-surface of the device are made as the function of the power take-off (PTO) damping force. It is shown that the wave pressure is significantly affected by the PTO system, in particular, at the edges, and the wave pressure varies under different wave conditions. From the results, conclusions can be drawn on how the PTO damping force and wave conditions affect the loads on the device, which is of engineering concern for constructing safe and reliable devices.

Experimental investigation on hydrodynamic performance of a dual pontoon–power take-off type wave energy converter integrated with floating breakwaters

As an extension of the single pontoon wave energy converter–type breakwater, a wave energy converter–type breakwater equipped with dual pontoon–power take-off system is proposed to broaden the effective frequency range (for transmission coefficient KT < 0.5 and capture width ratio η > 20%). The wave energy converter–type breakwater with dual pontoon–power take-off system consists of a pair of heave-type pontoons and power take-off systems for which the power take-off system is installed to harvest the kinetic energy of heave motion of the pontoon. In this paper, we experimentally confirm the advantage of the wave energy converter–type breakwater with dual pontoon–power take-off system over the one with a single pontoon–power take-off system. Both wave energy converter–type breakwater with dual pontoon–power take-off system and that with single pontoon–power take-off system are tested in regular waves. A (electronic) current controller–magnetic powder brake system is used to simulate the power take-off system. The characteristics of power take-off system are investigated and results showed that the power take-off system can simulate the (approximate) Coulomb damping force well. Experimental results reveal that the wave energy converter–type breakwater with dual pontoon–power take-off system broadens the effective frequency range compared with the single pontoon–power take-off system with the same pontoon volume (i.e. the displacement of the pontoon). Specifically, the transmission coefficient of the system is smaller while the system in relative longer waves. Furthermore, the capture width ratio of system can be improved.