Study on Performance of Savonius Rotor Type Wave Energy Converter Used in Conjunction with Floating Breakwater

In the present study,the performance characteristics of a Savonius rotor type wave energy converter used in conjunction with a conventional double-buoy floating breakwater is investigated using physical model studies.The Savonius rotor type converter is suspended under the double-buoy floating breakwater to achieve wave attenuation while generating electricity,thereby enhancing the overall wave-elimination effect of the combination.The Savonius rotor is tested with different water submergence depths,and a reasonable relative submergence depth is determined within the scope of the research parameters.The hydrodynamics and energy capture performance of the combined breakwater with four different sizes of Savonius rotor under different wave conditions are studied,and the transmission coefficient of the experimental device is analyzed.The results show that when the optimal relative submergence depth is 0.65D,where D is the impeller diameter,there is a correspondence between the optimal performance of Savonius rotor with different rotor sizes and the wave period and wave height.The optimal energy capture efficiency of the wave energy converter reaches 17%−20.5%,and the transmission coefficient is reduced by 35%−45%compared with the conventional double-buoy breakwater.

Performance studies on an oscillating water column employing a Savonius rotor

A new oscillating water column (OWC) design is proposed in this study to incorporate a simpler Savonius type turbine. Conventional OWC devices employ a bi-directional turbine such as a Wells or an Impulse turbine to extract energy from the air. The disadvantages of the Wells turbine include its inability to self start and stalling. The Savonius turbine is much cheaper and is an effective option at low Reynolds numbers. In the current rectangular OWC device, unlike the circular OWC, the width of entry of the capture chamber can be increased without being influenced by the diameter at the turbine section. To improve its primary capture efficiency, the front and rear walls of the OWC are inclined to minimize reflection. The Savonius rotor characteristics are studied with respect to the change in frequency of the incoming waves. The rotor rpm is sensitive to wave period and primary conversion efficiency while changes in depth only affect the rotor rpm at lower frequencies. The Savonius rotor shows promising results and can be incorporated into large scale OWC devices to reduce costs of the turbine component of the system.

Experimental Research on A New Type of Floating Breakwater for Wave-Absorbing and Energy-Capturing

To avoid the damage caused by big wind and wave in cage culture, and to solve the problem of energy supply faced by automatic breeding equipment, a new type of floating breakwater, named as Savonius double buoy breakwater(SDBB), is proposed in the paper. The floating breakwater is composed of HDPE cylindrical double buoys and horizontal axis Savonius rotors, and has the functions of wave-absorbing and energy-capturing. Based on the linear wave theory and energy conservation law, the Fourier Transform was applied to separate the two-dimensional wave frequency domain, and the energy captured by the rotors and absorbed by the floating breakwater were calculated.Experiments were conducted in a two-dimensional wave-making flume, and the transmitted waves at different wave heights and periods, the tension of mooring lines, and the rotational torque exerted on the Savonius rotor were measured. A series of performance comparison tests were also performed on the new floating breakwater and the traditional double-floating breakwater. Results show that the new floating breakwater is better than the traditional one in terms of reducing wave transmittance, and the combination of the floating breakwater with Savonius rotors can provide for marine aquaculture equipments with green power supply to a certain degree of self-sufficiency.

Effect of partial blockage of air duct outlet on performance of OWC device

The use of a Savonius rotor as turbine for an oscillating water column(OWC) is demonstrated.The effect of tuning the OWC using turbine duct blockage is also studied for different wave conditions.A horizontal turbine section OWC employing a Savonius rotor was tested by varying the opening of OWC exit(0%,25%,50%,75% and 100%) to study the behavior and performance of the device.The OWC model was tested at water depth of 0.29 m at frequencies of 0.8,0.9 and 1.0 Hz while the exit openings are varied.The static pressure,dynamic pressure,rotational speed of the Savonius rotor and the coefficient of power are presented as results.The OWC with exit opening of 25% showed greater performance in terms of rotational speed and CP compared to OWC with other exit opening percentages.This proves the ability of the OWC to be tuned by regulating flow in the turbine duct.