Experimental Research on Primary and Secondary Conversion Efficiencies in an Oscillating Water Column-Type Wave Energy Converter

Tengen Murakami,Shuichi Nagata,Manabu Takao,Toshiaki Setoguchi,Yasutaka Imai

doi:10.3390/su8080756

Tengen Murakami, Shuichi Nagata + Show 3 more

Open Access

https://doi.org/10.3390/su8080756

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Abstract

For the practical application of a fixed oscillating water column (OWC)-type wave energy converter, it is necessary to develop a design method which can consider the characteristics of incident wave motion, the motion of the internal free surface affected in the structure such as a partly submerged wall, the fluctuation of air pressure in an air chamber, and the rotation of the air turbine. On the other hand, the impulse turbine as the secondary conversion device in the OWC unit is expected to achieve high efficiency. In this paper, firstly, the steady air flow tests for a single-impulse turbine were conducted to grasp the characteristics of the turbine without the effect of water waves. Secondly, the 2-dimensional wave tank tests in regular waves for the performance evaluation of the fixed OWC-type wave energy converter with the same impulse turbine were conducted to obtain the data needed to make this design method. As the results, the effects of the air chamber length and the guide vane’s setting angle on the primary and secondary conversion efficiencies are clarified experimentally.

Highlights

For the leap in power technologies to become a sustainable society, we are under obligation to cope with the warming of the global environment and to conserve the natural ecosystem and coexist with nature
The effects of the air chamber length and the guide vane’s setting angle on the primary and secondary conversion efficiencies are examined with the 2-dimensional wave tank tests in regular waves, there are other geometric parameters such as the curtain wall shape and the rotor inlet/outlet angle having an impact on the efficiency
FigFuigruere131.3.VVarairaiatitoionnoofftuturrbbiinnee ppeerrffoorrmmaannccee dduuee ttoo sseettttiinnggaannggleleoof fgguuidide evvanaen.e.(a)(aS)ecSoencdoanrdyary cocnovnevresirosinonefefifcfiiceinecnyc;y(;b(b) )TToorqrquueeccooeeffiffcicieienntt;;((cc))IInnppuutt ccooeeffffiicciieenntt. This present paper shows the impulse turbine performance under a steady air flow condition, and the effects of the air chamber length L and the setting angle θ of the guide vane on the energy conversion efficiency of the fixed oscillating water column (OWC)-type wave energy converter under the oscillating air flow condition

Summary

Introduction

For the leap in power technologies to become a sustainable society, we are under obligation to cope with the warming of the global environment and to conserve the natural ecosystem and coexist with nature. There is an oscillating water column (OWC)-type wave energy converter as one of the WECs. There is an oscillating water column (OWC)-type wave energy converter as one of the WECs This device is composed of an air chamber, an air turbine and a generator and is considered to be safe even under storm conditions. The performance of the impulse turbine with fixed guide vanes in the model OWC is confirmed by the steady air flow test without the effect of water waves. The effects of the air chamber length and the guide vane’s setting angle on the primary and secondary conversion efficiencies are examined with the 2-dimensional wave tank tests in regular waves, there are other geometric parameters such as the curtain wall shape and the rotor inlet/outlet angle having an impact on the efficiency

Experimental Apparatus

Effect of Air Chamber Length

Effect of Setting Angle of the Guide Vane

Conclusions