Oscillating-water-column wave energy converters and air turbines: A review

Abstract

a b s t r a c tThe ocean waves are an important renewable energy resource that, if extensively exploited, may contribute significantly to the electrical energy supply of countries with coasts facing the sea. A wide variety of technologies has been proposed, studied, and in some cases tested at full size in real ocean conditions. Oscillating-water-column (OWC) devices, of fixed structure or floating, are an important class of wave energy devices. A large part of wave energy converter prototypes deployed so far into the sea are of OWC type. In an OWC, there is a fixed or floating hollow structure, open to the sea below the water surface, that traps air above the inner free-surface. Wave action alternately compresses and decompresses the trapped air which is forced to flow through a turbine coupled to a generator. The paper presents a comprehensive review of OWC technologies and air turbines. This is followed by a survey of theoretical, numerical and experimental modelling techniques of OWC converters. Reactive phase control and phase control by latching are important issues that are addressed, together with turbine rotational speed control.

Full-Scale Prototype of an Overtopping Breakwater for Wave Energy Conversion

“…The extracted energy is generally converted into electrical energy, and these innovative devices are commonly denominated Wave Energy Converters (hereafter WECs). Although more than 1000 WECs have been patented worldwide (Falcão and Henriques, 2016), this technology is currently in an early stage of development. A serious break on the growth and commercialization of these devices are their costs, still very high when compared with other more established renewable energy technologies such as wind turbines or solar panels, and their potential environmental risks (Azzellino et al, 2013).…”

“…A serious break on the growth and commercialization of these devices are their costs, still very high when compared with other more established renewable energy technologies such as wind turbines or solar panels, and their potential environmental risks (Azzellino et al, 2013). Other important constraints are the operational efficiency and the structural survivability of the devices, nowadays still low considering that several devices have been partially or, even more, completely destroyed during extreme storms (Medina-Lopez et al, 2015;Falcão and Henriques, 2016).…”

The investigation of a segment multi-chamber oscillating water column in physical scale model

“…Recently the successful deployment of a OWC at Jeju Island, South Korea, worked at rated power of 500 kW. These successful devices show that the obstacles can be overcome with further research [6]. Table 1 summarizes most of the OWC devices that have been installed in various countries with the real or expected capacity and the turbine type that was used to extract the power.…”

“…The proposed model has experienced various stages of development and research. Dorrell [6] describes the construction of a small multi-chambered OWC system. Then Hsieh et al [7] developed and analysed a two chamber OWC; they validated the increase in power output due to the use of the multiple chamber arrangement experimentally based on the wave conditions around Taiwan.…”

Wave energy conversion of oscillating water column devices including air compressibility

“…12 A recent review on the development of the OWC devices and air turbines has been given by Falcao and Henriques. 17 To understand and improve their power performance by the OWC devices, numerical methods have been developed and employed. Earlier theoretical work on the hydrodynamic performance of some simple OWCs has shown that the OWC devices could have a high primary wave energy conversion efficiency.…”