ABSTRACT

The oscillating water column (OWC) is one of the most efficient types among wave energy converters (WEC), and its design of the front lip wall is essential for its resilience against extreme weather and recurrent wave conditions. This study aims to present an enhanced design of OWC to resist the maximum hydrodynamic pressure and yield higher hydrodynamic efficiency. Comparative analysis is made for two OWCs with vertical and forward bend front lip walls from existing experimental and numerical studies using the open-source computational fluid dynamics (CFD) tool OpenFOAM. The numerical findings are validated by the experimental results of Ashlin et al. (2016). It is concluded that the OWC with forward bend lip wall shows better hydrodynamic results.

INTRODUCTION

The rise in global temperature/warming become a serious issue in current and forthcoming years due to the excess release of greenhouse gases. A recent study by the International Finance Corporation (IFC) reported that there will be an increase in greenhouse gas emissions by 31% by 2034. This will be a crucial factor for all living beings in the world. Hence, there is an increase in demand for renewable energy sources that can replace thermal power plants for electricity conversion in several developed and developing countries. This paper discusses the energy conversion through a typical wave energy converter (WEC) called an oscillating water column (OWC). As OWC is one of the most effective WECs in many countries (Lopez et al.(2013), several research studies have been conducted on its use as a hybrid structure that can be used as an integrated application (Doyle and Aggidis, (2019)). Later, OWC has been integrated with breakwater as a multipurpose/hybrid structure, as reported by Falcao and Henriques (2016), Vicinanza et al. (2019), and Sundar and Sannasiraj, (2022). Having been used as a hybrid structure, several real large-scale OWCs have faced issues in the field, in particular, the damage suffered by the front lip when being exposed to extreme waves, like in the Mutriku power plant in Spain and full-scale hybrid OWC in Pico power plant, Portugal as mentioned by Ning et al., (2023). Hence, it is essential to analyze the strength and resistance of the front lip wall of OWC to hostile marine environments in isolated and hybrid conditions. The main aim of this study is to introduce a well-configured OWC front lip wall with a bend at the entry of the chamber (Socrates et al. (2024)), named as OWC-Forward bend, that can sustain/dissipate extreme wave action and produce maximum energy conversion efficiency in isolated and hybrid conditions. Several numerical and experimental studies have been conducted on the different front lip wall shapes. Some lip wall configurations can dissipate excess incident wave pressure/energy but fail to perform maximum energy conversion efficiency (Socrates et al. (2023)). Limited studies have been conducted to identify the configuration of the lip wall in dissipating the wave pressure/force and to have higher wave energy conversion efficiency. The experimental work of Ashlin et al. (2016) on the OWC with curved bottom and vertical front lip wall, named as OWC-Vertical model, was reported to exhibit a better hydrodynamic performance. This OWC-Vertical model is chosen to compare with the performance of the newly configured front lip wall OWC, OWC-Forward bend model. The hydrodynamic characteristics, such as the hydrodynamic pressure on the lip wall, hydrodynamic efficiency, chamber air pressure, and chamber oscillations of the two models, are carried out in this study. The OpenFOAM tool is used to validate the previous experimental results and to investigate the comparative hydrodynamic performance of the two OWCs considered in this study. The 3D numerical model was preferred for the study. The performance characteristics of the two models considered herein are evaluated, and the results are discussed in this paper.

This content is only available via PDF.
You can access this article if you purchase or spend a download.