Geometric Analysis through the Constructal Design of a Sea Wave Energy Converter with Several Coupled Hydropneumatic Chambers Considering the Oscillating Water Column Operating Principle

Yuri Theodoro Barbosa De Lima,Elizaldo Domingues Dos Santos,Giulio Lorenzini,Luiz Alberto Oliveira Rocha,Liércio André Isoldi,Mateus Das Neves Gomes

doi:10.3390/app11188630

Abstract

The work presents a numerical study of a wave energy converter (WEC) device based on the oscillating water column (OWC) operating principle with a variation of one to five coupled chambers. The main objective is to evaluate the influence of the geometry and the number of coupled chambers to maximize the available hydropneumatic power converted in the energy extraction process. The results were analyzed using the data obtained for hydropneumatic power, pressure, mass flow rate, and the calculated performance indicator’s hydropneumatic power. The Constructal Design method associated with the Exhaustive Search optimization method was used to maximize the performance indicator and determine the optimized geometric configurations. The degrees of freedom analyzed were the ratios between the height and length of the hydropneumatic chambers. A wave tank represents the computational domain. The OWC device is positioned inside it, subject to the regular incident waves. Conservation equations of mass and momentum and one equation for the transport of the water volume fraction are solved with the finite volume method (FVM). The multiphase model volume of fluid (VOF) is used to tackle the water–air mixture. The analysis of the results took place by evaluating the performance indicator in each chamber separately and determining the accumulated power, which represents the sum of all the powers calculated in all chambers. The turbine was ignored, i.e., only the duct without it was analyzed. It was found that, among the cases examined, the device with five coupled chambers converts more energy than others and that there is an inflection point in the performance indicator, hydropneumatic power, as the value of the degree of freedom increases, characterizing a decrease in the value of the performance indicator. With the results of the hydropneumatic power, pressure, and mass flow rate, it was possible to determine a range of geometry values that maximizes the energy conversion, taking into account the cases of one to five coupled chambers and the individual influence of each one.

Highlights

The research and development of various energy conversion technologies focus on different possibilities, such as solar, wind, biogas, and energy from the ocean, and these are not the only ways to obtain energy [1], due to the growing demand for renewable energy as a sustainable energy source
The present work carried out a numerical study of an oscillating water column (OWC) wave energy converter, considering different numbers of coupled devices
The objective of the investigation was to evaluate the influence of the geometric variation and the number of coupled hydropneumatic chambers, keeping the volume of the device constant over the available hydropneumatic power converted by the devices

Summary

Introduction

The research and development of various energy conversion technologies focus on different possibilities, such as solar, wind, biogas, and energy from the ocean, and these are not the only ways to obtain energy [1], due to the growing demand for renewable energy as a sustainable energy source. Checking the Brazilian reality, the energy matrix present in the country has a higher consumption of non-renewable sources of energy than renewable ones. More renewable sources are used than the rest of the world, with 42.9% of the energy coming from clean energies [2]. The ocean is an excellent form of renewable energy. It can store thermal (heat), kinetic (tides and waves), chemical, and biological (biomass) sources of energy [3]. The highlight is the waves’ energy due to its high energy density, predictability, and wide availability [4]

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Conclusion