Author(s): Angel Molina Salas; Christian Quiros Nebrera; Francisco Mengibar Cabrerizo; Encarnacion Medina-Lopez; Maria Clavero Gilabert; Antonio Monino Ferrando

Linked Author(s): Angel Molina Salas, Antonio Moñino Ferrando

Keywords: Oscillating Water column; Polytropic index; Real gas; Wave energy converter; Renewable energy

Abstract: Energy from the ocean has become one of the most promising clean resources. The challenges for the future of clean energy face a major achievement in increasing the percentage of use from renewable sources. For example, as far as in the case of Europe, the horizon is set to 30% from renewable sources by 2030. In that sense, the available power from ocean waves, with estimates of around 3.2∙105 MW when that energy is transformed off-shore, reveals itself as a source to which both scientific and technical efforts must be paid. Not to mention the combined effects of off-shore waves and wind, which can become a reliable focusing for the near future. In the previous sense, the Oscillating Water Column (hereinafter OWC) represents one of the wave energy conversion technologies to which more research has been devoted during the last decades, with several plants in operation at present. In general terms the OWC consists of a partially submerged air chamber, open to the sea at the bottom and with a power take off usually consisting of a Wells turbine. The wave action induces the compression/expansion of air inside the chamber, and the Wells turbine transform the pneumatic power into electricity to be supplied to the grid. While the expected efficiency for OWC devices usually ranges close to 40%, actually the observed efficiencies hardly reach 10%. Previous research by the authors have revealed that implementation of a real gas model to describe the Thermodynamics of the dry air-water vapour mixture inside the chamber, helps explaining the deviations in the observed efficiency from expected values. This work advances in study of the OWC performance from the experimental focus, through the testing of a simple off-shore OWC device model with a turbine implemented as PTO. The analysis of experimental data is enhanced with the implementation of a real gas hypothesis to describe the compression/expansion cycle inside the chamber, following previous results. The final goal is to provide guidelines leading to a more competitive design of the OWC technology, in which the efficiency improves and the costs deployment, maintenance, repair, and replacement are reduced.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022710

Year: 2022