Numerical analysis of the distribution of incident wave energy on an onshore oscillating water column wave energy converter
Lucas Amaral Gaspar1; Paulo Roberto de Freitas Teixeira1; Eric Didier2; Maria da Graça Neves2
1 Universidade Federal do Rio Grande - FURG; 2 Laboratório Nacional de Engenharia Civil - LNEC
doi:10.20906/CPS/CILAMCE2017-0455
Resumo
Wave energy, which is a type of renewable energy with great potential, could be enough to supply the electric energy the world needs. However, the major disadvantage of wave energy converters is their low efficiency. Therefore, researches of devices that are able to extract this energy with viable efficiency are fundamental. In this study, a numerical analysis to evaluate the energy efficiency of an Oscillating Water Column (OWC) wave energy converter is carried out. The OWC device consists of a chamber partly submerged in which there is an opening below the water surface. Air is trapped above the water free surface inside the chamber. Incident waves cause oscillation of the free surface inside this chamber, compress and expand the air and force it to flow through a turbine that drives an electrical generator. The device geometry based on the pilot plant installed on Pico Island, Azores, Portugal, is studied. The methodology consists in calculating the percentage of the incident energy that is distributed along the wave energy conversion. The FLUENT® numerical model, which is based on the Reynolds-Averaged Navier-Stokes (RANS) equations, discretized by means of the Finite Volume technique, is used. The Volume of Fluid (VoF) method is employed to take into account the water and air fluids. The case study comprises a flume 10 m deep with an onshore OWC at its end. An incident wave, 1 m height and a 9 s period, and a Wells turbine model are imposed by means of User Defined Functions (UDFs). The distribution of the incident wave energy is determined in terms of reflected wave energy, water column oscillation potential energy, pneumatic energy and energy losses due to viscosity and turbulence dissipations. Results show that the incident wave energy is distributed around 37% for the sum of reflected wave energy and viscosity energy loss, 52% for pneumatic energy and 11% for water column oscillation potential energy. This methodology is a very good tool that allows understanding how the incident wave energy is distribut
Palavras-chave: wave energy converter; oscilating water column; computacional fluid dynamics; energy balance analysis; efficiency