CFD Modeling of a Small Scale Solar Pond
Abstract
A Salt Gradient Solar Pond (SGSP) is a basin of water where solar energy is trapped due to an artificially imposed salinity gradient. Three main zones can be identified: the surface and bottom zones that are both convective and an intermediate zone in between intended to be non-convective. This zone acts as a transparent insulation allowing the storage of thermal energy at the bottom, where it is available for later use. A numerical model where the SGSP dynamics is described in terms of velocity, pressure, temperature and salt concentration is presented. This model is based on the Navier-Stokes equations for an incompressible fluid, coupled to two advection-diffusion equations: one for temperature and another one for salt concentration. The fluid density ρ depends on temperature and salinity and the Boussinesq hypothesis is adopted. The variation of the daily solar radiation and its attenuation along the depth of the pond are also considered. The objective of this work is to reproduce existing experimental data with a model robust enough to describe the physical phenomena involved for a long period of time. A transient computation with the finite element deal.II library and a finite volume model in ANSYS Fluent account for the dynamic behavior of the pond. This way it will be possible to contribute to the correct design and operation of these long thermal storage energy devices.
Keywords
Solar ponds, Thermal storage, Numerical modeling, Finite elements, Double advection-diffusion.