Study of Buoyancy-Driven Flow Effect on Salt Gradient Solar Ponds Performance

Salt gradient solar ponds are the ponds in which due to existence of saline and salt gradient layers, lower layers are denser and avoid the natural convection phenomenon to occur so that solar radiation energy can be stored in the lowest zone. In this study, one-dimensional (1D) and two-dimensional (2D) numerical approaches have been implemented to simulate unsteady buoyancy-driven flow of solar ponds. In 1D method, the pond has been investigated in terms of the layers thicknesses so that the variation of temperature is calculated by energy conservation equation. The formulized radiation term was used as energy source term in energy equation. The results of 1D approach were validated with an experimental study and then optimization was carried out to determine the maximum thermal efficiency for an interval of layers height. Since the stability of the solar pond cannot be determined by 1D simulation, a 2D approach was considered to show the stability for different nonconvective zone (NCZ) heights and different salt gradients. In 2D study, in order to investigate hydrodynamic and thermal behavior of saltwater fluid, a numerical approach was used to simulate temperature gradients throughout the pond. The results of 2D numerical method are validated with an experimental data. The effect of linear and nonlinear salt gradient was considered.