Optimization of a salt gradient solar pond for air heating application

Abstract

In this study, it is demonstrated that when a solar pond is used for an air heating application like crop drying, domestic space heating, greenhouse heating etc., it is important to account for pumping power in the calculations. When air is the working fluid, the magnitudes of extraction and pumping power are comparable. Therefore, a new parameter is defined in context of solar ponds used for air heating, namely, effective power (defined as power extracted minus pumping power). At first, using a steady-state analysis, a closed form solution is derived for extraction power. The pertinent expression for pumping power is taken from the literature. Thus, an analytical expression for effective power is obtained and thereafter, an optimization analysis has been carried with the objective of maximizing this effective power. The analysis is used to calculate optimum values of air mass flow rate and pond’s non-convective zone thickness at which maximum effective power is registered. The corresponding maximum effective power and the associated air outlet temperature are also calculated. This work thus is believed to prove useful for designing of solar ponds that are used for air heating applications in a manner to ensure maximal system performance.