Gradient Zone Constraints in a Salt-Stratified Solar Pond

Abstract

An operational condition is defined for a salt-stratified solar pond. A criterion based on empirical evidence is formulated which shows a limit is approached as steady operating conditions are attained. For sodium chloride ponds, the criterion indicates a dependence between salt and temperature gradients during steady-state conditions. At the present time, appropriate data for explaining the physical basis of this relationship are not available. Significant results are found as a result of the gradient zone criterion. First, the gradient zone criterion leads to an explanation for the formation of an upper convecting zone. Results obtained with the gradient zone criterion relate to salt maintenance in a pond. Depending on the temperature operating conditions of a pond, a specific amount of salt must be in the pond. Also, salt concentration levels maintained in the upper and lower convecting zones are shown to significantly affect a pond’s thermal energy performance.