Stability analysis of solar ponds with non-constant temperature gradients

Abstract

For the sublayer stability analysis of operational solar ponds, the use of a more physically significant criterion, viz. observed ( dT dx ) ( dC dx ) ≥ F(C, T) (the stability factor) has been suggested. The plots of F( C, T) divide the plane [ F( C, T), x] into regions of stability and instability. The plots of the gradient ratios, ( dT dx ) ( dC dx ) , calculated from the observed values of temperature and concentration with pond depth, reveal the stability, or otherwise, of the sublayers in the different regions of the pond with depth. Stability analysis of Zangrando's UNM pond data, using this technique, shows that local instability extended to layers more than 15–20 cm thick before breakdown. Stability analysis of the thermal configurations of operational solar ponds shows that salinity gradients set up by natural diffusion of salts, in solar ponds in which the bottoms are maintained at constant saturation temperatures and the surfaces held at near-zero concentration, assure complete stability of the entire non-convective zone for a maximum bottom temperature of about 100°C.