The Stability and Thermal Performance of a Small Solar pond

A small salt gradient solar pond with an average surface area of 1.8 m2 and depth of 0.8m has been tested. The depths of storage, gradient and surface zones are 0.3, 0.27 and 0.07m, respectively. The temperature of the storage zone for the summer days reaches its maximum of 65˚ C after about 8 days. Daily variation of the storage zone temperature was about 8˚C which is due to small volume of this zone. The thermal absorption of the pond varies between 35 to 20 percent of the total solar radiation, depending on the temperature of the storage zone. Salinity of the storage zone is about 200 gr/kg and the density gradient of the gradient zone is about 5x10-3 gr/cm4 which with typical fluid velocity of the convective zone gives a Richardson number, Ri, of order of 104. Erosion of the gradient zone based on this Ri is about 2.5 cm/month which is in agreement with the observations. Although the temperature of the storage zone reaches high values, with sloped wall, no sign of double diffusive convection was observed.