Topics in gradient maintenance and salt recycling in an operational solar pond

The 3355 square meter solar pond facility located at Bruce Foods Corporation in El Paso, Texas has been in continuous operation for almost two and one half years. The salt gradient solar pond has maintained a temperature difference between the upper and lower zones of 55 to 70 degrees C while demonstrating the regular delivery of industrial process heat, grid-connected electrical power, and the experimental production of desalted water utilizing the thermal energy of the solar pond. Since this facility is inland it requires the ability to recycle the salt that reaches the surface of the pond. After measuring salt transport in the pond, which initially averaged approximately 60 kg per square meter per year, it was evident that the original evaporation pond system was undersized. In order to address this problem, a method that uses the main pond surface for initial brine concentration and short term storage was developed. The method involves adding a surface layer of fresh water to the pond and creating an internal convective zone near the surface. After a description of the El Paso solar pond facility and status update, this paper examines this method for brine concentration and storage, the effects of the internal convective zone on pond operation, and the installation of an enhanced evaporation net system and an automatic scanning injection system.