Method for monitoring stability within a solar pond salinity gradient

In order to operate a salinity-gradient solar pond at high temperature differences between the surface and lower zones, one of the most important parameters to monitor and control is the 'stability' of the salinity gradient as a function of height or depth. The stability is a function of the ratio between local salinity gradient and local temperature gradient strengths and a limit can in theory be calculated for the salt or salts being used in the solar pond. This paper briefly reports work on stability calculations and monitoring experience at an operating solar pond in El Paso, Texas. One significant conclusion is the fact that salinity gradient breakdown in the El Paso solar pond, operating at relatively high temperature differences, typically between 50 to 70 °C, occurs at a stability ratio approximately 60 percent higher than that value predicted and validated in indoor laboratory experiments.