Effect of peripheral heat conduction in salt-gradient solar ponds

Abstract

In this work, a detailed investigation on the effect of heat dissipation from side walls of a salt gradient solar pond on its various thermal aspects has been carried out. Both time-dependent and steady solutions have been reported. Finding the optimum thickness of side insulation is a challenge when it comes to setting up a solar pond system, as it requires a significant expenditure in the beginning. Here, the effects of side wall insulation on variable size of different zones and area of cross sections are studied using validated analytical and finite difference-based numerical approaches. Present study indicates that the heat extraction efficiency of a solar pond varies asymptotically with respect to the insulation thickness installed on the side walls, and the role of heat conduction within the middle layer is more than the radiative intensity reaching a given layer. It is highlighted that for a given insulation, there is always a unique value of non-convective zone where the pond's performance under a given operating condition becomes maximum. But, such optimal size does not exist for upper and lower convective zones, and beyond a certain value, further change in these zones is not useful. For a given insulation and other operating parameters, a circular cross section should always be selected for designing vertical-walled solar ponds. The impact of insulation is also found to depend on the radiative intensity and temperature profiles of a given location. The present work proposes cardinal guidelines regarding the suitability and the unsuitability of insulations along with appropriate selection of solar pond's design.