Solar pond design for Arabian gulf conditions

Collection and storage of solar energy in salt gradient solar ponds under conditions of high ambient and ground temperatures and all year-round sunny weather are investigated theoretically. A transient model based on measured local environmental conditions (solar insolation, ambient temperature and ground temperature) is developed to predict solar transmission, temperature distribution and salt distribution inside the pond for any day of the year. In the model the effects of heat dissipation into the ground, bottom reflection, pond dimensions, load extraction and variation of the pond's physical properties with temperature and concentration are investigated. The generated non-linear coupled system of heat and salt concentration equations for the composite media, considered to have isothermal boundary conditions, is solved numerically using the implicit finite-difference scheme. The results show that the optimum thickness of the gradient zone, under hot climatic conditions, is 1·5 m. Following the first year of operation, the pond with a thicker storage zone gives much less temperature fluctuation between winter and summer seasons and hence a better thermal performance. An energy analysis performed on the pond shows that about 32% of incident solar energy is lost to the air by evaporation, convection and thermal radiation, 6% is lost to the ground; 12% is the extracted load and the remainder (50%) is due to absorption and reflection at the surface of the pond. For a similar pond, operating under cold climates, air and ground losses are much higher while the useful load is relatively lower in comparison with the corresponding figures for hot climates.