Energy, exergy and thermo-economic analysis of solar distillation systems: A review

Desalinated water, the final product of a solar distillation system, is useful for drinking purpose, community services, industry and agriculture on a small scale. It is expensive and may be considered as an industrial product. In the present communication, it has been tried to collect information about the ongoing research activities in the field of solar distillation system with the aim to enhance productivity and efficiency through an effective thermodynamic tool i.e. energy and exergy analysis, especially of the solar stills, similar to its wide application in complex thermal systems such as steam or gas turbine, boiler and cogeneration systems. Thermodynamic models for the energy and exergy analysis have been presented based on the fundamental heat transfer correlations in literatures for the simple basin type solar stills. Energy efficiency and productivity of the conventional solar stills is found to be low in the range of 20–46% and less than 6L/m2/day, respectively, for most cases, even under optimized operating conditions. The exergetic efficiencies are estimated to be between 19% and 26% for a triple effect system, 17–20% for a double effect system, and less than 5% for a single effect system. Productivity increases significantly by the use of integrated solar stills with better efficiency. The overall energy and exergy efficiency of the integrated systems rises up to 62% and 8.5%, respectively, using single effect solar stills. An attempt has also been made to review works on economic and thermo-economic analysis of solar stills. The cost of desalination through solar stills is reported in the range of US$0.014 to 0.237/L. It decreases further with increase in efficiency. It is observed that integrated solar desalination systems and technologies will be better choice than the conventional solar distillation systems for rural as well as urban areas blessed with sufficient sunshine.