Improving the solar still performance by using thermal energy storage materials: A review of recent developments

In recent decades, energy and water desalination using solar energy has played a vital role for the survival of human beings due to the cost and shortage of clean water; and gave considerable impetus to decrease greenhouse gas effects produced from burning fossil fuels. Thermal energy storage materials (TESMs) are used to store the energy through the daytime (sunshine time) and discharge this energy during nighttime (sunset time) and hence they have been used in water desalination systems to enhance its performance. TESM such as phase change materials (PCMs), myristic acid, sponge’s cubes, cotton, jute, cloth, porous materials and sponge sheet, quartzite and natural rock, coated and uncoated metallic wiry sponges, sand, gravels and aluminum filling are quite attractive in the solar desalination, especially in solar stills (SSs), to enhance thermal performance of SS by improving its thermal energy storage capability. We found from this review that the TESMs have a significant effect on enhancing the fresh water output from the SS especially when paraffin wax is used as PCM, which has large storage density with narrow range of temperature difference. In this review paper, various solar TESMs, especially PCM, tested by the researchers to improve the freshwater output as well as thermal performance of SSs, are analyzed and discussed in detail.