A comprehensive review on solar water heaters

Solar water heating system proves to be an effective technology for converting solar energy into thermal energy. The efficiency of solar thermal conversion is around 70% when compared to solar electrical direct conversion system which has an efficiency of only 17%. Hence solar water heaters play a vital role in domestic as well as industrial sector due to its ease of operation and simple maintenance. Extensive works on improving the thermal efficiency of solar water heaters resulted in techniques to improve the convective heat transfer. Passive technique has been used to augment convective heat transfer. These techniques when adopted in solar water heaters proved that the overall thermal performance improved significantly. This paper reviews various techniques to enhance the thermal efficiency in solar water heater. In addition to this, a detailed discussion on the limitations of existing research, research gap and suggested possible modifications is made.