Review on the Progress of Solar Water Heaters and Their Future Perspectives

A solar water heater (SWH) converts solar radiation into thermal energy for various purposes, and its technology has experienced numerous developments. Many studies have focused on developing, optimizing, and analyzing the technological configurations of SWH to improve its thermal efficiency, but they rarely achieve 80% efficiency. This review aims to provide a broad overview of SWH, including the energetic and exergetic approaches and analyses, technological development, and examines advantages, disadvantages, and further developments. Various collectors of the SWH and related studies are also highlighted, and the results identify the technical and policy challenges of the implementation. Suggested potential solutions to these challenges are presented with further directions. Furthermore, this study also discusses the limitations of the current SWH technology by presenting the specifications and characteristics. It also presents the mathematical equation model often used, the technology potential, and the results of the latest studies and developments regarding SWH technology. The prospects for further development of the most promising SWH should be analyzed.