Solar water heating: comprehensive review, critical analysis and case study

Abstract

The increasing global demand for renewable energy sources underscores the significance of Solar Water Heating Systems (SWHS), emphasizing the need for thorough research and analysis in this domain. SWHS play a pivotal role in addressing energy efficiency and environmental sustainability, making it imperative to conduct in-depth studies on their utilization. Hence, this paper aims to provide a comprehensive overview of SWHS. It starts by explaining the principles behind these systems, including their components and classification. Moreover, this review consolidates various studies that have been conducted on SWHS to highlight both their advantages and disadvantages. Additionally, a case study is conducted in which it takes into consideration important economic and environmental factors. In particular, it focuses on several scenarios present in Lebanon such as family homes, schools, restaurants hotels and gyms to estimate potential cost savings achieved through implementing SWHS as opposed to relying solely on electric heaters. Furthermore, this investigation also examines the corresponding payback period associated with adopting SWHS along with assessing the significant reduction in carbon dioxide emissions possible if these systems were widely implemented. The findings of the study demonstrate that there is a direct correlation between the extent to which SWHS are utilized and both the payback period and reduction in CO2 emissions. It was observed that when SWHS are used more frequently, with a high percentage of time (Pr=0.9), significant advantages can be achieved. For instance, for different types of establishments such as family homes, schools, restaurants, hotels, and gyms, it was estimated that average payback periods would be 14.2 years, 4.6 years, 9.2 years, 4.4 years, and 5.3 years, respectively. These results indicate that adopting a greater dependency on SWHSs not only leads to quicker cost recovery but also significantly contributes towards reducing carbon dioxide emissions. The analysis reveals that the yearly decrease in carbon dioxide emissions per individual is 0.16 t within a household, 0.016 t per student in an educational institution, 0.04 t per customer within a dining establishment, 0.37 t for each occupied bed in a hotel accommodation, and 0.11 t per individual at a gym. This paper serves as guidelines to SWH community. Additionally, it adds a practical insights into economic and environmental issues relevant to both Lebanon and countries with similar climates.