Comparative Study of Air-Based and Water-Based Solar Collectors for Space Heating Applications

This study presents a comparative simulation-based analysis of air- and water-based flat-plate solar collectors for space heating applications in cold climatic conditions. Tashkent serves as the case location. Utilising a dynamic hourly energy balance model and standardised meteorological inputs, the thermal behaviour of both collector types was assessed over a representative winter day. The results indicate that water-based collectors consistently outperform their air-based counterparts regarding thermal efficiency and useful heat output. The water-based system achieved a peak outlet temperature of 52°C and an average daily thermal efficiency of 61%, delivering 2.35 kWh of sound energy daily. In contrast, the air-based collector attained a peak outlet temperature of 36°C and an average thermal efficiency of 45%, yielding 1.62 kWh/day. Despite the lower efficiency, air-based systems offer several operational advantages, including faster heat-up times, lower installation complexity, and freeze resistance. These render them suitable for specific low-maintenance or ventilation-based applications. Conversely, the water- based system is more appropriate for hydronic heating, where higher thermal loads and storage integration are requisite. This study provides a robust technical foundation for selecting suitable solar thermal technologies in building energy systems, particularly in cold regions. The findings underscore the necessity of aligning collector characteristics with application needs, operational constraints, and climatic conditions.