ABSTRACT
Active solar air systems can effectively cover part of the heating demand for space heating, ventilation air and DHW of high-performance houses. Such systems have important advantages: solar air systems do not drip or freeze, and are simple, efficient and proven systems. Solar air collectors perform comparably to water-based flat-plate collectors; but the collector inlet temperature is, most of the time, lower than is the case with a water collector. This results in higher thermal efficiency. Furthermore, air as the heat transport medium allows for a simple collector construction; but the low density and heat capacity of air require a much higher volume flow to transport the absorbed energy. A disadvantage is the higher electric consumption of the fans compared to that of a pump in a water-based system. To achieve small pressure losses and electric consumption, the hydraulic design of the whole solar air circuit must be optimized. Generously sized air ducts, minimal duct lengths and no sharp bends help in this regard.
