Low-emissivity Transpired Solar Collectors

Transpired Solar Collectors (TSCs) are used around the world for pre-heating of ventilation air in buildings and agricultural drying. The current generation of TSCs tend to use pre-finished steel for the perforated absorber and coatings which were not principally designed for solar thermal applications. This means that while they have a relatively high absorptivity, they also have a high-emissivity, which results in high radiative losses when operating at low flow rates. A number of studies have shown that development of a low-emissivity coating for TSCs could lead to increased energy savings for the current range of applications and enable their use in solar cooling. This paper reports on the development of a new long-life (design life of over 50 years) low-emissivity (less than 0.30) coating for TSCs that will enable them to achieve a higher air temperature rise when operating at a low flow rate. In addition, the architecturally attractive appearance of the new low-emissivity coating may increase the appeal of TSCs to architects, thereby broadening the range of buildings with which they may be incorporated.