Cost-effective designs of solar air heaters

We discuss some aspects of solar air heaters, which could lead to more economical designs. It is shown that a partial flow channel between two glazings increases the efficiency of the system. This procedure may eliminate the need for insulation material, at least on the two sides of the space between two glazings. The effect of glazing absorptance on system performance is also investigated. We conclude that the upper glazing should be as transparent as possible while the lower glazing should have higher absorptance.