A modified support pillar design for a flat vacuum-based solar thermal collectors

Abstract

Improving the efficiency of low-temperature solar collectors can be attained by decreasing the heat loss from the collectors. The current work proposes an efficient vacuum-based solar thermal collector design with a new support pillar design to reduce the thermal bridge through the support pillars. In addition, the absorber of this collector is isolated from the front and the rear side by a vacuum layer with transparent glazing. The absorption of front and backside ground reflected radiation, possibly achieving the concept of bifacial flat solar thermal collector. The results of the new support pillar are compared with those of stainless steel and glass support pillars under the same conditions. The results showed that using the new support pillar design decreases heat loss from the absorber. At the 6 mm support pillar diameter, replacing the stainless-steel support pillar with the new modified pillar reduces the heat flux through the front glazing from 59.7 W/m2 to 21.9 W/m2 at ASTM boundary conditions.