Direct Solar Energy
tube, a transparent cover, a frame and insulation (Figure 3.3a). For low-temperature applications, such as the heating of swimming pools, only a single plate is used as an absorber (Figure 3.3b). Flat-plate col- lectors demonstrate a good price/performance ratio, as well as a broad range of mounting possibilities (e.g., on the roof, in the roof itself, or unattached).
Unglazed Solar Collectors
Flat Plate Collectors
Single or Double Glazing
Serpentine Plastic Pipe Collector
Figure 3.3a | Schematic diagram of thermal solar collectors: Glazed flat-plate.
Typically 1 1/2’’ ABS Pipe
Evacuated-tube collectors are usually made of parallel rows of trans- parent glass tubes, in which the absorbers are enclosed, connected to a header pipe (Figure 3.3c). To reduce heat loss within the frame by convection, the air is pumped out of the collector tubes to generate a vacuum. This makes it possible to achieve high temperatures, useful
Figure 3.3b | Schematic diagram of thermal solar collectors: Unglazed tube-on-sheet and serpentine plastic pipe.
Vapor Rises to Top
Condensed Liquid Returns to Bottom
Copper Sleeve in Manifold
Aluminium Header Casing
Evacuated Glass Tube
Evacuated Heat Pipe
Figure 3.3c | Schematic diagram of thermal solar collectors: Evacuated-tube collectors.