Introduction

Flat plate collectors are generally covered by tempered glass glazings which provide excellent solar transmission as well as good protection from the weather. Polymeric materials have already substituted glass for different applications – examples are polycarbonate (PC) for airplane windows or poly(methyl methacrylate) (PMMA) as greenhouse cover. A substitution of the glass glazing of flat plate solar collectors with polymeric glazing materials could provide advantages mainly consisting in weight reduction and new possibilities in the manufacturing process. The glazing of a solar flat plate collector must resist different weather factors such as rain, snow, hail, UV-irradiation, wind, and elevated temperature loads. It also serves as a protection for the other collector parts, which makes its durability especially important. Because of the elevated investment cost of solar systems the durability of the collectors is expected to exceed lifetimes of 20 years.

Beside the resistance to weather factors, the transmittance to solar light is crucial for application in a solar collector. The solar transmittance of the glazing correlates directly with the collector efficiency and lies at about 91% for good low – Fe glasses. Polymeric materials are generally less transparent to solar light than glasses (Table 16.1) due to absorption bands in the near-infrared; nevertheless, thin films of fluorinated polymers have reached more than 95% of solar transmittance.

16.2.2

Updated: August 22, 2015 — 1:41 am