How does a cover affect the optical efficiency of a collector?

Approximate change of the U -value of the covering system as a function of absorber temperature (similar to ). Transmittance also has to be considered. With every additional cover, the total transmittance of the front side is diminished and therefore the optical efficiency of the collector is reduced.

What components are used in a solar system?

All use the best components available on the market at the moment: anti-reflective solar glass with transmittance of 0.96, full area direct flow aluminum absorber (by Savosolar) with absorber efficiency factor F' of 0.97, absorption coefficient of 0.96 and emission coefficient of 0.05 (see Fig. 3) .

How much W/m2 K can a solar flat plate collector absorb?

This paper presents the first integrated rear side vacuum super insulation in a solar flat plate collector. Thus, rear side losses between 0.25 and 0.8 W/m 2 K can be reached, depending on the VSI filling and the envelope material.

What is a good vacuum tube collector?

Comparison of new film and full area absorber based prototypes with market available high-performing flat plate collectors (Vaillant VFK 155, Tigi Honeycomb) and recent developments in the state of prototypes (ISFH, SRB, TVP Solar MT-Power) and a good vacuum tube collector (Vaillant VTK 1140).

What is vacuum super insulation?

Vacuum super insulation is the best know insulation technique. Therefore, it has been chosen to substitute the standard rear side insulation materials like mineral wool or PU foam in the collector. Principle, properties and applications of a VSI and the realization of the first VSI prototypes have been described in detail in . 3.1.

Which company makes a double-glass collector?

Austrian company Oekotech has a collector with a double-glass design at the front . Although the collector efficiency rises, it makes the collector quite heavy and expensive. The Israeli company Tigi sells an efficient collector with a polymer honeycomb structure .