The solar air collectors are multiwall sheets, which Rodeca GmbH produces using the polycarbonate Makrolon® from Bayer MaterialScience AG. Cold air flows into the sheets along the eaves, rises upwards, warms up, and is collected at the roof ridge. The warm air can be used for room heating or for heating domestic water by means of a heat exchanger, or it can be fed into a heat pump or a geothermal energy store. It is also ideal for operating agricultural and industrial driers, for example for drying tobacco, hay, grain, fruit, plaster or paint.
Production of the multiwall sheet requires less investment than conventional solar thermal collectors and does not require the use of expensive heat conductors like copper. The sheets consist of a dyed-black, glass-fiber-reinforced underside, which functions as an absorbent layer, and a transparent, concave surface with a co-extruded UV protective layer. The latter makes the sheets light- and weather-resistant. “Our polycarbonate Makrolon® is the ideal material for the collectors because of its transparency and, unlike other popular transparent thermoplastics, it withstands the thermal stress of the warm air thanks to its excellent heat resistance. Moreover, its high impact and break resistance ensure that the sheets are not damaged by hailstones – even at sub-zero temperatures,” says Axel Wetzchewald, head of the Extrusion Sheet segment for Europe in the Polycarbonates Business Unit of Bayer MaterialScience.
The first step during installation of the Bomatherm® solar air collector roof insulation system is to lay the vapor barrier onto the roof substructure. Next, the puren Profitherm thermal insulation system is laid on top of this to create an impermeable layer and fastened down using special fixing brackets in the roof substructure. Special sheeting that is permanently temperature-resistant up to 160 °C is then fitted. When fitted correctly, it forms a rainproof roof substructure. Finally, the solar air collectors are secured in the anchoring strips of the heat insulating elements using fixing brackets.
Thanks to its extremely low thermal conductivity (Thermal Conductivity Group 024), the full-surface heat insulation system based on polyurethane rigid foam insulates much more effectively than conventional insulating materials like mineral wool. It is based on Baymer® from Bayer MaterialScience. “Panels produced from this polyurethane system not only exhibit outstanding insulation properties even at minimal wall thicknesses, but are also extremely lightweight, exhibit long-term stability and are easy to process thanks to their excellent pressure resistance and dimensional stability,” explains Thomas Seeger, an expert in insulating materials made of polyurethane rigid foam in the Polyurethanes Business Unit of Bayer MaterialScience. The light weight of the insulating panels is one reason why the complete solar air collector roof insulation system only weighs half as much as a conventional tiled roof. This enables much slimmer roof structures as regards statics and the dimensions of the rafters, thereby cutting costs.
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