The air collector roof insulation system is laid like a roof and performs five functions at once, acting as a vapor barrier, thermal insulator, rainproof roof substructure, cladding and solar collector. Its key benefit is its outstanding energy efficiency, explains Guenther Winnerl, head of marketing, polycarbonate sheets at the Semi Finished Products segment at Bayer MaterialScience. The solar collector, which is made of highly heat resistant Makrolon sheet, produces usable energy in the form of hot air free of charge . In comparison to other technologies the energy can be used directly and without further conversion e.g. for heating.
Moreover, the insulation, which is based on polyurethane rigid foam, does not create thermal bridges, so only a negligible amount of heat energy escapes through the roof and the collector is optimally insulated against energy losses, adds Christoph Schlott of puren s project management. Rigid polyurethane foam offers very efficient thermal insulation, as well as being lightweight and durable. The panels produced from the Baymer system not only exhibit outstanding insulation properties even at minimal wall thicknesses, but are lightweight, durable and easy to machine thanks to their excellent compressive strength and dimensional stability, comments Thomas Seeger, an expert in polyurethane insulating materials at Bayer MaterialScience.
The system is based on a simple principle. Cold air flows through the collector. By means of an absorber, solar energy is transmitted to the air. The warm air can be used for room heating or for heating domestic water by means of a heat exchanger. It can also be fed into a heat pump or a geothermal energy store, or used to operate agricultural and industrial driers, for example for drying tobacco, hay, fruit, plaster or paint.
The Bomatherm system is equally suitable for private and industrial use. The energy savings and the low follow-up and operating costs mean that the investment pays off within a few years, especially as many of the costs would also be incurred with normal roof cladding.
The multiwall sheets are less expensive to produce than conventional solar thermal collectors and do not require the use of expensive heat conductors like copper. The Makrolon sheeting developed specifically for this application consists of a special black-pigmented coating on the underside, which functions as an absorbent layer, and a transparent surface with a high-tech co-extruded UV protective layer to ensure weather resistance. The multiwall sheets are optimized both thermodynamically and with respect to flow mechanics, and are the material of choice for this application. Unlike other transparent thermoplastics, Makrolon easily withstands the thermal stress of the warm air thanks to its exceptionally good heat resistance. Its high impact and break resistance also ensure that the sheets are not damaged by hailstones even at sub-zero temperatures, says Guenther Winnerl.
Thanks to its very low thermal conductivity (up to 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. The light weight of the insulating panels ensures that the complete solar air collector roof insulation system only weighs half as much as a conventional tiled roof. This allows much slimmer roof structures as regards statics and the dimensions of the rafters, thus cutting costs, notes Thomas Seeger.
The first step during installation of the Bomatherm solar air collector roof insulation system is to lay a vapor barrier on the roof substructure. Next, the puren thermal insulation system is placed on top of this and is fastened to the roof substructure using integrated battens. Special sheeting that is permanently heat-resistant at temperatures up to 150 C is then fitted. When fitted correctly, it forms a rainproof roof substructure. The roof is completed by securing the solar air collectors to the heat insulating elements by means of fastening strips.
China Chemical Weekly: http://news.chemnet.com/en/detail-1411716.html
