Low-cost TI curtain device

Within the framework of the passive solar energy research performed at the Fraunhofer Institute for Solar Energy Systems, a transparently insulated device, constructed with a double-sheet design, was developed for the exterior walls of buildings. Using the program TRNSYS, transient computer simulations estimated yearly heat gains of 41 kWh/qm for a massive south-facing wall in Freiburg. An opaque insulation with an U-value of 0.7 W/qm K (WVSO '82) has yearly heat losses of 57 kWh/qm. The energy efficiency of the TI curtain device was confirmed by experimental results. The absorber is manufactured by gluing a black, selective nickel laminate to a Polytetrafluoraethylen (PTFE) substrate. In March 1992, a sputtering technology, developed at the FHG- ISE, made it possible to cover large area PTFE substrates. Thus, a cost efficient manufacturing process for large absorber areas was enabled. In summer the double-sheets can either be rolled up or can be ventilated from behind by natural conve ction. First cost analyses show that the transparent insulated curtain device is competitive today.