Flat plate collector with bifacially irradiated absorber

A new flat plate collector has been developed which, especially during times of low radiation conditions, reaches higher efficiencies than any other collector known so far. The absorber plate is insulated with Transparent Insulation Material (TIM) on the front and on the rear side and both sides are irradiated. A prototype was built. Indoor and outdoor measurements were carried out to determine the optical efficiency Etasub0 and the U-value of the collector.