abstract
Many future applications of solar thermal energy, like heating with a high solar fraction and solar industrial process heat or solar cooling will require high collector efficiencies at temperatures above 80°C and/or at a low irradiance level. Advanced flat-plate collectors show a high potential for these applications, they are less expensive and mechanically simpler than evacuated tube collectors. To raise the performance of flat-plate collectors the thermal resistance of the transparent cover has to be increased, while keeping the solar transmittance at a high level. Within a research project1 ISFH achieved this goal by adding a second glass pane with a low emitting coating and using argon in the hermetically sealed gap, thus reducing heat losses by both convection and radiation (see Fig. 1). A high solar transmittance must be realized by using high quality glass with antireflective coatings and an optimized low-e coating. Long term reliability of the coated glass as well as of the glazing system for the use in solar thermal collectors has to be assured. The objective of the project is to assess the technological and scientific basics for this collector concept. This paper gives an overview of the main project results.