SEA 2 – Development and Measurement of Novel Solar Air-heating Collectors and Investigation of Suitable Energy Usage Concepts

The “SEA 2” project continues the FOSTA project “Development of Sandwich Element with Energy Accumulation, Energy Distribution, and Insulation (SEA)”. The concept plans for the design of solar air-heating collectors for facades and roofs – e.g., of halls – based on sandwich elements and steel profiles available in the market as well as transparent covers. The feasibility was already demonstrated in the first project. The new project was to focus on the development and standard-conform measurement of collectors optimized with respect to yield and practical usability. In this context, design parameters and operating conditions must be varied. Another objective of the project was the quantitative investigation of possible heating and cooling concepts based on SEA elements.

First, the two research entities Fraunhofer ISE and Engineering R. Koschade selected promising concepts from a greater selection of possible SEA designs based on components available in the market. The selection was based on the long-term experience of Fraunhofer ISE in solar thermal energy, especially in air collector technology, as well as of the experience of the Koschade engineering office in sandwich technology. Beyond that, calculations and simulations were performed considering the system. For example, the optimum mass flow per row of maximum net primary power saving (MPP) was also determined for the respective application. The collector from the previous SEA 1 project – consisting of sandwich elements and bonded trapezoidal profiles – was recreated as reference and measured according to standard in the TestLab Solar Thermal Systems of Fraunhofer ISE (collector SEA 2.1). A second collector (SEA 2.2.) was equipped with an additional polycarbonate cover to demonstrate its significant effect on the collector yield. Finally, a third collector (SEA 2.3) was designed, built, and measured. Here, a variant with corrugated profile was used, which also reduced the temperatures at the sandwich element. Prior to that, FEM simulations regarding flow and temperature distribution were performed, among others. A new tool was developed based on the previously used tool »ScenoCalc«, using which yearly yields can be calculated based on time series to investigate possible energy usage scenarios. Overall, it was demonstrated that significantly higher yields can be achieved using SEA 2.3 compared to the reference collector. Furthermore, a practical possibility was created with the new tool for assessing different system configurations with different collectors with respect to their energy savings potential and/or their solar fraction during heating or cooling of the building, e.g., of an ECB sample hall (ECB = EcoCommercial Building).