Workgroup Collectors

Our working group carries out research and development on solar thermal collectors and on the collector loop using a systemic approach. The focus is on cost reduction, increased operational reliability and integration into the building envelope. We target not yet established application areas such as combined heat and power supply, solar assisted district heating, and industrial process heating as well as heat pump systems. We do both theoretical and experimental work and consider the two essential aspects performance and reliability.

Stagnation-safe solar thermal systems

The stagnation behavior of solar systems is of crucial importance for their long-term reliability and economic viability. The evaporation of the collector heat carrier can damage temperature-sensitive components of the collector loop and cause additional costs. The group has a long experience with the analysis of the stagnation state as well as the development of strategies for minimizing risk. Within current projects we are developing new collectors which promise a significant reduction in the temperatures in the solar loop and a steam-free operation of the plants. Two different concepts are pursued and investigated: the control of two-phase heat transport in heat pipes and the use of solar absorbers with temperature-dependent optical properties (thermochromic layers).

Solar-active building envelopes

The integration of collectors into the building envelope enables architecturally attractive solutions as well as cost savings through synergy effects. Thus, it represents an important prerequisite for a higher acceptance and a successful dissemination of solar thermal systems in building practice. The solar activation of the building envelope requires a more holistic design approach: In addition to questions of system performance and reliability, also aspects related to building physics, thermal comfort and aesthetics have to be taken into consideration. In cooperation with manufacturers and architects we develop specific solutions for the façades and roofs of residential and non-residential buildings. The systemic focus is on the use of the building envelope as heat source in heat pump systems.

New application areas

Beside decentralized space and domestic hot water heating, solar-assisted district heating and industrial process heating also offer a significant potential for saving fossil fuels and reducing greenhouse gas emissions. Higher application temperatures, larger fields and very different load profiles require customized solutions for components and systems. The group deals with the development and testing of new concepts as well as with the analysis and optimization of the hydraulic behavior of collector fields. Another main research area is the combined heat and power supply with photovoltaic-thermal collectors. In close cooperation with other working groups of the departments Solar systems and Photovoltaics, we focus on the development of uncovered modules for efficient integration in heat pump-based energy supply systems.