Funding Phase II
Lightweight buildings show an increased sensitivity to thermal oscillations due to their reduced heat capacity. This means that the room temperature reacts more sensitively to external and internal influences such as fluctuating solar irradiation or varying room usage. The problem is further worsened by temperature amplitudes increasing with climate change and particularly affects building overheating during summer season.
As a possible solution, facade-integrated adsorption systems are investigated and developed for the first time in this subproject. These systems are characterized by a high heat storage capacity combined with a low storage mass. In addition, adsorption systems can also be operated as chillers to actively provide cooling power. In contrast to conventional, passive construction materials, this allows the complete compensation of thermal loads as well as the specific provision of cooling power at desired times and with defined power rates.
The adsorption material is decisive for the suitability of closed low-pressure adsorption systems for thermal management of lightweight buildings. A promising adsorption pair is given by the adsorbent zeolite and water. The system and process are shown schematically in the figure below. The adsorber (A) is realized as an outer element of the building envelope in such a way that it can directly absorb the incident solar radiation, but also selectively dissipate heat. In a first phase, the adsorber is heated by the solar radiation so that the bound water desorbs. The released vapor flows to the condenser (K) on the side facing away from the sun, where it condenses. At the beginning of the second phase, the adsorber is shaded and the condensate is partially pumped to the evaporator. As soon as the evaporator is connected to the adsorber, the adsorber adsorbs the vapor. This inevitably induces the evaporation of the water in the evaporator, which in turn cools the building interior.
In order to finally obtain a fully functional and fully-fledged adsorption facade element, it is necessary to take into account building physics requirements as well as architectural and construction design aspects. The building physics requirements concern, among others, moisture, heat and sound insulation as well as indoor climate and comfort. With regard to architectural design, the limited color spectrum of the dark solar collector surfaces in particular poses a particular challenge regarding the acceptance of the adsorption facade element, for which solutions must be found.
In the first phase of the subproject, suitable designs for the components and their envelope surfaces are determined through modelling and simulation. Based on this, the detailed technical designs will be developed. Subsequently, through experimental investigations will be carried out, using a laboratory test chamber. In parallel to the experimental investigation, concepts for integration into building facades will be elaborated and the technical designs will be modified accordingly. The subproject will conclude with the implementation of the adsorption facade element from the laboratory test chamber on the demonstrator building.
- Dr.-Ing. Micha Schäfer, Institut für Gebäudeenergetik, Thermotechnik und Energiespeicherung
- Prof. Dr. André Thess, Institut für Gebäudeenergetik, Thermotechnik und Energiespeicherung
- Prof. Dipl.-Ing. Arch. Dipl. Des. Martin Ostermann, Institut für Baukonstruktion
- Dr.-Ing. Sumee Park, Fraunhofer-Institut für Bauphysik
- Olaf Böckmann M.Sc., Institut für Gebäudeenergetik, Thermotechnik und Energiespeicherung
- Dipl.-Arch. Andreas Greiner, Institut für Baukonstruktion
- Simon Weber M.Sc., Institut für Akustik und Bauphysik