How can the reduced thermal capacity of lightweight buildings be compensated for? How can building façades be activated in order to utilise the incident solar energy for cooling purposes?
Due to their reduced thermal capacity, lightweight buildings are more susceptible to thermal oscillation. This means that the room temperature reacts more sensitively to external and internal influences such as fluctuating solar radiation or varying room utilisation. The problem is exacerbated by the increasing temperature amplitudes associated with climate change and particularly affects building overheating in the summer months.
As a possible solution, facade-integrated adsorption systems are being researched and developed for the first time in this sub-project. These systems are characterised by a high heat storage capacity combined with a low storage mass. In addition, adsorption systems can also be operated as chillers for the active provision of cooling. In contrast to conventional, passive building materials, this allows the complete compensation of thermal loads as well as the targeted provision of cooling at desired times and with defined output.
The adsorption material pair is decisive for the suitability of a closed low-pressure adsorption system for the thermal management of lightweight buildings. The adsorbent zeolite and water are a promising material pair. The system and the process are shown schematically in Figure 1 below. The adsorber (A) is realised as an element of the outer shell in such a way that it can directly absorb the incident solar radiation, but also dissipate heat in a targeted manner. In a first phase, the adsorber is heated by the incident solar radiation so that the bound water desorbs. The released vapour 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 conveyed into the evaporator. As soon as the evaporator is connected to the adsorber, the adsorber adsorbs the vapour. This inevitably leads to the evaporation of the water in the evaporator, which cools the interior.
This research project is a collaboration with the IGTE and IABP at the University of Stuttgart.
