Controllable thermal insulation

Kurzfassung

While vacuum insulation layers continuously provide thermal protection against thermal energy input and output on a high but pre-defined level, solar gains, ambient temperatures and internal thermal loads in turn are obviously subject to fluctuations on different time-scales. An opportunity to harmonize the steady-state insulation and the transient external as well as internal thermal fluctuations and with it reduce the energy consumptions of buildings could be supplied by a dynamic insulation layer with controllable heat flux across its boundaries. Therewith e.g. cooling effects during the night in summer can be beneficial for the indoor climate whereas the building is highly shielded from summer heat by day. With the aid of reversible gas-solid reactions the passive insulation layer can be turned into a controllable thermal barrier that consists of a combination of a porous insulation structure and a metal hydride reactor. Due to the porous insulation’s dependency of the thermal conductivity on the internal gas pressure, vacuum insulation panels can be converted into variable insulation layers. By adjusting the temperature of the endo-/exothermal metal hydride reactor the internal gas pressure and the heat transfer through the insulation layer can be adapted. Based on first theoretical investigations, a test bench was set up to investigate the single core components - the insulation panel and the metal hydride reaction system - as well as the overall coupled system. The main challenging question is the functional interaction of both components, regarding matching pore sizes and the internal pressure, adequate selection of suitable metal hydride reaction systems and also the dynamic behavior of the heat switch and the amplitude of switching factors. Therefore, our current work investigates insulating materials with different pore sizes in combination with different metal hydrides to better understand their interaction. The contribution will focus on the identification of potential limitations, the presentation of our approach to find optimal combinations and a discussion of different application possibilities.