Adaptive Thermal Insulation for Thermal Activation of Building Components

Abstract

Buildings are mainly constituted of load-bearing components. What if we were able to thermally activate such massive components, utilize them as thermal energy storages thus increase the buildings' energy efficiency? The solid elements, as walls or ceilings, could be loaded either by using excess electricity or by deploying rooftop photovoltaic or solar thermal installations. The essential precondition to activating building masses and integrate them into the thermal management is to control the transferred heat across the energy storage boundaries. Such a controllable insulation layer can be achieved by combining the gas pressure dependent thermal conductivity of porous structures with reversible gas-solid-reactions. The heat transfer mechanism in porous insulation materials is dominated by the Knudsen effect which describes the S-shaped thermal conductivity depending on the prevalent gas pressure in the insulation panel. In the presented system a vacuum insulation panel is connected with a reversible metal hydride reaction system. By adjusting the temperature of the metal hydride the endo-/exothermal reaction can be controlled and the according pressure can be set along the equilibrium line of the thermochemical material. The integral adaptive insulation system is built of the two core components: the porous vacuum insulation panel and the metal hydride reactor. Due to the physical coupling of both units the temperature setting of the metal hydride is directly linked to the gas pressure and thus to the thermal conductivity of the insulation panel. A test bench was set up to address the key questions of the adaptive insulation system. The central challenges in terms of system dynamic and energy efficiency are the functional interaction of pore sizes, gas pressure ratios and suitable metal hydride materials and also the effect of the parameters on the switching factors or the energy consumption for the temperature control. This presentation will outline experimental results of the proof of concept and the experimentally investigated influence of different pore-sized insulation panels in combination with the metal hydride reaction system on the system behavior.