Adjustable vacuum insulation elements in buildings - Adaptive facades and thermal component activation
ReVaD
In the ReVaD project, we are developing a controllable vacuum thermal insulation system to adapt the thermal transmittance of building envelopes and structures as required, as well as the thermal activation of storage masses. The aim is to demonstrate an adaptive insulation system under realistic building boundary conditions.
Test setup for the experimental investigation of pressure-dependent thermal conductivity in (vacuum) insulation panels
The accurate characterisation of the function and operating behaviour of the developed controllable insulation elements is the core task of the ReVaD project.
Over 50 % of the final energy demand in Germany is used to provide thermal energy, the largest share for the demand-intensive building sector - mainly through the combustion of fossil fuels. The reduction and decarbonisation of heating and cooling requirements in buildings are key components of the heating transition.
Adaptive facade elements allow the dynamic boundary conditions inside and outside buildings (day/night, summer/winter, weather, equipment, number of people, etc.) to be harmonised. The targeted control of heat flows through the facade makes it possible to utilise a passive cooling effect during summer nights, for example, while ensuring maximum insulation capacity during the hot daytime phase. In this way, buildings can be protected from overheating in summer and the necessary cooling load can be reduced.
In addition, the use of controllable insulation panels within the building allows the targeted activation of existing, solid building parts as thermal energy stores. Decarbonising heating energy requirements in winter is particularly difficult in existing buildings. For example, wall, floor or ceiling structures are transformed into modular building blocks of a heating system by electrically loading the massive structures using adhesive mats. Adjusting the heat output into the room as required using adaptive insulation. By utilising existing capacities, component activation can contribute to making the energy system more flexible while conserving resources.
The functional principle of controllable insulation is based on the non-linear gas pressure-dependent thermal conductivity of porous media - the lower the gas pressure inside a closed insulation panel, the lower the thermal conductivity and vice versa. The regulation of the gas pressure is based on the use of thermochemical reaction systems. By selectively adjusting the temperature of a metal hydride, the hydrogen pressure in a connected vacuum insulation panel can be specifically regulated and the thermal conductivity of the insulation element controlled accordingly. The targeted heating of the reactor results in an increase in pressure and a corresponding increase in heat transfer in the panel, while cooling the reactor leads to a reduction in pressure and a decrease in thermal conductivity.
Development goals in the project
As part of the ReVaD project, vacuum insulation panels based on textile materials are being developed in which a hydrogen gas pressure is regulated using thermochemical materials. To this end, a reactor component is being designed and constructed as a prototype with which the gas pressure can be regulated by adjusting the temperature in the reaction material. Numerical methods are used to investigate the integration of adaptive insulation elements in the building and to evaluate the thermal-energetic operating behaviour as well as the energy-saving potential.
The DLR Institute of Technical Thermodynamics is working on the project together with two other research institutes (IGTE and DITF). The consortium is supported by a project committee consisting of around 20 companies.
The project is initially divided into three sub-areas, each of which is being developed and driven forward by the participating research institutes:
Potential study & simulative integration of adaptive insulation elements in building models
Design of multimodal textile pore structures as core materials of the insulation panels
Development of customised thermochemical reactors as actuators for adaptive insulation
In addition, the sub-areas are synergistically combined within the project and demonstrated as an overall system in a prototype structure. With the help of the experimental demonstration under realistic building boundary conditions, the function of the adaptive insulation will be proven, the operating range determined and the dynamic and thermal-energetic behaviour of the adaptive insulation as well as the potential in the building context presented.
Prototype demonstration of controllable thermal insulation to activate storage masses as thermal energy storage units
The suitability of adaptive insulation elements for the targeted control of a heat flow from a building mass to the room (here an exemplary floor structure with impact sound insulation, solid screed layer, controllable thermal insulation and floor covering) is demonstrated both numerically and experimentally. It was shown that the gas pressure-controlled adaptive insulation as a thermal control component enables the targeted heating of the room. The screed layer serves as a heat accumulator that can be charged electrically in a cost-orientated manner and discharged thermally as required.
