Abstract :
[en] The present work deals in detail with two new, thermally active components for building renovation, namely the external wall tempering (aWT) and the external air tempering (aLT). With the help of these two components, existing buildings can be thermally activated as part of an energetic refurbishment. The installation of the two components is minimally invasive from the outside. Due to the position of the active layer in the wall structure, the use of very low fluid temperatures is possible (low-exergy approach).
Initially the theoretical principles for both components were developed and presented in accordance with standard literature for thermoactive component systems. Then characteristic values for the evaluation of the components (efficiency and utilisation rates) were developed and based on the theoretical principles, implementation concepts for both components were subsequently developed. Finally, a large-scale implementation of the two components could be realized on a facade. The aim of the implementation was not only to present the "feasibility" of the componentes but also to generate measurement data for the following considerations.
In the course of its development, some sources of error could be identified and a multiplicity of realizations were obtained. For example, for warranty reasons a compromise had to be made regarding the thickness of the plaster for plastering the capillary tube mats. Overall, both components were successfully implemented and put into operation. In coordination to the implementation the system costs of both components were determined. Here, similar values were achieved in the implementation as determined within the framework of sample planning (~70 €/m²).
With the help of the measurement data from the field test areas of the two components and two laboratory test benches, suitable modelling approaches could now be developed, verified and finally validated. Then stationary as well as transient measurements were carried out and compared and a good agreement between modelling and measurements could be determined. The comparison between idealized modelling and real-life components, which are under the influence of the (partly not unambiguously attributable) environmental conditions, causes difficulties. For the aWT, a maximum useful heat flow of around 60 W/m² in over-compensatory heating mode was determined. The useful heat flow is defined as the heat flow from the tempering level into the interior of the building. In a low-exergy operating mode, however, ~15 W/m² is more likely.
For such external components, the time constants are also relevant; for the aWT these are in the daily range, with dead times of 3-4 hours. At the same time, the thermal activation of the existing structure can make it usable as a storage mass. However, since validated simulation models are available after completion of the measurements, potential estimates and further considerations can be made at simulation level.
The simulation studies carried out on the building level show the potential, but also the important "sticking points" of the components. In summary, it can be stated that the aWT is more suitable for binary operation than a kind of base load tempering. Again, the pump power requirement in relation to the thermal input must be taken into account for long running times. The lower the heating requirement of a building, the more likely it is that the aWT can also be used as a independent system. When considering the aWT alone, control strategies adapted to the inertia of the aWT are the key to high cover shares.
The combination of aLT and aWT was found to be very suitable for the complete heating of a building. Here, the simulation achieves high cover ratios with low flow temperatures and simple control strategies.
Thus the feasibility of the ideas was shown, realistic system costs were determined and the basics were created on model level in order to investigate the further interesting aspects of the components by means of simulations and on the basis of the field test areas.
