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The objective of this project is to support and boost the introduction of building products and systems containing PCMs (phase change materials) to the market. PCM systems can be used for passive room cooling as well as to reduce temperature and cooling load peaks.
These systems are being integrated into demonstration buildings and measured under practical conditions. Besides product development, this research project primarily focuses on presenting buildings with demonstration character. The idea is to support the market launch of PCM systems by making correspondingly-equipped reference buildings accessible to the public and presenting them favourably in the media (internet, specialized journals, conferences, etc.).
seminar rooms office buildings
When system property data has been recorded, simulation tools can be validated and substantiated design guidelines compiled. Feedback from building users will provide a direct indication of how the products are accepted, which, in turn, will point out valuable optimization potential to manufacturers and planners. Evaluating the metrological data with respect to saving energy will enable energy suppliers to incorporate PCM systems into their energy consultations. Energy suppliers will also be in a position to evaluate the effects of wide-scale use of PCM systems on power plant and grid capacities by carrying out an energy-economical analysis on the basis of the load shift measured.

PCM systems

Rear-ventilated cooling ceilings with PCM
PCM foil bags with salt hydrates are already being implemented in passive cooling ceiling systems (metal cassette ceilings). Such systems are easy to install (see photo below) and yield a passive cooling capacity of 25 bis 40 W/m2.

Inserting PCM foil bags into a metal cassette ceiling.
Due to the lower thermal conductivity of, for example, gypsum boards, the cooling capacity of such a system is clearly reduced when the suspended construction is not made of metal. An active rear ventilation is therefore necessary. The regeneration of the system at night is achieved with the cool outside air.

Calculated temperature curve of an office with rear-ventilated ceiling construction with PCM (red). The temperatures without PCM (blue dots) are also shown as a comparison. The peak temperatures have been reduced by about 2K thanks to the PCM.

Such rear-ventilated cooling ceilings with PCM have been installed in two offices at EnBW in Karlsruhe as well as in a seminar room at the University of Würzburg. Cooling is achieved via recirculated air by day and the PCM is regenerated at night through the absorption of the cool outside air.

PCM boards being inserted into the suspended ceiling (left) and the requisite rear-ventilation system (right).
Water-flow cooling ceilings with PCM

Suspended water-flow cooling ceilings achieve high cooling capacities (about 100 W/m2) in short reaction times, but often require high peak loads to provide the cooler temperatures. By integrating PCM, a purely passive basic cooling capacity of about 40 W/m2 can be provided during the day when the cooling load is at its highest. The PCM is then regenerated at night with cold water. In this way, the peak loads during the day can be avoided and the cooling load balanced out. This presents clear advantages over producing cooling capacity via geothermal systems (probes), since geothermal probes have to be designed for the peak loads. By combining PCM systems with conventional technology, the advantage of short reaction times is maintained and only the peak loads that exceed the basic load have to be compensated.

Water-flow cooling ceilings with PCM have been integrated into a lecture theatre at Stuttgart University of Applied Sciences as well as two offices at Kassel City Hall. Cooling is achieved in the rooms passively by day, and cold water flows through the cooling ceilings at night to regenerate the PCM.

Cooling ceiling with PCM in a lecture theatre at Stuttgart University of Applied Sciences. The cooling ceiling elements have been installed in such a way that they can be pulled down and easily accessed.
Solar protection with PCM
Inside solar protection systems are implemented over large areas (no wind loads, cost-efficient), but have a higher energy yield (g-value) in comparison to outside systems. In addition, irradiation heats up inside systems to such an extent that people near to the windows feel uncomfortable due to the heat radiating from the blinds. This problem can be remedied using inside solar protection with PCM. The advantages are lower blind temperatures and reduced heat input into the room. Enough PCM is used to completely buffer a south facade on a sunny summer's day. The PCM is regenerated over night by the cool outside air.

Calculated frequency of functional room temperature in a large-scale glazed office with coated glazing and solar protection with (blue) and without (red) PCM. The PCM clearly reduces the hours with high room temperatures.

Solar protection systems using PCM have been installed in four offices (two in Kassel City Hall and two in the EnBW building in Karlsruhe). The solar protection system consists of vertical blinds; there is an approx. 1 cm thick layer of PCM in each of the slats. Operation is purely passive - the PCM blinds are used in the same way as conventional blinds, yet absorb excess solar radiation. The PCM is regenerated at night by cool air (from outside ventilation flaps or tilted-open windows).

PCM solar protection in an office in Karlsruhe