After optimising the products with the wall sample tests we equipped several office rooms with PCM plaster. But when measuring real office rooms with PCM, the different user be­haviour made comparisons very difficult. To avoid these problems and to quantify the PCM — effect without user-influence, the Fraunhofer ISE built up two new real size testrooms at the facade-testing-facility with a light weight construction and equipped them with a PCM and a reference plaster. Both rooms were provided with detailed measurement equipment and identically controlled. Figure 6 shows the exactly to the south arranged testrooms from outside. The two testrooms on top of each other at the left side were used for the measure­ments. The testrooms were built up in a typical light weight construction consisting of gyp­sum plasterboard mounted on wooden slats with insulation. This setup is mounted on the 14 cm thick PU-wall of the cabin. Both testrooms can be controlled ventilated and were equipped with outside shading. During the measurements both testrooms were run with the same conditions.

Within the project we tested two different PCM-products for a one year period each. In 2002 we tested a dispersion based plaster with 40% weight PCM and 6 mm thickness and in 2003 a gypsum plaster with 20% weight PCM and 15 mm thickness. In Figure 7, the measured wall — and air-temperatures of three days with night ventilation (ac/h=4) can be seen for the 6 mm PCM plaster. In the area of melting temperatures of the PCM (24-27°C) the temperatures of the PCM-testroom rise slower than the temperatures of the reference — testroom. After achieving 27°C the temperature in both testrooms rises parallel, so that a temperature difference of 4K in the maximum was achieved. Additionally, the temperature — maximum was reached one hour later in the PCM-room. During night the temperatures in the PCM-testroom are higher than in the reference testroom. But still the storage is over­loaded without shading at the big south window (Fig. 7, last day). Therefore we have in­stalled an outside shading, which is going to be activated automatically on hot days. Fig­ure 8 shows the resulting temperatures curves. The temperature in the PCM-testroom lies at the maximum about 2K under the reference temperature. The accumulated amount of hours at a certain temperature during three weeks with shading are shown in figure 9.

In the reference room the temperature lies more than 50 hours beyond 28°C whereas the PCM testroom is only in about 5 hours warmer than 28°C.

SHAPE * MERGEFORMAT

Figure 6: Fraunhofer ISE Facade-testing-facility. The two rooms at the left side were used for the PCM measurements

00:00 12:00 00:00 12:00 00:00 12:00 00:00 time [date, hh:min]

temperature [°C]

24/08 25/08 26/08 27/08 28/08 29/08 30/08 31/08

time

16 18 20 22 24 26 28 30 32

Figure 8: Wall-temperatures with night ventilation and shading

remperature [° C]

Figure 9: cummulative frequency function of room temperature

Reference Wall—————- PCM Wall ————-

Figure 10: measured temperature profile during experiment with the gypsum PCM-plaster

00:00 06:00 12:00 18:00 00:00 Reference Wall — PCM Wall Middle — PCM Wall surface — PcM Wall rear —

30

10/09 12/09 00:00 00:00

14/09 16/09 18/09 00:00 00:00 00:00

35

15

Fig. 10 and fig. 11 shows the same measurements for the 15 mm gypsum plaster in 2003. Again it was possible to lower the temperatures in the PCM equipped room for up to 4 K and the reduce the hours above 28°C significantly.

Figure 11: cummulative frequency function of room temperature

One of the main limitations of that system is the heat sink at night. On order to function properly, the passive systems need a higher airchange at night. Since this might still limit the systems, active cooled systems (e. g. with a cooling tower and capillary tubes in the plaster) are under development.

Results and discussion

Figure 12: Two office buildings equipped with PCM-plaster (source: maxit)

Microencapsulation gives us the possibility to implement PCM into conventional building materials. The microencapsulation has the advantages of easy application, good heat transfer and no need for protection against destruction. The measures data shows the potential for PCM products to reduce the cooling demand and increase the comfort in lightweight buildings. It is important that PCM areas are dimensioned according to the ex­pected loads and existing shading devices. It is also necessary to ensure that the storage can be discharged during night with an adequate ventilation. The ventilation can be real­ized by mechanical ventilation or through constructional designs for example with associ­ated atrium. Products are on the market and first office buildings have been realised. Active, water cooled systems are under development, which may overcome the limits of night cooling for the passive systems.

Acknowledgements

The authors are grateful to German ministry of science and work (grant no. 0329840 a-d) for funding this work and to their industrial partners BASF, caparol, maxit and sto.

Literatur

[1] Neeper DA. Thermal dynamics of wallboard with latent heat storage. Solar Energy 2000;68:393 403.

[2] Khudhair A, Farid M, Ozkan N, Chen J. Thermal performance and me­chanical testing of gypsum wallboards with latent heat storage. In: Pro­ceedings of Annex 17, advanced thermal energy storage through phase change materials and chemical reactions feasibility studies and demon­stration projects (www. fskab. com/annex17), Indore, India, 2003.

[3] Farid MM, Kong WJ. Under floor heating with latent heat storage. Proc Instn Mech Engrs 2001;215:601 9.

[4] PSchossig, H.-M. Henning, T. Haussmann, A. Raicu Phase change ma­terials in constructions;Phase Change Material Slurry Scientific Confer­ence and Business Forum 23-26.April 2003 Yverdon-les-bains Switzer — land, Proceedings Page 33-43