The effect of the PCM during winter season was evaluated in the experimental set-up during a free — floating temperature test. Fig. 11 shows the outside ambient temperature and the inside ambient temperature of the brick cubicles and Fig. 12 presents the data for the alveolar brick cubicles.

In the second week of December the temperature was very low, never reaching 15 °C (Fig 11a). The inside temperature in the RT27-PU cubicle follows the same tendency as in the PU cubicle with a higher absolute value. At the beginning of the week the temperatures were almost the same but the difference increased to 0.4 °C at the end of the week. Similar results were observed in January, February and March (Fig. 11b to Fig. 11d) with temperature differences around 0.3 °C, especially during the cold hours of the day. This effect can be caused by the low thermal conductivity of the PCM (0.2 W/mK), which works as insulation.

Referring to the alveolar brick and PCM-alveolar brick cubicles, Fig. 12a presents the data of the outside and inside temperatures during the second week of December. A similar effect as in the brick cubicles is observed. Although the temperature of both cubicles presents the same tendency, the SP25- alveolar one is between 0.1 °C and 0.5 °C warmer than the alveolar. Similar results are obtained for January, February and March (Fig. 12b to Fig. 12d). In those cases the effect in more visible at the beginning of the week and decreases with time.

15 10 5 Е ш 3 0 ш а. -5 I- -10 -15

PU cubicle

c) February Fig. 11 Comparison of the inside temperatures of PU and RT27-PU cubicles.

RT-27+PU cubicle — — — Ambient temperature |

a) December

b) January

8 0:00 8 0:00 8 0:00 8 0:00 8 0:00 8 0:00 8 0:00 8 0:00 0:00
Period

I PU cubicle………………………. RT-27+PU cubicle ■ • ■ Ambient temperature]

d) March

SHAPE * MERGEFORMAT

Fig. 12 Comparison of the inside temperatures of Alveolar brick and SP25-Alveolar cubicles.

In this work the benefits of using PCM in conventional and alveolar brick construction are studied. Both free-floating temperatures and energy consumptions are analyzed for summer and winter periods.

During summer period, a reduction of the energy consumption of the HVAC system was achieved for set points higher than 20 °С. When the set point was reduced the PCM effect decreased since it is not melting properly.

The experimental results of the winter period showed a positive effect of the PCM. The increase of the insulation effect introduced by the PCM results in higher temperatures in the cubicles, especially during the cold hours of the day.

Acknowledgements

The work was partially funded with the project ENE2005-08256-C02-01/ALT, the project 2005SGR 00324 and with a collaboration with the companies Synthesia, Honeywell, Gremi de Rajolers,

Hispalyt, Tealsa, Europerfil, Prefabricats Pujol, Prefabricats Lacoma, Ceramicas Sampedro and Cityhall of Puigverd de Lleida.

Marc Medrano would like to thank the Spanish Ministery of Education and Science for his Ramon y Cajal research appointment.

References

[1] I. O. Salyer, A. K. Sircar, R. P. Chartoff, D. E. Miller, Advanced phase change materials for passive solar storage applications, in: Proceedings of the 20th Intersociety Energy Conversion Engineering Conference, Warrendale, PA, USA, (1985), pp. 699-709.

[2] M. Shapiro, D. Feldman, D. Hawes, D. Banu, PCM thermal storage in drywall using organic phase change material, Passive Solar Journal 4 (1987) 419-438.

[3] D. Banu, D. Feldman, F. Haghighat, J. Paris, D. Hawes, Energy-storing wallboard: flammability tests, Journal of Materials and Civil Engineering 10 (1998) 98-105.

[4] A. M. Khudhair, M. M. Farid, A review on energy conservation in building applications with thermal storage by latent heat using phase change materials, Energy Conversion and management 45 (2004) 263-275.

[5] B. Zalba, J. M. Marin, L. F. Cabeza, H. Mehling, Review on thermal energy storage with phase change: materials, heat transfer analysis and applications, Applied Thermal Engineering 23 (2003) 251-283.

[6] A. Hauer, H. Mehling, P. Schossig, M. Yamaha, L. F. Cabeza, V. Martin, F. Setterwall, International energy agency implementing agreement on energy conservation through energy storage, Annex 17 Final report, 2005.

[7] L. F. Cabeza, C. Castellon, M. Nogues, M. Medrano, R. Leppers, O. Zubillaga, Use of microencapsulated PCM in concrete walls for energy savings, Energy and Buildings 39 (2007) 113-119.