There are two ways to store heat and even out the diurnal or daily temperature swings in buildings. One is with massive material's like stone, brick, and concrete the other is with phase change materials or PCM's.
A material is said to “change phase” when energy is either added or removed to cause it to change from a liquid state to a solid state or from liquid state to a gaseous state. For example, it takes a considerable amount of energy to transform ice into water and in the process the temperature remains at 32° F. This energy storage capacity within the phase change is called “latent heat” and when harnessed allows for the storage of heat energy in a fraction of the volume required by materials like stone or concrete.
For building applications, you want this phase change to occur at or near the desired room temperature, so custom wax formulations are usually the material of chose. As the cost of energy has increased, interest in PCM technology has also increased.
In 2005, Oak Ridge National Laboratory teamed with Advanced Fiber Technology and BASF, demonstrated that a 2x6 wall insulated with cellulose insulation seeded with 22% PCM reduced the surface heat flow rate by 40%.
PCM seeded insulation is not yet commercially available, however BASF has developed a drywall product called SmartBoard™ that is available in the EU that incorporates microscopic polymer spheres filled with wax. Applying this 15-mm (0.59 inch) thick drywall product is the equivalent of adding a 9-cm (3.54 inches) thick layer of concrete. SmartBoard™ is supplied with a choice of two “switching” or PCM melt temperatures, 23°C(73.4°F) and 26°C(78.8°F) designed to accommodate both heating dominated and cooling dominated climates.
For complete article go to: http://sunhomedesign.wordpress.com/2008/05/19/phase-change-materials-%e2...
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