Phase-change materials: what are they and how they can be used

The use of phase change materials in the building industry is expanding, not only on an experimental basis, but also conventional in construction, for sale. Unlikely are used "loose", but most often are encapsulated in containers or with different technologies, depending on the type of use that the phase change materials are intended to have.

The functions performed by the PCM in the building industry are many and there are many types of products on the market, many times unknown or rarely used.

Here is a study on the containers for PCM and their uses.

In the construction sector the PCM can be used:

• bulk

• with micro-encapsulation,

• With macroencapsulation,

• immersed in porous matrices.

The instructions for use are varied, depending on the purpose they want to achieve. A first major distinction concerns the application. Have distinguished the following main building applications:

• opaque envelope: PCM inserted in addition to the traditional insulation, the interface between inside and outside, or in some cases (very rare) in the inner walls;

• ceiling or radiant floors: items inserted into radiant floors or ceilings, which can obtain from these systems contained air conditioning better results;

• transparent casing: in replacement of an air gap present between glass plates or in addition to it, with appropriate shielding plates or reflective;

• technological systems and air conditioning systems: PCM inserted into shell and tube heat exchangers that increase the performance, or inserted directly into the terminal part of the ventilation system in the case of all-air systems.

These are the main applications now used in construction, but they are not the only ones. They are in fact several ongoing trials to apply the PCM in many other parts of the building, not mentioned in the above list since it is not directly used.

Curiosity about PCM

PCM containing a first home was built in 1946 and completed in 1948, the United States, on an estate, 5 km from Boston. Villa with an area of 135 square meters, only occurred on one floor.

Solar energy collection was thanks to 18 solar collectors consist of panels made from thin sheets of galvanized painted black. The heat generated by these panels was transferred through a fan to three storage bins located on both sides of the rooms.

In the bins were contained 21 tons of Glauber's salt with a storage capacity of 11 MJ. This was able to accumulate heat for 12 days and the melting temperature of these salts was 32 degrees centigrade. The results were very positive and the internal temperature was constantly 21 degrees, without the aid disistemi additional heating.

Merits and Flaws of Phase Change Materials (PCM)

After describing briefly the characteristics of PCM and their main uses in construction, I conclude with those who are the strengths and weaknesses identified by the study of these materials:

ADVANTAGES

• Materials readily available in the market

• Presence of many manufacturers and different types of encapsulation

• Theoretical results very good experimental

• Reduction of the costs of heating and cooling theory, in the order of 5-10%

• Can be used on both new construction and building rehabilitation in cases of

• Application in technological systems and air conditioning systems, as well as passive solar insistemi.

DISADVANTAGES

• No real results and reliable applications that justify the use

• Poor information on prices and affordability of such an investment

• Poor circulation on the Italian market

• Possibility, after several cycles of use, changes in heat storage capacity