Civil Engineering Reference
In-Depth Information
space heating and cooling, basically smoothing the indoor temperature by
increasing the energy inertia of the building envelope. When refurbishment, the
system considered in passive systems has to be evaluated on its ability to be
included in the refurbishment carried out, that is, for example, the use of PCM
incorporated in walls would only be possible either if major refurbishment is
carried out, where complete walls are substituted, or by the addition of building
elements in already existing walls, such as gypsum boards including PCM. On the
other hand, it is true that in some refurbishments carried out, the use of PCM could
only be the only possibility for drastic energy refurbishment, since the scarcity of
space is a real problem in such actions and the energy density of PCM can be an
advantage.
One of the oldest options studied and published were PCM wallboards to
improve the thermal comfort of lightweight buildings (Sharma et al.
2009
), since
they are very suitable for the incorporation of PCM (Soares et al.
2013
). The
efficiency of these elements depends on several factors such as:
1. how the PCM is incorporated in the wallboard;
2. the orientation of the wall;
3. climatic conditions;
4. direct solar gains;
5. internal gains;
6. colour of the surface;
7. ventilation rate;
8. the PCM chosen and its phase-change temperature;
9. the temperature range over which phase change occurs; and
10. the latent heat capacity per unit area of the wall.
The PCM can be added impregnated to the building materials, Schossig et al.
(
2005
) showed that but when added microencapsulated leakage problems are
overdue (Fig.
2
).
An example of the use of PCM in wallboards was de development of the
Dupont product Energain, studied and characterised in several papers (Kuznik
et al.
2008a
,
b
,
2011
; Kuznik and Virgone
2009
). Kuznik et al. (
2008a
) performed
an optimisation process using interior/exterior temperature evolutions within a
period of 24 h to optimise the thickness of a PCM wallboard to enhance the
thermal behaviour of a lightweight internal partition wall. The PCM wallboard was
composed of 60 wt% of microencapsulated paraffin, which has a melting tem-
perature of about 22 C (Fig.
3
). The optimal thickness found was 1 cm. This
1 cm wallboard allows a doubling of the thermal inertia of the building. Kuznik
et al. (
2008b
) carried out an experimental research in a full-scale test cell under
controlled thermal and radiative effects, to evaluate the performance of walls, with
and without PCMs, during a summer day. The authors used the same PCM
composite of Fig.
3
to show that PCM wallboard reduces the air temperature
fluctuations in the room and the overheating effect. The authors also concluded
that the available storage energy is twice higher with 5 mm of PCM wallboard,
