Abstract
Phase Change Material (PCM) based products represent an emerging technology for the building sector. For their application in the building envelope, they are usually macro-encapsulated in plastic/metal containers or placed in bags/pouches that allow an easier and safer installation. Unfortunately, most of the product data on PCMs are obtained by means of the differential scanning calorimetry method (DSC) applied to bulk PCMs. This method, even though accurate, can lead to results that are not fully representative of the complex behavior of PCM-based products. The results of an experimental laboratory campaign, aimed at characterizing the thermal properties of a full-scale PCM product, are presented in this paper. Tests were carried out on a commercial macro-encapsulated PCM considering three different melting temperatures. The obtained results show that the overall equivalent thermal properties of the macro-encapsulated PCM products maybe somewhat different from those of bulk PCMs. In a second step, two PCM products were selected and applied to a parallel roof testing room system, directly exposed to the outdoor environment. The results of the monitoring of this system have demonstrated the effectiveness of PCMs in reducing the peak heat gains through the roof components by up to 48%. Nevertheless, by comparing the laboratory results with the monitored data, it was also possible to observe that the latent heat capacity of the PCM was never fully exploited. Thus, greater benefits could be achieved in different monitoring periods, or if a PCM with a lower melting temperature were adopted.
Highlights
The increasing demand for comfortable and more energy efficient buildings has generated growing interest in the development and application of new materials and technologies for the building envelope, especially for the energy retrofitting of existing buildings and for the design of new nearly Zero Energy Buildings.One of the passive approaches used to improve building energy efficiency and indoor thermal comfort is to develop envelope solutions that implement phase change materials (PCMs)
This paper presents the results of laboratory and in-field analyses that were performed on a series of macro encapsulated PCMs
0.540–1.088 W/mK range) is generally reported in literature for salt hydrate PCMs with melting temperatures close to the indoor temperature [9,31,32,33]. This difference can be explained by considering that the literature data were determined using the differential scanning calorimetry method (DSC) method on bulk PCMs, while the thermal conductivity measured in this study is an equivalent value of the whole PCM sample (PCM and container), which is influenced to a great extent by the presence of air pockets and by the envelope material of the container
Summary
The increasing demand for comfortable and more energy efficient buildings has generated growing interest in the development and application of new materials and technologies for the building envelope, especially for the energy retrofitting of existing buildings and for the design of new nearly Zero Energy Buildings (nZEB). As a result of the high latent heat capacity of PCMs, their integration into building envelopes improves the thermal comfort of a building by minimizing the internal temperature peaks and fluctuations. This provides several benefits, such as the prevention of building overheating, with a consequent reduction of the cooling loads, which in turn allows the technical equipment used for cooling to be downsized [1,3]. Other studies have been carried out to demonstrate how the application of phase change materials to the roof of buildings contributes to reducing the thermal loads and the energy consumption of the building, especially during days with high solar radiation. From the laboratory characterization results and from the application monitoring experience, some design guidelines were drawn up to maximize the exploitation of the PCM latent heat storage capacity
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