**1. Overview**

Nowadays, the building sector has become the main consumer of energy in the developed countries. Taking the EU as an example, the building sector accounts for around 40% of the total CO2 emissions. In Tunisia, the building sector consumes about 30% of the total final energy and is consumed by domestic water heating systems and air conditioning equipments (**Figure 1**) [1]. In order to reduce the energy consumption in buildings and to improve the thermal comfort of occupants, many researchers are focusing on storing of the thermal energy excess as latent heat by using specific phase change material (PCM). PCM may be integrated into the construction material in three ways: by direct incorporation, impregnation or encapsulation. It has been shown that the incorporation of the microencapsulated PCM into the building material is a particularly attractive technology. Recently, many experimental investigations have been conducted about the incorporation of the microencapsulated PCMs into different building elements, such as into plaster, cement, concrete walls or concrete floors. These investigations were aimed to assess

to perform the analysis of the storage unit, a simulation program was developed. Using the program, many computer simulations were performed. In their work, Łukasz et al. presented important conclusions regarding the selection of PCM, and mainly its melting temperature range was formulated. Xiaoming et al. [15] studied the potential of exploiting ventilation systems with thermal energy storage (TES) and by using phase change materials (PCMs) for space cooling in air conditioned buildings during the summer. A dynamic computational model was achieved in order to simulate the indoor thermal environment and energy consumption of the room. The results showed that the electricity energy saving ratio (ESR) by using the TES system over the base case ranges between 16.9 and 50.8%, while considering the conventional NV system, the ESR ranges between 9.2 and 33.6%. Stropnik et al. [16] presented a study a system assuring self-sufficient heating and cooling of building from solar energy and interconnection between PV, electrical storage, heat pump, thermal energy storage and building energy management system. They showed that with such a smart energy system the almost zero-energy buildings can be reached in residential sector. The results show that thermal energy storage unit with integrated PCM modules supplies desired quantity of water temperature for longer period of time. Pushpendra et al. [17] presented a detailed review of various approaches to integrate the PCM in the building envelope. They showed that this method not only improves the indoor thermal behavior of the buildings but also reduces the cooling load without or little compromise with the mechanical strength of the building structure. They studied also the effect of the PCM integration on indoor thermal behavior and reduction in cooling load. They presented also an investigation of various materials used for making containers for encapsulation and it was also investigated. From the studied technologies, a great attention was given to investigate the effects of design parameters on thermal performances of PCM radiant floor heating system integrated in buildings. In this context, Li [18] proposed a numerical investigation aiming at the evaluation of the thermal performance of different kinds of roofs with and without PCM installed in Northeast China. They showed that the effect of transition temperature and latent heat of PCM on the thermal performance of roofs is relatively weak, compared with the roof slope, PCM layer thickness and absorption coefficients of external roof surface. In 2015, Joulin et al. [19] proposed an experimental and a numerical investigation of

*Energy Storage in PCM Wall Used in Buildings' Application: Opportunity and Perspective*

*DOI: http://dx.doi.org/10.5772/intechopen.92557*

a PCM-27 conditioned in a rectangular container located between two heat exchangers. It was found that the PCM needs about 1.48 h to melt during the charging process. The evaluation of the effect of the integration of PCM inside a building was also studied with experimental and simulation methods by Huang et al. [20]. They showed that the PCM floor is able to supply about 37.7 MJ heat for 16 h in a building. In the same context, Prieto et al. [21] concluded that the integration of solar collectors holding PCM as storage material provided about 18–23% of total daily thermal energy needs of the building. Krese et al. [22] present also an experimental study of a small-scale wall composite containing PCM-27. The result of the investigation indicates that the heat recovery throughout the night is about

The aim of the research presented in this chapter is to evaluate the effectiveness of a PCM wall used as a storage medium in reducing the building's air temperature and in improving the occupant's thermal comfort in a Tunisian real house. A specific experimental framework was presented to characterize the PCM wall behavior during the storage and the discharging process (**Figure 2**). In this experimental

**2. Experimental methodology and framework**

25 W/m<sup>2</sup>

**149**

.

**Figure 1.**

*The rates of energy expenditure in Tunisia (Mehdaoui et al. [1]).*

the potential of PCM integration in walls and/or building envelopes to increase their thermal inertia to improve their energy performance [2–7]. In this context, Soares et al. [8] proposed the study of the incorporation of PCM drywalls in lightweight steel-framed building envelop. The authors evaluated the impact of PCM drywalls in the annual and monthly heating and cooling thermal performances and energy savings. It was seen that the energy savings due to PCM drywall incorporation range from 46 to 62%. Navarro et al. [9] studied the incorporation of the PCM inside the concrete core slab for cooling purposes. In this context, a prefabricated concrete slab incorporating PCM was used as internal separation inside the building. The results show that the energy savings in building were registered between 30 and 55%. Solgi et al. [2] presented that PCMs have a great influence on enhancing the performance of night purge ventilation and cooling load reduction of buildings in hot-arid climate. It was found that paraffin with 27°C melting point permits the reduction of about 47% in cooling energy. A performance of a collector storage wall system using PCMs was investigated by Zhou et al. [10]. PCM slabs were integrated in the gap-side wall surface to enhance the heat storage. The test was carried out for a whole day with charging period of 6.5 h and discharging period of 17.5 h. They investigated the variations of surface temperature as well as the indoor temperatures. It was found that the indoor temperature was about 22°C during the whole discharging period under given conditions. Barzin et al. [11] presented an experimental study dealing with the building's space cooling by using PCM energy storage in combination with night ventilation. Hence, two experimental tests were achieved: one with PCM-impregnated gypsum boards and the other with normal gypsum board. The result of the experimental investigation shows that substantial electricity saving is about to 73%. Sajjadian et al. [12] presented the study of the potential of using PCMs to reduce domestic cooling energy loads for current and future UK climates. The study used simulations of a high performance detached house model with a near Passivhaus Standard in London, where the impact of climate change effect is predicted to be significant. It was shown that appropriate levels of PCM, with a suitable incorporation mechanism into the building construction, have significant advantages for residential buildings in terms of reducing total discomfort hours. In this context, Royon et al. [13] studied the optimization of PCM implanted in a floor panel envelope of buildings. The study is mainly based on numerical investigation. The numerical results were confronted to experimental ones with the same boundary conditions in order to validate the model. Łukasz et al. [14] presented a parametric study of the thermal performance characteristics of thermal energy storage unit based on PCM integrated in building structure. In order

### *Energy Storage in PCM Wall Used in Buildings' Application: Opportunity and Perspective DOI: http://dx.doi.org/10.5772/intechopen.92557*

to perform the analysis of the storage unit, a simulation program was developed. Using the program, many computer simulations were performed. In their work, Łukasz et al. presented important conclusions regarding the selection of PCM, and mainly its melting temperature range was formulated. Xiaoming et al. [15] studied the potential of exploiting ventilation systems with thermal energy storage (TES) and by using phase change materials (PCMs) for space cooling in air conditioned buildings during the summer. A dynamic computational model was achieved in order to simulate the indoor thermal environment and energy consumption of the room. The results showed that the electricity energy saving ratio (ESR) by using the TES system over the base case ranges between 16.9 and 50.8%, while considering the conventional NV system, the ESR ranges between 9.2 and 33.6%. Stropnik et al. [16] presented a study a system assuring self-sufficient heating and cooling of building from solar energy and interconnection between PV, electrical storage, heat pump, thermal energy storage and building energy management system. They showed that with such a smart energy system the almost zero-energy buildings can be reached in residential sector. The results show that thermal energy storage unit with integrated PCM modules supplies desired quantity of water temperature for longer period of time. Pushpendra et al. [17] presented a detailed review of various approaches to integrate the PCM in the building envelope. They showed that this method not only improves the indoor thermal behavior of the buildings but also reduces the cooling load without or little compromise with the mechanical strength of the building structure. They studied also the effect of the PCM integration on indoor thermal behavior and reduction in cooling load. They presented also an investigation of various materials used for making containers for encapsulation and it was also investigated. From the studied technologies, a great attention was given to investigate the effects of design parameters on thermal performances of PCM radiant floor heating system integrated in buildings. In this context, Li [18] proposed a numerical investigation aiming at the evaluation of the thermal performance of different kinds of roofs with and without PCM installed in Northeast China. They showed that the effect of transition temperature and latent heat of PCM on the thermal performance of roofs is relatively weak, compared with the roof slope, PCM layer thickness and absorption coefficients of external roof surface. In 2015, Joulin et al. [19] proposed an experimental and a numerical investigation of a PCM-27 conditioned in a rectangular container located between two heat exchangers. It was found that the PCM needs about 1.48 h to melt during the charging process. The evaluation of the effect of the integration of PCM inside a building was also studied with experimental and simulation methods by Huang et al. [20]. They showed that the PCM floor is able to supply about 37.7 MJ heat for 16 h in a building. In the same context, Prieto et al. [21] concluded that the integration of solar collectors holding PCM as storage material provided about 18–23% of total daily thermal energy needs of the building. Krese et al. [22] present also an experimental study of a small-scale wall composite containing PCM-27. The result of the investigation indicates that the heat recovery throughout the night is about 25 W/m<sup>2</sup> .
