There has been a continuous increase in world population and industrialization. In parallel, energy consumption grew substantially in the world. The residential buildings constitute the majority of the total consumption in the developed world. Therefore, energy saving and reducing heat losses of buildings are of major concern for our society. At this point, phase changing materials (PCMs) show up as one of the most useful materials in building design. In this study, PCMs, which are used at places such as facade of buildings, bricks, and inside of concrete in order to be able to reduce the energy consumption due to heating and cooling, to provide comfort temperature inside buildings, are extensively reviewed.
TopIntroduction
The requirement for energy has been rising with the increasing population and developing economy. Most of the energy is consumed for heating and cooling purposes in buildings. Especially recently, with the increase of time spent at home, energy consumption levels have significantly increased. This causes great environmental problems (Du et al., 2018; Cao et al., 2017). Depending on the climatic conditions, the amount of energy used in buildings for the heating and cooling purposes can constitute a remarkable portion of the whole consumed energy. It has been informed that buildings represent nearly 30% of the total amount of energy used throughout the year. Besides, 28% of the annual CO2 emissions emerge from heating-cooling energy consumption in buildings (Hekimoğlu et al., 2021). The reduction of energy consumption can be achieved by minimizing the heating and cooling energy used in buildings. With the developing engineering technologies and innovative materials, energy consumption can be reduced considerably, and comfortable living temperature can be provided by less energy consumption in buildings (Cao et al., 2019). Energy-efficient design of the building not only enhances the indoor thermal behavior of the building, but it also increases the utilization of renewable sources of energy like solar energy and wind. Improving thermal energy storage capacity of the building is one of the efficient techniques of developing energy-efficient building. Generally, bricks, cement and concrete are used as sensible heat storage techniques to absorb, store, and release the heat energy in buildings (Rathore & Shukla, 2021).
There are three types of thermal energy storage system used for this purpose. These are latent heat storage, sensible heat storage and chemical reaction heat storage. Latent heat storage material can stock heat at almost constant temperature while undergoing a phase transition and store 5-14 times more energy per unit volume in comparison to sensible heat technique for storage. Thereby, the latent heat storage can be an influential method for thermal energy storage in buildings (Rathore & Shukla, 2021). Phase change materials based on latent heat storage are used in buildings because phase change materials (PCM) are in an advantageous position due to their high heat storage density and low level of temperature and volume changes during phase change (Xu & Li, 2014). Most of these PCMs retain their latent heat even after thousands of cycles without a change in their physical and chemical properties (Ling & Poon, 2013). Phase change materials, which have been considered as thermal storage materials since before 1980, have become a solution even for lightweight buildings due to the PCMs used in gypsum, plaster, concrete and other wall covering materials for thermal storage (Ling & Poon, 2013; Cabeza et al., 2007). Depending on their types, PCMs are compounds which absorb, store, and release the energy during the process of changing phase at certain temperature ranges. During hot times, PCM raises above the melting point and converts into liquid from solid, absorbing the heat. During cold times, when the temperature is under the PCM’s melting point, PCM solidifies and the heat spreads back into the ambient. This solidifying and melting cycle proceeds depending on the temperature rates. PCMs keep buildings at ideal temperatures and reduce their heating and cooling requirements. This cycle is visualized in Figure 1.
Because of its high latent heat storage capacity, using Phase Change Material (PCM) for thermal energy storage has become a center of attraction among researchers and scientists more and more. Thus, to develop the energy efficiency of buildings, PCMs are often embedded with the existing thermal masses of the building like wallboard, bricks and concrete slab (Rathore & Shukla, 2021).
In this work, the type and characterization of Phase Change Materials for the applications of thermal energy storage in buildings have been extensively studied. This work emphasized that PCMs can have an important role over decreasing energy consuming and increasing temperature comfort in buildings.
Figure 1. Heating and cooling function for concrete wall merged with PCM to ensure agreeable temperature for people in the room (Ling & Poon, 2013)