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In general, one of the promising methods to reduce energy consumption and off peak load is the employment of cold thermal energy storage (CTES) in energy systems. In this paper, a numerical investigation is conducted on a CTES system mounted in a freezer to find out the effective phase change material (PCM) volume. A large amount of the cold thermal energy is stored as latent heat during solidification of eutectic solution NaCl-H2O as PCM with −21 °C melting temperature. This latent cold thermal energy is then released into the freezer compartment when the compressor of the refrigeration cycle is off. Because of the space limitation in freezer cabin, CTES system should be designed as much as compact and efficient. Thereby, PCM boxes with the maximum exposed area and different PCM thicknesses of 0.5, 1, 2, 3, 4, 5 and 6 cm are simulated using computational fluid dynamics (CFD) method. The total discharged cold thermal energy, as well as its period, was obtained for all 7 PCM thicknesses. Discharging time per unit of PCM mass (τdisch) is introduced as the ratio of the discharging time of PCM (time of off-compressor) to the total PCM mass to comparison the effectiveness of CTES system. It is revealed that the τdisch does not rise with the PCM volume, proportionally. Just when the PCM thickness is raised from 2 cm to 3 cm, the τdisch improved significantly for 45% and weakly increased afterward. It means that container with 3 cm thickness would be the best one for this type of storage system.

High energy demand, and excessive consumption of natural resources, have become one of the most critical global challenges. The building sector is one of the most energy consumers, and it almost consumes one-third of final energy worldwide. Hence, it is one of the most significant CO2 emission sectors. Utilization the renewable energy in building such as solar energy connected with latent thermal energy storage (LTES) using phase change materials (PCM) is a promising solution to reduce conventional energy consumption and diminish greenhouse gas emissions. Separately, a proper heating system selection preparing a comfortable heating condition is a priority. Underfloor heating systems (UFHSs) can maintain indoor air temperature more comfortably than other heating systems. This study used parabolic trough solar collector (PTSC) as a heating source for two test cubicles equipped with underfloor heating systems. In situ latent energy storage using hydrate salt with 32 °C melting temperature is used in one test cubicle and it compared with the typical underfloor heating system embedding pipes under sand in the other same cubicle. Results revealed that the latent thermal energy stored in PCM can maintain the indoor air temperature of the cubicle in comfortable condition for more than 4 h after sunset. Furthermore, PTSC provides more than 80% of cubicles heating loads during the coldest time in Tehran, Iran.

Given exterior walls as the main drawback of buildings, the present experimental study was conducted to investigate the effect of phase-change material (PCMs) as the building envelope layer on the thermal effectiveness and indoor air conditioning. Two 1 × 1 m2 cubicles with the same geometry, orientation and construction materials were built as an experimental set-up while adding a PCM layer to the walls of only one of the cubicles referred to as the PCM cubicle and leaving the other wall layers unchanged. The other cubicle is referred to as the Ref. cubicle. Several K-type thermocouples were mounted within the layers at the centre of both cubicles. The same air cooler used to match the indoor conditions of the two cubicles at the beginning of all the examinations was shut down after achieving the desirable temperature at their centre to allow the environment to naturally change the indoor conditions of the cubicles. The indoor cubicle temperature as well as temperature at the interface of layers are acquired. The data collected within nine days respectively showed reductions of 1.5 and 2.3°C in the average and peak indoor air temperature of the PCM cubicle in summer compared to those of the Ref. cubicle. Using the PCM panel in the eastern wall (hot wall) also decreased the heat gain by 44%.

This paper examines the thermal properties of pure tetracosane paraffin, tetracosane-graphene, and tetracosane-carbon nanotube mixed phase change materials (PCM). The most important properties studied were thermal capacity in constant volume (Cv), mean square displacement of atoms (MSD), radial distribution function (RDF), density, phonon density of states (PDOS) and thermal conductivity (k) under different temperatures. The results show that graphene and carbon nanotube increase the thermal conductivity of the tetracosane at different temperatures, but decrease the molecular movement and its thermal capacity (except after about 360 K), and it can be said that this slightly decreases the paraffin melting temperature. It was demonstrated that carbon nanotube is more efficient than graphene to increase the thermal conductivity of the proposed PCM.