**6. Applications of microencapsulated PCMs**

Microencapsulated PCMs due to their unique properties such as solid-to-liquid phase transition, chemical and thermal stability and higher amount of energetic changes, has received special attention for their applications in in our ordinary daily life and various industries. In recent years, PCMs have been designed and fabricated *Design and Fabrication of Microencapsulated Phase Change Materials for Energy/Thermal… DOI: http://dx.doi.org/10.5772/intechopen.102806*

to meet the requirements around the world. The potential applications of PCM microcapsules are shown in **Figure 3**, and discussed as bellows:

#### **6.1 Application in fibers and textiles**

In textile industries, microencapsulated PCMs are embedded within the fibers or coated onto the surface of fabrics which are used in the preparations of outdoor dress such as snowsuits, trousers, gloves, ear warmers and boots etc. The microencapsulated PCMs enhance the thermal storage capacities of the fibers/fabrics (2.5–4.5 times) and thus protect from extremely cold weather [46]. Microencapsulation is a promising technology for applications in the textile industry such as agriculture textiles, medical textiles automotive textiles and sportswear/protective clothing. Scacchetti et al. explored the thermal and antimicrobial properties of cotton with silver zeolites functionalized via a chitosanzeolite composite and microcapsules of PCMs [79]. They suggested the use of chitosan zeolite for the production of textiles for superior antibacterial and thermoregulating properties. Microencapsulated PCMs increase the flame-retardant property thermal and comfort of the textiles, as these PCM microcapsules were scattered homogeneously onto textile substrates and were durable with repeated washings [80].

#### **6.2 Application in slurry**

PCM microcapsules with high latent heat are used in the slurry industry as an enhanced heat transfer fluid (HTF) and a thermal storage medium (TSM). Song et al. considered laminar heat transfer of PCM microcapsules slurry and proved that the heat transfer coefficient improved with increasing Reynolds number and volume concentration of microcapsules [81]. Roberts et al. compared the heat transfer capability of metal-coated and nonmetal-coated PCM microcapsules slurry and noticed an additional 10% increment in heat transfer coefficient and PCM microcapsules inducing pressure drop in slurry [82]. Zhang and Niu reported higher thermal storage capacity for PCM microcapsules slurry storage devices and stratified water storage tanks [83]. Xu et al. prepared PCM microcapsules with Cu-Cu2O/CNTs shell and their dispersed slurry for direct absorption solar collectors [84]. They reported that the PCMs@Cu-Cu2O/CNTs microcapsule slurry had high heat storage competency and outstanding photothermal conversion performance which made it as one of the most potential HTFs for direct absorption solar collector.

#### **6.3 Application in energy-saving building**

Another amazing application of PCM microcapsules is their utilization in building materials to overcome overheating problems in summer and provided a new effective solution for thermal management and energy saving in buildings. The PCM microcapsules in construction materials boost the thermal and acoustic insulation of walls. Usually, the PCM microcapsules are embedded into concrete mixtures, cement mortar, gypsum plaster, wallboards, sandwich, slabs, panels and to fulfill the energy demand of the building for heating, cooling, lighting, air conditioning, ventilation and domestic hot water systems [85]. Many researchers around the world worked on the application of PCMs microcapsules in the building industry. Cabeza et al. reported an innovative concrete material with high thermal properties by mixing it with PCM microcapsules [86]. It was found that the concrete wall with PCM

**Figure 3.** *Potential applications of PCMs microcapsules.*

microcapsules increase its overall mechanical resistance and stiffness and causes even temperature fluctuations and thermal inertia, making it to be a promising technology to save energy for buildings [87]. Su et al. studied nano-silicon dioxide hydrosol as the surfactant for the preparation of PCM microcapsules for thermal energy storage in buildings [88]. Essid et al. investigated the compressive strength and hygric properties of microencapsulated PCMs concretes [89]. They reported that the use of concrete containing PCM microcapsules as structural material is sufficiently safe, though its compressive strength is lower and porosity is higher than the pure concrete. Schossig et al. [90] directly integrated formaldehyde-free microencapsulated paraffins in building materials and studied their effect for application in conventional construction materials. They observed that the utilization of these PCMs microcapsule could help to keep the indoor temperature up to 4°C lower than typical conditions and could reduce the number of hours that the indoor temperature was greater than 28°C.

*Design and Fabrication of Microencapsulated Phase Change Materials for Energy/Thermal… DOI: http://dx.doi.org/10.5772/intechopen.102806*

### **6.4 Application in foams**

The application of microencapsulated PCMs in foams can enhance their thermal insulating efficiency. Borreguero et al. reported that the thermal energy storage capacity of rigid polyurethane foams was improved when it was embedded with PCM microcapsules investigated rigid polyurethane foams containing and indicated that improved [91]. Li et al. introduced a new approach to enhancing the latent heat energy storage ability by embedding PCM microcapsules in metal foam [92]. They observed that compared to the surface temperature of virgin PCM modules, the surface temperature for the PCM microcapsule/foam and PCM/foam composite modules was reduced from about 90 to 55 and 45°C, respectively. PCM microcapsule/foam composites solved the problem of low thermal conductivity and leakage. Bonadies et al. synthesized poly(vinyl alcohol)- (PVA-) based foams containing PCM microcapsules and investigated their thermal storage and dimensional stability [93]. They observed that the formation of crystalline domain and amount of water uptake was influenced by microcapsules which in turn affected the number of intra- and intermolecular hydrogen bonds as many PVA –OH groups interact with microcapsule shells.

### **6.5 Others applications**

There are many other potential applications of PCM microcapsules. These include biomedical applications, solar-to-thermal energy storage and electrical-to-thermal energy storage [65]. Zang et al. prepared multifunctional microencapsulated PCMs that can be used for sterilization [94]. They reported that these microcapsules have high antibacterial activity against *Escherichia coli*, *S. aureus*, and *Bacillus subtilis*, and the antibacterial efficiency of 2-hour contacting PCM microcapsules was inhibited up to 64.6%, 99.1%, and 95.9%, respectively. Zhang et al. also studied solar-driven PCM microcapsules with efficient Ti4O7 nanoconverter for latent heat storage [95]. The solar absorption capacity of the novel PCM microcapsules was found to be 88.28%, and the photothermal storage efficiency of the PCMs@SiO2/Ti4O7 microcapsules was 85.36% compared with 24.14% for pure PCMs. Zheng et al. proposed a joule heating system to reduce the convective heat transferring from the electrothermal system of the surrounding by inserting the highly conductive and stable PCMs microcapsules [96]. They showed that the working temperature could be improved by 30% with the loading of 5% PCMs microcapsules even at lower voltage and ambient temperature.
