**2. PCM and their applications in TES**

PCMs are cutting-edge tech with potential to boost efficiency, reduce environmental impact, and enhance sustainability in engineering applications. The area of PCM application has been discussed in the following sections.

#### **2.1 Thermal management of electronics**

Moore's Law, which forecasts the doubling of computing chips' density and processing power every 2 years, has significantly increased the need for advanced cooling solutions due to higher heat dissipation and reduced form factors. This trend poses challenges for thermal engineers in developing efficient chip-cooling technologies to prevent chip damage and maintain performance by keeping temperatures below critical levels. Portable electronic devices, designed for intermittent high computational activity, require cooling systems that can efficiently manage sudden heat spikes without draining the battery or accelerating aging. Phase change materials (PCMs) are ideal for this purpose, absorbing energy peaks and gradually releasing heat during standby, thus maintaining a stable operating temperature and effectively managing the thermal load. A study by Joshi and Pal demonstrated the efficacy of PCMs, like

*A Review on Phase Change Materials for Sustainability Applications by Leveraging Machine… DOI: http://dx.doi.org/10.5772/intechopen.114380*

paraffin and eutectic alloys (**Figure 3**), in providing passive thermal management for mobile devices, showcasing their ability to control system temperature during variable power operations [33, 34].

A study by Amon and Vesligaj on the impact of transient loads on electronics, with a duty cycle involving a 10 W peak for 45 minutes followed by 30 minutes of standby, showed that Phase Change Materials (PCMs) effectively mitigate temperature fluctuations, limiting the temperature to 31°C compared to 37°C without PCMs [35]. This demonstrates that PCMs provide reliable passive cooling for small electronic packages, reducing the need for moving parts found in active cooling systems. Incorporating PCM-based heat spreaders addresses design challenges in modern applications by meeting geometric constraints and minimizing solidification time.

#### **2.2 Advances in PCM technology for data center cooling**

Data centers, crucial for digital infrastructure, comprise IT equipment, infrastructure support, communication links, and security devices, operating continuously. This operation generates significant heat, requiring management for reliability and sustainability. User load varies diurnally, with "peak hours" during the day and "off hours" at night, challenging cooling systems, especially as server upgrades alter thermal characteristics.

Data centers utilize various cooling strategies, including Computer Room Air Conditioning (CRAC) units, airflow management, free cooling, liquid cooling, and thermosyphons, broadly categorized into airside and liquid-side systems [36]. Airside cooling, particularly CRACs involving chillers, water pumps, fans, and cooling towers, is preferred for its reliability, lower initial costs, and maintenance ease. However, vapor compression systems, integral to CRACs, consume substantial energy due to year-round operation. Current practices also involve energy management, airflow optimization, single-phase, and phase change cooling to enhance efficiency, as detailed in **Figure 4**.

A review by Ma et al. [38] highlights the limited research on data center cooling systems incorporating cold energy storage for power outages. Simulations by Wang et al. demonstrated that PCM plates could maintain data center temperatures below

**Figure 3.** *Comparison of temperature response of a heat dissipating system with and without PCM.*

**55**

**Figure 4.** *Currently available high-performance and effective cooling technologies applied in data centers [37].*

35°C for 9 hours during emergency power failures [39]. Another study optimized a latent heat storage system with a tube-in-tank design, finding that thermal conductivity enhancements significantly 0.2 to 1 W/(m·K) [40] increased its capacity effectiveness. Zheng et al. designed an air-based phase change material storage system for emergency cooling in data centers, showing through simulations that it could discharge over 2.5 kW for 30 minutes during power outages, offering a promising solution for maintaining critical temperature thresholds [41].

Phase change cooling (PCC) vastly surpasses traditional air-cooling methods, offering over a thousand times the cooling capacity [42]. It utilizes an underevaporation technique, allowing for the use of various low-boiling electrolyte fluids and refrigerants [43], with the choice of refrigerant being key to its performance. Extensively researched and applied in data centers, PCC demonstrates exceptional thermal efficiency and energy conservation [44]. The incorporation of phase change materials (PCMs) further boosts PCC's efficiency by enhancing evaporation and condensation processes, enabling the temporary storage and release of excess heat [45, 46]. This prevents overheating in data centers, reducing dependence on conventional cooling methods and lowering energy consumption.
