Effective energy use and passive cooling in data centers using heat pipes and PCM-integrated TEG systems

The rapid development of big data and cloud computing technologies has significantly increased energy consumption in data centers, with cooling systems accounting for 30–50 % of total energy usage due to conventional Computer Room Air Conditioning (CRAC) systems. This study proposes a novel thermoelectric power generation and passive cooling system that integrates thermoelectric generators (TEGs), heat pipes, and phase change materials (PCMs) to enhance energy efficiency and waste heat utilization. Heat is removed from servers into a water stream, which transports it to the thermoelectric generator, where waste heat is converted into electricity. The PCM stabilizes temperatures on both sides of the TEG, ensuring steady and efficient power generation, while the recovered heat is reused for domestic heating. The proposed system was modeled in Engineering Equation Solver (EES) and analyzed comprehensively from thermodynamic and heat transfer perspectives. Key parametric investigations assess the system's performance under varying operating conditions, focusing on thermoelectric power output, energy and exergy efficiency and heat reuse metrics. Applied to a 42 U data center rack with a CPU power of 25 kW, the system generates 125 W of thermoelectric power and delivers 68 °C hot water with a heating output of 20.1 kW per rack. The system yields energy and exergy efficiencies of 80 % and 33 %, respectively. Additionally, an energy reuse factor (ERF) of 0.7541 is achieved, and a novel exergy reuse factor (ExRF) is introduced to quantify the quality of energy recovery, with a calculated value of 0.060 for a single-stage system, serving as an indicator of the system's exergy reuse potential. An alternative dual-stage TEG-PCM configuration further enhances performance, increasing thermoelectric power output to 219 W, leading to ERF and ExRF values of 0.755 and 0.063, respectively. These results underscore the potential of integrating thermoelectric power generation with passive cooling technologies to provide uninterrupted cooling and enable waste heat recovery in data centers.