Optimization of a latent heat thermal energy storage device for waste heat recovery in data center campus

Waste heat recovery is critical for improving data center (DC) energy efficiency, particularly in high-altitude regions such as the Qinghai Plateau. Here, the intermittency of solar energy disrupts thermal stability, while winter electric heating elevates carbon emissions. To address these challenges, a latent heat thermal energy storage (LHTES) system integrated with photovoltaic (PV) power and waste heat was designed specifically for DCs on the Qinghai Plateau. To enhance heat storage efficiency, a validated 2D computational fluid dynamics (CFD) model based on the enthalpy-porosity method was established to simulate the phase-change heat transfer process. Multi-parameter optimization of heat transfer fluid (HTF) tube diameter, eccentricity, and layout was then conducted using a robust orthogonal design. Economic viability was evaluated by comparing the investment payback periods of different design configurations. Key findings indicate that eccentricity exerts the most significant influence on heat storage efficiency. The case with a 30 mm eccentricity cuts melting time by 27% and increases heat storage efficiency by 44% via natural convection compared to the baseline. Notably, variations in tube diameter have negligible impact on heat storage capacity. The optimal HTF tube configuration was identified as 30 mm eccentricity, 15 mm diameter, and uniform layout. This configuration reduces melting time by 34.5%, increases storage efficiency by 62%, and improves total thermal capacity by 6%. Economically, the optimized system lowers the levelized heat cost by 27% with a short payback period of 1.3 years. These results demonstrate the feasibility of integrating LHTES systems with PV power and waste heat for DCs on the Qinghai Plateau.