Numerical analysis of an optimal metal wool-phase change material for thermal energy storage with exceptionally high power density

The adoption of thermal energy storage (TES) systems based on phase change material (PCM) remains limited by their low thermal conductivity, which restricts power density. Existing heat transfer enhancement techniques are often costly or come with significant drawbacks, leaving a gap for an effective and affordable solution. This study highlights metal wool as a promising alternative, offering low cost, ease of application, and retrofitting potential. While previous experiments demonstrated substantial improvements in power density using copper wool, a comprehensive numerical model to further optimize this technique is presented here. The model, incorporating CFD simulations and uncertainty analysis, was validated for bulk PCM and two copper wool-PCM composites before being extended to a wool material analysis. First, possible alternatives to copper as wool material were tested, highlighting aluminum as a viable candidate. Then, the proposed composite was found to match the discharging performance of a PCM with an effective thermal conductivity of 2.5 W/mK, a value rarely achieved by conventional enhancement techniques. Additionally, a techno-economic comparison revealed that copper wool delivered a 14.7-fold increase in thermal conductivity relative to liquid PCM at 6 Euro per kg of PCM additivated - a performance unmet by metal foams and nanocomposites. These findings confirm metal wool as a viable cost-effective and high-performance solution for improving TES systems, partially bridging the gap between efficiency and affordability.