Investigation of hybrid sensible-latent packed bed thermal energy storage system

Reliable and cost-effective energy storage is essential to accelerate the adoption of renewable energy systems such as concentrated solar power (CSP) technologies. Single-tank Packed Bed Thermal Energy Storage (PBTES) offers a promising, lower-cost alternative to traditional two-tank systems for high-temperature storage. This study explores a hybrid sensible-latent PBTES system that integrates two types of Phase Change Materials (PCMs), strategically placed at opposite ends of a sensible-based PBTES, to enhance performance in terms of storage density and outlet fluid temperature stability. This is the first study to systematically evaluate metallic PCMs in multi-layered hybrid PBTES. A comprehensive numerical investigation, spanning PCM volume fractions from 0 to 30 % for each PCM, is conducted using a validated concentric dispersion model. The results show that PCM integration significantly boosts storage capacity, improves thermal stability, extends temperature plateaus during charging and discharging cycles and increases the energy density by up to 250 %. These hybrid configurations also extend the useful operation time by up to 220 % during charging and 300 % during discharging cycles with up to 250 % of useful energy capacity increase. Economic analysis showed a payback period of 4.8–5.5 years, with reductions in PCM layer at the top of the TES unit and encapsulation fabrication costs providing the most significant improvements in overall cost. While the hybrid system enhances temperature stability and energy utilization, it introduces trade-offs in terms of cost and efficiency, underscoring the importance of optimized PCM selection and its operating conditions. This work demonstrates the transformative potential of hybrid PBTES systems in delivering efficient, stable, and tailored energy storage solutions for future energy systems.