Nature-Inspired Lotus-Shaped Fins Combined with Hybrid Nanoparticles and Metal Foam for High-Performance Latent Heat Thermal Energy Storage

Latent heat thermal energy storage (LHTES) systems play a critical role in renewable energy integration by providing high energy density and nearly isothermal operation during phase transitions. However, their performance is often limited by slow melting/charging rates, which motivates the search for enhanced heat transfer designs. This study investigates the melting behavior of RT-82 phase change material (PCM) using novel lotus-shaped fins combined with copper metal foam and conductive graphene nanoparticles and carbon nanotubes. A two-dimensional enthalpy-porosity model in ANSYS Fluent was developed to simulate the charging/melting process, capturing non-thermal equilibrium between the foam and PCM/nano-PCM. In this study, effects of fin geometry, nanoparticle concentration, and foam porosity on melting dynamics and cost-performance trade-offs were investigated. Results showed that natural convection accelerated melting by ~12% compared to conduction-only scenarios. Optimized lotus-shaped fins with higher fin density (T3F4 and T3F10) achieved up to 63% faster melting relative to sparse configurations. Graphene nanoparticles improved thermal conductivity, with a 6% volume fraction, by reducing melting time by ~6.9%, while their combination with 75% porosity foam achieved a maximum reduction in the melting time of ~51% compared to pure PCM. Cost-performance analysis identified T3F4 as the most balanced design, offering rapid thermal response without excessive material costs, while moderate-density designs like T3S6 provided economical alternatives with acceptable performance. These results highlight the performance enhancement that can be achieved by integrating bio-inspired fins, nanoparticles, and foams, into compact and efficient LHTES for solar heating, building thermal management, and industrial waste-heat recovery applications.. Authors: Saini, Prashant [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000176649939); Osorio, Julian [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000207619899); Shah, Munjal [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000261206016); Patel, Umang [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000280019064); Nelapudi, Akhil [Clemson University]. DOE Contract: AC36-08GO28308. Subjects: 25 ENERGY STORAGE; 36 MATERIALS SCIENCE; melting/charging; nature-inspired shaped fins; performance enhancement; phase change material; solidification/discharging; thermal energy storage