Thermal energy storage systems using phase change materials (PCMs) play a critical role in balancing intermittent renewable generation, particularly solar energy. However, conventional shell-tube designs suffer from extended charge-discharge cycles that reduce their practical effectiveness in grid and building applications. Researchers have developed an improved system incorporating metal foam and fin structures alongside PCM to dramatically accelerate thermal transfer rates.
The study compared three configurations across multiple operating modes. The metal foam-fin design with PCM significantly outperformed alternatives, storing approximately 24% more energy than finned-PCM designs and 51% more than PCM alone. During simultaneous charging-discharging operations—a critical real-world scenario—the foam-fin system achieved 126.5% higher combined storage and output versus pure PCM, and 261% improvement in total performance metrics.
Parametric testing revealed that higher inlet temperatures for the charging fluid markedly improved energy storage capacity, a finding that aligns with solar thermal systems where fluid temperatures naturally vary with incident radiation. Conversely, elevated discharging fluid temperatures slightly increased stored energy but reduced discharge output, suggesting optimal operating windows must be carefully managed.
The metal foam structure enhances performance through increased surface area and superior thermal conductivity pathways, enabling faster heat transfer between the working fluid and PCM. This addresses a fundamental constraint in thermal storage: the poor thermal conductivity of many PCMs themselves. By embedding foam and fins, the system effectively distributes heat more uniformly and rapidly.
The results position this technology as particularly valuable for distributed solar thermal systems on building rooftops, where space constraints and the need for fast response times create significant operational challenges. The foam-fin configuration's rapid thermal response could reduce thermal losses during idle periods and improve round-trip efficiency. Further optimization and real-world field testing will be necessary before widespread commercial deployment, but the performance gains demonstrate clear potential for advancing solar energy utilization at utility and building scales.
