Prototype latent heat storage system with aluminum-silicon as a phase change material and a Stirling engine for electricity generation

In this work, we present the design and experimental results of a prototype latent heat thermal energy storage system. This prototype used 100 kg of aluminum-silicon as a phase change material with embedded heat pipes for effective heat transfer, a valved thermosyphon to control heat flow out of the thermal storage system, and a Stirling engine to convert heat to electricity. We tested this system for 11 simulated days of operation; each day included charging of the thermal storage tank, simultaneous electricity generation with heat input, and electricity generation from stored heat alone. On each simulated day, we set the engine to a different power level, allowing us to investigate the response of heat pipes and our valved thermosyphon to part-load conditions. The prototype demonstrated a maximum efficiency of 18.5% in converting stored heat to electricity, at a maximum power output of over 1kW_e. Extending these results to a commercial scale system with solar heat input, our modeling indicates that a discharge efficiency of over 30% and an annual efficiency of 18% could be achieved. This performance represents an advancement in established efficiency for any system that combines latent heat storage with electricity generation, and demonstrates that this system has potential for future commercial development.