Design and Analysis of Low-Cost Thermal Storage System for High Efficiency Concentrating Solar Power Plants

The ability to efficiently and cost-effectively incorporate thermal energy storage (TES) systems is an important advantage of concentrating solar power (CSP) in comparison to other intermittent forms of renewable energy, such as wind or photovoltaics. As such, TES allows CSP plants to continue to provide electricity to the grid even at times when the resource (the sun) is not available, such as cloud transients or at night. Advanced power cycle systems with supercritical carbon dioxide (sCO2) as the working fluid provide high power conversion efficiency because of high temperatures attained, and less compression work and are being explored for integration with concentrating solar power plants. Currently, there is no cost-effective way to store energy at high temperatures (>565 degree Celsius). The present work analyzes the thermal performance of a novel, cost-effective thermal storage system based on elemental sulfur as the storage media. The analysis is based on a detailed system-level computational modeling of the complex conjugate heat transfer and fluid flow phenomena at multiple scales to provide a scientific basis for engineering, designing and optimizing the novel thermal storage system for transient operation. The validation of the computational model based on data from experiments and full-scale plant operation is also reported. Our studies have shown sulfur-based TES to be a promising candidate for high temperature CSP.