Thermodynamic Modeling of Thermal Energy Storage Systems Using Novel Storage Media
Thermal energy storage (TES) has been widely researched across a variety of applications, and has shown promise to enable renewable energy technologies and provide the capability to shift or shave peak electricity demand. Various storage media have been successfully demonstrated for specific temperature ranges, though few candidates have been modeled for high-temperature (> 650?C) applications. The thermodynamic model and analysis described in this dissertation is aimed to contribute to this emerging knowledge base.
The numerical model investigates the transient thermodynamic and heat transfer characteristics of the TES system by coupling energy and exergy analyses with fluid property models to calculate the spatial and temporal variations in material properties during the entire charge-discharge cycle of the TES system. Sub-models for additional system components, such as the solar field and power block in concentrating solar power (CSP) plants, are included to analyze an integrated TES system accurately. This model provides the capability to study TES design and operational parameters based upon user-defined specifications, and optimization allows the user to determine optimal plant design and dispatch control for the TES system.
The subsequent technical and economic (techno-economic) analysis presents a detailed investigation of applications, technical characteristics, market status, and recommendations for deployment of the TES system. The analysis utilizes probabilistic cost modeling to allow the user to conduct uncertainty and sensitivity analyses based upon user-specified data sets for cost indices.
Overall, of all the storage media evaluated, elemental sulfur showed the most promise across a range of operating temperatures. Some chief advantages include high thermal stability at elevated temperatures, high enthalpy of reaction, simplicity of design and operation, well-established knowledge base of handling and transportation, and low unit price. Future work is necessary to determine the material compatibility of elemental sulfur with common piping materials at high temperatures.