A cost and performance comparison of packed bed and structured thermocline thermal energy storage systems

Abstract

A structured concrete thermocline thermal energy storage (TES) system is proposed as an alternative to currently-used TES systems. The issues of material settlement and thermal ratcheting found in packed bed thermocline TES systems is avoided by replacing the packed aggregate bed with structured high-temperature concrete. A summary of all utility scale TES systems with integrated TES in existence today is provided and discussed. Cost reduction options such as replacing two-tank systems with single-tank systems and replacing liquid storage media with solid storage media are discussed along with limitations of both options. Numeric models are developed to simulate the performance of utility scale packed bed and structured thermocline TES systems; efficiencies of 92.37% and 84% are modeled for packed-bed and structured systems. A complete cost analysis of utility-scale, 2165MWh packed bed and structured systems is conducted; capacity costs of $30/kWh and $34/kWh are determined for packed bed and structured systems respectively. A structured concrete thermocline is deemed to be a viable TES option due to its low cost and the fact that there are no concerns of thermal ratcheting of the tank.