Simplified mathematical model and experimental analysis of latent thermal energy storage for concentrated solar power plants

Abstract

Depletion of fossil reserves and environmental concerns arising from their use has led to the development of renewable energy technologies. Concentrated solar power (CSP) is one of the promising alternative energy solutions that can be built in higher capacity (hundreds of megawatts) and provide higher thermal efficiencies compared to other technologies. However, almost all CSP systems require thermal energy storage (TES) to improve the capacity factor and bridge the gap between supply and demand. In the current work, a reduced-order one-dimensional mathematical model of a phase change material (PCM) based TES is proposed and experimentally validated on different sets of data including different PCM, operating ranges and storage size per geometrical unit of the CSP. The model considers single EPCM as a lumped thermal mass without much compromise on the accuracy having less than 9% overall error in terms of predicting energy storage capacity when compared to experimental data. Additionally, an experimental setup for encapsulated-PCM (EPCM) is developed using NaNO3-KNO3 as the PCM. This system has a storage capacity of 9.7 MJ and a storage time of 6 hours is required to completely charge the system at selected conditions. An analysis of the system performance is presented under different experimental conditions. The model development, experimental analysis and validation shall provide reliable design estimates while designing EPCM-TES for large-scale applications. Therefore, the current simplified mathematical model best fits such applications where a design engineer needs to make quick decisions regarding the selection of an EPCM-TES system or where a reduced-order model of entire CSP plant is required.