Coupled Transient System Analysis: A New Method of Passive Thermal Energy Storage Modeling for High Temperature Concentrated Solar Power Systems

Abstract

A comprehensive analysis of passive storage systems was developed consisting of sizing, transient performance and cost models. The sizing model is described in an earlier paper. The transient model, written in TRNSYS, was developed to predict the performance of each storage system when coupled with a realistic solar field and powerblock. This effort includes the creation of a time and space discretized numerical, adaptive grid model and a suite of controllers. The model in TRNSYS was implemented to provide hourly or sub-hourly performance data for an entire CSP plant with passive storage. During the course of the work passive phase change material storage was the focus; although purely sensible passive storage systems, such as concrete and ceramic, were also considered. It was found that previous sizing model methodology developed in both industry and academia is insufficiently robust and does not produce trust-worthy sizing information when used to cost passive storage systems. Furthermore, it was found that, especially for passive TES systems, transient coupled system modeling is a requirement for correct size and cost calculations. Finally, it was found that the current figures of merit, namely cost per kWh LSC, are ineffective means of capturing the real comparative cost of a storage system. In the course of the work a new storage control paradigm for passive systems has been developed. Additionally, new modeling methodology, figures of merit, and performance sizing criteria are presented.