Nuclear renewable hybrid energy system assessment through the thermal storage system

Abstract

In support of the use of more efficient and low-carbon nuclear energy along with solar energy in power generation systems, the present paper presents a technical-economic analysis of a nuclear renewable hybrid energy system (NR-HES) case study for a given electricity and residential heat demand profiles of a typical remote community in Canada. The studied hybrid energy system is composed of a small modular nuclear reactor (SMR), a concentrated solar tower (CST), and a thermal energy storage (TES) unit. A fossil fuel backup energy source is also considered to generate excess electricity as needed. The CST and nuclear reactor both share the same TES system. Five different thermal storage fluids are examined: Therminol, Dowtherm, solar salt, Hitec salt, and Hitec XL salt. A transient thermodynamic mathematical model is developed in order to determine the overall configuration, performance, and operation strategy for the NR-HES. The operational strategy of the NR-HES is based on the steady-state full-power operation of the SMR, storing the excess energy in the TES system when the combined nuclear and solar power generation exceeds the power demand of the electrical grid and using the stored thermal energy during the periods of peak demand A detailed economic analysis of the NR-HES is conducted for each operational scenario, including the annualized cost of the TES system and the NR-HES plant, as well as annual revenue and profit generated by the TES system. The developed model is used to obtain the most economical thermal storage fluid and to optimize the size of TES system in order to minimize the use of fossil fuels and maximize profit. Parametric studies of reactor thermal power and CST's field area are conducted to determine their effect on the performance and configuration of the NR-HES. Based on the current case study in terms of demand profiles, the results revealed that Therminol is the most economical thermal storage fluid for the present NR-HES with a charging capacity and round-trip storage efficiency of 237 268 MWh/year and 96%, respectively. The optimum Therminol storage tank size is evaluated to be 14 m in height and 10 m in diameter with a yearly average power cycle efficiency of ~36% and economic profit of 1 158 30 CAD/year. The parametric studies indicated that a larger TES size may decrease the usage of fossil fuel energy sources; however, it increases system total capital cost and decreases the power cycle efficiency and TES profit at given load. The results of this study indicate that an NR-HES is a promising low-carbon power generation system with the potential to meet the electricity and residential heat demand of remote communities.