Thermodynamic performance of a flexible retrofit Carnot battery energy storage system in a coupled thermal power plant

doi:10.19799/j.cnki.2095-4239.2024.0996

Abstract

Abstract:

The integration of energy storage technology with thermal power plant retrofitting enables stable grid connection of renewable energy and flexible peak shaving of coal-fired units. This study proposes a molten salt Carnot battery energy storage system integrated with a thermal power plant to enhance peak-shaving flexibility. Using a typical 600 MW subcritical coal-fired power plant as a reference, a coupled system model—including the coal-fired power plant, a heat pump thermal energy storage unit, and a steam thermal energy storage unit—is developed using Aspen Plus. The study analyzes the efficiency, peak-shaving capacity, and depth of three thermal energy storage modes- steam thermal energy storage (STES), steam combined with heat pump thermal energy storage (SHPTES), and heat pump thermal energy storage (HPTES) across different operational stages. Additionally, the efficiency and peak-shaving performance of the coupled system under various energy storage and release loads and schemes are evaluated. The results indicate that the STES approach achieves higher coupled system efficiencies when the coal-fired power plant operates at low loads. In contrast, HPTES demonstrates superior peak-shaving performance, with its maximum peak-shaving capacity per unit of heat storage load increasing by 69% compared to STES. The addition of thermal energy storage devices substantially enhances the peak-shaving performance of the coal-fired power plant while causing only a minimal efficiency loss. When operating at a rated load with a heat storage load of 90 MW, the SHPTES approach increases the peak-shaving capacity and depth by 78.29 MW and 13.04%, respectively, with an efficiency loss of only 0.16%. Furthermore, coupling schemes for STES are examined. During energy storage, reheated steam is extracted and returned to the deaerator after heat release. In the energy release process, a portion of the feedwater is heated and directed to the boiler via a bypass. This coupling scheme effectively balances heat storage capacity, peak-shaving capacity and depth, and system efficiency. This study provides valuable guidance for retrofitting coal-fired power plants with molten salt Carnot batteries to improve operational flexibility.

Key words: Carnot battery, thermal power plant retrofitting, molten salt thermal storage, peak shaving

CLC Number:

TQ 028

Boxu YU, Rui HAN, Qian LIU, Zhirong LIAO, Xing JU, Chao XU. Thermodynamic performance of a flexible retrofit Carnot battery energy storage system in a coupled thermal power plant[J]. Energy Storage Science and Technology, 2025, 14(4): 1461-1470.

Figures/Tables 15

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策略	储能过程热负荷/MW	释能过程热负荷/MW
策略a	30	30
策略b	60	60
策略c	90	90
策略d	90	60
策略e	60	30
策略f	90	30

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