Improving the Flexibility of Combined Heat and Power (CHP) Units by the Integration of Molten Salt Thermal Energy Storage

Molten salt thermal energy storage (TES) provides an efficient solution to improve the flexibility of combined heat and power (CHP) plants. This study investigated two operation modes of TES: the Power-Augmenting TES Mode (Mode 1), which enhances power generation flexibility, and the Heating-Augmenting TES Mode (Mode 2), which improves the flexibility of industrial steam supply. Based on a validated thermodynamic model, the flexibility, energy efficiency, exergy efficiency, and economic performance of the integrated system are evaluated. Results show that Mode 1 offers stronger peak-shaving capability, while Mode 2 achieves comparable peak-topping performance and is more suitable for high industrial heating load scenarios due to its inherent heat–power decoupling effect. Mode 2 exhibits more pronounced energy efficiency improvement, whereas both modes reach identical maximum exergy efficiency. Additionally, the integration of molten salt TES significantly enhances profitability, increasing annual profit to 97.3 million RMB under Mode 1 and 85.4 million RMB under Mode 2 from a baseline of 79.7 million RMB. While Mode 1 generates higher profit at lower heating loads, Mode 2 becomes progressively more advantageous as industrial heating load increases.