A steam combination extraction thermal energy storage scheme in boiler side for coal-fired power plant flexibility retrofit

The low-carbon energy system has introduced the urgent demand for the ability of peak-shaving for coal fired power plants (CFPPs). A novel and efficient integration concept of the high temperature molten salt thermal energy storage (TES) system with CFPP in the boiler side is proposed in this paper. The concept integrates the TES system with the 350 MW CFPP by extracting the main steam and the reheat steam to exchange heat with the molten salt to enhance the CFPP flexibility, which considers the safety and flexibility of the unit by splitting the heat exchange process of the reheat steam. The sensitivity of the novel concept to the critical design parameters has been analyzed. The power generation load of the novel integrated system can be reduced to 16.31 % of the rated load and the equivalent round-trip efficiency can reach 75.38–77.33 %. The relative value of the reheat steam flow rate flowing at the boiler side in the novel system varies from 0 to 16 % under off-design conditions. The power generation load of CFPP can be increased by 9.56 % THA under the heat discharg mode. The equivalent round-trip efficiency of the novel system can reach 67.61 %–84.87 % under off-design conditions, as well as the exergy efficiency of the TES system can reach 77.48 %–81.38 %. Finally, the levelized cost of delivery of the novel system reaches 135.35 USD/MWh, which can reduce CO 2 emissions by 59.58–66.16 tons under different operating conditions (The storage capacity of TES system is 212.21MWh). The results demonstrate that the flexibility enhancement concept of CFPP based on molten salt TES proposed in this paper would be useful to respond to the significant increase in renewable energy.