Modeling of a cold thermal energy storage for the flexibility of thermal power plants coupled to Brayton cycles

Abstract As the share of variable renewable energy in the electricity generation continues to increase, electricity markets are facing significant variations of electricity prices. Thermal power plants that generate base-load electricity are not the most suitable for such markets. In the work reported here, a cold thermal energy storage coupled to a Brayton power conversion cycle for peak capacity generation is studied. Peak capacity is usually reached due to hot thermal storage, which increases the maximum temperature of the cycle. However, it is also possible to reduce the minimum temperature reached by the cycle to increase the power cycle efficiency. For this purpose, a cold thermal energy storage is used. It is designed to meet the needs of primary and secondary reserves required for grid frequency control. This typically represents a 7% power increase reached within 2 min over a time span of 15 min. A dynamic model of the entire 559MWe power plant is used to assess storage capacity, electrical power dynamics and impact on the plant. Since only 1700 m3 of chilled water are required, the results obtained are promising. The chilled water is generated either by a refrigeration system when the demand for electricity is low or by an absorption chiller operated by the waste heat generated by the Brayton cycle. In the past, important research work has been devoted to the development and deployment of large cold thermal energy storage for air conditioning. As a result, for such Brayton power cycles, it is possible to extend the time of peak power generation to several hours.