An analysis of the operation of a flexible oxy-fired CFB power plant integrated with a thermal energy storage system

• An oxy-fired CFB power plant integrated with an energy storage system is analyzed.
• The power output is modified by a ratio of 5 with a constant coal thermal input.
• With a thermal input of 214 MWt, 150 MWe can be delivered using the energy storage.

This work analyzes the performance of an oxy-fired CFB power plant integrated with an energy storage system. The system contains two silos connected to a combustor to allow the power output to be modified while operating at a constant coal firing rate. During low energy demand periods, part of the thermal power released in the combustor is stored as sensible heat in a high temperature silo by feeding in solids from a low temperature silo. The energy stored can then be used during high demand periods to deliver additional power. In order to optimize the generation of power, two steam cycles have been integrated within the system by making use of the different heat exchangers available. While one cycle is operating at base-load in order to respond at least to the power requirements associated to power plant auxiliaries, the other enters into operation only during high demand periods. The effect of the different variables involved in the process has been analyzed. The arrangement proposed in this work is able to modify the power output by a ratio of 5. The system is able to operate for 8 h and deliver a net power output of only 30 MWe. A net power output of 150 MWe can be generated during a period of 4 h with a thermal input of 214 MWt by using the energy storage system.