CAES system with synchronous reserve power requirements
View Patent ↗A CAES system ( 10 ) includes an air storage ( 18 ), a compressor ( 20 ) supplying compressed air to the air storage, a power generating structure ( 11, 102 ), a heat exchanger ( 24 ), an auxiliary combustor ( 27 ), an air expander ( 30 ), and an electric generator ( 32 ). The system operates in one of modes a) a main power production mode wherein the auxiliary combustor is inoperable and the power generating structure is operable, to produce power by the air expander, fed by the heated compressed air received from the air storage, in addition to power produced by the power generating structure, or b) a synchronous reserve power mode wherein the auxiliary combustor is operable and the power generating structure is inoperable, with compressed air withdrawn from the air storage being preheated by the auxiliary combustor that feeds the air expander, with the air expander expanding the heated air and the generator providing immediate start-up power.
1. A method of operating a Compressed Air Energy Storage (CAES) system, the system including an air storage for storing compressed air, an auxiliary compressor for supplying compressed air to the air storage, a power generating structure, a heat exchanger constructed and arranged to receive heat from the power generating structure and to receive compressed air from the air storage, at least one auxiliary combustor constructed and arranged to receive compressed air from the air storage, an air expander constructed and arranged to be fed with heated air from one of the heat exchanger or the at least one auxiliary combustor and to expand the heated air, and an electric generator, associated with the expander, for producing electric power, the method including
selectively operating the system in one of the following power production modes of operation:
a) a main power production mode by:
ensuring that the at least one auxiliary combustor is inoperable and the power generating structure is operable,
providing heat from the power generating structure to the heat exchanger and providing compressed air from the air storage to the heat exchanger so that the compressed air received from the air storage is heated in the heat exchanger, with the heat exchanger feeding the heated compressed air to the air expander,
expanding the heated compressed air in the expander, and
providing the electric power via the generator in addition to power produced by the power generating structure, or
b) a synchronous reserve power mode by:
ensuring that the at least one auxiliary combustor is operable and the power generating structure is inoperable,
withdrawing compressed air from the air storage,
preheating the withdrawn compressed air in the at least one auxiliary combustor that feeds the air expander,
expanding heated air received from the at least one combustor in the air expander, and
providing substantially immediate start-up power via the generator.
2. The method of claim 1 , wherein the power generating structure is a combustion turbine assembly including a main compressor constructed and arranged to receive ambient inlet air, a main expansion turbine operatively associated with the main compressor, at least one main combustor constructed and arranged to receive compressed air from the main compressor and to feed the main expansion turbine, and an electric generator associated with the main expansion turbine for generating electric power, and
wherein the step of providing heat to the heat exchanger includes providing exhaust heat from the main expansion turbine of combustion turbine assembly.
3. The method of claim 1 , wherein the power generating structure is a diesel generator, and
wherein step of providing heat to the heat exchanger includes providing exhaust gas heat from the diesel generator of the power generation structure.
4. The method of claim 1 , further including operating the auxiliary compressor to supply compressed air to the air storage during off-peak hours.
5. The method of claim 1 , wherein the power generating structure is a combustion turbine assembly including a main compressor constructed and arranged to receive ambient inlet air, a main expansion turbine operatively associated with the main compressor, at least one main combustor constructed and arranged to receive compressed air from the main compressor and to feed the main expansion turbine, and an electric generator associated with the main expansion turbine for generating electric power,
wherein in the main power production mode of operation, compressed air withdrawn from the air storage is preheated in the heat exchanger by receiving exhaust from the main expansion turbine and is sent to the air expander to expand the heated compressed air to exhausted atmospheric pressure for producing the electric power, and at least a portion of airflow extracted from the air expander is injected, under certain conditions, into the combustion turbine assembly increasing power of the combustion turbine assembly.