Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
View Patent ↗A compressed-air energy storage system according to embodiments of the present invention comprises a reversible mechanism to compress and expand air, one or more compressed air storage tanks, a control system, one or more heat exchangers, and, in certain embodiments of the invention, a motor-generator. The reversible air compressor-expander uses mechanical power to compress air (when it is acting as a compressor) and converts the energy stored in compressed air to mechanical power (when it is acting as an expander). In certain embodiments, the compressor-expander comprises one or more stages, each stage consisting of pressure vessel (the “pressure cell”) partially filled with water or other liquid. In some embodiments, the pressure vessel communicates with one or more cylinder devices to exchange air and liquid with the cylinder chamber(s) thereof. Suitable valving allows air to enter and leave the pressure cell and cylinder device, if present, under electronic control.
1. A method comprising:
allowing a compressed gas to enter a cylinder device;
promoting heat exchange between the compressed gas and a liquid within the cylinder device;
causing movement of a moveable member by expansion of the compressed gas within the cylinder device;
generating power from movement of the moveable member;
allowing the expanded gas to leave the cylinder device;
separating the liquid from the expanded gas in a gas-liquid separator; and
flowing the expanded gas from the gas-liquid separator to a next expansion stage.
2. A method according to claim 1 wherein promoting heat exchange comprises spraying a mist of the liquid.
3. A method according to claim 1 wherein promoting heat exchange comprises bubbling the compressed gas through the liquid.
4. A method according to claim 1 wherein valving allows the compressed gas to enter the cylinder device.
5. A method according to claim 4 further comprising controlling a valve timing to admit to the cylinder device a volume of compressed gas to achieve a desired expansion ratio.
6. A method according to claim 4 further comprising dynamically adjusting a valve timing.
7. A method according to claim 6 wherein the valve timing is dynamically adjusted as a compressed gas storage tank depletes.
8. A method according to claim 1 wherein valving allows the expanded gas to leave the cylinder device.
9. A method according to claim 8 wherein the moveable member is configured to be driven by a mechanical linkage to exhaust the expanded gas from the cylinder device.
10. A method according to claim 9 wherein the mechanical linkage is configured to convert reciprocating motion into shaft torque.
11. A method according to claim 10 wherein:
the moveable member comprises a reciprocating piston; and
the mechanical linkage comprises a crankshaft connected to the piston by a piston rod.
12. A method according to claim 11 wherein the piston is driven to exhaust expanded gas to the gas-liquid separator from momentum of the crankshaft and/or from motion of an out-of-phase piston.
13. A method according to claim 1 further comprising:
causing the moveable member to move to compress gas within the cylinder device; and
introducing liquid to the compressed gas.
14. A method according to claim 13 further comprising allowing compressed gas to flow from the cylinder device for separation of liquid from the compressed gas.
15. A method according to claim 1 wherein electrical power is generated from a mechanical linkage with the moveable member.
16. A method according to claim 15 wherein the moveable member comprises a reciprocating piston, and the mechanical linkage converts reciprocating motion of the piston into shaft torque.
17. A method according to claim 16 wherein the mechanical linkage comprises a crankshaft coupled to the piston by a piston rod.
18. A method according to claim 1 wherein electrical power is generated from a hydraulic linkage with the moveable member.
19. A method according to claim 18 wherein the hydraulic linkage comprises a hydraulic motor.
20. A method according to claim 19 wherein the hydraulic motor is in physical communication with an electrical generator through a shaft.
21. A method according to claim 4 further comprising controlling the valving to allow compressed gas to enter the cylinder device and expand to drive an electrical generator in communication with the moveable member to supply electricity over a ramp up period, in response to a signal indicating ramp up of a generation asset.