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. An apparatus comprising:
a cylinder device including a moveable piston in communication with a mechanical linkage to transmit power of gas expanding within a chamber, out of the cylinder device;
a liquid source in fluid communication with the chamber of the cylinder device;
a compressed gas source in selective fluid communication with the cylinder device through valving;
the cylinder device in selective fluid communication with an outlet through the valving; and
a control system configured to control timing of the valving electronically to operate in the following states:
expansion wherein the valving admits compressed gas from the compressed gas source to the cylinder device and does not allow fluid communication between the cylinder device and the outlet such that the compressed gas expands in the cylinder device to drive the piston, and then later the valving blocks fluid communication with the compressed gas source as the compressed gas continues to expand in the cylinder device, and
exhaust wherein the valving allows expanded gas to pass to the outlet.
2. The apparatus of claim 1 further comprising a gas-liquid separator between the valving and the outlet.
3. The apparatus of claim 1 wherein the valving comprises:
a first valve between the compressed gas source and the cylinder device; and
a second valve between the gas-liquid separator and the cylinder device,
wherein during the expansion the first valve is open and the second valve is closed, and then the first valve is closed as the gas continues to expand, and
wherein during the exhaust the first valve is closed and the second valve is open such that expanded gas passes through the gas-liquid separator.
4. The apparatus of claim 1 wherein the source of compressed gas comprises a pressure vessel.
5. The apparatus of claim 1 comprising multiple stages, the source of compressed gas comprising a higher-pressure expansion stage.
6. The apparatus of claim 1 wherein the source of compressed gas comprises a compressor.
7. The apparatus of claim 6 wherein the compressor is in communication with the mechanical linkage.
8. The apparatus of claim 1 further comprising an electrical generator in communication with the mechanical linkage.
9. The apparatus of claim 8 wherein the control system is configured to:
receive a signal; and
based upon the received signal, electronically control the valving to be in the expansion state such that the electrical generator supplies electrical power to a power supply network to cover a ramp up period of a generation asset.
10. The apparatus of claim 1 wherein the mechanical linkage is configured to convert reciprocating motion to shaft torque.
11. The apparatus of claim 10 wherein the shaft comprises a crankshaft.
12. The apparatus of claim 10 wherein the shaft is in selective communication with a source of shaft torque to cause the piston to compress gas within the chamber.
13. The apparatus of claim 12 wherein the shaft comprises a crankshaft.
14. The apparatus of claim 12 wherein the source of shaft torque comprises a motor.
15. The apparatus of claim 12 wherein the control system is configured to control timing of the valving electronically to operate in the following states:
intake wherein the cylinder device is in fluid communication with the outlet and is not in fluid communication with the compressed gas source; and
compression wherein the cylinder device is not in fluid communication with either the outlet or the compressed gas source, and the shaft is in communication with the source of shaft torque.
16. The apparatus of claim 15 further comprising a gas-liquid separator between the valving and the compressed gas source.
17. The apparatus of claim 16 wherein the valving comprises:
a first valve between the gas-liquid separator and the cylinder device; and
a second valve between the outlet and the cylinder device, the second valve allowing fluid communication between the cylinder device and the outlet during the intake, and not allowing fluid communication between the cylinder device and the outlet during the compression.
18. The apparatus of claim 17 comprising multiple stages, the source of compressed gas comprising a higher-pressure stage.
19. The apparatus of claim 1 further comprising a nozzle between the liquid source and the cylinder device.
20. The apparatus of claim 19 wherein the nozzle is configured to produce a spray of droplets wherein a ratio of the total surface area of the droplets, to a number of moles of gas in the chamber, is between about 1-250 m 2 /mol.