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 valve configured to selectively admit compressed gas to a cylinder;
a piston moveable within the cylinder in response to expansion of the compressed gas;
a rotating shaft configured to be driven by the piston via a linkage;
a nozzle configured to effect gas-liquid heat exchange in the cylinder; and
a host computer comprising a processor in electronic communication with a non-transitory computer-readable storage medium, the non-transitory computer readable storage medium having stored thereon one or more codes to instruct the processor to,
receive a first input signal indicating a torque of the rotating shaft;
calculate an output power from the first input signal; and
based upon the output power, control a timing of the valve.
2. The apparatus of claim 1 wherein the non-transitory computer readable storage medium has code stored thereon to instruct the processor to control the timing of the valve to admit a larger quantity of the compressed gas when a greater amount of output power is desired from a given expansion cycle.
3. The apparatus of claim 1 wherein the non-transitory computer readable storage medium has code stored thereon to instruct the processor to control the timing of the valve to admit a smaller quantity of the compressed gas when a lesser amount of output power is desired from a given expansion cycle.
4. The apparatus of claim 1 wherein the piston comprises a solid piston.
5. The apparatus of claim 1 wherein the piston comprises a liquid.
6. The apparatus of claim 1 wherein the linkage comprises a piston rod.
7. The apparatus of claim 6 wherein the piston rod is connected to the rotating shaft comprising a crankshaft.
8. The apparatus of claim 7 wherein the piston is single-acting.
9. The apparatus of claim 7 wherein the piston is double-acting.
10. The apparatus of claim 1 wherein the linkage comprises a hydraulic liquid.
11. The apparatus of claim 1 wherein the timing of the valve is controlled according to a desired expansion ratio.
12. The apparatus of claim 11 wherein the non-transitory computer readable storage medium has stored thereon one or more codes to instruct the processor to:
receive a second input signal indicating a pressure within a pressure vessel from which the compressed gas is flowed to the cylinder; and
control the timing of the valve based upon the first input signal and the second input signal.
13. The apparatus of claim 12 wherein the timing is adjusted dynamically as the pressure vessel depletes.
14. The apparatus of claim 1 wherein the non-transitory computer readable storage medium has code stored thereon to instruct the processor to control the timing of the valve to admit a quantity of the compressed gas such that when the piston reaches an end of an expansion stroke, a desired pressure within the cylinder is achieved.
15. The apparatus of claim 14 wherein the desired pressure is approximately equal to a pressure of a next lower pressure stage or to atmospheric pressure.
16. The apparatus of claim 14 wherein the desired pressure is within 20 psi of a next lower pressure stage or of atmospheric pressure.
17. The apparatus of claim 1 wherein the valve is also configured to selectively exhaust expanded gas from the cylinder.
18. The apparatus of claim 1 further comprising a second valve configured to selectively exhaust expanded gas from the cylinder.
19. The apparatus of claim 1 wherein the shaft is in selective communication with a source of shaft torque to cause the piston to compress gas within the cylinder.
20. The apparatus of claim 19 wherein the source of shaft torque comprises a motor.