Systems and Methods for Improving Drivetrain Efficiency for Compressed Gas Energy Storage

• US 20100229544A1
• Filed: 03/12/2010
• Published: 09/16/2010
• Est. Priority Date: 03/12/2009
• Status: Active Grant

• Current Assignee: SustainX, Inc. (General Compression, Inc.)
• Original Assignee: SustainX, Inc. (General Compression, Inc.)
• Inventors: McBride, Troy O., Bollinger, Benjamin R., Schaefer, Michael
• Granted Patent: US 7,963,110 B2
• Time in Patent Office: Days
• US Class Current: 60/413
• CPC Class Codes: F15B 1/024 used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
• CPC Class Codes: F15B 21/08 Servomotor systems incorporating electrically operated control means F15B21/02, F15B21/065 take precedence
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators
• CPC Class Codes: F15B 2211/216 the pressure sources being pneumatic-to-hydraulic converters
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/6655 Power control, e.g. combined pressure and flow rate control
• CPC Class Codes: H02J 15/006 in the form of pneumatic energy, e.g. compressed air energy storage [CAES] accumulators for supplying fluid under pressure F15B1/04
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator

Abstract

Generally, the invention relates to power generation and energy storage. In particular, to systems and methods for providing constant power from hydraulic inputs having widely-varying pressures. More particularly, the invention relates to hydraulic-pneumatic energy storage and recovery systems that include either a fixed or variable displacement hydraulic motor and control systems that allow a user to maintain constant power from the fixed or variable displacement hydraulic motor.

Claims

1. A system for providing a constant electrical output from a compressed gas energy storage and recovery system, the system comprising:

a hydraulic-pneumatic energy storage and recovery system configured to provide a varying pressure profile at, at least one outlet;

a variable displacement hydraulic motor-pump in fluid communication with the at least one outlet; and

a control system in communication with the variable displacement hydraulic motor-pump for controlling at least one variable selected from the group consisting of pressure, piston position, power, flow rate, torque, RPM, current, voltage, frequency, and displacement per revolution.

2. The system of claim 1 further comprising an electric motor-generator mechanically coupled to the variable displacement hydraulic motor-pump, wherein the variable displacement hydraulic motor-pump converts hydraulic work to mechanical energy to drive a drive shaft of the electric motor-generator, and the electric motor generator converts the mechanical energy to electrical energy.

3. The system of claim 2 further comprising power electronics in communication with the electric motor-generator to synchronize an output of the electric motor-generator to a power supply.

4. The system of claim 1, wherein the control system is configured to vary the displacement per revolution of the variable displacement hydraulic motor-pump in response to the varying pressure profile at the at least one outlet.

5. The system of claim 1, wherein the control system varies flow rate inversely with pressure as a function of time.

6. The system of claim 2, wherein the control system is configured to maintain at least one of constant torque or RPM of the variable displacement hydraulic motor-pump to maintain an output by the electric motor-generator.

7. The system of claim 2, wherein the control system controls the variable displacement hydraulic motor-pump to maintain an output at the electric motor-generator that matches a required input for a power supply.

8. The system of claim 1 further comprising a graphical display in communication with the variable displacement hydraulic motor-pump and configured to display one or more parameters selected from piston position, power, pressure, flow rate, torque, RPM, current, and voltage versus time.

9. The system of claim 1, wherein the hydraulic-pneumatic energy storage and recovery system uses staged hydraulic conversion to provide the varying pressure profile and comprises:

a cylinder assembly including a staged pneumatic side and a hydraulic side, the sides being separated by a movable mechanical boundary mechanism that transfers energy therebetween; and

a compressed gas storage system in fluid communication with the cylinder assembly.

10. The system of claim 9, wherein the hydraulic-pneumatic storage and recovery system further comprises a heat transfer subsystem to provide isothermal expansion and compression of the gas.

11. A system for providing a constant electrical output from a compressed gas energy storage and recovery system, the system comprising:

a hydraulic-pneumatic energy storage and recovery system configured to provide a varying pressure profile at, at least one outlet;

a fixed displacement hydraulic motor-pump in fluid communication with the at least one outlet;

an electric motor-generator mechanically coupled to the fixed displacement hydraulic motor-pump; and

a control system in communication with a control device for controlling at least one variable selected from the group consisting of power, flow rate, torque, RPM, current, voltage, and frequency.

12. The system of claim 11, wherein the control system is configured to vary a flow rate of the fixed displacement hydraulic motor-pump in response to the varying pressure profile at the at least one outlet.

13. The system of claim 11, wherein the control device comprises a variable frequency drive coupled to the electric motor-generator to control a load on the hydraulic motor-pump.

14. The system of claim 11, wherein the control device comprises a continuously variable transmission disposed between the hydraulic motor-pump and the electric motor-generator to control a load on the hydraulic motor-pump.

15. The system of claim 11, wherein the control device comprises power electronics in communication with the electric motor-generator to synchronize an output of the electric motor-generator to a power supply.

16. The system of claim 11, wherein the hydraulic-pneumatic energy storage and recovery system uses staged hydraulic conversion to provide the varying pressure profile and comprises:

a cylinder assembly including a staged pneumatic side and a hydraulic side, the sides being separated by a movable mechanical boundary mechanism that transfers energy therebetween; and

a compressed gas storage system in fluid communication with the cylinder assembly.

17. The system of claim 16, wherein the hydraulic-pneumatic storage and recovery system further comprises a heat transfer subsystem to provide isothermal expansion and compression of the gas.

18. A system for providing a constant electrical output from a compressed gas energy storage and recovery system, the system comprising:

a hydraulic-pneumatic energy storage and recovery system configured to provide a varying pressure profile at, at least one outlet;

a digital displacement hydraulic motor-pump in fluid communication with the at least one outlet; and

a control system in communication with the digital displacement hydraulic motor-pump for controlling at least one variable selected from the group consisting of pressure, piston position, power, flow rate, torque, RPM, current, voltage, frequency, and displacement per revolution.

19. The system of claim 18 further comprising an electric motor-generator mechanically coupled to the digital displacement hydraulic motor-pump, wherein the hydraulic motor-pump converts hydraulic work to mechanical energy to drive a drive shaft of the electric motor-generator, and the electric motor generator converts the mechanical energy to electrical energy.

20. The system of claim 19 further comprising power electronics in communication with the electric motor-generator to synchronize an output of the electric motor-generator to a power supply.

21. The system of claim 18, wherein the control system is configured to vary the displacement per revolution of the digital displacement hydraulic motor-pump in response to the varying pressure profile at the at least one outlet.

22. The system of claim 19, wherein the control system is configured to maintain at least one of constant torque or RPM of the digital displacement hydraulic motor-pump to maintain an output by the electric motor-generator.

23. The system of claim 19, wherein the control system controls the digital displacement hydraulic motor-pump to maintain an output at the electric motor-generator that matches a required input for a power supply.

24. The system of claim 18, wherein the digital displacement hydraulic motor-pump comprises:

a high pressure input-output;

a low pressure input-output;

an off-center rotating cam;

a plurality of radial piston assemblies coupled to the off-center rotating cam; and

a control valve arrangement responsive to the control system for operating the hydraulic motor-pump at, at least one of a substantially constant pressure, power output, flow rate, torque, RPM, or displacement per revolution.

25. The system of claim 24, wherein the control valve arrangement comprises pairs of high speed valves in fluid communication with each piston assembly and the control system actuates the high speed valves to control aggregate displacement of the hydraulic motor-pump.

26. The system of claim 24, wherein the digital displacement hydraulic motor-pump further comprises a plurality of high-pressure inputs-outputs and a plurality of low-pressure inputs-outputs.

27. The system of claim 18, wherein the hydraulic-pneumatic energy storage and recovery system uses staged hydraulic conversion to provide the varying pressure profile and comprises:

a cylinder assembly including a staged pneumatic side and a hydraulic side, the sides being separated by a movable mechanical boundary mechanism that transfers energy therebetween; and

a compressed gas storage system in fluid communication with the cylinder assembly.

28. The system of claim 27, wherein the hydraulic-pneumatic storage and recovery system further comprises a heat transfer subsystem to provide isothermal expansion and compression of the gas.

29. A method of providing a constant output from a compressed gas energy storage and recovery system, the method comprising the steps of:

providing a hydraulic-pneumatic energy storage and recovery system configured to provide a varying pressure profile at, at least one outlet;

providing a variable displacement hydraulic motor-pump in fluid communication with the at least one pressure outlet;

providing an electric motor-generator mechanically coupled to the variable displacement hydraulic motor-pump, wherein the variable displacement hydraulic motor-pump converts hydraulic work to mechanical energy to drive a drive shaft of the electric motor-generator, and the electric motor generator converts the mechanical energy an electrical output;

monitoring a pressure of the at least one hydraulic outlet;

monitoring at least one operational parameter of at least one of the variable displacement hydraulic motor-pump or the electric motor-generator; and

operating a control system to vary an operational parameter of at least one of the variable displacement hydraulic motor-pump or the electric motor-generator to maintain at least one output parameter of the system constant.

30. The method of claim 29, wherein the at least one constant output parameter is selected from the group consisting of a torque, RPM, power, voltage, current, and frequency.

31. The method of claim 29, wherein the operational parameter of the hydraulic motor-pump is selected from the group consisting of pressure, piston position, power, flow rate, torque, RPM, and displacement per revolution.

32. The method of claim 29, wherein the operational parameter of the electric motor-generator is selected from the group consisting of power, torque, RPM, current, voltage, and frequency.

33. The method of claim 29, wherein the step of operating the control system includes varying a displacement per revolution of the variable displacement hydraulic motor-pump to maintain the at least one output parameter constant.

34. The method of claim 29, wherein the step of operating the control system includes varying a displacement per revolution of the variable displacement hydraulic motor-pump in response to the varying pressure profile.

35. The method of claim 34, wherein the control system is configured to increase the flow rate of the variable displacement hydraulic motor-pump in response to a decreasing pressure at the at least one outlet.

36. The method of claim 29, wherein the step of operating the control system includes maintaining at least one of constant torque or RPM of the variable displacement hydraulic motor-pump to maintain a constant output at the electric motor-generator.

37. The method of claim 29, wherein the step of operating the control system includes synchronizing an output of the electric motor-generator with a power grid.