Transient energy systems and methods for use of the same

• US 7,425,807 B1
• Filed: 11/29/2006
• Issued: 09/16/2008
• Est. Priority Date: 11/29/2006
• Status: Expired due to Fees

• Current Assignee: Piller USA, Inc. (Langley Holdings PLC)
• Original Assignee: Active Power Incorporated
• Inventors: Perkins, David E, Andrews, James A, Badger, David A, Schuetze, Karl T, Logan, Scott D, Hudson, Robert S
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US11/606,434
• Time in Patent Office: 657 Days
• Field of Search: 318/161, 318/150, 745/721, 322/4
• US Class Current: 318/161
• CPC Class Codes: F01D 15/10 Adaptations for driving, or combinations with, electric generators
• CPC Class Codes: F02C 1/04 the working fluid being heated indirectly in a fluidised-bed combustor F02C3/205
• CPC Class Codes: F02C 6/14 Gas-turbine plants having means for storing energy, e.g. for meeting peak loads
• CPC Class Codes: H02J 15/007 involving storage in the form of mechanical energy, e.g. fly-wheels
• CPC Class Codes: H02K 7/025 for power storage
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids
• CPC Class Codes: Y10T 74/2117 Power generating-type flywheel

Abstract

This disclosure relates to transient energy systems for supplying power to a load substantially instantaneously on demand. Transient energy systems may include a flywheel coupled the rotor of an induction motor generator. One embodiment of the disclosure refers to systems and methods for reducing loads on a bearing in a transient energy system. In another embodiment, the disclosure refers to an induction motor generator that is optimized for high power transient power generation, yet low power motor operation. Yet another embodiment of the disclosure refers to using a flywheel as a drag pump to cool components of a transient energy system. In yet another embodiment, a slip control scheme is discussed for regulating a DC bus. In yet a further embodiment of the disclosure a method is provided for reducing unnecessary turbine starts by making turbine start a function of the rotational velocity of a flywheel.

Claims

1. A flywheel energy storage system, comprising:

a flywheel that rotates about a substantially vertical axis in an atmospheric environment; and

a transient induction motor generator (IMG) comprising;

rotor circuitry mounted to the shaft and having rotor circuitry resistance and reactance, the flywheel mounted to the shaft; and

stator circuitry mounted to a non-rotatable portion of the transient IMG and having stator circuitry resistance and reactance,

wherein the values of the rotor circuitry resistance and reactance and the stator circuitry resistance and reactance are such that the transient IMG generates sufficient power in a generation mode to fully supply electrical power to a critical load and charge a DC bus.

2. The system of claim 1, further comprising:

conversion circuitry coupled to a DC bus and the IMG, the conversion circuitry operative to;

provide a low level current from the DC bus to the IMG during a motor mode; and

provide a high level current from the IMG to the DC bus during the generation mode.

3. The system of claim 1, wherein the transient IMG is operative to rotate the flywheel in a motor mode within a predetermined flywheel speed range, the speed range determined by a plurality of performance requirements.

4. The system of claim 3, wherein the plurality of performance requirements comprise energy storage requirements, material property limits, drag loss requirements, and packaging constraints.

5. The system of claim 1, further comprising a flywheel noise reduction enclosure which is constructed to extend around at least a portion of the flywheel.

6. The system of claim 5, the flywheel noise reduction enclosure comprising:

at least one inner exhaust port fluidically coupled to receive gas being driven by the rotating flywheel;

at least one outer exhaust port fluidically coupled to the atmospheric environment and to the at least one inner exhaust port, the at least one outer exhaust port is offset with respect to the at least one inner exhaust port to provide at least one baffle through which the gas traverses before exiting out of the at least one outer exhaust port.

7. The system of claim 1, further comprising control circuitry operative to:

monitor DC bus voltage level of the DC bus; and

switch the transient IMG from a motor mode to the generation mode when the DC bus voltage level drops below a first predetermined voltage level,

wherein the transient IMG is operative to charge the DC bus before the DC bus voltage level drops below a second predetermined voltage level.

8. A method for using flywheel energy storage system to prevent substantial reduction of voltage on a DC bus, the flywheel energy storage system comprising:

a flywheel that rotates about a substantially vertical axis in an atmospheric environment;

a transient induction motor generator (IMG) comprising;

rotor circuitry mounted to the shaft and having rotor circuitry resistance and reactance, the flywheel mounted to the shaft; and

stator circuitry mounted to a non-rotatable portion of the transient IMG and having stator circuitry resistance and reactance,

wherein the values of the rotor circuitry resistance and reactance and the stator circuitry resistance and reactance are such that the transient IMG generates sufficient power in a generation mode to fully supply a critical load and charge a DC bus, the method comprising;

generating power in the generation mode to fully supply the critical load and charge the DC bus.

9. The method of claim 8, further comprising:

monitoring a DC bus voltage level of the DC bus;

switching the transient IMG from a motor mode to the generation mode when the DC bus voltage level drops below a first predetermined voltage level; and

charging the DC bus before the DC bus voltage level drops below a second predetermined voltage level.

10. The method of claim 8, further comprising:

providing a low level current from the DC bus to the IMG during a motor mode.

11. The method of claim 8, further comprising:

providing a high level current from the IMG to the DC bus during the generation mode.

12. The method of claim 8, further comprising:

rotating the flywheel in a motor mode within a predetermined flywheel speed range, the speed range determined by a plurality of performance requirements.

13. The system of claim 12, wherein the plurality of performance requirements comprise energy storage requirements, material property limits, drag loss requirements, and packaging constraints.

14. The system of claim 8, further comprising:

reducing windage noise generated by the rotating flywheel.

15. The system of claim 8, further comprising:

rotating the flywheel, the rotating flywheel providing a high-to-low pressure drop across the transient IMG which causes ambient air to flow through the transient IMG; and

cooling at least a portion of the transient IMG with the ambient air.

16. The method of claim 8 further comprising:

providing a slip demand;

generating a stator frequency based on the slip demand and a received mechanical frequency;

integrating the stator frequency to provide a phase angle sweep at the stator frequency; and

scaling the slip demand to provide a scaled slip demand; and

adjusting the phase angle of the integrated stator frequency with the scaled slip demand.

17. The method of claim 8 being implemented in a system comprising a compressed gas system, the method further comprising:

using the compressed gas system to provide backup power to a load;

monitoring step changes in the load demand, the step changes comprising sudden step changes; and

using the flywheel energy system to assist the compressed gas system in compensating for step changes in the load by supplying power to the load in the event of a sudden increase in load demand and absorbing power produced by the compressed gas system in the event of a sudden decrease in load demand.