Abstract: A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power includes a flywheel supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with the flywheel, and having a stator with multiple armature windings and a field coil. The field coil generates flux that passes through the armature windings as the rotor rotates to produce torque for accelerating the flywheel during charging, and produces electrical power from the flywheel during discharge. The armature windings are energized by a DC buss that is supplied by a rectifier connected to primary power. The flywheel system provides instantaneous full power capability along with output control for extracting more energy from the flywheel. The field coil is oversized and is powered in standby operation to produce an armature back emf that is at least 75% of the DC buss voltage.

Abstract: A life counter that calculates and records the life utilized of the flywheel in a flywheel energy storage system and indicates when it should be removed from service, based on operational history instead of monitoring for symptoms of failure. The life counter can effectively monitor and measure any or all of the flywheel energy storage system parameters, such as the flywheel structural life, vacuum system life, bearing system life and electronics life. The life counter ensures safe operation of highly stressed flywheels by indicating when the safety margin for the flywheel is reached so that the flywheel energy storage system can be removal from service prior to encountering a risk of catastrophic failure. In some cases, failures may not be preceded by measurable warning symptoms, so removal from service at a calculated end of life would be desirable.

Abstract: The invention, intended primarily for use in a steel flywheel power source (30), provides a vacuum system and a method of maintaining a vacuum inside a flywheel chamber (32) for the life of the power source (30). The vacuum system combines the use of cleaning and de-gassing treatments in the chamber (32) and vacuum tempering of the steel flywheel (31) with the use of a chemical type metal alloy nonevaporable getter, such as zirconium-vanadium-iron, that cooperatively matches the outgassing of the flywheel (31) and chamber (32) by sorbing those gases that are released. The getter may be reactivated throughout the life of the flywheel system by reheating it with an integral heater that is triggered by a timer instead of a vacuum gauge to increase the system reliability, using power taken directly from the energy stored in the flywheel.

Abstract: A wind turbine for generating electrical power from wind energy includes a turbine rotor mounted for rotation in wind, and having multiple blades for converting energy in the wind into rotational energy. A generator is coupled with said turbine rotor such that said turbine rotor drives said generator. The generator has a stationary air core armature that is located in a magnetic airgap between two generator rotor portions. The generator rotor portions have circumferential arrays of multiple alternating polarity permanent magnets attached to ferromagnetic back irons such that the permanent magnets drive magnetic flux back and forth between each rotor portion and through the stationary air core armature. The stationary air core armature has multiple phase windings of multiple individually insulated strand conductor wire that is wound with two separate portions including an active length portion and an end turn portion.

Abstract: A brushless electrical machine, usable as a motor, generator, or alternator, has a rotor that is comprised of a rim portion and a substantially open center portion. The rim portion has a partially hollow core in which a stationary field coil is supported. Current to the field coil generates magnetic flux that circulates in a poloidal flux path in the rim, crossing a single magnetic air gap formed by the rim. Protrusions in the rim located around the circumference form poles all having the same polarity. As the rotor rotates, the flux exiting the poles passes through multiple stationary armature windings around the circumference that are located in the single air gap. An AC voltage is induced in the armature windings from rotation.

Abstract: A flywheel energy storage system has a tubular cylindrical steel flywheel rim that spins, with a peripheral speed greater than 200 meters per second in normal, fully charged operation, about a vertical axis inside an evacuated chamber for energy storage and retrieval. The steel rim is heat treated to a tensile yield strength greater than 100 ksi and plane strain fracture toughness in the hoop direction greater than 70 ksi(in)1/2. A motor generator is coupled to the flywheel for accelerating the angular velocity of the flywheel for storage of energy, and for converting angular inertial of the flywheel back into electrical energy. The motor/generator may include an assembly of permanent magnet pieces substantially filling the circumference of the inner diameter of the flywheel rim.

Abstract: An improved airgap armature for use in brushless rotary electrical machines is constructed with multiple phase windings comprised of wires that are wound onto and bonded to a supporting form constructed from nonmagnetic and electrically nonconductive material. The form has two ends, each with features for holding end turns of the multiple phase windings. The multiple phase windings have active lengths and end turns, with the active lengths being located on one side of the form and the end turns located on the opposite side of the form. The active lengths, which are located in the armature airgap of the electrical machine, lie flat against the form for minimal thickness, and the airgap armature can achieve maximum winding density. The form provides an easy method for winding as well as increased structural integrity in the final armature to enable it to transfer torque between the rotor and stationary housing.

Abstract: A flywheel uninterruptible power supply includes a solid steel cylindrical flywheel levitated for rotation about a vertical axis at tip speeds greater than 250 m/s on magnetic bearings in a low pressure housing. The cylindrical flywheel has a length L and a diameter D, wherein L/D≧1.0. A motor/generator attached to said flywheel accelerates the flywheel and maintains it at operating speed for storage of energy; and decelerates the flywheel for retrieval of the stored energy. The flywheel inertia section operates with a maximum stress of greater than 60% and less than 80% of the material yield stress when spinning at fully charged operating speed. The flywheel is constructed from steel with an ultimate strength greater 150 ksi and a toughness greater than 100 ksi (in)^1/2. The flywheel is a solid steel cylinder that is hardened to centerline structure throughout the axial thickness of the large diameter portion that is greater than 40% martensite.

Abstract: A flywheel uninterruptible power supply has an energy storage flywheel supported in a low pressure containment vessel for rotation on a bearing system. A brushless motor/generator is coupled to the flywheel for accelerating and decelerating the flywheel for storing and retrieving energy. The flywheel is rotated in normal operation at a speed such that the generator voltage is higher than the output voltage. Power supplied to the load from the generator is a regulated output that is maintained at a substantially constant voltage level by using switching regulation of the alternating current voltage generated by the generator. The switching regulation of each generator phase occurs at a frequency equal to or less than twice the frequency of the generator alternating current. As so operated, the flywheel uninterruptible power supply efficiently maintains power to an electrical load during an interruption of primary power by supplying power generated from the flywheel generator.

Abstract: A magnetic bearing system for support of a body, such as an energy storage flywheel, for rotational about a substantially vertical axis of rotation through its center of mass. The bearing system includes a rotating portion and a stationary portion on each axial side of the center of mass. Two or more concentric axially magnetized ring poles on an axial surface of the rotating body are constructed of multiple individual permanent magnet pieces, arranged in rigs inside a containment cup in the end face of the rotor with radially adjacent rings having alternating magnetic polarities. On the stationary portion, two or more concentric axially magnetized pole rings of permanent magnet material cooperate with the rotating ring magnets to produce both an axial attractive force and a radial centering force.

Abstract: A flywheel energy storage system includes a housing adapted to be evacuated and maintained at a low pressure atmosphere, a cylindrical steel flywheel supported for low-loss rotation in the low pressure atmosphere within the housing on a bearing system, a nonevaporable getter for maintaining the low pressure atmosphere in the housing, and a motor/generator for accelerating and decelerating the flywheel for storing and retrieving energy. The motor/generator includes a rotor that is coupled to and rotates with the flywheel, and a stationary stator that cooperates with the rotor for converting between electrical and mechanical energy in the flywheel system and contains electromagnetic coils. The stator has a thin barrier coating for minimizing degradation of the low pressure atmosphere by minimizing outgassing from the stator into the housing.

Abstract: An inductor alternator flywheel system, for converting between electrical and kinetic energy, includes an annular steel flywheel mounted on bearings for rotation about an axis. The flywheel has an inwardly facing radial surface forming multiple protrusions or teeth extending radially inwardly. A yoke has a field coil for producing homopolar flux which creates magnetic poles in the teeth. A cylinder constructed of substantially high permeability material, and having an outer radial surface, is mounted concentrically in the bore of the annular flywheel and is spaced apart radially from the teeth such that an armature air gap is formed between the teeth and the outer surface of the cylinder. A ring of armature coils is mounted within the air gap such that the flux induces an alternating voltage in the armature coils when the rotor rotates about its axis.

Abstract: A flywheel energy storage device, for producing electrical power in an allowable range of operating voltages for an output load, includes an energy storage flywheel supported for rotation on a bearing system, and a brushless motor and a brushless permanent magnet generator for accelerating and decelerating the flywheel for storing and retrieving energy. The generator has a multiplicity of windings for producing output power from the generator by a magnetic coupling that provides output power DC voltage. An out regulator circuit provides variable DC voltage that is maintained within the allowable range for connected loads as the flywheel slows during discharging. The output regulator circuit includes electronic switches for switching connections of the windings to change the number of windings connected to the output to maintain output power DC voltage within the allowable range. The switching occurs less than once per every 10 revolutions of the flywheel.

Abstract: A composite flywheel rotor includes an annular rim mounted on a hub for high speed rotation in an evacuated flywheel enclosure. A smooth epoxy layer is applied to the rim and is cleaned or maintained clean in preparation for a metal coating on the rim. The rim may be baked in a vacuum furnace to drive off the volitiles and water vapor, and a thin metal coating is applied over the entire rim to retard outgassing from the resin in the flywheel composite rim. The metal coating on flywheel rim is preferably aluminum because aluminum adheres well to epoxy and is economical. The metal coating is deposited on the flywheel rim by physical vapor deposition and may be built up after an initial PVD coating by electroplating. A tough protective polymer is applied over the metal coating to protect metal coating from mechanical damage during handling.

Abstract: A brushless electrical machine for converting between electrical and mechanical energy includes a rotor supported on bearings for rotation about an axis of rotation, and a stator that is stationary and magnetically acts upon the rotor. The rotor includes two ferromagnetic rotor portions separated by a magnetic insulator, forming an axial armature air gap between the ferromagnetic rotor portions. At least one of the two ferromagnetic rotor portions has multiple axial extending protrusions facing the axial armature air gap around a circumference. An air core armature having multiple phase windings is located in the axial armature air gap. A ferromagnetic yoke and homopolar flux generator are mounted to the stator. The homopolar flux generator generates homopolar flux in the protrusions of the rotor and the ferromagnetic yoke forms two rotor-to-stator air gaps with the rotor.

Abstract: A flywheel energy storage system includes an energy storage flywheel supported for rotation about a substantially vertical axis on a combination bearing system comprised of a mechanical and a magnetic bearing. A motor and generator accelerates and decelerates the flywheel for storing and retrieving energy. The mechanical bearing is located at one axial end of the flywheel and provides axial downward force to the flywheel and is connected to the mechanical rolling element bearing using a low radial stiffness connecting element. The magnetic bearing is located at the axial end of the flywheel opposite the end with the mechanical bearing and provides axial upward force to support the weight of the flywheel, and also provides passive magnetic radial centering force to the flywheel.

Abstract: A device for preventing power interruptions to a DC bus includes a flywheel supported on bearings for rotation inside a chamber having a drag reducing atmosphere within a container. During charging, the flywheel is driven by an integral brushless permanent magnet excited motor/generator for storing energy, and during retrieval of the stored energy, the flywheel drives and is decelerated by the same motor generator. A closed loop operated synchronous inverter delivers synchronous electrical power to the armature coils of the motor/generator for accelerating the motor/generator. A rectifier connects the armature coils of the motor/generator to the DC bus. Upon an interruption of primary utility power, the motor/generator supplies unregulated voltage power to the DC bus through the rectifier, and the voltage of the unregulated voltage power to the DC bus falls as the flywheel slows during discharge of useable energy from the flywheel through the motor/generator to the DC bus.

Abstract: A flywheel energy storage system that allows high-speed operation with use of mechanical rolling element bearings for radial support of a vertical axis flywheel while they allow it to be mechanically free or unrestrained in the axial direction. Magnetic bearings are used to carry the flywheel weight axially. The axial unconstraint by the mechanical bearings allows the flywheel to freely grow or shrink in axial length from Poisson Effect contraction that occurs when rotating to very high speeds and stress levels as well as from thermal expansions from motor/generator heating or other sources, and also insures that the magnetic bearing carries all of the flywheel weight, thus greatly extending the life of the mechanical bearings. Radially compliant elements mechanically in series with the mechanical bearings provide for a lower radial stiffness, which allows the flywheel to traverse its rigid body resonance at a low speed.

Abstract: The invention, intended primarily for use in a steel flywheel power source (30), provides a vacuum system and a method of maintaining a vacuum inside a flywheel chamber (32) for the life of the power source (30). The vacuum system combines the use of cleaning and de-gassing treatments in the chamber (32) and vacuum tempering of the steel flywheel (31) with the use of a chemical type metal alloy nonevaporable getter, such as zirconium-vanadium-iron, that cooperatively matches the outgassing of the flywheel (31) and chamber (32) by sorbing those gases that are released. The getter may be reactivated throughout the life of the flywheel system by reheating it with an integral heater that is triggered by a timer instead of a vacuum gauge to increase the system reliability, using power taken directly from the energy stored in the flywheel.

Abstract: A flywheel energy storage system includes an energy storage flywheel supported on a bearing system for rotation about a substantially vertical axis inside in an evacuated chamber enclosed within a sealed container. A motor and a generator accelerates and decelerates the flywheel for storing and retrieving energy. A tilt sensor detects if the orientation of the axis of rotation is outside of tolerance limits from vertical and triggers a signal to signal appropriate system functions to protect the system from damage.