Rotating Machines as Energy Storage and Power Management Systems
Mike [email protected]
February 10, 2010
Electric Power
Space
Transportation
• Advanced Generators
• Electric Grid Control
• Energy Storage
• Distributed Generation
Technology
• Advanced Trains
• Hybrid Vehicles
• Active Suspension for Vehicles
• Wheel Motors
• Intelligent Highways
• Space Power
• Electromagnetic Launch
• Satellite Attitude Control
Defense• Missile and Aircraft Launcher
• All Electric Ship
• Advanced Wheeled and
Tracked Vehicles
• Electromagnetic Guns
• Electromagnetic Armor
Oil & Gas• Exploration• Transmission
Biotech• Electromechanical cell
manipulation
Areas of TechnologyVG 12983a
Flywheel Energy Storage
*Holm et. al., “A Comparison of Energy Storage Technologies as Energy Buffer in Renewable Energy Sources with respect to Power Capability.”
Wikipedia definition: “A flywheel is a mechanical device with a significant moment of inertia used as a storage device for rotational energy.”
Flywheels have a much broader range of usage than given credit for.
Kinetic Energy
*Burr, “Mechanical Analysis and Design, 1981
Specific Strength of Selected Materials
Flywheel energy storage efficiency is dependent on material and mass distribution
Flywheel Highlights
• Conducted flywheel tests, including
– Flywheel only tests to identify failure modes and structural margins
– Flywheel burst tests to test candidate containment designs
• Demonstrated life of more than 110,000 cycles with a 50% DOD
Containment System
MagneticBearings
Gimbal Shaft
Motor Generator
Composite Flywheel
Backup Bearings
VG 12973e
Flywheel Challenges• Losses
– Vacuum air gap significantly reduces windage losses at the price of vacuum pump auxiliary
– Bearings• Roller bearing require lubrication• Magnetic bearings expensive and require touch-down bearings• Superconducting bearings need development
• Carbon fiber material and manufacturing cost– Demand for high modulus/high strength carbon fiber– Industrial participation/competitiveness will bring mfg cost down
• Flywheel safety– Design margin– Flywheel health monitors/fault protection– Containment
Kinetic Energy Storage
Application dictates flywheel topology that meets energy and power requirements
VG 12973a
Non-Integrated Topology Partially-Integrated Topology Fully-Integrated Topology
Flywheel Spin Tests• Flywheel tests to-date:
– Numerous burst tests (modified design for containment proof tests)
– Loss of vacuum test– Over-speed “As Built” Test
- Preload loss- 1120 m/s- Benign and recoverable
– Coupon/Fatigue tests
VG 12973f
Hydroburst test coupon High temperature & pressure autoclave
4-axis filament winder
Multi-ring preloaded flywheel
Technical Successes - Flywheel
• Record tip speed for composite flywheel/arbor assembly (1.34 km/s)
• Key features – Composite structural arbor design – Detailed material and
manufacturing process QA
VG 12973g
Parameter NASA FESS ALPS System Bus System CHPS SystemFunction Energy Storage Load Leveling Load Leveling Leveling/Pulsed
Energy Stored (kWhr) 3.6 133 2 7
Peak Power (kW) 5 2,000 150 5,000
Typical Discharge Time 30 minutes ~ 3 minutes 30 seconds 3 seconds
Rotational Speed (RPM) 53,000 15,000 40,000 20,000
Machine Weight (lbs) 250 19,000 450 1,100
Motor/Generator Permanent Magnet Induction Permanent Magnet Permanent Magnet
Topology Partially Integrated Non-Integrated Partially Integrated Fully Integrated
Cooling Cold Plate Air/Oil and Water Oil and Water Oil
Bearings Homopolar Magnetic Hompolar Magnetic Homopolar Magnetic Homopolar Magnetic
Backup Bearing Duty Limited Limited Significant Significant
Gimbal NA (Torque Balanced) Required Required Required
Flywheel Design CEM Cylindrical CEM Cylindrical CEM Cylindrical CEM Mass Loaded
Rotor Tip Speed (m/s) 920 1,015 935 600
Safety RSL&NDE RSL & Containment RSL&Containment RSL
Designed DesignedBuilt & tested
Built & tested
CEM Flywheel Comparison
FW Battery (+ Electronics) (+ Electronics)
Nominal Power 4.1 kW 4.1 kWPeak Power 6.6 kW 6.6 kWEnergy Delivered 5.6 kW-hr 4.6 kW-hrContingency Power 2 orbits 1 orbitLife Expectancy >15 years 5-6 years
Flywheel Energy Storage System for the International Space Station (FESS)
• Operations advantages– Higher round trip efficiency– Known state-of-charge– Offer more flexibility in
charge/discharge profiles– Doubled contingency power
(energy)
• Significant life cycle cost savings– Reduced logistics (up-mass & down-mass)– Reduced maintenance (EVA- IVA Hr/Yr)
Advanced Locomotive Propulsion (ALPS) Program Flywheel
• electrical load leveling for hybrid electric locomotive
• flywheel stores 480 MJ• @ 15,000 rpm• 2 MW motor/generator – ~3 min discharge
• Testing with high input and output power
VG 12973h
Backup BearingsRadial BearingStator WindingPermanent Magnet RotorComposite Flywheel
Combo Bearing
Transit Bus FlywheelEnergy Storage:
Power:2 kWhr stored, 1 kWhr delivered150 kW peak, 110 kW cont.,Between 30,000 and 40,000 RPM
Composite tip speed:Application:
930 m/s at 40,000 rpmPower averaging for 15 tonHybrid Electric Bus
Permanent Magnet
AluminumCeramic
WindingsTitaniumInconelCompositeStainless SteelSteel
Materials
CEM Flywheel Energy Storage Systems for Military Applications
VG 11536.ppt
Electromagnetic Aircraft Launch System (EMALS) Energy Storage System
(2006)
Iron Core Pulse Alternator800 MW, 10.5 kW-h
(1987)
Composite Rotor Pulse Alternator664 MW, 2.5 kW-h
(1991)
S 4101.0607
S 3010.1993
Composite Rotor Pulse Alternator2.4 GW, 11 kW-h
(1995)
S 3910.1748
Composite Rotor & Stator Pulse Alternator3 GW, 6.4 kW-h
(1997)
?
Current EM Gun Power SupplyResearch is Ongoing at CEM
(2009)
Homopolar Generator (HPG) Flywheels• Faraday disks• 1/10s to 10s of second discharge rates• Very high current/low voltage machines• CEM HPGs used for variety of applications
– Large x-section resistive welding—12” sch. 60 pipe welds– Railguns—90mm, 9MJ muzzle energy – High-field, single-turn magnets—9MA, 20T toroidal magnet
60 MJ HPG Set—6 ea, 100V, 1.5MA/gen
All Iron Rotating (AIR) HPG6.2 MJ, 50 V, 750 kA
Flywheel vs. Electrochemical Energy Storage
100,000 1,000,000
1 236
4
5
9
10
11
12
13
7
8
Summary
• Advanced carbon materials and manufacturing methods enable– Energy densities comparable to chemical storage devices– Extremely high power densities for pulsed power applications
• Flywheels capable of wide range of energy storage applications: .01s to 1800s
• Many challenges have been overcome: additional R&D could improve energy storage capacity, efficiency and usage