Technology Roadmap for Large Electrical Machines Joe Beno, Ph.D. j.beno@cem.utexas.edu (512) 924-2241 Kiruba Haran, Ph.D. kharan@illinois.edu page 1
Grainger CEME/IEEE Workshop Technology Roadmap for Large Electrical Machines April 5 6, 2016, University of Illinois at Urbana-Champaign Industry Academia Government page 2
Why? SIEMENS Financial Tribune GE ABB Offshore Wind Tidal Oil & Gas Mining NASA GE ABB AFRL Aviation Ship propulsion High Speed Rail Defense A number of emerging applications can be significantly transformed by new electric machines and drives technology. Significant progress being made in enabling technologies: new materials, power electronics, manufacturing techniques, etc. Key stakeholders can benefit from expert opinion on projected technology advances in the next decade or so. page 3
2016 Grainger CEME/IEEE Workshop: Technology Roadmap for Large Electrical Machines Workshop goal: Draft a consensus-based technology roadmap with a 5 10 year time frame for large (1-10MW) electrical machines (that convert electrical energy to mechanical, and viceversa) and required auxiliaries. Six working groups on sub-topics: Advanced Non-Cryo Machines: Chair - Joe Beno, UT-CEM Superconducting Machines: Chair - Haran Karmaker, TECO-Westinghouse Enabling Materials: Chair - Tim Haugan, AFRL Modeling Tools: Chair - Scott Sudhoff, Purdue Power Electronics: Chair - Ian Brown, Illinois Institute of Technology System Integration: Chair - Dave Torrey, General Electric Recommendations: Meet periodically at relevant conferences to update roadmap (e.g. next EnergyTech?) Share results broadly through publications in trade journals Engage AIAA and IEEE on collaborative events symposiums, webinars page 4
Status Roadmaps: Advanced Non-Cryo Machines Roadmap document still being worked, needs additional inputs. Some aspects being submitted for publication in IET Special Issue on High Speed Machines Superconducting Machines Roadmap being published in IOP SUST Collaboration: The workshop reinforced the need to bring together electrical engineers and aerospace experts as the industry looks to more electric propulsion technologies. The AIAA (led by the Aircraft Electric Propulsion Working Group - Marty Bradley, Chair) and IEEE (led by the Transportation Electrification Community - Yaobin Chen, Chair) are discussing an MOU for a two-day symposium that will focus on electric aircraft technology, in July 2018. Education: Exploring co-sponsored tutorials and webinars by AIAA & IEEE (+ INCOSE?) page 5
SC Machines Working Group Tabea Arndt, Siemens Corporate Technology, Germany Haran Karmaker, TECO-Westinghouse Motor Company, USA Kiruba S. Haran,University of Illinois at Urbana-Champaign, USA Swarn Kalsi, Kalsi Green Power Systems, USA Rod Badcock, Victoria University of Wellington, New Zealand Bob Buckley, Victoria University of Wellington, New Zealand Timothy Haugan, The Air Force Research Laboratory, Wright-Patterson AFB, USA Mitsuru Izumi, Tokyo University of Marine Science and Technology, Japan David Loder, Rolls-Royce North American Technologies, Inc. Liberty Works, USA James W. Bray, General Electric - Global Research Center, USA Philippe Masson, University of Houston, USA Ernst Wolfgang Stautner, General Electric - Global Research Center, USA page 6
SC Machines Roadmap Summary Projection A. Fully superconducting machines have the potential to attain the highest efficiency by minimizing losses in both the field and armature windings. To attain this, significant advances in ac-capable superconductors must be made. To obtain superior efficiency, the ac losses in a superconducting armature must be less than 0.1% of the machine rating. This has to be achieved within ac flux on the order of 10 3 Tesla/second to be competitive in power density with the partially superconducting machines. B. Partially superconducting machines also have potential for increased specific power, with complete elimination of ferromagnetic components and higher operating flux density. For the full entitlement of these topologies to be realized, HTS conductors capable of high fields at high temperatures need to be matured and composite structures developed to replace relatively heavy vacuum vessels and torque tubes. C. Machines with bulk superconductors is another area of active research, though they are currently at a lower technology readiness level. Improved bulk superconductors capable of operation at liquid nitrogen temperatures and ways to magnetize the bulks at high fields would further increase the potential for these machine types. page 7
SC Machines - recommendations For the promised benefits of superconducting machines to be achieved, further progress must be made in: Unit length of HTS conductors (500m+) Mechanical properties of the conductors Critical current at high temperatures and magnetic fields Supporting materials (insulation, mechanical support) Composite structures Quench detection and control High current brushes Light weight cryostats Dedicated cooling technology/coolers adopted to cooling power needs Specific cost ($/kam) at operating point (temperature and magnetic field) AC loss reduction Description of system level value add Awareness and training of engineers in conventional technologies Creating an economy of scale effect by (small, but steady) market demands page 8
Grainger CEME/IEEE Workshops on Technology Roadmap for Large Electrical Machines Advanced Machine category, focused on MW Class Electrical Machines including cryo-cooled machines but not including Superconducting Machines. Amrhein, Marco, PC Krause and Associates Beno, Joe, University of Texas, CEM Bortoni, Edson, UNIFEI Bowman, Cheryl, NASA Filipenko, Mykhaylo, Siemens Hull, John, Boeing Huynh, Phuc, University of Illinois Klontz, Keith, Advanced Motor Tech Knight, Andy, University of Calgary Krien, Phil, University of Illinois, Urbana- Champaign Madavan, Nateri, NASA Rico, Raul, Siemens Rong, Charles, U.S. Army Research Laboratory Saban, Dan, Meggit Sanchez, Reed, University of Illinois Sarlioglu, Bulent, University of Madison Shah, Manoj, GE Global Research Tangudu, Jagadeesh K, United Technologies Torrey, Dave, General Electric Wu, Thomas, University of Central Florida Yi, Melody, University of Illinois Yoon, Andy, University of Illinois Zhang, Xiaolong, University of Illinois page 9
Some Conventional Metrics Specific Power (W/kg) Power Density (W/m^3) Specific Energy (MJ/kg) Involve Speed Energy Density (MJ/m^3) Torque Per Unit Rotor Volume (TRV, N-m/m^3) page 10
Focus Applications Many variations for machine design and machine topologies Common for machine design to be uniquely optimized for particular applications. Advanced Machines focused on small number of high pay-off applications: Aircraft Propulsion Electrification generally employing distributed electric propulsor motors and a smaller number of turbine driven generators Stand-Alone Micro-Grids that are sufficiently large to benefit from MW class electric machines Renewable Energy Generation that interfaces with large utility grids, generally wind generation. Focus applications considered as high pay-off because they: Have a high pay-off for society Represent unique opportunities at this time in our nation s history Also have large benefit to other applications Are synergistic with each other (e.g., large commercial electric aircraft are micro-grids with unique challenges) Have a high level of funding support. page 11
Most Relevant Transmission Systems Aircraft Propulsion Electrification: Often powered by high-speed turbo-generators feeding variable voltage dc bus, fixed frequency ac bus, or variable frequency ac bus ac bus frequencies often fixed by the gas-turbine, possibly with a fixed reduction. Stand-Alone Micro-Grids (e.g., electric ship, hybrid electric combat vehicles with pulse weapons): Often powered by high-speed turbo-generator or diesel generator feeding a variable voltage dc bus, fixed frequency ac bus, or variable frequency ac bus Load requirements often determine type of bus. Renewable Energy Generation: Interfaces with large utility grids Bus operates at a fixed frequency, fixed voltage, stiff, highly regulated grid. Machine types for focus applications often depend on type of power transmission system. page 12
Considerations for Optimization of Machine Size, Mass and Efficiency Basic physics of rotating electrical machines that impact size/mass: Power equals torque times rotational speed: P = w Torque Torque is function of the air gap magnetic radial and circumferential fields produced by the rotor and stator (B r and B q ); Torque = radius airgap s (B q B r / m o ) da = radius airgap (length rotor * 2 * pi * radius airgap ) < B q B r > airgap / m o = 2 Volume rotor < B q B r > airgap / m o where < > denotes average value Airgap fields: limited by motor material properties limited to ~ 0.5 to 1.5 Tesla for traditional iron-core machines. page 13
Considerations for Optimization of Machine Size, Mass and Efficiency (cont) Torque = 2 Volume rotor < B q B r > / m o B airgap limited by material properties in the motor Torque per unit Rotor Volume (TRV) is often used figure of merit for evaluating machine size Stator surrounds the rotor, adding to the overall machine volume and mass To maximize TRV: Maximize flux density in airgap and minimize space dedicated to other components (e.g., windings). Large machines win because they have: Enough space to accommodate liquid cooling to operate at higher current densities and reduce space devoted to windings Typical TRVs Motor Type TRV (kn-m/m^3) Fractional horsepower, totally enclosed, fan cooled industrial motors 1.4 4 Integral horsepower totally enclosed, fan cooled industrial motors 15 30 High-performance servos 20 45 Aerospace machines 45 75 Very large Liquid cooled machines 130 220 Enough surface area to accommodate high pole count and reduce backiron thickness page 14
Considerations for Optimization of Machine Size, Mass and Efficiency (cont) TRV Comments and Consequences: Minimum required rotor volume of electric machine is effectively determined by the required machine torque and material properties. True for all rotating electromagnetic devices, including motors, generators, and magnetic gears. For generators, focused on a specified output power, rotor volume and therefore overall generator volume can usually be reduced if the input shaft speed can be increased which serves to decrease the required operational torque (P = t w). Motors often have specified power and specified output shaft speed, which defines required output torque. page 15
Motivation: Look at System Mass Reduction Opportunities Subsystem/Component Mass at Motor/Generator Level 1/20 hp Shaded Pole - General Categories Item grams % of Total Casing (stator, fan, front and back plates) 692 35.4% Stator Laminations 664 34.0% Rotor + Shaft 438 22.4% Windings 160 8.2% Total 1954 3 hp 3-Phase - General Categories Item kg % of Total Casing (stator, fan, front and back plates) 12.715 43.7% Stator Laminations 7.518 25.9% Rotor + Shaft 6.6 22.7% Windings 2.242 7.7% Total 29.075 Mass fractions are consistent over a wide range of motor types and power. Casing is the largest single element in all motors. (~40%) Stator Laminations are second (~30%) Rotor + shaft are third (~20%) Neither the windings (10%) nor the magnets (2%) are major contributors to mass Prius Motor Mass Distribution Item kg % of Total Casing 14.1 38.3% Stator Laminations 10.36 28.1% Rotor + Shaft 6.7 18.2% Windings 4.93 13.4% Magnets 0.77 2.1% Total 36.86 page 16
Motivation: Look at System Mass Reduction Opportunities (cont) Opportunities for Mass Reduction at Motor/Generator Level page 17
Enabling Materials page 18
Aircraft Propulsion Electrification (generally employing distributed electric propulsor motors and a smaller number of turbine driven generators) page 19
Distributed Aircraft Propulsion Majority of large jet-powered transport aircraft have thrust-generating engines under the wings or on the fuselage to minimize aerodynamic interactions on the vehicle operation. Advances in computational and experimental tools and new technologies in materials, structures, and aircraft controls, etc. enable a high degree of integration of the airframe and propulsion. Distributed propulsion fully integrates the propulsion system within an airframe to take exploit the coupling of airframe aerodynamics and propulsion thrust stream by distributing thrust using many propulsors on the airframe. page 20
Distributed Aircraft Propulsion Benefits Improvement in aircraft performance, noise reduction to the surrounding community, and/or providing the capability of Short Take Off Landing (STOL). Reduction in fuel consumption by ingesting the thick boundary layer flow and filling in the wake generated by the airframe with the distributed engine thrust stream. Spanwise high lift via high-aspect-ratio trailing-edge nozzles for vectored thrust providing powered lift, boundary layer control, and/or supercirculation around the wing, all of which enable short take-off capability. Better integration of the propulsion system with the airframe for reduction in noise to the surrounding community through airframe shielding. Reduction in aircraft propulsion installation weight through inlet/nozzle/wing structure integration. Elimination of aircraft control surfaces through differential and vectoring thrust for pitch, roll, and yaw moments. High production rates and easy replacement of engines or propulsors that are small and light. For the multi-fan/single engine core concept, the propulsion configuration provides a very high bypass ratio enabling low fuel burn, emissions, and noise to surrounding communities. Hyun Dae Kim (NASA GRC), Distributed Propulsion Vehicles, 27 th International Congress of the Aeronautical Vehicles, 2010 page 21
Projected Timeframe to Tech Readiness Level 6 Power Level for Electrical Propulsion Technologies benefit more electric and all-electric aircraft architectures: High-power density electric motors replacing hydraulic actuation Electrical component and transmission system weight reduction Superconducting Machines 5 to 10 MW Turbo/hybrid electric distributed propulsion 300 PAX >10 MW Hybrid electric 150 PAX Turboelectric 150 PAX 1 to 2 MW class 2 to 5 MW class Hybrid electric 100 PAX regional Turboelectric distributed propulsion 150 PAX All electric 50 PAX regional (500 mile range) Hybrid electric 50 PAX regional Turboelectric distributed propulsion 100 PAX regional All-electric, full-range general aviation kw class All-electric and hybrid-electric general aviation (limited range) Today 10 Year 20 Year 30 Year 40 Year page 22
Electric Machine Related Technologies That Enable/Accelerate Turbo-Electric and Hybrid Aircraft Electric Machine Topologies: Higher efficiency designs: reduce the losses in the motor through better topologies without sacrificing power density Ironless or low magnetic loss Concepts which allow motor to be integrated into the existing rotating machinery (shared structure) Concepts which decouple motor speed and compressor speed Electric Machine Components and Materials Flux diverters or shielding to reduce AC loss or increase performance Composite support structures Improvements in superconducting wire: especially wire systems designed for lower AC losses Rotating Cryogenic seals Bearings: cold ball bearings, active & passive magnetic bearings; hydrostatic or hydrodynamic or foil for systems w/ a pressurized LH2 source Flight qualification of new components Cryocoolers Flight weight systems for superconducting and cryogenic machines, converters and transmission lines Vehicle and thermal management concepts need to be defined alongside propulsion systems to assure that the full system is lightweight and thermally balanced. page 23
Stand-Alone Micro-Grids (that are sufficiently large to benefit from MW class electric machines) page 24
Advanced Machines for General Purpose Microgrids Connected to 60 Hz terrestrial power grid but with islanding capability, or to provide an extension or smaller scale reproduction of the same terrestrial grid in isolated areas or in emergency situations. These microgrids will probably dominate commercial sector in for 10-15 years Mostly of the conventional 3600 RPM machine types driven by cost. Unlikely that the commercial suppliers of these microgrids will embark on an extensive R&D effort. Exceptions: Mobile applications (e.g. quick response unit for disaster relief) Non-permanent reconfigurable installations (e.g. forward operating bases). Current state of the art in commercially viable portable megawatt scale power generation systems: Skid or trailer mounted gas turbines driving generators at 1,800 or 3,600 rpm through a speed reducing gearbox to provide 60 Hz output Typically designed for industrial applications 3 MW system weighs on the order of 65,000 lbs, transported overland by tractor trailer. Technology development most likely to take place in this area is in modular, MW-scale portable power systems capable of flexible customization and rapid transport page 25
Technology Roadmap As Seen By the US Navy Primary Microgrids of Interest: Variable frequency including DC and variable voltage page 26
Some State of the Art Considerations for Improving Performance of Microgrid Machines High tip speeds, high frequency, high shaft speeds: ~ 300 m/s; > 300 m/s may require vacuum Allowable stress/strain limits: Inconel, Titanium and a high performance Toray T1000G graphite composite Operating temperature limits: typically ~ 220 C Slot current density: typically 5 MA/m^2 advanced state of the art for the ac armature winding slot current density. For dc field windings, a value closer to 8 MA/m^2 Soft magnetic materials: M19, M43 Hiperco page 27
Projections From Commercial Designs of Size Reduction for 25 MW Generators Text page 28
Roadmap for Advanced Machines for Microgrids for the Next 10 15 Years Roadmap for advanced machine development for stand-alone microgrids should include the following general tasks Demonstration of reliable, multi-phase, MW level machines at frequencies higher than 200 Hz Demonstration of a composite enclosure machine performance Demonstration of a cost effective, reliable liquid cooled windings in both stator and rotor Demonstration of new concepts for noise abatement Material development: higher strength composite filaments for banding insulation systems rated for operation above 220 C soft magnetic materials with improved magnetic, mechanical, chemical properties hard magnetic materials with better performance and less dependent on strategic elements Development of a generator designed with the HIA topology with power density comparable to that of wound rotor or permanent magnet machines Study the potential system advantage of using doubly-fed machines and their attendant converters in a microgrid application. page 29
Renewable Energy Generation (that interfaces with large utility grids, generally wind generation) Under development : Dave Torrey, GE Global Research page 30
Upcoming Events IEEE and AIAA Electrification of Aircraft Transportation Symposium, Summer 2018, Cleveland page 31
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