Juni 2015 Development of a Superconducting High-Speed Flywheel Energy Storage System W. Walter 8. Braunschweiger Supraleiterseminar 2015
Outline Background SC bearing prototype Technology demonstrator Summary Page 2
Babcock Noell: Member of Bilfinger SE Bilfinger SE Business Segment Industrial Business Segment Power Business Segment Building & Facility Business Segment Construction Piping Systems Power Systems Babcock Noell GmbH Nuclear Services Nuclear Technologies Magnet Technologies Environmental Technologies Page 3
We are Magnet Technology Physicists, Engineers and Technicians work hand-inhand More than 30 years magnet technology experience Cooperation with research institutions and industry WE MAKE RESEARCH WORK! Page 4
Background Liberate superconductivity from the research world BNG is well known as a manufacturer of superconducting magnets for science Extend this know-how to applications beyond science Develop superconducting flywheel for multiple applications Page 5
Storage of Energy a Growth Market Technological solutions are required for increasing problems Rapidly transforming energy markets New challenges for stable grid operation Decentralized generation from renewable sources Imbalances of generation and demand of electric power Unstable network levels: hazard to electrical equipment and grid infrastructure Risk of large scale black outs Measures Global approach: DC-Transmission Power highways Large scale electricity storage Local approach on low- to medium voltage distribution level: Smooth feed-in of fluctuating renewable sources Regulate voltage levels at local nodes Source: Bilfinger Construction GmbH Page 6
Flywheel The Power Storage Energy storage systems by energy density and power density Flywheel Absorption and release of energy in short time Power storage` Short term storage (hours) Low energies (kwh) Source: TU Braunschweig, Prof. Canders Page 7
UPS (Uninterruptible Power Supply) Parameters Performance: 250 kw per unit Capacity: < 5 kwh Maintain mains voltage for more than 20 sec. (until diesel generator starts) Improvement of power quality Benefits No air conditioning and safety infrastructure Long life-time Low maintenance and operating costs Modularity and compactness Source: Bilfinger HSG Page 8
Power Quality Market Parameters Performance: 500 kw per unit Capacity: 5-10 kwh Smoothing/buffering of renewable energy feed-in Grid stabilization and support at local nodes Power management in industry and public transport Applications and benefits Renewable energy producers: Meet feed-in req. of utilities Grid operators: Installation of Flywheels avoid costly line upgrades Industry/transport: Reduce peak power consumption, enhance power quality Page 9
Flywheel Generations Source Powerthru Source Calnetix 1.5 G 2 G Active bearings Composite rotor 3G Passive SC bearing Composite rotor Source Enercon GmbH 1G Active bearings Steel rotor Roll bearings Steel rotor Page 10
Superconducting is better Advantages for flywheels The use of superconducting bearings in a flywheel has the following advantages: Rotor hub Vacuum vessel Low friction Self centering Passive control (compared to electromagnetic solutions) Vacuum compatible Bearing unit Vacuum pump Cryocooler However this solution requires: cryogenic cooling at least to LN2 temperatures additional costs for the HTS material integrated to the system market barrier: novel technology in a conservative market Motor-generator Bearing excitation system (Permanent magnets) Composite rotor ( Flywheel ) ~ = Bidirectional inverter HTS bearing stator (High Temperature Superconductor) Page 11
Roadmap at Babcock Noell Project achievements in the past years 2010 2011 2012 2013 2014 2015 2016 Bearing prototype HTS material tests Technology demonstrator Prototype Page 12
Bearing prototype HTS radial bearing Goals: First experience with HTS bearing design Handling and machining of bulk HTS Develop calculation tools for bearing design Develop tooling for fabrication and assembly Qualification of cooling system Main specs: Internal rotor Air gap 5 mm Design axial stiffness: ~60 kg/mm 30 kg rotating mass Page 13
Bearing prototype Design and development Optimization of the PM side of the bearing using a 2D planar model and current sheet approximation for the SC. 1 2 1.The vector potential at the freezing state is calculated. 2.The freezing state is used as a boundary condition at the surface of the SC while the PM are moved thus the forces and stiffness are calculated. This method overestimates the bearing stiffness but allows comparison between different designs Page 14
Bearing prototype Test station Setup: gear (rotary feedthrough) Modular vacuum vessel Stirling cryocooler 16 W @ 77 K Positioning system for the rotor Clutch in the vacuum side and rotating feedthrough External motor Position measurement system Temperature and vacuum diagnostics activation support bearing: permanent magnets bearing: HTS rotating mass Nächste Schritte: cryocooler Page 15
Bearing prototype Test results The HTS side of the bearing reached nearly 70 K Temperature gradients between the cryocooler tip and the bearing within 2 K Levitation of the 30 kg mass was achieved Displacement after release of 0.7 mm (design 0.5 mm) freezing position Bearing stability up to 85 K (above LN2 limit) Bearing capability > 40 kg/mm up to 80 K test mass levitates after release rapid loss of bearing force Page 16
Material qualification 1/2 Setup Measurement Rotary feedthrough Vertical movement of of permanent magnets Force measurement typical material sample Typical force curve freezing position Permanent magnets HTS magnets vertical movement Cryocooler experimental setup Page 17
Material qualification 2/2 T = 75K T = 75K Full cycle measurement Initial tests results Results with position feedback Page 18
Technology demonstrator Specifications System specifications: power: 250 kw / capacity: 3 kwh 20000 rpm / rotating mass 225 kg Bearing specifications: external rotor with an air gap of 4 mm design axial stiffness at freeze point: -780 N/mm design radial stiffness at freeze point: -430 N/mm Additional components: motor-generator composite materials rotating mass cooling system: LN2 or cryocooler stirling cooler positioning diagnostics HTS bearing support and positioning unit motorgenerator Composite rotating mass support and positioning unit Page 19
Technology demonstrator Test campaign Vacuum 10-4 mbar range 77 K reached < 3 hours using LN2 Attempts with cryocoolers reached 85 K Page 20
Technology demonstrator Rotation and levitation Results: Observation of levitation Levitation of 225 kg rotor at 2.7 mm below freezing point Stable rotation up to 2000 rpm Limits of system: Alignment of the rotating mass No oscillation damper freezing position release of rotor free levitation Page 21
Flywheelprototype Implemented the know-how acquired with the technology demonstrator Specific design for a stand-by system System specifications: Power: 250 kw / capacity: 3 kwh 16000 rpm / rotating mass ~225 kg System tests foreseen in 2016 Page 22
Conclusion Experience has been acquired on all the main components of the flywheel and their integration in the system Design and assembly of a full functioning prototype in 2015 The test infrastructure required to fully characterize the system is available Page 23
THANK YOU FOR YOUR ATTENTION If you have questions or are interested in the project contact me at wolfgang.walter@bilfinger.com Page 24