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A High Useable Energy Density Flywheel System Making Solar-Powered HALE UAV a Realistic Technology
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Abstract
Proposed high altitude long endurance (HALE) unmanned aerial vehicle (UAV) concepts for solar powered aircraft indicate that energy storage devices will be required that significantly improve power, energy density, efficiency, and depth-of-discharge over state-of-the-art electrochemical (NiH2) batteries, without which these aircraft systems cannot become a reality. Flywheel energy storage systems offer the potential for making these systems concepts practical. However, current concepts for flywheel energy storage systems rely on energy conversion and power generation approaches that limit the available energy for aircraft use to near 60% of the fully charged capacity of the fly wheel, with efficiencies below 90%. With useable specific energy capacities below 50 Whr/kg, these systems are in capable of enabling solar-powered HALE UAV technology.
In this paper, the performance of a high-power, ultra-low loss, “ironless” motor/generator design is outlined as part of a supercritical self-balancing flywheel energy storage module (FESM). The super high-speed “ironless” generator design enables a 99% energy conversion efficiency and a 90% depth-of-discharge (DOD). The design approach outlined combines the ironless stator design with a super sonic magnet array (> Mach 1.5) to achieve a cruise power output of 9 kW for 10 hours, and peak power output capability of 275 kW over the full range of the module. Analytical trade studies indicate stator power losses well below 10's of watts at cruising power, with maximum losses of 4 kW associated with 275 kW pulse output at minimum generator speed. Stress analyses indicate critical components affecting energy storage capacity are flywheel hub stress, hub-to-rotor interface stresses, and magnet contact stresses. Analysis indicates a low stress flywheel hub approach provides a flywheel specific energy of 120 Whr/kg, and unit specific energy of 84 Whr/kg. Electromagnetic analyses indicate useable specific energy of 75 Whr/kg, which is enabling for HALE UAV technology.
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Authors
Citation
Swett, D. and Ramirez, H., "A High Useable Energy Density Flywheel System Making Solar-Powered HALE UAV a Realistic Technology," SAE Technical Paper 981276, 1998, https://doi.org/10.4271/981276.Also In
References
- Halbach, K. July 1986 “Specialty Magnets,” Lawrence Berkeley Laboratory Report LBL-21945 Berkeley, CA
- Hanselman, D.C. 1994 “Brushless Permanent-Magnet Motor Design,” McGraw-Hill, Inc. New York
- Jensen, C.C. Profumo, F. Lipo, T.A. 1992 “A Low-Loss Permanent Magnet Brushless dc Motor Utilizing Tape Wound Amorphous Iron,” 646 651 IEEE Transactions on Industry Applications November
- Rahman, M.A. 1979 “High efficiency permanent magnet synchronous motors,” 561 564 Conf. Rec. 1979 IEEE Industrial Applications Soc. Ann. Mtg.
- Reinhardt, K.C. Lamp, T.R. Geis, J.W. Colozza, A.J. 1996 “Solar-Powered Unmanned Aerial Vehicles,” 41 46 Proceedings of the Intersociety Energy Conversion Engineering Conference Washington, D.C.
- Richter, E. Miller, T.J.E. Neumann, T.W. Hudson, T.L. 1984 “The Ferrite Permanent Magnet ac motor - A Technical and economic assessment,” 1353 1358 Conf. Rec. 1984 IEEE Industrial Applications Soc. Ann. Mtg.
- Swett, D.W. Shiflett, G.R. 1997 “Edge Stresses in a Composite Strip Subjected to Axial Temperatures, Part I: Development of the Theoretical Solution,” Journal of Composite Materials 31 13
- Swett, D.W. 1994 “Analysis and Design of a High Energy Density Composite Material Flywheel,” presented at the Second Annual General Motors Hughes Electronics Advanced Composite Materials Symposium Tuscon, AZ
- Swett, D.W. 1994 “Dynamic Analysis of a Flexible Hub Composite Flywheel Assembly” presented at the Third Annual Hughes Electronics Structural and Thermal Analysis Workshop and Symposium El Segundo, CA
- Vinson, J.R. Sierakowski, R.L. 1987 “The Behavior of Structures Composed of Composite Materials” Martinus Nijhoff Publishers Dordrecht, The Netherlands