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Principles of Regenerative Electric-powered Flight J. Philip Barnes 04 April 2014 Update

Principles of Regenerative Electric-powered Flight J. Philip Barnes 04 April 2014 Update . Presentation Contents. Nature’s “Regen” ~ the Great Frigate Bird Regen aircraft elements & operating modes “Windprop” aero design and performance

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Principles of Regenerative Electric-powered Flight J. Philip Barnes 04 April 2014 Update

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  1. Principles of Regenerative Electric-powered Flight J. Philip Barnes 04 April2014 Update Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  2. Presentation Contents • Nature’s “Regen” ~ the Great Frigate Bird • Regen aircraft elements & operating modes • “Windprop” aero design and performance • DC motor-generator, controller, and battery • “Regenosoar” vehicle & system performance • Summary & Recommendations

  3. Nature’s Regen Aircraft ~ the Great Frigate Bird • Flight sustained by atmospheric vertical motion • Energy rate sensor ~ air temp, air pressure...? • Permeable plumage ~ no water landing or takeoff • Feed by surface plucking ~ Pterodactyl heritage? • Thermal day and night up to 2800 m • Lowest wing loading of any bird • Self-contained takeoff • Emergency thrust • Sortie radius to 1800 km • Sortie duration up to 4 days 30-year lifespan Data: Henri Weimerskirch, et.al. Nature Jan 2003 Photography: Phil Barnes Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  4. Regen Aircraft Elements and Operation • Windprop • Fixed rotation direction • Sign change with mode • Thrust, Torque • Power, Current Speed Control Motor Gen Optional solar panel ESU • Energy Storage: • Battery • Ultra capacitor • Flywheel motor-generator • Self-contained takeoff • Emergency cruise/climb • Exploit vertical air motion Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  5. Thermal Updraft Contours Elevation, zo ~ m • 1oC warmer-air column • 20-minute lifetime • ~ solar power x 10 U ~ m/s 1 2 3 Total Energy = Kinetic + Potential 4 Total Energy = Kinetic + Potential + Stored Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  6. Dual-role Propeller andAirborne Wind Turbine

  7. Propeller Wake, Pitch, and Blade Angles Horseshoe Vortices • Wake induces downwash • (normal to local section) • Pitch: • helix length per rotation • htip = 2 p R tan btip • Uniform pitch: • r tanb = R tanbtip • Blade tip angle (btip): • 14o ~ low pitch • 30o ~ high pitch R r • More blades at fixed thrust & diameter: • More wakes (one per blade) • Higher pitch ~ wakes farther aft / rotation • Lower rotational speed, lower tip Mach • Upshot: ~ similar efficiency, 2 to 8 blades Blade angle (b) at radius (r) is measured from rotation plane to the chord line at (r) Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  8. Windprop Blade Angle and Operational Mode b Turbine Propeller Pinwheel L b b v v v w r -L w r w w r w w • Pinwheeling: Zero angle of attack, root-to-tip • - No thrust, no torque, small drag • Efficient prop: Rotate ~115% of “pinwheel RPM,” or fly at 87% of “pinwheel airspeed” • Efficient turbine: Rotate ~ 87% of “pinwheel RPM,” or fly at 115% of “pinwheel airspeed” • Specify symmetrical sections & uniform pitch • Define: “Speed ratio,” s v / vpinwheel = v / [ wr tanb ] Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  9. o o b b = 14 = 30 Low-RPM8 Blades, tip tip 1.0 Efficiency 0.8 c c l_min l_max Blades_btip 2_14o 8_30o 0.6 h Propeller f v / (t w) Turbine t w / (f v) 0.4 0.2 Speed Ratio, s ≡ v / (w R tan btip) 0.0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.0 0.9 Propeller ~ climb Force Coefficient, F ≡ f/(qpR2) 0.8 High-RPM2 Blades, B=8 0.7 B=2 0.6 0.5 0.4 0.3 F Propeller ~ cruise Sym. Sections 0.2 b b tan R r = tan tip Max efficiency 0.30 0.1 Blade Geometry Regeneration Max capacity 0.25 0.0 Regeneration Pinwheel 0.20 R Chord, c/ -0.1 0.15 F= -0.011 @ B=2 Thickness 2 -0.2 0.10 F= -0.008 @ B=8 8 hub -0.3 0.05 Speed Ratio, s≡ v / (w R tan btip) R r / -0.4 0.00 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 0.00 0.25 0.50 0.75 1.00 Windprop Efficiency and Thrust Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  10. How Flow the ElectronsMotor-generator principlesSynergy: motor-gen & windpropDC Voltage conversion

  11. Motor-generator Principles t Electromotive force, e = potential energy / charge = work / charge, (Fp / q) L = 2 N w (D/2) B L e = NDBL w ≡ k w (+) Charge (q) with velocity, V in magnetic field of strength, B: Force vector, F = q V x B L N turns B w Fq e i i Fp Torque, t = 2N (D/2) B (dx/dt) dq = 2N (D/2) B (dq/dt) dx t = NDBiL = NDBL i = k i vi B vq E tw=ei Both modes t Motoring N turns w Fq e i i Fp vi B vq E Change to generator mode: Same direction, rotation, w Same sign for EMF, e Sign change of torque, t Sign change of current, i Generating Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  12. System Motoring and Regeneration Efficiencies Pulse-width modulation (PWM) d ≡ “Duty cycle” ; h ≈ 0.99 d 0.25 (Refs 1,2) Vm Vb Inverter (for brushless MG) h ≈ 0.98 (Ref.3) Rm Rb t+Dt eb Quote regen power here w Torque loss brushes, iron loss, windage... em eb Motor Regen i • "Ideal system efficiency" ignoring controller & torque losses • system motor ≈ t w/(eb i) ≈ e i / (eb i) = e/ eb = k w / eb • system regen ≈ ebi / (tw) ≈ eb i / (ei) = eb / e =eb / (k w) Refs: (1) AiAA 2010-483, Lundstrom, p.8 ; (2) NASA CP 2282, Echolds, p.89 ; (3) Technical Soaring, Vol. xxi, No. 2, Rehmet, p. 39 Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  13. Motor-generator & Battery ~ Performance Envelope and Data 100% Duty Cycle eb /(kw) CURRENT GROUP, i Rt / eb THEORETICAL EFFICIENCY, kw/eb TORQUE GROUP, t Rt / (k eb) REGENERATION LMC "generator curve" 48V / 3,600 RPM k = 0.16 N-m/A Rt = 0.041 Ohm LMCLTD.net MOTORING EEMCO 427D100 24V / 15,000 RPM k = 0.015 N-m/A Rt = 0.075 Ohm i t Phil Barnes Apr-08-2011 Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  14. “Low-tech” Regen DC Electric Propulsion With Battery Shuffler Battery Series “Totem Pole” Voltage Node Positive terminal of battery number: BATTERY SHUFFLE SWITCH Negative terminal of battery number: Takeoff / climb A B 1 5 Cruise D C E B C ~Pinwheel 4 2 A F B E Motor Gen Voltage Node 3 Best regen D D C 3 C D B E Max regen E 2 4 A D Phil Barnes 07 Apr 2011 B C Electrical Ground Rotate 80o Clockwise, then counter clockwise 5 1 F Battery effective shuffled position Periodic (about once per minute) battery shuffle via rotary switch ensures equal time for all batteries at each “totem pole” position Applicable: Brushed or Brushless, but no pulse-width modulation Regeneration enjoys reduced active battery resistance Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  15. DC boost converter enables efficient motoring & regen L VB C M-G iGBT PWM • DCBC: Key enabler, efficient bi-directional power management • Only the motoring mode is shown in the introductory graphic above • “Boosts” DC voltage ~ 0-500 % with minor input/output ripple • Enables low-voltage battery to drive high-voltage LED lamp* • Enables reduced battery totem pole length, i.e. Toyota Prius* • DC voltage “boost” is controlled by PWM “duty cycle” • Power in ~ Power out: DC output current is thus reduced • Options: brushed-DC/low voltage or brushless/high voltage • Adjusts effective battery voltage to efficiently drive the M-G • Boosts motor-gen effective EMF for efficient battery recharge * Wikipedia, “DC boost converter” Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

  16. DC boost converter – Equivalent circuits VM L Mot-gen VB C iGBT PWM iGBT on iGBT off iB iB VM VM iM iM L diB /dt L diB /dt C dVM/dt VB VB C dVM/dt dt |--t--| iGBT gate PWM d≡ duty cycle ; t≡ period Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

  17. DC boost converter – Voltage gain & conversion efficiency Time segment 1: iGBT on for Dt = dt Segment 2: iGBT off for Dt = (1-d)t [a] Voltage loop: VB - L DiB1 /(dt) = 0 [b] VB - L DiB2 /[(1-d)t] = VM iB iB VM VM [c] Output current: iM - C DVM1 /(dt) = 0 [d] iB - C DVM2 /[(1-d)t] = iM [e] PWM cycle: DiB1 + DiB2 = 0 [f] DVM1 + DVM2 = 0 iM iM L DiB2 /[(1-d)t] L DiB1 /(dt) C DVM1/(dt) [g] Combine [a,b,e]: VM/VB = 1/(1-d) [h] via [c,d,f]: iM/iB = 1-d C DVM2 /[(1-d)t] VB VB Combine [g,h]: h ≡iMVM /(iBVB) = 1 • Voltage & current gains set by duty cycle (d) alone [high-frequency assumed] • Efficiency is unity (resistance neglected) and is thus unaffected by L, C, d, t • “Deltas” (D) represent ripple applied to input current (iB) & outputs (iM, VM) Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

  18. DC boost converter - efficiency and regen application 233 Vdc in Regen 5 10 15 20 kW Motor "Evaluation of 2004 Toyota Prius," Oakridge National Lab, U.S. Dept. of Energy L VB M-G C iGBT PWM • 90o rotary mode selector switch for motoring or regeneration • Low-voltage option: Batteries in parallel, brushed-DC motor-gen • Hi-voltage option: Batteries in series, inverter & brushless DCMG Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

  19. "RegenoSoar" Air Vehicle and System Performance

  20. RegenoSoar Design Rationale • Configuration Rationale • Maximum laminar airflow aero & counter-rotation props • Pusher avoids windprop helix downstream aero upset • One-person handling/steering (remote or in the cockpit) • Winglets include tip wheels (wings flex up under load) Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  21. RegenoSoar ~ In Flight • Applications and Operations • Fleet broadcast energy rate • High-altitude earthwatch • Jet-stream rider • Storm rider Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  22. Vehicle Performance ~ New Formulation, New Insight Derive steady-climb Equation v L= nn w T-D f g g w Note:nn= cosg /cosf cL= nn w / (qs) • Regen T/D • climb:  6.3 • cruise: = 1.0 • solar-augmented glide: 0.5 • pinwheel glide:  -0.1 • efficient regen (thermal):  -0.4 • capacity regen (descent):  -1.0 • Frigate Bird • T/D=0 (no thrust) • sink rate (-dz/dt) = nn(D/L)v • Frigate Bird and Regen • sink increases with g-load (nn) • sink increases with airspeed (v) Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  23. Regenerative Flight Equation “Total Climb” Updraft “Total Sink” Rate of change of total specific energy Effect of windprop Still-air “clean” sink rate • “Exchange Ratio,” as applicable: • turbine system efficiency ~71% • 1 / propeller system efficiency • 0 for pinwheeling (no exchange) Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  24. Climb and Regeneration in the Thermal (minimum-sink airspeed) Elevation, m Elevation, m Climb rate Contours Energy rate Contours Optimum Elevation, m Equilibrium Regeneration Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  25. Regenerative Flight Equation Applied for RegenoSoar 0.82 0.87 0.82 0.88 Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

  26. Summary and RecommendationsRegenerative Electric-powered Flight

  27. Regenerative Electric-powered Flight • The Great Frigate Bird ~ nature’s “regen” • Self-contained takeoff & emergency thrust on demand • Energy extracted from vertical atmospheric motion • Energy rate sensor, flight sustained day-and-night • “Energy Synergy” of the Windprop & Motor-Gen • Optimum “speed ratios” about 87% & 115% by mode • Windprop: 8 blades spin slow, quiet, & efficient • Pinwheeling ~ imposes only minor performance penalty • DC boost converter - efficient bi-directional power • Climb/sink rates, any mode, g-load, orientation • Climb in the thermal, even with maximum regen • Regen in ridge and wave lift to extend flight • Regenerative Flight Equation ~ total energy rate • We’re good to go ~ Let’s emulate the Frigate Bird Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

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