Developments in electric propulsion in the Deregulated sectors. Paul Dewhurst, Flylight Airsports Ltd

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1 Developments in electric propulsion in the Deregulated sectors Paul Dewhurst, Flylight Airsports Ltd

2 What are Footlaunched and Sub-115 Aircraft? Footlaunched: Must be Footlaunched Max 60 Kg unladen weight (inc fuel), or 70Kg for two place Max fuel capacity 10 litres Max stall speed 35knots (by default V fast runners required!) Generally fall into two groups Paramotor and Powered Hanglider

3 Sub-115 Single seat only Max empty weight 115Kg less fuel MTOW 300Kg Max stall speed 35 knots Two main groups - Flexwing and Fixedwing

4 The Dream of Electric Flight Almost no engine noise No emissions at point of use Potential to use green supply of charging power Instant power and no warm up requirement Reliable starting Almost zero maintenance Low vibration Engine not affected by density altitude only prop No carb icing Not oily! Doesn t care which way up it is aerobatics?!

5 Feasibility powerful rare-earth magnets for use in electric motors SmCo magnet holding 1000x it s own weight

6 Feasibility lithium-polymer rechargeable cells LiPo LiPo - lithium polymer cells: 150 Whr/kg 1000 W/kg w1.siemens.com (Pictures of the Future Fall 2007)

7 Electric vs. Petrol Energy content of petrol = 45 MJ/kg = 12.5 kwhr/kg of which ~30% can be turned into power = 3.7 kwhr/kg 4-stroke petrol aero-engine power rating ~ 1HP/kg = 0.75 kw/kg

8 Electric vs. Petrol Energy content of petrol = 45 MJ/kg = 12.5 kwhr/kg of which ~30% can be turned into power = 3.7 kwhr/kg 4-stroke petrol aero-engine power rating ~ 1HP/kg = 0.75 kw/kg High-tech. electric motors have an efficiency of ~90% and a power rating of 6 kw/kg LiPo cell storage capacity is ~ 0.15 kwhr/kg

9 Electric vs. Petrol Energy content of petrol = 45 MJ/kg = 12.5 kwhr/kg of which ~30% can be turned into power = 3.7 kwhr/kg 4-stroke petrol aero-engine power rating ~ 1HP/kg = 0.75 kw/kg High-tech. electric motors have an efficiency of ~90% and a power rating of 6 kw/kg LiPo cell storage capacity is ~ 0.15 kwhr/kg (1/25 of net petrol) A 75 kw electric motor saves 85 kg in weight, but this only corresponds to 13 kwhr of battery capacity = 4 kg of petrol

10 Electric vs. Petrol Energy content of petrol = 45 MJ/kg = 12.5 kwhr/kg of which ~30% can be turned into power = 3.7 kwhr/kg 4-stroke petrol aero-engine power rating ~ 1HP/kg = 0.75 kw/kg High-tech. electric motors have an efficiency of ~90% and a power rating of 6 kw/kg LiPo cell storage capacity is ~ 0.15 kwhr/kg (1/25 of net petrol) A 75 kw electric motor saves 85 kg in weight, but this only corresponds to 13 kwhr of battery capacity = 4 kg of petrol Hence, an electric aircraft must be very efficient

11 How to do more with less? Power requirement for level flight resolves into: Sinkrate x Weight = Thrust Horsepower* 550 High speed = high Ld required Low speed = low span loading more important than drag = our machines very suitable.

12 An electric airliner? Boeing : 60,000 kg max. (60 t.) 30 t. empty weight 15 t. payload (168 passengers) 15 t. fuel => LiPo cells = 2.25 MWhr capacity Assuming L/D = 15 at 560 mph (= 10 MW aero) and 60% efficient drive = 17 MW electrical

13 An electric airliner? Boeing : 60,000 kg max. (60 t.) 30 t. empty weight 15 t. payload (168 passengers) 15 t. fuel => LiPo cells = 2.25 MWhr capacity Assuming L/D = 15 at 560 mph (= 10 MW aero) and 60% efficient drive = 17 MW electrical Flight time = 8 minutes (=> 75 miles)!!

14 An Electric Paramotor Total weight ~ 120Kg Sink rate ~ 4.2FPS 2Thp 1.5Kw /.5 drive eff 3kWhr requirement 12kg cells = 1.8kWhr Duration = 36 mins - less climb, 100% discharge

15 An Electric Powered Hanglider Rigid wing best efficiency Sink Rate ~ 2.5FPS Weight 140Kg 1.4THP 1kW /.5 2kWhr requirement 12kg cells = 1.8kWhr Duration = 54 mins less climb, 100% discharge

16 More Cells, more duration? Pramotor limited by weight a person can realistically carry on their back. Powered Hanglider limited by 60Kg max weight with fuel Good solution though for what are essentially Self Launched Gliders

17 Current Footlaunched Projects Neil Andrews UK

18 Current Footlaunched Projects Dr Ing Werner Eck - Germany

19 E-Lift system 10Kw direct drive brushless motor 14 cell Lithium Ion cell pack 31Ah fast chargeable 61Kg max static startboost 52 continuous Own design folding prop 22Kg Paramotor system 22mins flight time no lift Climb height 800m Climb rate 1.2m/s

20 Elift System for Powered Hangliders Overall harness weight 28Kg 30 mins flight time no lift Climb height 1100m/3600 Climb rate 1.8m/s

21 :21:17 13:21:30 13:21:43 13:21:56 13:22:09 13:22:22 13:22:35 13:22:48 13:23:01 13:23:14 13:23:27 13:23:40 13:23:53 13:24:06 13:24:19 13:24:32 13:24:45 13:24:58 13:25:11 13:25:24 13:25:37 13:25:50 13:26:03 13:26:16 13:26:30 13:26:43 13:26:56 13:27:09 13:27:22 13:27:35 13:27:48 13:28:01 13:28:14 13:28:27 13:28:40 13:28:53 13:29:06 13:29:19 13:29:32 13:29:45 13:29:58 13:30:11 13:30:24 13:30:37 13:30:50 13:31:03 13:31:16 13:31:29 13:31:43 13:31:56 13:32:08 13:32:21 13:32:34 E-Lift measured values flown on with rigid wing Atos VR Kapazität in 0,1Ah Drehzahl in 10/1/min altitude 1200m Strom in Ampere Schub in Newton I-Vario in cm/s Höhe in metern Spannung in 0,25V Leistungsabgabe in 10W average motor power 7kW Start thrust 61,5 kp average thrust 48km/h average climb rate1,8m/s used capacity 29,8Ah from 31Ah average current 175 A low rpm at /min constant voltage at 47 Volt climb time 11min.

22 Current Footlaunched Projects Yuneec China!

23 E-Pac system 160mm direct drive brushless motor 10kW, 1.2M prop 1.7kWh capacity 3 blocks of lithium polymer cells 25Kg unit weight 50Kg max static thrust 25-35mins duration

24 Scalextric anyone!

25 Randall Fishman USA Electraflyer Corp Sub-115 projects

26 18Hp direct drive motor(12kg), folding prop Up to 5.6kWhr cell pack (40Kg) 112Kg weight with large pack 63Kg max static thrust at 1800RPM Experimenting with redrive for greater thrust 70Kg (non folding prop) You can buy it now!

27 Werner Eck Aeriane Swift Lite conversion (SWIFT =Swept Wing Inboard Flap Trim!)

28 24:1 Ld max.65ms min sink 80Kg empty weight less Cells 190Kg MTOW 1.5m/s climb rate

29 Werner Eck Flylight Dragonfly In process! 65Kg less cells 185/ 200Kg MTOW 10:1 LD Min sink 1.1m/s 3.5kW required Around 50 mins duration on 24kg cell pack

30 Dr Eck Aerola Alatus 100Kg less cells 235Kg MTOW 27:1 LD Min sink 0.8m/s

31 Yuneec E200 project High wing strut braced conventional layout Twin pylon mounted 10-15Kw motors 50Kg cell payload Flying as giant RC model at present! Video of test flights show at end

32 Hummingbird Hummingbird Dr Paul Robertson Paul Dewhurst 80 kg empty 250Kg MTOW 1 m Tubular aluminium Fibre-glass fairings Fabric wing covering 10 m wingspan 6 m long

33 Hummingbird figures: Glide Ratio L/D Glide Ratio L/D vs. Airspeed Airspeed (mph) L/D max is ~18:1 at 45mph Min sink ~ 200fpm Stall speed ~ 32mph Aero. Power vs. Airspeed Power reqd. to maintain level flight = Drag Airspeed Hence, propeller Thrust must exceed Drag for climbing Power (kw) Airspeed (mph)

34 Electric Powertrain Modelling of motor & prop. performance:- Thrust & power required? 200 kg weight with L/D = 45 mph 11 kgf (= m/s, this is an aerodynamic power requirement of 2.2 kw) Each motor/prop. must therefore produce mph airspeed to maintain level flight Extra thrust (x 5) is required for take-off and climb

35 Electric Powertrain Test modelling of motor & prop. performance Theory Experiment

36 Electric Powertrain Modelling of prop. characteristics allows motor power (= current x voltage) to be determined Thrust (kgf) Static thrust data 22"x12" 4-blade prop. Theory Expt. Good agreement with theory - high motor efficiency Power (W)

37 Electric Powertrain Twin brushless aero-motors, 10 kw each 25 Thrust at various airspeeds 5mph 45mph 70 mph Prop. thrust (kgf) Prop. power input (kw)

38 Electric Powertrain Twin cell stacks 12 x 3.7 V, 40 Ahr LiPo (3.5 kwhr) Integrated control system required for battery safety Lithium polymer cell stack Brushless motor controller Brushless dc aero-motor 31 x 12 3-blade CF prop. Battery Management System Throttle lever Pulse width controller Monitor individual cells: voltage ( V) current (0-200 A) temperature (0-50 C)

39 Electric Powertrain Twin cell stacks 12 x 3.7 V, 40 Ahr LiPo (3.5 kwhr) Integrated control system required for battery safety Lithium polymer cell stack Brushless motor controller Brushless dc aero-motor 31 x 12 3-blade CF prop. Battery Management System Throttle lever Pulse width controller Monitor individual cells: voltage ( V) current (0-200 A) temperature (0-50 C)

40 Electric Powertrain Full-scale static tests 35 Static Thrust vs. Electrical Power 30 Thrust (kgf) Theory Expt Power (kw)

41 Powertrain testing next step? First air tests will use an existing airframe An old Lazair; which meets <115kg rules. and is a twin!

42 Hummingbird Performance Duration ~40 minutes Range 35 miles Max. rate of climb 650 ft/min Max. speed 80 mph (+80% more duration with additional cell packs)

43 But how are we going to charge the batteries? Mains power Wind turbine Fuel powered generator eg. LPG, fuel cell

44 Wind turbine Post-code check for windspeed (5.5 m/s avg.) 1.8 m dia., 35% efficient turbine will generate ~1500 kwhr of electricity per annum Assuming 67% charge efficiency = 270 recharges This equates to ~180 hours flying each year

45 Wind turbine Post-code check for windspeed (5.5 m/s avg.) 1.8 m dia., 35% efficient turbine will generate ~1500 kwhr of electricity per annum Assuming 67% charge efficiency = 270 recharges This equates to ~180 hours flying each year This is actually quite feasible Note: if all the parts were made from aluminium, the aircraft and wind turbine would cause ~1000 kg of CO 2 to be released during manufacture.

46 Costs? Lithium polymer cells around 150 kg Life of cells circa 1000 cycles to deplete to 80% capacity Mains recharge approx 10p kwh No maintenance Footlaunched: Approx 4 per motorised flight hour electric Approx 4 for petrol with 2 stroke IC motor + maintenance

47 Hybrid? Fuel cells too heavy for us. But how about?: Electric drive with medium sized cell stack Small IC motor running at best fuel specific RPM used as generator Sized to provide cruise power at best Ld speed plus small reserve Cells used for takeoff and climb boost and trickle charge in the cruise - Student study project at Cambridge

48 Conclusions Light electric leisure aircraft (especially those with a soaring slant) are now just about feasible - on both technical and economic grounds Battery performance will continue to increase - and become cheaper A wind turbine offers a feasible and carbon-neutral approach to re-charging the batteries between flights Hybrid-powered aircraft, particularly for GA, will become a reality in the near future

49 Any questions??

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