HARNESSING HIGH-ALTITUDE WIND

POWER

Date;19/09/2012 1

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MAJOR JET STREAMS - BOTH HEMISPHERES

Sub-Tropical Jet

Polar Front Jet

“These enormous energy streams are formed by

the combination of falling of the tropical region’s

sunlight and Earth’s rotation. This wind resource

is invariably available wherever the sun shines

and the Earth rotates.”

INTRODUCTION

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Tethered balloons

Tethered fixed-winged craft

Tether climbing

Descending kites

Rotorcraft

METHODS TO HARNESS HIGH ALTITUDE

WINDS

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No adverse environmental consequences.

Highest power density for a large renewable energy

resource

Total power dissipated =10 W

Power densities >10 kW/m

UPPER ATMOSPHERIC WINDS

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DESCRIPTION AND ELECTRICAL

SYSTEM DETAILS

Four identical rotors mounted in an airframe.

TETHERED CRAFT

“single, composite ,electromechanical insulated aluminum

conductors of high strength fiber.”

Bring power to ground

Wound with strong Kelvar family cords.

Conductor weight is a critical compromise between

power loss and heat generation.

Tether transmission voltages is15 kV and higher

TETHERS

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Electrical losses b/w tethers & Converted power’s

insertion into the commercial grid ≈ 20%.

power transmission ; 4 and 8 km

Rated capacity ; 3–30 MW.

Location much closer to demand load centers.

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FOUR-ROTOR ASSEMBLY

Four identical rotors

Two forward and two afterward

The plan-form of the rotor centerlines is approximately

square

. Adjacent rotors rotate in opposite directions.

Diagonally opposite rotors rotate in the same direction

“When operating as an electrical power source rotors

are inclined at an adjustable, controllable angle of up to

50 to the oncoming wind.”

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DETAILS OF A 240 KW

DEMONSTRATION CRAFT

Sky Wind Power Corporation - 240 kW

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Connected to four separate gearboxes, -drive four

motor/generator units supplied by AC propulsion

High armature speed for satisfactory power-to-

weight ratio

Electrically linked for constant rotor speeds

Armature speeds are 24000r/min

Weight of the craft is estimated at around 1140 lb

(520 kg)

Four, two bladed - paired counter-rotations

10.7 m in diameter with solidity of 5%

Collective pitch control via electric actuators

Designed for operations up to 15000 ft (4600 m)

ROTORS

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ELECTROMECHANICAL TETHER

240 kW at a voltage of 15 kV

The electrical transmission efficiency is 90%

Two insulated aluminum conductors embedding

a Vectron fiber composite

Specific weight ; 115 kg/km

The electrical ground facility is configured for a

dc supply to and from the platform

The motor/generators are series connected

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Power consumption 15 000 ft (4600 m)=75kW

Rotor speeds = 130–300 r/min

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Withstand a wind of 35 m/s at 15 000 ft (4600 m)

The craft’s rated output

Wind speed 18.4m/s

Altitude of 15 000 ft (4600 m)

CRAFT

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The surface of HK -an array of small units

THE HK DESIGN

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Each unit -four rotors and two generator

Conductive tether

THE HK DESIGN

Anchors the kite to the ground station

Transmission of generated electrical power

Drives a ground-based generator.

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Four savonious style rotors (SSR) in a frame

Adjacent savonious rotors rotate in opposite direction.

To minimize the turbulence interaction and air friction

between rotors

The contra-rotor generators

Have two rotors,

Need two prime movers to rotate

ROTOR

opposite direction

Generator

lower weight

No brush

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Free rotation of rotors in this mode,

Drag coefficient of unit =minimum value.

OPERATING MODES OF HK DESIGN

Blocked mode:

Rotor are blocked in vertical position respect to incoming wind,

Drag coefficient = maximum value.

Rotating Mode:

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GENERATORS

Permanent magnet,

Produce direct current

Can be easily connected in parallel or series configurations.

Diode , -avoid reverse flowing of current into the generators.

The generators in each unit are paralleled together,

Ideal way to provide the reference data for

control.

Error sources

effects through the atmosphere,

satellite orbit and timing errors,

GPS receiver noise

signal reflection (multipath).

FLIGHT CONTROL USING GPS

AND GYRO DATA

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Relationship between the achievable GPS-derived

heading and pitch accuracy and antenna separation

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AERODYNAMIC PERFORMANCE

power output Vs αc(constant tip speed ratio μ.)

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C Coefficient of power

Control axis angle

V Velocity wind

Tip speed ratio

Ω Rotor speed

preferred generating conditions

power coefficient of around 0.4

control axis of about 50

tip speed ratio of 0.075.

AERODYNAMIC PERFORMANCE

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conditions when wind speed is insufficient to support the

craft and its tether.

system is on the point of collapse.

minimum wind speed to stay aloft occurs when the craft

nose-up attitude is around 24

corresponding tip speed ratio of 0.10

minimum wind speed for autorotation is around 10 m/s-(at

4600m)

Autorotation conditions:

AERODYNAMIC PERFORMANCE

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ENERGY STORAGE ISSUES

Pumped water storage

Compressed air energy storage (CAES)

Hydrogen.

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SCALABILITY CONSIDERATIONS

COST AND PERFORMANCE

PROJECTIONS AT THE LARGE SCALE

scalable in size and output- from small prototype

configurations of less than 240 kW, ( 3–30 MW per

craft.)

Larger sizes are more economical

utilize more than four rotors to maintain economy

and manageability of materials.

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PROJECTED COE

(AOE) = (LLC)+(O&M),+ (LRC).

O&M =$82 000 per year estimate for a 3.4MW

FEG, multiplied by 29.4 FEGs/100 MW plant.

Replacement cost = 80% of the initial capital

cost.

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AOE Annual operating expences

LLC Land lease cost

O&M Operation and maintance

LRC Levalised replacement cost

FCR Fixed charge rate

ICC Intial capital cost

AEP Annual energy production

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PLACE AOE COE

TOPEKA $0.0102/KWH $0.0194/KWH

DETROIT $0.0103/KWH, $0.0196/KWH

SAN DIEGO $0.0129/KWH $0.0249/KWH

FEGs harness powerful & persistent winds –source

for grid connection, for hydrogen production.

Main resource is the upper atmospheric winds

Less environmental impacts

Rural/remote area installations

CONCLUSION

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REFERENCE

[1] K. Caldeira, Seasonal, global wind resource diagrams [Online].

Available:

www.skywindpower.com

[2] R. J. O’Doherty and B. W. Roberts, “Application of upper wind

data in one

design of tethered wind energy system,” Solar Energy Res. Inst.,

Golden,

CO,Tech. Rep. TR-211-1400, Feb. 1982, pp. 1–127.

[3] J. D. Atkinson et al. , “The use of Australian upper wind data in

the design

of an electrical generating platform,” Chas. Kolling Res. Lab., Univ.

of

Sydney, Sydney, Australia, TN D-17, Jun. 1979, pp. 1–19.

[4] B. W. Roberts and J. Blackler, “Various systems for generation

of elec-tricity using upper atmospheric winds,” in Proc. 2nd Wind

Energy Innov.

Syst. C onf., Solar Energy Res. Inst., Colorado Springs, CO, Dec.

1980,

pp. 67–80.

[5] B. W. Roberts and D. H. Shepard, “Unmanned rotorcraft to

generate

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THANK YOU

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