HARNESSING HIGH-ALTITUDE WIND
MAJOR JET STREAMS - BOTH HEMISPHERES
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.”
UPPER ATMOSPHERIC WINDS
Highest power density for a large renewable energy
Total power dissipated =10 W
Power densities >10 kW/m
No adverse environmental consequences.
DESCRIPTION AND ELECTRICAL
Four identical rotors mounted in an airframe.
“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
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.
Four identical rotors
Two forward and two afterward
The plan-form of the rotor centerlines is approximately
. 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.”
DETAILS OF A 240 KW
Sky Wind Power Corporation - 240 kW
Connected to four separate gearboxes, -drive four
motor/generator units supplied by AC propulsion
High armature speed for satisfactory power-to-weight
Electrically linked for constant rotor speeds
Armature speeds are 24000r/min
Weight of the craft is estimated at around 1140 lb
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)
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
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)
Power consumption 15 000 ft (4600 m)=75kW
Rotor speeds = 130–300 r/min
THE HK DESIGN
The surface of HK -an array of small units
THE HK DESIGN
Each unit -four rotors and two generator
Anchors the kite to the ground station
Transmission of generated electrical power
Drives a ground-based generator.
Four savonious style rotors (SSR) in a frame
Adjacent savonious rotors rotate in opposite direction.
To minimize the turbulence interaction and air friction
The contra-rotor generators
Have two rotors,
Need two prime movers to rotate
OPERATING MODES OF HK DESIGN
Rotor are blocked in vertical position respect to incoming wind,
Drag coefficient = maximum value.
Free rotation of rotors in this mode,
Drag coefficient of unit =minimum value.
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,
FLIGHT CONTROL USING GPS
AND GYRO DATA
Ideal way to provide the reference data for
effects through the atmosphere,
satellite orbit and timing errors,
GPS receiver noise
signal reflection (multipath).
Relationship between the achievable GPS-derived
heading and pitch accuracy and antenna separation
power output Vs αc(constant tip speed ratio μ.)
preferred generating conditions
C Coefficient of power
Control axis angle
V Velocity wind
Tip speed ratio
Ω Rotor speed
power coefficient of around 0.4
control axis ◦
of about 50
tip speed ratio of 0.075.
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
ENERGY STORAGE ISSUES
Pumped water storage
Compressed air energy storage (CAES)
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
Larger sizes are more economical
utilize more than four rotors to maintain economy
and manageability of materials.
(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
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
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
 K. Caldeira, Seasonal, global wind resource diagrams [Online].
 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.,
CO,Tech. Rep. TR-211-1400, Feb. 1982, pp. 1–127.
 J. D. Atkinson et al. , “The use of Australian upper wind data in
of an electrical generating platform,” Chas. Kolling Res. Lab., Univ.
Sydney, Sydney, Australia, TN D-17, Jun. 1979, pp. 1–19.
 B. W. Roberts and J. Blackler, “Various systems for generation
of elec-tricity using upper atmospheric winds,” in Proc. 2nd Wind
Syst. C onf., Solar Energy Res. Inst., Colorado Springs, CO, Dec.
 B. W. Roberts and D. H. Shepard, “Unmanned rotorcraft to