HighAltitude Wind Power: Harnessing the Jet stream

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High-Altitude Wind PowerHarnessing the Jet
stream

• Trevor Clark
• Jonny Hayworth
• Charles Clear
• Chris Gentile
• Samantha Brovko

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Flying Electric Generators (FEG)

• Several types were investigated tethered
  balloons, tethered fixed-winged craft, tether
  raising and lowering kites, and rotorcraft. Most
  of the data herein is based off of simulations
  and several prototypes
• Kite plants can be located much closer to demand
  sites, and can be constructed in places where
  airspace is already restricted.

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Importance of the Tether

• Kites sole connection to the ground, electricity
  storage device, without the tether, no
  electricity would be produced
• Non-negligible weight
• Power losses through imperfect conductive
  materials, sigma denotes conductivity and is
  based on the properties of the material used
• Demonstrates the biggest obstacle to implementing
  wind power on large scales. Altitude affects the
  transmission efficiency of the tethers. Losses
  can be as much as 20.

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Tethers

• Kevlar
• 5 times as strong as steel
• Light weight
• Well tested (Bullet-Proof Vests)
• Aluminium-Spectra composite
• Spectra is 10 times stronger than steel
• Conducts
• Carbon NanoTube
• Could make kite-based wind power even more
  efficient

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Ladder Kites

• Tether with multiple kites attached
• Land Based drum hooked to generator
• Also reels in kites when needed
• 2 Types
• Single Line
• Only 10 reeled in
• Best option
• Loop
• Runs continuously

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Prototype Ladder Kite

• Net loss of power
• New model being designed to with net power gain
• 2kW
• Next model
• 4kW
• predicted to have net gain

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Control Methods Ladder Kite

• 3 Main Controls
• Drag Flaps
• Winch
• Slide Mechanism
• Help to guide kite in optimal figure 8 pattern

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Rotating Kite

• Rotating Aerostat
• aka floating balloon that spins
• Spins via Magnus Effect
• Also produced some lift
• Same thing that makes tennis balls curve when
  spun
• Operate at 600-1000ft

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Operation

• Operates in 4-60mph wind
• Too much drag to Sustain high velocities
• Closest to implementation
• Mageen spent 4.5 million
• Scaled prototype has been created

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TurnTable Kite

• Least explored type, as great danger for kite
  tethers to tangle
• What it is A series of kites attached to a round
  rotating platform. The kites catch the jetstream
  wind and spin the platform about the axis of
  vertical symmetry.
• How it works A generator would connect to the
  turntable and from its rotation electricity would
  be produced.
• The simplest generator employs Faradays law
  (changing magnetic fields and natures natural
  inclination to maintain constant flux) to induce
  an electric current.
• The kites would be attached using simple tethers.
  These tethers would not need to conduct the power
  to earth, as the electricity would be generated
  on the ground, and hence can be made of strong,
  light-weight material of any type.

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Rotorkite

• What it is Four rotors that generate power and
  keep the craft aloft are attached to a sturdy
  frame. Power is then transferred to the surface
  via a long conducting cable which doubles as an
  anchor to the ground, power transporter
• How it works The speed of the rotors produces
  enough buoyant lift to keep the craft aloft and
  keeps steady from paired counter-rotation. The
  rotors are connected to gearboxes that drive four
  motor/generator devices, which are in turn
  connected to the tether where the power is
  transported to the surface.

Most promising and efficient design available
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Sky WindPower Corps already built and running
demonstration crafts

• Produces cost competitive electricity
• 240 kW capability
• 10.7 m diameter rotors
• Optimal altitude of 15,000 feet, nose-up attitude
  between 10o-40o
• Weight of 1140 lbs (mass of 520 kg)
• Tether capabilities of 240kW at 15 Volts, 90
  transmission efficiency
• Comprised of two insulated aluminum conductors
  embedded in a Vectran fiber composite
• Specific weight of 115kg/km

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Challenges

• Tracking Kites
• Optical GPS system
• Force Sensor
• Improvements need to be made in control AI
• Large jump to multiple kites
• Control as kites are reeled in
• Maintanence Costs
• Rope slips and cuts itself

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Wind Speeds

• Wind speeds of 125-160mph at mid level jet
  streams
• Wind speeds of 60mph are normal outside of jet
  streams

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Power Available

• kW
• gt10kW/m2 seasonal average power in jet streams
• 17kW/m2 in US 19kW/m2 in Australia
• Tot Wind 1015W tot Thermal power cons 1013W
• Maximum efficiency of tether power transmission
  of 90

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Capacity Factor

• Is amount percentage of power actually produced
  over rated power for a period of time
• US avg 80 capacity factor at 10,000ft not
  including maintenance
• SkyWind corp is assuming 10 downtime for storms
  and maintenance
• Patiala, India gest an average of 37 capacity
  factor during the summer and 90 capacity factor
  during the winter
• High capacity factor for a ground site is 35 a
  normal amount is 30
• California 1999 19.2 for ground based wind

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Yearly Variation In Wind Speeds

• Winter winds are much stronger than summer ones

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Estimated Price

• 2/kWh for Rotorkite
• 5/kWh for Laddermill
• similar to current grid price for Rotating Kite
• Used in conjunction with gasoline generator it
  can produce energy at 20cents per kW, compared to
  25 to 99cents/kW for gas only generators
• 0.2/kWh for Turntable kite claimed on wiki but
  can't confirm.
• Costs decrease as arrays increase in size

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Environmental Benefits

• Renewable
• Non-polluting
• No GHG emissions
• Help reduce dependency on foreign oil
• Help progress a hydrogen economy

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• Power potential 1,040 billion kWh
• Carbon Dioxide displaced 960 million metric tons
• In 2004, U.S. produced about 6000 million metric
  tons

Based on the projected electricity use in 2025,
an estimated 20 of demand could be covered by
FEGs.
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Advantages and Disadvantages over Present Ground
Turbines (Wind Mills)

• Advantage
• Less visual pollution
• Avoids noise pollution
• Eliminates impact on wildlife
• Disadvantage
• High maintenance cost
• Dangerous if they were to fall
• Except Ladder Mills and Turntable Kites where
  generator is land based

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Cost of electricity

• AOE annual operating expenses includes land
  lease costs, operations and management, and
  overhaul costs
• ICC increased cost of compliance
• FCR Fixed charge rate
• AEPnet annual energy performance

Estimates from IEEE article (2007) Detroit
0.0196/kWh San Diego - 0.0249/kWh
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Cost of production

• A 3.4MW FEG is estimated to cost
• 2.26 million dollars this includes ground
  systems and production profits.
• Total initial capital cost for a 100MW array of
  FEGs 71.2 million dollars
• this includes site preparation, facilities,
  equipment, spare parts, and construction.

from IEEE article Harnessing High-Altitude Wind
Power (2007)
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Crashes

• Kites falling and crashing
• Although the probability of a kite falling a
  crashing is low, the consequences are great
• Considering that these kites need to be
  relatively close to its supplying source (town or
  city), a crash into a populated area would be
  devastating.
• Since kites will be in farms rather than just by
  themselves, a falling kite could crash into
  another kite and potentially bring down a few
  more kites in the process
• Planes hitting kites
• Chances of a plane hitting a kite are low since
  kites are required to have a significant amount
  of visibility and warning messages
• Only one reported case of a plane hitting a
  tethered flying object
• Pilot could have been a Darwin Award Candidate
  (no instrument usage, in restricted airspace
  without authorization etc.)
• The increased concentration of kites (less than
  0.25 of US airspace) is going to increase
  chances of a mid-air collision

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Wind Consistency

• Weather will partition wind output
• Although the wind in the jet stream is reliable,
  various weather will cause periodic breaks in
  power output due to reeling in kites from storms,
  tornadoes, etc.
• Summer winds milder than the wind season of the
  Winter months
• Jet stream moves
• Since the jet stream is not completely
  stationary, moving the kites will be necessary to
  follow the winds.
• Builds over several days and moves from West to
  East coasts
• This will cause retracting and launching of the
  kites every time the jet stream passes through
  the area.

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Space needs

• Any area wind farms that are placed will have to
  become restricted airspace
• Additionally, since the jet stream meanders, this
  restricted airspace will either have to be a
  moving restricted airspace or encompass a large
  enough area to encompass the variation
• An estimated 1/400 of the US airspace is enough
  to power all the US energy needs
• 1/400 of US airspace concentrated into the jet
  streams path turns out to be a large barrier
• Airlines commonly use jet streams for flight
  paths
• This is going to lead to a dispute between energy
  suppliers and airline companies as to whether or
  not it becomes a designated wind power farm.

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Environmental effects

• Negative Effects-adverse consequences not
  anticipated
• Chaotic system, difficult to predict consequences
• Speculation that critical balance could be
  disrupted
• Positive Effects
• Reduced greenhouse emissions
• Potentially reduce storm energies
• No hazardous waste to dispose of
• i.e. CO2, nuclear waste

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Should We Use it?

• HECK YES!!
• Reduced wastes and environmental effects
• Economically viable
• Safe
• Still research to be done, but very promising
  option for the future