High-altitude wind power

"HAWP" redirects here. For the webseries, see Hey Ash, Whatcha Playin'?.

High-altitude wind power (HAWP) is the harnessing of the power of winds high in the sky by use of tether and cable technology. An atlas of the high-altitude wind power resource has been prepared for all points on Earth.[1] A similar atlas of global assessment[2] was developed at Joby Energy. The results were presented at the first annual Airborne Wind Energy Conference held at Stanford University by Airborne Wind Energy Consortium.[3]

Various mechanisms are proposed for capturing the kinetic energy of winds such as kites, kytoons, aerostats, gliders, gliders with turbines for regenerative soaring,[4] sailplanes with turbines, or other airfoils, including multiple-point building- or terrain-enabled holdings.[5] Once the mechanical energy is derived from the wind's kinetic energy, then many options are available for using that mechanical energy: direct traction,[6][7] conversion to electricity aloft or at ground station, conversion to laser or microwave for power beaming to other aircraft or ground receivers. Energy generated by a high-altitude system may be used aloft or sent to the ground surface by conducting cables, mechanical force through a tether, rotation of endless line loop, movement of changed chemicals, flow of high-pressure gases, flow of low-pressure gases, or laser or microwave power beams.

There are two major scientific articles about jet stream power. Archer & Caldeira[8] calculated that, if the world's entire electrical energy demand were supplied by HAWP, the climatic impact would be negligible. Miller, Gans, & Kleidon[9] claim that the jet streams can generate the total power of only 7.5 TW, and that the climatic impact will be catastrophic.

High-altitude wind for power purposes

Winds at higher altitudes become steadier, more persistent, and of higher velocity. Because power available in wind increases as the cube of velocity (the velocity-cubed law),[10][11] assuming other parameters remaining the same, doubling a wind's velocity gives 23=8 times the power; tripling the velocity gives 33=27 times the available power. With steadier and more predictable winds, high-altitude wind has an advantage over wind near the ground. Being able to locate HAWP to effective altitudes and using the vertical dimension of airspace for wind farming brings further advantage using high-altitude winds for generating energy.

High-altitude wind generators can be adjusted in height and position to maximize energy return, which is impractical with fixed tower-mounted wind generators.

In each range of altitudes there are altitude-specific concerns being addressed by researchers and developers. As altitude increases, tethers increase in length, the temperature of the air changes, and vulnerability to atmospheric lightning changes. With increasing altitude, exposure to liabilities increase, costs increase, turbulence exposure changes, likelihood of having the system fly in more than one directional strata of winds increases, and the costs of operation changes. HAWP systems that are flown must climb through all intermediate altitudes up to final working altitudes—being at first a low- and then a high- altitude device.

Methods of capturing kinetic energy of high-altitude winds

Energy can be captured from the wind by kites,[12] kytoons, tethered gliders,[13] tethered sailplanes, aerostats (spherical as well as shaped kytoons), bladed turbines, airfoils, airfoil matrices, drogues, variable drogues, spiral airfoils, Darrieus turbines, Magnus-effect VAWT blimps, multiple-rotor complexes, fabric Jalbert-parafoil kites, uni-blade turbines, flipwings, tethers, bridles, string loops, wafting blades, undulating forms, and piezoelectric materials,[14] and more.[15]

When a scheme's purpose is to propel ships and boats,[16][17] the objects tether-placed in the wind will tend to have most of the captured energy be in useful tension in the main tether. The aloft working bodies will be operated to maintain useful tension even while the ship is moving. This is the method for powerkiting sports. This sector of HAWP is the most installed method. The folklore is that Benjamin Franklin used the traction method of HAWP. George Pocock was a leader in tugging vehicles by traction.[18]

Controls

HAWP aircraft need to be controlled. Solutions in built systems have control mechanisms variously situated. Some systems are passive, or active, or a mix. When a kite steering unit (KSU) is lofted, the KSU may be robotic and self-contained; a KSU may be operated from the ground via radio-control by a live human operator or by smart computer programs. Some systems have built sensors in the aircraft body that report parameters like position, relative position to other parts. Kite control units (KCU) have involved more than steering; tether reeling speeds and directions can be adjusted in response to tether tensions and needs of the system during a power-generating phase or return-non-power-generating phase. Kite control parts vary widely.[19][20]

Methods of converting the energy

The mechanical energy of the device may be converted to heat, sound, electricity, light, tension, pushes, pulls, laser, microwave, chemical changes, or compression of gases. Traction is a big direct use of the mechanical energy as in tugging cargo ships and kiteboarders. There are several methods of getting the mechanical energy from the wind's kinetic energy. Lighter-than-air (LTA) moored aerostats are employed as lifters of turbines. Heavier-than-air (HTA) tethered airfoils are being used as lifters or turbines themselves. Combinations of LTA and HTA devices in one system are being built and flown to capture HAWP. Even a family of free-flight airborne devices are represented in the literature that capture the kinetic energy of high-altitude winds (beginning with a description in 1967 by Richard Miller in book Without Visible Means of Support) and a contemporary patent application by Dale C. Kramer, soaring sailplane competitor, inventor.

A research on airborne wind turbine technology innovations reveals that the “Kite type AWTs” technique, the most common type, has high scope of growth in the future; it has contributed for about 44% of the total airborne wind energy during 2008–2012. The kite type AWTs extract energy through wind turbines suspended at high altitudes using kites such as multi-tethered kite, kite and dual purpose circular fan,rotary wing kites etc.[21]

Electric generator position in a HAWP system

Electricity generation is just one of the optional choices of using captured mechanical energy; however, this option dominates the focus of professionals aiming to supply large amounts of energy to commerce and utilities. A long array of secondary options include tugging water turbines, pumping of water, or compressing air or hydrogen. The position of the electric generator is a distinguishing feature among systems. Flying the generator aloft is done in a variety of ways. Keeping the generator at the mooring region is another large design option. The option in one system of a generator aloft and at the ground station has been used where a small generator operates electronic devices aloft while the ground generator is the big worker to make electricity for significant loads.

Carousel generator

The “Carousel” configuration several kites fly at a constant height and higher altitudes, pulling in rotation a generator that moves on a wide circular rail. For a large Carousel system, the power obtained can be calculated as of the order of GW, exposing a law that see the power attainable as a function of the diameter raised to the fifth power, while the increment of cost of the generator is linear.[22]

Aerostat-based HAWP

One method of keeping working HAWP systems aloft is to use buoyant aerostats whether or not the electric generator is lifted or left on the ground. The aerostats are usually, but not always, shaped to achieve a kiting lifting effect. Recharging leaked lifting gas receives various solutions. In case of productive winds the aerostats are typically blown down by the aerodynamic drag applied on the wide and unavoidable Reynolds surface excluding them de facto from the HAWP category.

TWIND TECHNOLOGY

Non-airborne HAWP

Conceptually, two adjacent mountains (natural or terrain-enabled) or artificial buildings or towers (urban or artificial) could have a wind turbine suspended between them by use of cables. When HAWP is cabled between two mountain tops across a valley,[5] the HAWP device is not airborne, but borne up by the cable system. No such systems are known to be in use, though patents teach these methods. When non-cabled bridges are the foundation for holding wind turbines high above the ground,[29] then these are grouped with conventional towered turbines and are outside the intent of HAWP where the tethering an airborne system is foundational.

HAWP Safety

Lightning, aircraft traffic, emergency procedures, system inspections, visibility marking of system parts and its tethers, electrical safety, runaway-wing procedures, over-powering controls, appropriate mooring, and more form the safety environment for HAWP systems.

Challenges of HAWP as an emerging industry

There have been several periods of high interest in HAWP before the contemporary activity. The first period had a high focus on pulling carriages over the lands and capturing atmospheric electricity and lightning for human use.[30] The second period was in the 1970s and 1980s when research and investment flourished; a drop in oil price resulted in no significant installations of HAWP. Return on investment (ROI) has been the key parameter; that ROI remains in focus in the current development activity while in the background is the renewable and sustainable energy movement supporting wind power of any kind; but HAWP must compete on ROI with conventional towered solutions.

Early references to HAWP

Early centuries of kiting demonstrated that the kite is a rotary engine that rotates its tether part about its mooring point and causes hands and arms to move because of the energy captured from higher winds into the mechanical device. The tension in the lofted devices performs the work of lifting and pulling body parts and things. Airborne wind energy (AWE) for HAWP was birthed thousands of years ago; naming what happened and developing the implied potentials of tethered aircraft for doing special works is what is occurring in AWE HAWP. What is "low" for some workers is "high" for others.

See also

References

  1. ↑ Global Assessment of High-Altitude Wind Power
  2. ↑ High Altitude Wind Resource Modeling & Analyses, Archan Padmanabhan
  3. ↑ http://www.aweconsortium.org/
  4. ↑ Flight Without Fuel - Regenerative Soaring Feasibility Study
  5. 1 2 Wind Turbines on Mounts
  6. ↑ SkySails
  7. ↑ Anne Quéméré, the Oceankite and Extreme Weather
  8. ↑ Archer, C. L. and Caldeira, K. Global assessment of high-altitude wind power, IEEE T. Energy Conver., 2, 307–319, 2009. Retrieved on January 16, 201208.
  9. ↑ L.M. Miller, F. Gans, & A. Kleidon Jet stream wind power as a renewable energy resource: little power, big impacts. Earth Syst. Dynam. Discuss. 2. 201-212. 2011. Retrieved on January 16, 201208.
  10. ↑ Wind Power Curves
  11. ↑ The Power of the Wind: Cube of Wind Speed by the Danish Wind Industry Association
  12. ↑ Windswept and Interested ltd publish open source plans to make cheap lightweight rotary kite sets for tensioned torsion energy transfer.
  13. ↑ Makani Power, Inc. reported that they have progress on a tethered circling turbine glider-like craft that is powered at times and unpowered at times during energy generation. Report was at HAWP 2009 conference at Cleanteach Innovation Center in November 2009.
  14. ↑ Piezoelectric materials
  15. ↑ Joby Energy
  16. ↑ KiteShip - Innovation in Tethered Flight
  17. 1 2 John Gay's Work for Boys. Four volumes. The summer volume had Chapter XVIII titled Kite-Ship that well described HAWP kite-tugging dynamics.
  18. ↑ Mechanics of classical kite buggying or how Mr. Pocock gained 9 m/s by his Charvolant
  19. ↑ SwissKitePower; designer of KCU was Corey Houle.
  20. ↑ KiteGen project control as key technology for a quantum leap in wind energy generators by M. Canale, L. Fagiano, M. Milanese, and M. Ippolito.
  21. ↑ "Airborne Wind Turbines – A Technical Report". Scope e-Knowledge Center Pvt Ltd. 2013.
  22. ↑ "100_to_watch". i3connect cleantech group. Retrieved 2016.
  23. ↑ TWIND
  24. ↑ Magenn Power, Inc.
  25. ↑ LTA Windpower
  26. ↑ Funneled-Wind Turbine Aircraft Application for patent Patent application: Pub. No.: US 2008/0290665 A1, Publication date:November 27, 2008. Inventor: Lynn Potter of Barstow, California (US).
  27. ↑ Airship power turbine, US Patent 4166596 by William J. Mouton, Jr., and David F. Thompson, filed April 28, 1978.
  28. ↑ HAWE system Omnidea
  29. ↑ Bahrain World Trade Center examples a completed bridge holding wind turbines high above the ground; as the turbines are not tethered into the wind, this examples a twin-tower non-tethered non-airborne arrangement.
  30. ↑ Pocock’s ‘The Aeropleustic Art’
  31. ↑ The Aeropleustic Art
  32. ↑ The paradise within the reach of all men, without labor. Volumes 1-2 By John Adolphus Etzler. "We might extend the application of [wind] power to the heights of the clouds, by means of kites."
  33. ↑ US Patent 2368630 filed June 3, 1943.
  34. ↑ http://www.meaus.com/articles/futureTasks.html
  35. ↑ Tapping High Altitude Wind, 'Ladder' of Kites Viewed as Energy Source
  36. ↑ Selsam Innovations
  37. ↑ BBC News, SciTech.
  38. ↑ J. Energy, 1980, vol. 4., no. 3.
  39. ↑ Robert's Rotorcraft photograph of experiment in Australia. PJ Shepard places year at 1986 at best memory. Bryan Roberts recalls the photograph was at his session in May 1986. In the photograph the powered craft was almost in autorotation; actual electricity generation was done briefly in another test. A video is available where electric generation was effected. The shown craft had two rotating hubs; at each hub radiated a lifting rotor blade and a shorter streamlined blade with a counter-balancing mass at its tip Professor plans flying power station; total craft weighed 64 lb. From left to right the people: Hasso Nibbe, Alan Fien, Grahame Levitt, and Bryan Roberts; all were employees of the University of Sydney. Site: Mt. Pleasant Farm at Marulan in New South Wales. Wind: approximately 15 knots. AWECS inventor David H. Shepard after much correspondence finally met face-to-face in 2006 Professor Bryan Roberts; such are part of the foundations of HAWPA company Sky WindPower.

External links

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