AIRBORNE WIND ENERGY SYSTEM

SUBMITTED BY

ANKIT PANGHAL

CONTENTS INTRODUCTION HISTORY LAYOUT OF AWES CONCEPTS FOR EXTRACTING HIGH ALTITUDE WIND

ENERGY SOME IMPORTANT TERMS WHICH IS USED IN AWES CLASSIFICATION OF AWES ADVANTAGE OF AWES DISADVANTAGE OF AWES APPLICATION OF AWES ENVIRONMENTAL CONCERNS CONCLUSION REFERENCES

INTRODUCTION• Wind is a clean, renewable energy source.• Airborne Wind Energy System (AWES) is a high altitude

energy extraction technology.• Normally the wind turbine work at low altitude (below

400 feet), but at low altitude wind has low speed and is non-steady.

• But the AWES work at higher altitude (600-1000 feet), and at higher altitude wind has high velocity and is turbulence free.

• At high altitude wind is more persistent, so capacity factor for wind turbine can increase[1].

HISTORY

Miles L. Loyd proposed and analyzed an efficient AWES  in his work "Crosswind Kite Power" in 1980.

The first work aimed at evaluating the potential of AWES as a renewable energy resource has been presented by Archer and Caldeira in 2009.

A balloon concept developed by Magenn Power Inc. namely Magenn Air Rotor System.

Airborne wind turbines proposed by Sky Wind Power, Joby Energy and Makani Power[2].

LAYOUT OF AWES

CONCEPTS FOR EXTRACTING HIGH ALTITUDE WIND ENERGY

Generally stronger and more persistent wind is obtained at higher altitudes[3].

The concepts for extracting energy from high altitude wind can be categorized according to the position of the electrical generator as

a) Groundgen concept

b) Flygen concept

GROUNDGEN CONCEPT :-

The “groundgen” concept consists a generator kept at ground level is connected to a suitable rotating mechanism such as cable drum which is linked to a tethered airfoil or power kite[4].

Fig.1 Groundgen Concept[4].

FLYGEN CONCEPT :-

In the “flygen” concept, the propeller turbine on the flying device or the flow induced rotational motion of the complete device drives on-board generators from where the electrical energy is transmitted to the ground by a conductive tether[4].

Fig.2 Flygen Concept[4].

SOME IMPORTANT FORCES WHICH IS USED IN AWESAERODYANAMIC FORCE ( ): Aerodynamic force is exerted on a body by the air (or some other

gas) in which the body is immersed, and is due to the relative motion between the body and the gas. It is having two components lift force and drag force[1].

= +

LIFT FORCE: The lift force is acting perpendicular to the body surface.

DRAG FORCE: Drag force acting in effective wind’s direction[1].

CLASSIFICATION OF AIRBORNE WIND ENERGY  Ground-Base Power Generation On-Board Power Generation  Multiple Wing System Lighter Than Air System

1. GROUND-BASE POWER GENERATION Basically it generate the power based on groundgen concept It does not need high voltage electrical power transmission via

the tether Directly uses the strong tether tension to unroll the tether from a

drum, and the rotating drum drives an electric generator

As both the drum and generator can be placed on the ground, we call this concept ground-based generation or traction power generation. For continuous operation; one has to periodically retract the tether.

Fig.3: Ground based power generation[5]

Two phase are there, power production phase is also called reel-out phase, and the retraction phase or reel-in phase[5,6].

This allows one to reel in the tether with a much lower energy investment than what was gained in the power production phase.

Fig.4: Reel In Reel Out Phase[6].

2. On-Board Power Generation In an On-Board Power Generation, electrical energy is

produced on the kite or balloon and it is transmitted to the ground via a special rope which carries electrical cables.

On-Board Power Generation produces electric power continuously while in operation except during take-off and landing maneuvers in which energy is consumed.

Among On-Board Power Generation it is possible to find cross wind systems and non-cross wind systems depending on how they generate energy[5].

On-Board Power Generation[5]

3. MULTIPLE WING SYSTEM Due to the fact that tether drag is a significant obstacle to high

gliding numbers it would be beneficial to have short tethers. On the other hand, a long tether is needed to reach high

altitudes. For this reason, some concepts use multiple kites and decouple

the two roles of the tether by introducing two sorts of tether: first, a primary tether that allows the AWE system to reach altitude, and second, two or more secondary tethers that are attached to the end of the primary tether, and connect it with the kites, which are attached at their ends.

The first description of such a system, that was not yet built, can be found in the patent with on-board generation[7].

Fig 5: Multiple Wing System[7]

• This configuration allows the kites to loop fast around the attachment point between the two tethers.

4. Lighter Than Air System While most airborne wind energy systems rely on

aerodynamic lift in one form or the other in order to keep the system airborne, a few systems rely on aerostatic lift to stay aloft, i.e. the airborne part of the system is lighter than air.

The advantage is that they can stay airborne in the absence of wind indefinitely, and without power consumption.

They also need a considerable volume to compensate the weight of the rest of the airborne system – this volume is typically filled with Helium.

Two of the lighter than air systems that have been realized in recent years, the systems by Magenn power and Altaeros Energies[8].

Fig 6: Magenn Airborne Wind Power[8]

ADVANTAGE OF AIRBORNE WIND ENERGY SYSTEM

Deliver time-averaged output much closer to its rated capacity

Can be placed closer to demand centres, reducing transmission line costs and transmission line loses

Can operate in wind speeds between 5 – 65 mph can be raised to higher altitudes without having

to build an expensive tower can be easily moved to different locations

DISADVANTAGE OF AIRBORNE WIND ENERGY SYSTEM

Bad weather in the form of thunder and lightning strikes pose very serious risk to the destruction of any airborne device.

No power is generated if the device is retracted during bad weather.

Safety hazard as the airborne devices and power cables may become detached or damaged falling to the ground.

Kites and wings must be light and durable to fly in the high altitude winds.

Electrical energy losses in the long conducting cable from the airborne generating system to the ground.

APPLICATION OF AIRBORNE WIND ENERGY SYSTEM Can be used off-grid for cell-towers, exploration equipment,

communities, farms and factories Can be rapidly deployed to disaster areas for power to

emergency and medical equipment, water pumps, and relief efforts

Wind farm deployment For military purpose In developing nations where infrastructure is limited or non-

existent it can easily provide electricity

CONCLUSION

High altitude wind energy is currently a very promising resource for the sustainable production of electrical energy. The amount of power and the large availability of winds that blow between 300 and 10000 meters from the ground suggest that Airborne Wind Energy Systems (AWESs) represent an important emerging renewable energy technology. In the last decade, several companies entered in the business of AWES, patenting diverse principles and technical solutions for their implementation.

In the next years, a rapid acceleration of research and development is expected in the airborne wind energy sector. Several prototypes that are currently under investigation will be completed and tested.

REFRENCES[1] C.L. Archer and K. Caldeira, “Global Assessment of High-Altitude Wind Power,” Energies Vol.2,

pp. 307–319, May2009.

[2] M. Ahmed et al., “Power Maximization of a Closed-orbit Kite Generator System,” 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC) Orlando, FL, USA, December 12-15, 2011.

[3] F. Lorenzo, “High-Altitude Wind Power Generation,” IEEE Transactions on Energy Conversion, Vol. 25, No. 1, March 2010.

[4] S. Roland, “Kiting for Wind Power,” Wind Systems, No. 7, pp. 36-43, 2012.

[5] Lansdorp et al. ,“Towards Flight Testing of Remotely Controlled Surfkites for Wind Energy Generation,” AIAA Paper 2007-6643 In Proceedings of the AIAA Atmospheric Flight Mechanics Conference and Exhibit, Hilton Head, SC, USA, Aug. 20–23,2007. doi: 10.2514/6.2007-6643

[6] Williams et al.,“Modeling and Control of a Kite on a Variable Length Flexible Inelastic Tether,” AIAA Paper 2007-6705 In Proceedings of the AIAA Modeling and Simulation Technologies Conference and Exhibit, Hilton Head, SC, USA, Aug. 20–23 2007.doi: 10.2514/6.2007-6705

[7] P.R. Payne and C. McCutchen, “Self-Erecting Windmill.” US Patent US 3,987,987, issued 26 Oct 1976

[8] B. Lansdorp and W.J. Ockels, “Comparison of concepts for high-altitude wind energy generation with ground based generator,” Paper presented at the 2nd China International Renewable Energy Equipment and Technology Exhibition and Conference, Beijing, China, 25–27 May 2005

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