An Innovative Approach to Wind Energy: Kite Power Technology Report

This report provides an in-depth analysis of kite energy systems as an innovative approach to harnessing wind power. It begins with an overview of the history of using kites for energy, tracing early research and development in the field. The core of the report focuses on the operational principles of kite power, differentiating between ground generation and fly generation methods, detailing the mechanics of energy conversion, and the role of hydraulic accumulators and robotic control. The report also highlights the benefits of kite energy, such as cost-effectiveness, reduced environmental impact, mobility, and ease of installation and maintenance compared to traditional wind turbines. Furthermore, the report examines the working of a WindLift prototype, detailing its components and operational processes. The report concludes with a discussion of the potential for the widespread adoption of kite power, emphasizing its role in sustainable energy generation and its advantages over conventional wind power solutions.

AN INNOVATIVE WAY TO USE OF WIND: KITE ENERGY
Prepared by: Drashti J Sutaria (1259566), Hiral V Prajapati (1259427),
Mohmedhusein I Kapadia (1260163)
ABBREVIATION
KT – Kite Technology
KP – Kite Power
KPS – Kite Power Systems
KPP- Kite Power Plant
Objective:
The main purpose of our project is to find a different way to use wind energy. In
yesteryears, people use kites and balloons for entertainment purpose, which also
depends on wind energy. Our purpose of studying this project is to use wind energy
to produce electric energy by using a kite. Amount of electricity from wind energy
directly depends on the velocity of the wind. Thus, to increase electricity
production, it becomes necessary to install the windmill on a height. As height
increases initial cost, as well as the maintenance cost, is also growing. To minimize
this cost, researchers are working on easy to install props to generate electricity
from the wind.
Electricity from wind energy by using kite is one of the cheapest and easiest ways.
The central working part of this system is hydraulic accumulator which stores
potential energy in the form of pressure that can be used to drive the generator to
smoothen out insists kite speed. Kite operated in crosswind (in the shape of eight).
This high traction force converted into electrical energy by generator unit installed
at a ground level. The kite will be controlled by the robot. This generated electricity
supplied to the electrical grid. KP Solutions is going to start the UK’s first
commercial KP plant at Stranraer, Scotland, soon.
History:
Dr. J. S. Goela, Professor at the Indian Institute of Technology in Kanpur (India), was
one of the first people to investigate the feasibility of using kites to harness wind
energy. Dr. Goela and his research assistants published several yearly reports
documenting his progress (Goela, 1983). Many other researchers researched
electric energy using kite, which will include briefly in our project report.

Kite Electric Energy.
These are kites fitted with wind turbines to generate electricity. The kind of power
form kites is called kite power. Simply, kite power is the power generated from
airborne wind turbine whose generator shaft is not supported by any tower. The
kites used are autonomous in that they can be able to drive themselves in the air
without the need of an operator.
KP is a source of renewable energy and it is a cost-effective method. [4]. It has a
low footprint when it comes to the amount of carbon dioxide released into the
atmosphere.
The kite and balloons are made of a material that is very light. Both the wing and
the traction tether are made of cloth or nylon material. The wings are inflatable. the
absence of a support tower means that the kite offers more aerodynamics and
mechanical options and can be used in places with strong winds. They can also be
used in places with high altitude where the speeds of wind are severe. Heavy
generators are placed on the ground.
Energy Conversion in a Power Kite.
There are two cases of Power kites. The ones that produce the power on the ground,
ground generation and the one whose power is generated on the air, is called fly
generation [5].
For ground generation, the wind acts on wing and produce tension on the tethers.
The created force becomes the input force for the generator. The force is used by
regenerative motors which is placed on the ground to produce electricity. All the
electronics and mechanics involved in power generation is at ground level.

Fig: Ground generation.
For fly generation, the power regenerative motors are carried up in the air by the
kite or balloon. The production of electricity does not happen at the ground levels
but instead in the air. The tether used in fly generation types needs to conduct the
electricity from the generator to a place where distribution can be done. The
generated power is transmitted to the ground by a conductive tether [6].

Fig: Fly generation [6].
In all ways, the generation of power is done in pumping cycles which are periodic.
They alternate between real in and real out of the tether. Real in happens when the
kite is flying. At this time, the speeds are between 70 to 90 km/h relative to the
faces of the wing [7]. As a result, a traction force, which is used to generate the
power on the onboard generators or for the case of ground generation, transmitted
to the ground where generation happens, is created.
When the kite reaches the maximum height, the wing is rotated as a whole by
releasing a steering wheel which depowers the kite. The kite losses its energy and
start to fall down. This is when the real out happens. When the kite falls, the tension
force on the tether is reduced by 80%. Thus, only a small percentage of power is
generated during this phase.

Fig: Real out and real in [7].
The most important element for these kites is the synchronization and the
automatic control. The controller keeps all the activities during real in and real out
in the right sequence and synched. The power frequency has to be made as
constant s possible thus the need for an automatic control.
Fig: The working of a ground generation kite [8].
The tether is pulled out and the generator is rotated thus generating the electricity.
The kite extends outwards until the tether is fully stretched. Maximum speeds of
winds are achieved when the kite is at maximum distance from the ground. At
round 300 meters from the generator, the speeds of wind rotating around the kite
usually reaches 100 miles per hour [9]. The springing action of the tether line will
cause the kite to spring back. As a result, the kite retracks back until it is at that
point when it is exactly above the generator. Traction happens and the kite moves
forward again and the cycle continues.
Two kites can be used for one generator such as the one shown on the figure above.
Using two kites makes sure that the alternate generation of electricity is continuous.
At all time there is power generation. In order to achieve a smooth power
generation, the sequence cycle of the two kites is kept out of phase by half the

period time. This way, when one kite is fully extended, the other one is fully
retracted and the two will be operating precisely the opposite of the other. [10].
The figure below shows the working of a WindLift prototype.
Fig: WindLift prototype. [17].
The Wind Lift generator is a ground type generator. Inside the generator is a drum,
a transmission system, the motor generator, level wind mechanism, steering
motors, steering carriages, linear slides, a turntable, a slip ring and an enclosure.
The steering cages controls the length of the tethers to allow the kite to be turned
in air. The lengths are adjusted to permit the traction and retraction of the kites.
They slide over the linear slides. The linear slides are lubricated in to reduce sliding
friction. What moves the steering carriage along the linear slides is the steering
motors. These motors use DC current. They are connected to the carriage by a
movable belt mechanism. The tethers that which are connected to the kite are
attached to a drum. In this prototype, three tethers are used. the middle tether is
used to hold the kite while the outer tethers are used for steering the kite. The work
of the drum is to holds the three tethers. The tethers are coiled inside the drum.
Mechanical energy is converted to electrical energy by motor generator. The kite
pulls the tethers an in turn turns makes the drum to rotate. The rotation of the drum
is utilized through a belt system to rotate the generator shaft and electricity is
generated. The drum and the motor- generator are connected together through a
transmission system. To keep the tethers neatly wound around the drum, a level

wind mechanism is used. The mechanism also keeps the tethers free from inter-
twinging during traction and retraction of the kite. The Windlift prototype rotates
about a vertical axis to enable wind traction. The whole generator rests on a, mild
steel turntable. The turntable hosts angular contact bearing which permit rotation of
the generator. The generator is pivoted to this turntable though a slip ring. The slip
ring houses a mechanism that enables the generator to transmit signals and
electrical power through the base when the generator is rotating. All the generator
electrical equipment and rotating members are housed by enclosers. [17].
Benefits of Kite Energy.
First, the design of the kite eliminates the use of a wind tower associated with wind
turbines with all the disadvantages that comes with it. The construction expenditure
associated with wind towers is ne of the problems which is eliminated since the
tethers used are much less expensive than tons of tower for the normal turbines.
There are more options in aerodynamics and mechanical characteristics than the
common turbines. Pease note that the turbine is not fixed in the air and as a result,
the axes of rotation of the wings or rotors adapts in order to fit the direction of the
wind. The tethers can be lengthened in order to reach higher altitudes where the
wind velocity is high. The dynamic stalling in axis Wind turbines which is caused
when the wind changes its direction or in the case of a turbulent wind, is reduced
since the kite is flexible and can change the orientation of the wings and blades. As
a result, there are more aerodynamic options than the normal turbines that we
know.
Perhaps the best benefit is their mobility. The kites are not connected permanently
to the ground. The common turbines require a robust structure to support the tons
of blade and rotor above them. They are fit in to a foundation to support this
weight. On the other hand, the kites are light. And they van be carried by an
individual. The ground generators are usually mounted on tow trucks to enhance
their portability. They are a good source of electricity in parties or functions done
ones per season. One can carry a small kite turbine in his car to use during
camping. They can be deployed in les than a day in areas having disasters such as
earthquakes and floods [11].
The KPT is cost effective. There are few components used and the kites a re small
thus reducing the weight of the material used and as a result reducing the
manufacturing cost. The Horizontal axis wind turbine that produce 20 KW per day is
16 tonnes. The blades are over 30 meters. This means that a special transport
facility is required in order to install them in the wind power station. On the other
hand, a kite of the same capacity is less than 80 kg. It requires only a tow truck not
a trailer to transport the generator. The installation expenses of the kites are cut
short. It is estimated that by 2030, the wind turbine power will have fallen to
$95/MWh from $175/MWh while for KP it will have fallen to $50MW/h.

The kites are easier to install than the Horizontal axes wind turbine. No site
preparation is required. Light elements are installed thus eliminating the need for
cranes. For instance, the kites for ground generation are made of a fabric material
which is lighter than the aluminum blades for typical wind turbine. Few installation
procedures are used. The only connection that is required is to join the tethers to
the generator and you are ready to start generating power. In the typical wind
turbines, due to their large size and weight, the turbines are transported in parts.
They have to be reassembled back together on the site by the help of the cranes.
Therefore, a KPP is easier to install.
KP is easier to maintain and service as compared to other turbines. The flexibility of
the kites makes maintenance easier. The kites can be lowered any time there is
need for servicing or maintenance. The axis turbines (typical wind turbines) require
that a person climbs up to the rotor level in order to maintain the gearbox. The
small sizes and light weight elements used for the KPT are easily carried around and
their handling during installation is simple. The generators for the ground
generation is at ground level. No climbing to the kite is needed. All these properties
make the maintenance involved in Kite power generation easier [12].
KP has environmental advantages over the wind turbines. It has a lower carbon
footprint than an axis wind turbine of equivalent power. Feasibility study has shown
that a kite power production produces less carbon dioxide to the environment than
an axis wind turbine. Wind turbine, though a source of renewable and green energy
produces mounts of carbon dioxide during manufacturing, transportation,
installation and maintenance that leads to global warming. On the other hand, low
carbon footprint associated with KP means that the it helps in conserving the
environment more than the wind turbine. Wind turbines produces noise. People
living near the wind turbine stations usually complain of noise. This is not the case
with kite turbine. The kite turbines are the most silent turbines.
What is better than a power plant that can be installed on the sea? Kite turbines can
be built on land as well on the sea. On the sea, kite turbines are installed on floating
platforms. Wind turbines can be installed in the sea but only on shallow sea bed
such on sea shores. Kite turbines, due to their flexibility and lightweight are able to
be installed on floaters.
Many Kite turbine can be installed per area of land. This means that a small piece of
land is used in power generation [12]. Wind turbines requires massive piece of land
due to their large infrastructure. People have to be displaced from wind turbine
sites. More power per area of land is capable with the Kite turbines since many kites
can be installed in a small piece of land.
Limitation of Kite Energy.
There is reduced sustainability of soft kites, the ones made of fabric, when the
velocity of wind is very small. Low velocity causes soft kites to crumple. For

crosswind generation, the power output potential is reduced when wind velocity is
low.
If generation is done on the ground, there is high variability in the cycles of
electricity generation. Solving this problem calls for more sophistications. The
electricity needs to be smoothened and that is only achievable when the electricity
is stored after being controlled by an intelligent controller. Even when very
intelligent control circuits re used, the power is not smooth. This adds to cost [11].
The technology requires a complex control system. The production of electricity
needs to have a constant frequency which calls for a synchronous control to
coordinate the real in and real out of kites. Hard wings type of kites (the one used in
fly generation) requires intelligence and onboard power to fly which leads to more
weight.
Lighter than air kites, balloon, uses helium which is expensive.
Airborne devices used for fly generation requires more maintenance. The rotorcraft
requires a lot of time to maintain. A typical rotorcraft takes around five hours to
maintain. The kite fabric is degraded and torn by the sun. [10] All the delicate and
complex control system needs to be thoroughly inspected before the kite is
deployed into the air. All this increases the maintenance.
Tether failure for single tethered devices may occur. This failure makes the devices
to be dragged by wind to far distance thus damaging the device.
Safety challenges. There are safety concerns with fly generation since. The KP
stations can be likened to an airport with numerous helicopters on air, they can
collide and fall any time. This has discouraged secondary use of land in those sites.
During storms, airborne devices can be carried be wind and landed to some other
areas.
Flying generation requires conductive tether cables for transmission. This limits the
application on high altitude since the cables would be very heavy.
Economic and environment-friendly efficient ways to resolve the
limitations
There are various ways on how Kite projects are implemented to promote economic
viability. We saw that kite turbine because of their light weight, can be installed in
the ocean. No people need to be replaced when kites are installed on the ocean.
Meaning less cost of the project. Putting them on the ocean, where there are strong
winds means that more energy will be produced. Kite turbines should also be used
in high altitude areas where the velocity of winds is high. As a result, high power will
be generated.
In kite turbines just like any other machines produces noise. Noise pollutes the
environment. Placing wind turbines in areas of low population is recommended. The

power generators need a design which does not produce high levels of noise or one
which uses noise absorbers [13].
To avoid tether failure, multiple tethered devices are used. This means that when
one tether fails, the other tethers will hold device and keeps it from falling until a
maintenance team arrives to repair. This also increases the device safety in case of
extreme winds.
To reduce the shadows created by the kites, the kites are designed to fly above 100
meters. The sun dissolves the shadows of objects placed a height which is a
hundred times its with.
The installation of kites on the ground makes the scene to be ugly and unattractive.
Architects have come up with fascinating solutions of placing the kites in a manner
which will be attractive. Kites are placed along a circular path. This is demonstrated
by the image below.
Fig: Kites arranged in a circular manner to make scene attractive [14].
Glance on kite farms and what are the parameters required for kite farms.
Various parameters are considered when setting up KPP. Such parameters are the
site location, the wind resources, the wind generator selection, environmental
impact, public safety and reliability.
In site selection, one determines where he want to place his turbines. Is it on flat
plains, on hills, on the sea or on a building? Fly generation due to its safety issues
requires an open space. Ground generation can be used on buildings e.g. on roof
tops. The place of location should have strong winds. The evidence of strong winds
is indicated by bent vegetation. The outward and inward movement of the power
kites calls for a place without tall trees. For big projects, the sites should be easily
accessible for construction and maintenance. Some lands are not permitted for
transmission lines or the owners might refuse to give out the land. In some
countries, the government may recommend or ban wind generation in some regions
of the country. Thus, it is advisable to consider government restrictions when

setting up a KPP. Even when you identify a place for the kites, you also need to look
for a place where you can be monitoring your KP station.
Another parameter that you need to consider is the wind resources. Does the wind
have enough speed? Does the wind have enough density? How much wind do you
have for electricity generation? This will also determine the altitude of your kite. If
you desire more electricity, you might look for a high-altitude tether line for your
kites [15].
The impact the farm will have on the environment is also a key factor. If your
devices produce a lot of noise, then you have to look for a means of reducing the
noise or locate your farm in a remote place. It is not also advisable to use wind
turbines in game parks as they will interfere with the ecosystem.
Lastly, Public safety concern have to be considered. Kite turbines and all wind
turbines are known for shadow flicking and visual impairments. It is thus not suited
in areas of high population such as near towns. A farm which uses flying generation
is like an airport with hundreds of helicopters overhead. Meaning that these farms
pose a major safety risk.
A good example of a kite farm is located at Stranraer, Scotland. The farm is owned
and managed by KPS. The KPS company has is also developing balloon/ kite hybrids
that will be flied more than 2 miles from the ground to harness wind energy.
In 2017, KPS said that it intended to have a 500-kW plant in the region.
The UC3M grouped launched a project in Spain. The project is a facility where the
government and universities research about airborne energy [16].
Other KPP are illustrated below.
COMPANY COUNTRY GENERATOR FLYER
Altaeros Energies United States Airborne Lighter than air turbine
Ampyx Power Netherlands Ground based Rigid wing “glider”
Enerkite Germany Ground based Flexible wing
Kitegen research Italy Ground based flexible wing
Kitenergy Italy Ground based flexible wing
Magenn Power Canada Airborne Lighter than air turbine
Makani Power United States Airborne Rigid wing

Sky Windpower United States Airborne Multiple sets of rotating
blades
Skysails Power Germany Ground based flexible wing
Wind Lift United States Ground based flexible wing
Table: KPP companies in the world. [17].
BIBLIOGRAPHY
[1] Goela, J.S., “Wind Energy Conversion Through Kites," Indian Institute of
Technology Kanpur, India, 1983.
[2] Fechner, U., Schmehl, R., “Design of a Distributed Kite Power Control
System," in Proceedings of the IEEE International Conference on Control
Applications, Dubrovnik, Croatia, 2012, pp. 800–805.
[3] Senthur, B.E., Shanthakumari, G., Karthik, R., Devharsha, Ch., “Kite Power
Production of electricity from the wind current using kites," Sri Sairam
engineering college, India, 2018.
[4] Carlos, “Renewable energy generation with kites and drones”, Physorg,
(2019), Available: https://phys.org/news/2019-02-renewable-energy-kites-
drones.html.
[5] Hsu, “Design Of Wind Power Generating Stations”, (2009), Available:
http://Tutorial%20on%20wind%20power.pdf.
[6] Ippolito, “Agreement with Saipem for Production and Deployment”, KiteGen
Research, (2019), Available: http://www.kitegen.com/en/.
[7] “Generating power From Kites” Wired Staff Science, (2006), Available:
https://www.wired.com/2006/10/generating-power-from-kites/.
[8] “The Future of Renewable energy: Kite power”, Idea to Value, (2016),
Available: https://www.ideatovalue.com/curi/nickskillicorn/2017/08/future-
renewable-energy-kite-power/.
[9] Barnard, “Airborne Wind Energy: It’s All Platypuses Instead of Cheetahs”,
Clean Technica, 2015, Available:
https://cleantechnica.com/2014/03/03/airborne-wind-energy-platypuses-
instead-cheetahs/.