These turbines are useful when we
travel to remote locations where the electrical outlets are not available and
are capable of charging our devices anytime. They are also useful when used at
locations such as highways where the artificial air velocity created due to
movement of vehicles on both sides of the turbines is capitalized to rotate the
turbines and generate the electricity to lighten up the highways as well as to
run the sign-boards.
These turbines produce a power
output of 11.85 W at a wind speed of 5 m/s. This power is enough to charge two
small portable devices or one high power device at a time. This eliminates the
requirement of continues power source.
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The aim of this research paper
was to design a portable MWTs using folding mechanism. The MWTs are designed by
using the tripod stand folding mechanism and telescopic folding mechanism. The
turbines have an original height of one meter and convert into the total height
of 0.5 meters for transportation. All parts of the turbines are detachable from
each other. Hence, the total setup changes into three parts with 0.5-meters
The side arms, blades and
vertical shaft are detachable from each other. The length of each part is 0.5
meters, which makes it compact enough to place inside the rucksack or the
traveling bags. They are handy to carry when traveling by car as they easily
accommodate in the backside of the car.
These wind turbines use tripod
stand mechanism for legs and telescopic folding mechanism for side arms. The
tripod stand brings extra stability to the turbines while installation and the
side arms grant great variation in the projected area.
Portability of wind turbines
This power generated by the
turbines is directly proportional to the wind velocity. Hence, it increases
with the increase in the wind speed. It
gives a power output of 94.815 W and 320W at a wind speed of 10 m/s and 15m/s
x 1.29 x 0.5 x 53 x 0.294
The values of air density (1.29)
and power coefficient (0.294) at the sea level have been considered for
calculations. Now, for designed turbines, if the air is blowing at the speed
of 5 m/s, then the power generated by
the turbines is 11.85 watts (W).
Cp= Power Coefficient.
V = wind speed (m/s)
A = projected area (
? = air density (kg/
= power (W)
Power is also an important factor
for the designed turbines. They must be powerful enough to charge the devices.
The electric power generated by VAWTs is calculated by using the following
Figure 7: design of micro VAWT *
The movement of the blades result
into rotation of the vertical shaft that generates electricity. The electricity
generated is stored in the batteries. Two charging outlets of 5 W capacity and
one charging outlet of 10W capacity are placed at the bottom of the vertical
shaft. This increases the ease of connecting devices to the turbines for
The micro VAWTs with a
combination of a telescopic mechanism and a tripod stand mechanism, as
discussed above, is shown in figure 7. It consists of three symmetrically
arranged Darrieus airfoils. They are mounted on the telescopic side arms, which
are flexible in length. The battery and the generator are situated inside the
vertical shaft, and the power outlets are provided at the bottom part of the
vertical shaft. The vertical shaft is circular in shape, which helps in
accommodation of the battery and generator.
Figure 6: Tripod stand mechanism, (SIRUI T2204X
4-Section Al (2)) 8
Selecting a tripod stand mechanism improves the stability of the Micro
VAWT. And it is also helpful in accommodating the vertical shaft. Moreover, it
simplifies the location of charging outlets. The side arms and blades are made
detachable from the vertical shaft to make it convenient to carry.
Tripod stand mechanism
Figure 5: Telescopic mechanism, (ESTO
In case of Darrieus VAWT, the blades are mounted on the Vertical shaft
with the help of a side arms. To make it portable during transport, reducing
the length of side arms is necessary. The telescopic mechanism is used to
adjust the length of the arms. Also, it provides us with the flexibility of the
cross-section area of the wind turbine.
Telescopic folding mechanism
After observing these available portable WTs,
the combination of the folding mechanisms (telescopic mechanism, tripod stand mechanism)
output obviously varies depending on wind-speed, but the turbine can reportedly
produce a constant output of 5 watts if the wind is blowing at 18 km/h (11
Figure 4: Nil’s Ferber Folding
turbine. (Folding turbine makes smartphone charging in the wild breeze ) 6
Nils Ferber has built this turbine as the project for his Master’s
course of product design at the Ecole Cantonale d’art Lausanne (ECAL). It
weighs 1 kg. The umbrella folding mechanism is used to make the Savonius blades
portable. The turbine installed by pulling on the telescopic shaft based on
tension and compression. It is secured with the help of guide ropes.
Nils Ferber’s folding WTs for charging smartphones.
figure 3: Trinity
holds a 15W generator and a 15,000 mAh battery inside the vertical shaft. It
has a weight of about 1.8 kg. The use of tripod stand mechanism helps to reduce
the height of Trinity wind turbine to 12″ from a total height of 23″. 2
Skajaquoda has designed the Trinity wind turbine. It consists of legs
and three blades made up of aluminum and plastic. Trinity uses tripod stand
folding mechanism for legs to make it portable. It is basically a Savonius wind
The Trinity wind turbines
The folding mechanism plays a
vital role to make VAWT portable. The folding mechanisms used in existing
portable WTs are studied. They are as follows:
Selection of folding mechanisms
The available portable WTs are Savonius WTs.
Instead of having high start-up velocity, Darrieus WTs have better efficiency
than that of Savonius WTs. Darrieus WT is the one which should be taken into
consideration. Hence Darrieus WT is selected.
Darrieus wind turbine 4
This turbine consists of two or three blades
mounted on the rotating shaft or framework. This arrangement is equally useful,
no matter in which direction wind is blowing. It is a lift type device, and the
blades are always symmetrically arranged. Their efficiency is more than that of
the Savonius wind turbines.
Darrieus wind turbines
Savonius Wind Turbines R 7
blades are used to convert the force of the wind into torque on a rotating
shaft. The turbine consists of many airfoils, but not always vertically mounted
on a rotating shaft or framework. It is one of the simplest turbines.
Aerodynamically, it is a drag type device which consists of two or three
scoops, ‘S’ shape in cross-section. These turbines are used whenever cost or
reliability is much more important than efficiency.
Savonius wind turbines
on the types of blades, there are two primary types of VAWTs: drag-type
(Savonius) and lift-type (Darrieus). A drag-type turbine performs better at the
initial start-up wind speed and lift-type turbines have higher efficiency.
Selection of the blade type
The objective is to generate a small amount
of power, and the turbine should be portable enough to carry. Hence the micro
VAWT is selected for the desired goal.
MWTs have less cost of installation compared
to other renewable energy resources and are used in places where the
electricity is not available. 5
“According to the IEC 61400-2 standard of the
International Electrotechnical Commission (IEC), WTs are again divided into two
classes: small WTs (SWTs), having a rotor-swept area of 200 m2 or
less, and large WTs (LWTs), with a rotor-swept area larger than 200 m2.
According to the Small and Medium Wind UK Market Report 2013, commercially
manufactured SWTs are analyzed in three classes: micro WTs (MWTs), SWTs, and
small-medium WTs (SMWTs).” 5
1) The axis of rotation is parallel to the direction
of wind flow.
1) The axis of rotation is perpendicular to the direction
of wind flow.
2) Air strikes from one direction.
2) Air strikes from all directions.
3) Gearbox cannot be placed on the ground.
3) Gearbox can be placed on the ground.
4) The tower is essential; hence the cost of
erecting is high.
4) The tower is not essential, hence reducing the
cost of erection.
5) A yaw mechanism is required.
5) A yaw mechanism is not required.
6) Control system is required.
6) Control system is not required, hence reducing
the cost of frequent maintenance.
1: Difference between HAWTs and VAWTs *
Wind turbines are divided into two main types: Horizontal Axis Wind
Turbines (HAWTs) and Vertical Axis Wind Turbines (VAWTs). They are used all
over the world for high-scale and low-scale power generation.
Types of turbines
Design of wind turbines
The first step is to become familiar with different types of wind
turbines, blades and then select the best. The primary focus is on the folding
mechanism. This research paper considers the existing folding mechanisms, to make
the wind turbine portable.
The objective of this research is to make use
of wind turbines as a never-ending source of energy to charge portable devices.
To achieve this goal,
folding mechanisms are selected to make it portable to carry and powerful
enough to charge the devices.
To charge portable devices, these WTs should become portable otherwise
it is difficult to carry them. This paper intends to research on a folding
mechanism for WTs to make them easy to carry and to provide a clean and
unlimited source of power for different portable devices. Chapter three
describes the process of selecting the type of turbines, blades and folding
mechanisms for the proposed wind turbines. Results and calculations are discussed
in the later part of the paper.
Wind turbines (WTs) are a clean
and unlimited source of energy. However, most of the innovations in wind energy
have been intended to produce power on a large scale. Those devices are
enormous and are not useful in charging portable devices. One step closer to
the wind energy leads to the use of micro wind turbines(MWTs) to charge these
devices using the unlimited power of the wind. 2
Batteries are the primary power source of
these devices; their capacity is one of the limiting factors. They depend on electrical outlets to power them. Most
electrical outlets are stationary, which reduce their availability and
flexibility while charging. 9
Energy is input to drive and improve the life of human beings. The
consumption of energy is directly proportional to the progress of humanity in
various forms. Nowadays, many people are using portable electronic devices
which are accessible and technologically advanced; hence humans have become addicted to them. They all need
the energy to run. With our increasing dependency on
technology and portable devices, it is impossible to keep charging these
Humans are using a variety of renewable
sources of energy for a long time. But, the power generation using these
sources is done on a large scale and the devices used for this purpose are huge
in size. They are not available for small power generation. Today, the use of
portable devices has increased to a large extent and have become an inseparable
part of daily life. They work on electricity and must be charged whenever they
run out of charging. Considering their daily use, they need charging every now
and then as their power source i.e. batteries have low capacity. Wind is an
unlimited source of energy and is one of the solutions to this problem. The
micro wind turbines (MWTs), are small in size and generates a small amount of
energy. This paper works toward making the MWTs portable. These turbines are
made convenient to carry using folding mechanisms to charge the devices. The
side arms and stand are made compact using a telescopic and tripod stand
folding mechanism respectively. The designed turbines generate an electrical
output of 11.85 watts when the wind is blowing at a velocity of 5 m/s, which
increases with increase in wind velocity. The whole wind turbine converts into
three different parts of 0.5 meters length each for transportation and are easy
to install. They are capable of charging two small portable devices at a time.
This eliminates the need for an unlimited source of power to charge the devices
irrespective of the time and place.
Dhiraj Umaji Devardekar
South Westphalia University of Applied Sciences
Micro Wind Turbines