# The vertical shaft. This increases the ease of connecting

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.

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 charging.

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Figure 7: design of
micro VAWT *

1
Results

1.1
Power calculations

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 formula.

= 0.5
? A

Cp

Where,

= power (W)

? = air
density (kg/

)

A =
projected area (

)

V =
wind speed (m/s)

Cp= Power Coefficient.
10

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).

= 0.5
? A

Cp

= 0.5
x 1.29 x 0.5 x 53 x 0.294

=
11.85 W

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 respectively.

1.2
Portability of wind turbines

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.

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.

2
Conclusion

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 length.

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.

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.