Sun Tracker System for Solar Panels
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Transcript of Sun Tracker System for Solar Panels
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N.Arunraja
S.Gowtham Aswin
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The modern demands for electricity is pushing the energy sector to its limits. With the risk of exhausting the fossil fuels becoming a reality, it is necessary to focus more on renewable sources such as solar energy.
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To make use of this bounty-full source, one of the prominent methods is to use solar panels, to get electrical energy out of solar energy.
But to achieve maximum potential power extraction, the solar panel must be held normal to suns radiation at all times.
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OBJECTIVE DESCRIPTION
This project aims at
maximizing the power
output of a solar panel by
orienting the solar panel
according to the position of
sun throughout day.
The system uses a simple
traveling nut actuator to
impart the required motion
to the solar panel. A
microcontroller is used to
operate the stepper motor to
effectively control the
panel's position with respect
to the sun.
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Azimuth : It is the
angle by which the sun
is displaced from the
exact centre of the sky.
Zenith : It is the actual
inclination of the sun to
the apparent horizontal
plane.
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AZIMUTH ZENITH
The azimuth of the sun to a location varies from one place to another.
It is in direct proportion to the latitude of the considered location.
Generally, for southern India it is about 15 degrees in average.
The corresponding arrangement can be adjusted by changing the lengths of the
The zenith of the sun varies
approximately from 0 to 180
degrees throughout the day.
To achieve normal orientation
of the panel to the suns rays, a
simple timed motor controlled
using a microcontroller is
used.
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The basic idea is to use a simple mechanical system which aligns the solar panel using a linear actuator. The solar panel is mounted on a rotating shaft.
This shaft is fixed to the frame through bearings. One end of the shaft is fixed with an extended lever arm which is connected to a linear actuator.
Any linear motion to the arm rotates the solar panel by an angle corresponding to the linear displacement.
The linear actuation is provided by a stepper motor which has been coupled to the lead screw and nut arrangement
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The major components in the
setup include
1. Frame and bearings
2. Shaft
3. Panel holder
4. Lever arm
5. Lead screw and Nut
arrangement
6. Stepper motor
7. Microcontroller setup
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SOLAR PANEL :
A 18 cell 9V 5W solar panel was acquired from Free Spirits
Green Labs. It is a polycrystalline solar panel, which has a life of
more than 25 years.
MICROCONTROLLER :
An Arduino platform board with Atmega-8 microcontroller was
used for the project.
STEPPER MOTOR :
After initial calculations a simple and mass produced 5V stepper
motor (28BYJ-48) is selected. It is 12 steps per revolution,
geared motor with a gear ratio of 64:1.
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TRAVELLING NUT ACTUATOR :
It is a simple leadscrew and nut arrangement where theleadscrew is fixed. The nut moves linearly with respect to the rotarymotion of the leadscrew.
SHAFT AND PANEL HOLDER :
The solar panel is kept in a panel holder of suitable design, thispanel holder is fixed to a rotating shaft which in turn is fixed to theslider arm.
SLIDER ARM :
As the nut moves corresponding to the leadscrew movement, itslides in a slider arm connected to the shaft which converts thelinear motion into corresponding rotary motion.
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DRIVE SETUP :
The stepper motor is independently fixed to the panel with the help
of two screws. The drive from the plank is transmitted through a
pair of gears to lead screw. A M6 thread rod of pitch 1mm is used
as the lead screw in this arrangement.
The thread rod is cut to a required length and is put in the steel
plank through a drilled hole. The lead screw is held in place using a
lock nut, thus allowing free rotation. The gear ratio given to the
motor and the shaft is 2.5.
The nut arrangement is provided by the connection joint, which is
drilled with a 6mm bit and tapped with a M6 tap. This is threaded
along the lead screw providing the nut arrangement of the lead
screw.
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A. Lead Screw Calculation
Moment required to turn the solar panel :
Weight of the solar panel setup = 15 N
Distance of CG of solar panel from shaft axis = 50mm
Moment required = W*d = 7.5N-mm
Force to lift the connection joint :
Radius of the lead screw = 3mm
Force = (Moment)/(Radius of lead screw)
Force to lift setup = 25N
Torque required to drive the lead screw:
T = (F*d/2)*((1+d)/(d-l))
Taking
Coefficient of friction for steel, = 0.15 Applying to the torque equation,
Required torque, T = 15.35 N-mm
Thus the stepper motor has a rated torque of 64 N-mm, which is well above the minimum required torque for the lead screw.
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B.Slider Calculations
The required stroke length of the travelling nut is calculated from trigonometric relations :
cos(/2) = R(max)/R(min) Taking an angle, = 105 (by careful considerations) R(max) = 30/cos 52.5 R(max) = 49.28 mm Slider length = R(max) - R(min) = 20 mm Total stroke length = 2*R(max)*sin(/2) = 84mm C.Alignment Calculations
From 9am to 4pm; Total hours = 7 hrs. Angular rotation = 15 degrees per hour By ignoring the linear to angular motion inequivalency, Required displacement per hour = 84/7 = 12mm Pitch of the lead = 1mm Required revolutions per hour = 12/1 = 12mm Having a motor actuation for every 10 minutes, Required revolutions per 10 mins = 12*10/60 = 2
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The required interfacing of stepper motor and microcontroller is
through simple C programming in Arduino IDE, which is imported
to the microcontroller.
The following conditions are achieved in the programming logic :
1. Two rotations per every 10 minutes from 9 a.m to 4 p.m.
2. Complete reset to the original position after 42 complete rotations.
RESULTSIn increased output is observed. Various studies from external
sources indicate an increase of output by 15-20%.
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THANK YOU
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