S.NO TOPIC PAGE NO.
6. Methodology and Result
8. Future prospects
Abstract- Sun tracking solar panel system is a way of generating power that uses sunlight as its source. This method of power generation is simple to understand and is taken from natural resource found in our surrounding. This needs only the maximum sunlight to generate power by using sun as the natural source. In this text, we try to understand how to generate power by setting the equipment in such a way that we get maximum sunlight from the sun automatically without any physical labor. This system is utilizing the maximum intensity of light. When the system observes a decrease in the intensity of light, it automatically changes its direction to get maximum intensity of light.
Fig. 1: Solar tracking system
INTRODUCTION-The extraordinary increase in the demand for electricity rapid growth of population and the recent change in the environmental conditions such as global warming led to a need for a new source of energy that is cheaper and sustainable with less carbon emissions. Solar energy has offered promising results in the quest of finding the solution to the problem.
Solar Panels are a form of solar power generation which utilizes sunlight as its source. Solar Cells, or known otherwise as photovoltaic cells, are arranged on the surface of the solar panel. Solar panels are made up of silicon, which is used in other industries (microprocessor industry), gallium arsenide (which is expensive ) and silver wirings which is produced exclusively for use in photovoltaic cells. Solar panels are a system that collects the solar energy from the sun and converts that energy to electricity. Solar panels comprises of several individual solar cells. These solar cells work exactly like large semiconductors and utilize a large area p-n junction diode. When the photons strike the solar panel, electrons get out of their orbits, these electrons are then pulled in by the electric field of the solar cell and are then converted into directional current, thus in this way the solar cell generates electricity. With better quality and large number of solar cells in a solar panel, we can increase the quantity as well as the quality of energy generated by the solar panel. The process or term that relates to the conversion of solar energy from the sun’s rays to electrical energy is known as “Photovoltaic Effect”.
A solar tracker is a device that helps the solar panel change its direction toward the sun. The use of solar trackers can increase the production of electricity by the solar panel up-to 30%-40% when compared with similar devices that are fixed at an angle. In any solar device, the efficiency is improved when the modules are continuously adjusted to the angle at which the sun is oriented in the sky. With the improved efficiency, one can increase the yield thus sun tracking solar devices have become quite popular.
As we all know that the sun continuously changes its position in the sky, thus we have developed two types of solar tracking devices:
1. Single axis sun tracking solar panel
2. Double axis sun tracking solar panel
Single axis sun tracking solar panels can either have a horizontal or a vertical axle. The horizontal type of sun tracking solar panel are used in tropical regions where the sun gets very high at noon, but the days are short such as Malaysia and Singapore. The vertical type of sun tracking solar panels are used in high latitudes where the sun does not get very high, but summer days can be very long such as United Kingdom and Norway.
Fig. 2: Single axis solar tracker
Double axis sun tracking solar panels have both a horizontal and a vertical axis and thus they can track the sun’s orientation at any part of the world, it is thus used to control astronomical telescopes and so there are a lot of systems available to automatically track the orientation of sun at any part of the sky. Double axis sun tracking solar panels track the sun both east to west and north to south for added power output and convenience.
Fig. 3: Dual axis solar tracker
Solar tracker devices are divided into three main types according to their positioning:
1. Passive Trackers: These type of trackers use the sun’s energy to heat the gases so that the solar panel is able to face the direction of the sunlight. This mechanism utilizes two compressed gas fluid cylinders which are places on the east and west side of the panel, thus when one cylinder gets heated up, the other side of the piston rises up to make the solar panel face the direction of the sun.
2. Active Trackers: These type of trackers use light sensors which help it to determine the direction of maximum intensity of light. These are paired with stepper dc motors which help move the solar panel to the required direction.
3. Open Loop Trackers: These type of trackers don’t use any sensors but instead use pre-recorded data to predict the movement of the sun.
Fig. 4: Passive tracker
Fig. 5: Active tracker
Resistors that depend on the intensity of light are made up of high resistance semiconductors. If light is of high enough frequency, photons that are absorbed by the semiconductor give the bound electrons enough energy to jump into the conduction band. The resulting free electron conducts electricity and thus lowering resistance. Hence, light dependent resistors are very useful in this light sensing circuit. LDR is of a very high resistance. A sensor is a device that measures a physical quantity and converts it into a signal.
The 555 timer is a very cheap, popular and reliable timing device that can be used as a simple timer to generate single pulses. The 555 timer chip is highly robust and stable 8-pin device and is very accurate. The single 555 timer chip in its basic form is a Bi-polar 8-pin mini dual-in-time package (DIP) device consisting of some 25 transistors, 2 diodes and 16 resistors arranged to form two comparators, a flip-flop and a high current output stage.
The 555 timer name comes from the fact that there are three 5 kilo ohm resistors connected together internally producing a voltage divider network between the supply voltage at pin 8 and ground at pin 1. The two comparators produce an output voltage dependent upon the voltage difference at their inputs which is determined by the charging and discharging action of the externally connected RC network. The
outputs from both comparators are connected to the two inputs of the flip-flop which in turn produces either a HIGH or LOW level output at Q based on the states of its inputs.
Fig. 6: 555 timer block diagram
The CD4017B is a 5-stage divide-by-10 Johnson counter with 10 decoded outputs and a carry out bit. These counters are cleared to their zero count by a logical 1 on their reset line. These counters are advanced on the positive edge of the clock signal when the clock enable signal is in the logical 0 state. The configuration of the CD4017B permits medium speed operation and assures a hazard free counting sequence. The 10/8 decoded outputs are normally in the logical 0 state and go to the logical 1 state only at their respective time slot. Each decoded output remains high for 1 full clock cycle. The carry out signal completes a full cycle for every 10/8 clock input cycles and is used as a ripple carry signal to any succeeding stages.
Fig.7: Pin configuration
The Darlington pair is basically a combination of two bipolar transistors. This circuit is used for amplifying currents, i.e. the amplified current from the first transistor is further amplified by the second transistor.
Fig. 8: Darlington Pair
ULN2003 is a high voltage and high current Darlington array IC. It contains seven open collector Darlington pairs with common emitters. A Darlington pair is an arrangement of two bipolar transistors. ULN2003 is commonly used while driving stepper motor.
Fig. 9: Motor driver IC
A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The stepper motor is used for position control in application like disk drives and robotics.
The name stepper is used because this motor rotates through a fixed angular step in response to each input current pulse received by its controller. In recent years, there has been widespread demand of stepper motor because of the explosive growth of computer industry. Their popularity is due to the fact that they can be controlled directly by the computers, microprocessors and programmable controllers. Stepper motors are ideally suited for situations where precise position and precise speed control are required without the use of closed-loop feedback.
The stepper motor converts digital signals into a fixed mechanical increment of motion. It thereby provides natural interface with the digital computer. It is a synchronous motor such that rotor rotates a specific increment number of degrees for each pulse input given to the motor system. These motors can provide accurate positioning without the need of position feedback sensors when compared to other motors. The position is known simply by keeping track of the input step pulses
Fig. 10: Stepper motor & its internal diagram
METHODOLOGY & RESULTS
Fig. 11: Block diagram of solar tracking system
Components used: i) Light sensing circuit:-
b) 555 Timer
ii) Motor controlling circuit:-
a) Decade counter
b) Darlington pair ( TIP 120, TIP 120 )
c) ULN2003 Driver IC
d) Stepper motor ( 5W, 12V )
Fig. 12: Block diagram for motor control
Fig. 13: Light sensing circuit
Fig. 14: Output pulse from light sensing circuit
Working of light sensing circuit:
In this circuit constant current is given in LDR and constant voltage is given across 555 timer. In monostable circuit a triggering pulse is needed; this pulse is given by LDR. LDR has a negative temperature coefficient, so when the circuit is kept under light, the resistance across the LDR decreases. As current across the LDR is constant and resistance decrease with light intensity, voltage starts to change its state, this voltage is working as triggering pulse in monostable circuit. From monostable multivibrator circuit we get voltage waveform, which remains in high state at first, then changes its state with varying light intensity.
Working of above CRO circuit:
Here Cd4017 is a decade counter, this counter gives medium speed operation and hazards-free counting sequence, output pulse from light sensing circuit act as clock pulse in decade counter ( i.e. at pin no. 14 ). Here output is taken from ( 00, 01, 02, 03 ) pins which are connected through resistance to Darlington pair. Darlington pair is used to obtain high current gain because current obtained from decade counter is amplified by Darlington pair ( which is a arrangement of bipolar transistor ). This high current gain is needed for driving more load. Diode is connected across the Darlington pair to remove spike in case of inductive load. Resistance is connected in the base of Darlington pair to control the leakage current across CE. Output pulse of Darlington pair is connected across ( 1,2,3,4 ) pins of ULN2003 ( which acts as motor driver IC ). This gives more current gain as it is a Darlington pair IC to drive the load. Stepper motor is connected with it, which moves in a step. As output of decade counter changes sequentially, speed increases motor torque decreases which gives movement to load ( i.e. solar panel ).
RESULTS AND PERFORMSNCE ANALYSIS
• Low cost
• We can monitor directly using pc
• Tracking accuracy is more
• Reduce the usage of power from power grid
The oldest solar application is day lighting the use of window and other means allowing indirect sunlight to provide effective internal illumination inside buildings.
Solar thermal, when used for space heating is needed mostly in the winter cold and temperature climates.
For process heat, which include solar domestic hot water, as well as heat for industrial processes, the active solar thermal systems shine because year round usage can make this still relatively inexpensive system easily economic.
A solar tracking system comprising a first set of solar transducers that produce first electrical output signals to drive a reversible first motor for changing angle of the solar collector, each of the transducer having a thermistor in thermal contact with a thermal mass, where as the thermal mass comprises a mass of conducting material to elevate in temperature while illuminated by the sun, and wherein the thermistor senses the temperature of the thermal mass and produces a corresponding one of the electrical output proportional to the temperature, and each of the transducers having the thermistor and thermal mass contained in a solar energy collecting in a solar energy collecting and heat insulating enclosure that is solar energy transparent.
By using real time clock we can adjust the panel directions according to the sun’s angle without using sensors.
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