Mechanical Solar Tracking Mechanism

The mechanical solar tracking mechanism is a solar tracking mechanism which utilizes only electromechanical means to track sunlight.

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Most contemporary implementations of the solar tracking mechanisms in solar installations around the world are completely programmed. The mechanical solar seeker aims to improve the efficiency of contemporary programmed tracking mechanisms by only electromechanical means.

This project also aims to offer a low-cost solar tracking solution so that solar-powered systems can be easily installed and maintained in under-developed and developing countries.

  • Introduction:
    • In photovoltaic systems, solar tracking mechanisms help minimize the angle of incidence (the angle that a ray of light makes with a line perpendicular to the surface of reception) between the incoming light rays and solar panel, which increases the amount of energy that an installation produces. In simple words, solar trackers continuously direct solar panels or modules towards the sun for better energy output.
    • Although the invention of a tracking mechanism was a breakthrough in harvesting solar energy more efficiently, the contemporary implementations of solar tracking mechanisms have some significant drawbacks.
    • Through this project, I offer an alternative design which is significantly more efficient in terms of power output, durability, production cost and repairability than contemporary models. 
  •  Objective:
    • Most contemporary implementations of the solar tracking mechanisms in all solar installations around the world are completely “programmed”. The mechanical solar seeker aims to improve the efficiency of contemporary “programmed” tracking mechanisms by only “electromechanical” means.
    •  This project also aims to offer a low-cost solar tracking solution so that solar powered systems can be easily installed and maintained in under-developed and developing countries.
  •  Materials used:
    •  Light Dependent Resistor (LDR), two solar panels, fours NPN transistors, two reed switches, IC 555 components, assorted resistors, 1000 µF 16 V capacitor, Two BC 557 transistors (PNP), Light Emitting Diodes (LEDs), 12 V DC gear motor, battery power source(9V), one battery clip, two magnets, wooden frame.

  • Underlying Principles of Operation and Innovation:
    • We first discuss the operation principle of a contemporary programmed solar tracking mechanism and then that of our mechanical version.
    • Programmed Solar Tracker :
      •  On the sunlight reception surface of the programmed tracker, there are a large number of light dependent resistors (LDR) which show variable resistance depending upon the intensity of light falling on each of them.
      • The intensities of sunlight received by LDRs on two halves of the sunlight reception surface help in figuring out the position of the source of light. A ratio of intensities of light falling on two halves of the surface is computed as per the resistances shown by the LDRs embedded in both the halves.   
      •  This ratio, computed by an appropriate program, tells the microcontroller to turn the frame (or sunlight reception surface) towards the source of light till the intensities of sunlight on both halves of the surface become equal to each other i.e. the intensity of sunlight falling on the surface becomes uniform which will also be the maximum intensity of the source of light.  
    • Some drawbacks to be noted about the programmed tracker:
      • The programmed tracker “tracks” sunlight at every small instant of time. As soon as the ratio of intensities on the two halves of the surface changes, the microcontroller turns the surface to attain equilibrium. However, this feature of continuous movement is not really necessary because the sun undergoes an extremely small displacement from its position in small instants of time. In such cases, energy lost in moving the surface towards source of light is more than that gained by the tracker. (DRAWBACK 1)
      •  As the programmed tracker continuously tracks sunlight, a program logic is carried out at all times to compute the relevant intensities. This is the most energy consuming process in the programmed tracking mechanism. Even when the surface is positioned to receive maximum intensity of light, the program logic keeps on consuming energy. (DRAWBACK 2)
    • Broadly speaking, we also understand from the above discussion that a solar tracker carries out two basic processes:
      • Moving the reception surface (or frame) towards the source of light. This process is termed...
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  • 1
    Development instructions for LDR circuit
      • LDR circuit: 
        • The LDR circuit consists of a light dependent resistor and a class B amplifier         arrangement. The class B amplifier arrangement is just a combination of PNP (positive-negative-positive) and NPN (negative-positive-negative) transistors which are so matched that the PNP transistor is biased (conducts electricity) for half cycle and NPN transistor is biased for the second half cycle of the input. Circuit diagram 1 shows the LDR circuit. The output from the LDR circuit is recorded by IC 555. The LDR circuit arrangement should be as follows:

                                                                       Circuit diagram-1

      • At the “sun-bright” position, LDR shows low resistance due to high intensity light falling on it. As a result, the base of the NPN transistor receives high negative voltage as per circuit diagram. This causes the NPN transistor to remain turned off and it does not conduct any current. However, the PNP transistor remains biased and allows the flow of current from it which contributes towards the output supply. This output resets the IC 555 and triggers the DC gear motor to stop. Hence, the reception surface or frame stops at the sun-bright position.
      • In case the frame is not in sun-bright position, the LDR shows high resistance due to low intensity light. However, this time NPN transistor gets low positive voltage from the main positive line. As the output from the NPN transistor is turned on, the output from the PNP transistor is cut off and the IC 555 is reset again which triggers the DC gear motor to move the frame till the maximum intensity light is found again.

  • 2
    Development instructions for magnetic proximity circuit
    • Magnetic Proximity Circuit:
      •  The magnetic proximity circuit comprises of an IC 555, two reed switches, two magnets attached behind the frame and a H-bridge arrangement. The H-bridge arrangement is a combination of 4 NPN transistors or switches in general that enable a voltage to be applied across a load in opposite direction. It is crucial in switching the polarity of DC gear motor and reversal of the motion of frame. Reed switches are switches which can turn on or off when subjected to a magnetic environment. Circuit Diagram-2 shows the magnetic proximity circuit.
    •                                                                Circuit Diagram 2
      • In the magnetic proximity circuit, the output from the LDR circuit is received by the IC 555. The output from the IC, connected to the DC gear motor via pin number 3 and 7, controls the motion of the frame.  Pin number 8 is connected to the positive power supply. Reed switches are connected to pin number 2 and pin number 4.
  • 3
    Separating out the tracking and stopping principles through continuous oscillations
    • The oscillation process of the frame is made possible by defining clear bounds for the maximum angle of dip of the frame on either side of the axle of the DC gear motor by using small magnets. At the maximum angle of dip of the frame on either side, the magnets reach sufficiently close to the reed switches to impose a strong magnetic on them. This causes the reed switches to form closed circuits allowing current to flow through them. This change (drop) in resistance offered by the reed switch is recorded by the IC 555 which changes the polarity of DC gear motor. This process can be understood from Block Diagram-1. 
    •                                                        Block Diagram 1
    • Changing of the polarity of DC gear motor is established through the H-bridge arrangement. Input of the H-bridge is provided through two opto-coupler circuits which provide optical isolation between IC 555 and H-bridge. 
    • This is the most important step without which it is difficult to separate out the tracking process from the stopping process(at sun-bright position).

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