Design and Construction of a Single Axis Solar Tracker System Based on Microcontroller Circuits

Abstract

Emphasizing the importance of the new and renewable energy sources, sun will be the major primary source of energy which will satisfy our needs for the coming years ahead. Also, there is an urgent need for enhancing the utilization of solar energy with maximum possible efficiency. So, during the course of the present thesis, a prototype single- axis solar tracking system was designed, implemented and tested in-door and out-door, where its operation is proved to be satisfactory.

Basically, the operation of the implemented model of the device is based on a servo motor intelligently controlled by an electronic dedicated drive unit, based on microcontrollers (Arduino Uno), which moves the proposed solar cells or panels (monocrystalline and polycrystalline silicon solar cells and panels as well polymer solar panels) according to the received signals from two simple but efficient light sensors (Light Dependence Resistors, LDRs) to the maximum rays of the sun or light.

The axis of rotation for the proposed tracker is vertical with respect to the ground, in order to ensure its rotation from East to West over the course of the day. As a result, it is proved that the proposed tracker ensures the optimization of the conversion of solar energy into electricity by properly orienting the photovoltaic cells and panels in accordance with the real position of the sun.

Finally, during the course of the work, design steps, simulations, tests, experimental implementation of the proposed solar tracker and its in-door and out-door applications were carried out as follows:

First: Detailed design, block diagram, flow chart, and program of the prototype solar tracker were investigated.

Second: Different simulation programs (Proteus, PVEducation and Solar Electricity Handbook) were used for detailed simulation tests for each:

1- Light sensor electronic control circuit: comprises of two LDRs and the microcontroller. 2- Electronic control circuit of motor: comprises of servo motor and the microcontroller. 3- The solar tracker control unit system: the final design for the solar tracker control unit. 4- The electrical and physical characteristics of monocrystalline silicon solar cells. 5- Studying the solar irradiance and the optimum tilt angle of a certain solar panel whenever located at cites: Cairo-, Al-Arish-, and Aswan- Egypt.

Third: Detailed experimental tests for the implementation steps of the proposed solar tracker system were investigated, as:

1- Calibration of the different light sources (Fluorescent, Cold White Flood LED and Incandescent). In this concern, their light intensity and heat emission were carefully studied in different experimental conditions.

2- Detailed in-door characterization study (I-V, P-V) and performance measurements of the proposed photovoltaic cells and panels under a wide spectrum of light sources and different illumination levels ranging from 0.14 klux up to 50 klux. Also, for the proposed samples, their electrical characteristic parameters (short circuit current Isc, open circuit voltage Voc, maximum output power Pmax, fill-factor F.F. and efficiency η), were plotted as a function of the illumination levels for all the proposed light sources, where the following was obtained: a- Short circuit current: is a direct increasing function of the light intensity. b- Open circuit voltage: is a direct increasing function of light intensity up to around 10 klux, but for higher illumination levels, it tends to be saturated. c- Maximum output power: is a direct increasing function of the light intensity. d- Fill-factor: for all samples and under the influence of the different light sources, it shows an average values around 0.4-0.5 at all the different illumination levels for all the proposed samples. e- Efficiency: During the study it was observed that the value of the efficiency increases with different rates within light illumination levels up to 10 klux. But for higher illuminations, up to full solar level, it shows a steady state values.

3- Finally, the spectral responses of the proposed solar cells and panels were plotted in comparison with the emission spectra of the used artificial light sources. The output of the solar cells and panels is shown to be dependent on the following: their different materials and spectral response as well the intensity of the incident light and its wavelength. In this concern, a- The absorption spectra of the monocrystalline silicon solar cells are lying between 400 nm to 950 nm from the solar spectra and its peak absorbance is between 500 nm to 700 nm. b- The absorption spectra of polycrystalline silicon solar panels are lying between the range 300-1200 nm from the solar spectra, where its peak is between 600-950 nm. c- For the polymer solar panels its absorption spectra is in the range of 300-800 nm from the solar spectra and its peak absorbance is between 400-600 nm.

From the above results, one can identify the most suitable materials for solar cells and panels for using in in-door solar energy systems. In this concern, it is appear that monocrystalline and polycrystalline silicon solar cells and panels have high efficiency with incandescent lamps. On the other hand, the polymer solar panel has its high efficiency with cold white flood LED.

4- Calibration of LDRs based on a potential divider circuit was investigated at different illumination levels ranging from complete darkness (0.0 lux) up to full solar illumination level (100 klux). For the investigated illumination levels, the output voltage of the light sensor (LDR) was decreased from 5.0 Volts down to 0.05 Volt.

5- Implementation and construction of the prototype single-axis solar tracker according to the following steps: a- Electronic control circuit of servo motor with Arduino Uno. b- Electronic control circuit of the system.