Solar arrays through power generation & tracking

International Journal of Mechanical Engineering and Technology ENGINEERING –
INTERNATIONAL JOURNAL OF MECHANICAL (IJMET), ISSN 0976
6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME
AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online) IJMET
Volume 3, Issue 3, Septmebr - December (2012), pp. 203-213
© IAEME: www.iaeme.com/ijmet.html
Journal Impact Factor (2012): 3.8071 (Calculated by GISI)
©IAEME
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SOLAR ARRAYS THROUGH POWER GENRATION & TRACKING
Babu Suryawanshi1, Ibrahim Patel2, Dr. K. Prabhakar Rao3

(1) Prof and, HOD. of Mechanical Engg., Maharashtra Engg.college Nilanga (M.S)
babu.suryawanshi@gmail.com
(2) Assoc. Prof. Dept of ECE Dr. B.V. Raju Inst. of Technology Narsapur Medak (Dist) A. P.
ptlibrahim@gmail.com
(3) Prof. Dr. Colonel (Retd.) Principal Raja Mahendra college of Engg. Ibrahmpatanam RR (Dist)
mailstokprao@yahoo.com

ABSTRACT

This paper explores the use of Mechatronics in the development of intermittent energy. The paper draws
an idea from the fact that the sun bathers the earth with more energy per minute then the world consumes
in one year. The paper effectively demonstrates and suggests the use of solar energy which is the most
inexhaustible instead of going for short term & self exhaustive energy sources. The paper proposes a
fuzzy algorithm to achieve optimal solar tracking with greater efficiency. The proposed system uses a dc
motor and light sensor & fuzzy logic.

KEYWORD: - Solar Cell, DC Motor, Solar Energy, fuzzy-logic, Light Sensor, Mechatronics System,

I. INTRODUCTION

Extraction of useable energy from the sun made possible by the invention of the Photovolatile
device and successive growth of the solar cell. The cell is a semiconductor material that converts visible
light into a direct current. By using solar arrays, a series of solar cells electrically connected, a DC voltage
is generated which can be physically used on a load. Photovolatile arrays or panels are being used
increasingly as efficiencies reach upper levels, and are particularly fashionable in remote areas where
placement of electricity lines is not cost-effectively viable. As shown in fig. 1

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

Fig.1: Solar arrays stationary setup

This substitute power supply is always achieving greater popularity especially since the
realization of fossil fuels shortcomings. Renewable energy in the form of electrical energy has been in use
to some measure as long as 75 or 100 years ago. Sources such as Solar, Wind, Hydro and Geothermal
have all been utilized with varying levels of success. The most widely used are hydro and wind power,
with solar power being moderately used worldwide. This can be attributed to the relatively high cost of
solar cells and their low conversion efficiency. Solar power is being heavily researched, and solar energy
costs have now reached within a few cents per kW/h of other forms of electricity generation, and will
drop further with new technologies such as titanium oxide cells. With a peak laboratory efficiency of 32%
and average efficiency of 15-20%, it is necessary to recover as much energy as possible from a solar
power system. As shown in the fig. 2.

Fig. 2: Block diagram of the solar systems.

II. STATE –OF-ARTS

The research surrounding solar energy has a brief history of rapid growth. Bell Telephone
Laboratories originally created Solar Cells during the 1970s (Nansen, 1995). Utilization of this
developing technology may lead to long-term solutions to the growing energy crisis. With the continued
damage to the environment and growth of energy demands new sources of energy must be realized for
continued prosperity. Experts can all agree that two basic criteria must be observed to be considered a
viable option. Energy must be low cost and reliable (Meisen, 2002; Nanson, 1995). Other criteria to be
considered are environmental effects (Meisen, 2002; Nanson, 1995) and usability of the type of energy
(Aronson, 2009; Nanson, 1995). Aronson (2009) said: “Solar and wind energy, classified as intermittent

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power, are potential sources of tremendous energy. But, the long-standing challenge is converting that
energy into usable power. (p. 48)” Mechatronics Application to Solar Tracking Continued
experimentation has driven the growth of this technology to levels of practical application. The advances
in manufacturing and growing markets demand has lowered the cost of solar cells to one-seventh of the
production cost during 1980 (Wolcott, 2002). Nansen said, “worldwide output of solar cells has increased
fifty-fold since 1978 (p. 92).” Meisen said,” IIASA/UNDP have offered a radically different scenario that
shows renewable energy, especially solar, becoming a major market share by 2050 (p. 117).” Aronson
has identified the following “categories of solar power systems.”
As our current utility systems are based on the burning of carbon fuels environmentalists are studying
the effects on the environment. Energy utilities Mechatronics Application to Solar Tracking produce
greenhouse gasses. As energy demand rises, the production of greenhouse gasses will also rise. Nuclear
power is another alternative that is harmful to the environment. Nansen (1995) said: “Nuclear power uses
a depletable resource and also leaves in its wake toxic nuclear waste.” “Hydroelectric power is generated
by a wonderful renewable source, but there are few rivers left in the world to dam and there is a growing
concern over the impact dams have on the fish population (p. 7).” From Nansen’s statement we see the
implications of hydroelectric power and how its effects the ecosystem in rivers. Rose and Pinkerton
emphasize the pollution caused by coal and nuclear power. Rose and Pinkerton (1981): “Solar cells have
no known adverse environmental impacts during operation.
Another study was conducted by Mohammed S. Al-Soud, Essam Abdallah, Ali Akayleh, Salah
Abdallah, and Eyad S. Hrayshat developed a parabolic solar cooker that automatically tracked the sun. The
cooker consisted of a parabolic array of mirrors focusing on a black steel tube in the center. Two motors
controlled the tilt and rotation of the cooker. Water was pumped into the black steel tube on one end and
exited the other end. A PLC controlled the system and adjusted the cooker based on previously calculated
solar angles. Incremental position adjustments were made in 10-20 minute increments on the horizontal
axis and 15-35 minute increments on the vertical axis (Al-Soud, et al., 2010). The parabolic solar cooker
heated the tube water to temperatures of 90̊C in Amman, Jordan (Al-Soud, et al., 2010).
Ibrahim Sefa, Mehmet Demirtas, and Ilhami Colak (2009) designed a single axis sun tracking system in
Turkey. The sun tracking system developed by Sefa and others included a serial communication interface
based on Rs 485 to monitor whole processes on a computer and record the data. Feedback data was
recorded by two photoresistors. The solar cell was aligned at a fixed 41̊ facing south (Sefa, et al., 2009).
A microcontroller observed and controlled the east-west rotation of the tracker by means of 24V 50W dc
motor (Sefa, et al., 2009). The results of the measured energy showed an increase up to 46.46% of
collected solar energy (Sefa, et al., 2009). Yusuf Oner, Engin Cetin, Harun Kemal Ozturk, and Ahmet
Yilanci (2009) developed a solar tracker utilizing the application of a spherical motor. The motor contains
a rotor containing a four pole magnet surrounded by eight individually energized stator poles (Oner, et al.,
2009). With the magnet in the middle direction is controlled by the surrounding stator poles (Oner, et al.,
2009). This design allows for three degrees of freedom. The degrees of freedom being forward and back
tilt, a left and right lateral tilt, and rotation along a z-axis.

III. PHOTOVOLTAICS DESCRIPTION

Photovoltaic (PV) cells utilize semiconductor technology to convert solar radiation directly into
an electric current which can be used immediately or stored for future use. PV cells are often grouped in
the form of “modules” to produce arrays which have the capability to produce power for orbiting satellites
and other spacecraft. Recently, with the continual decline of manufacturing costs (declining 3% to 5% per
year in recent years), uses of PV technology have grown to include home power generation, and grid-
connected electricity generation.

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On the other hand, the holes created in the n-material, which are positively charged, are pushed over
into the p-material. In fact, what is really happening here is that an electron from the p-material, which
was also made mobile by the adsorption of a photon, is pushed by the electric field across the junction and
into the n-material to fill the newly created holes? This completes the circuit as the electrons flows in all
the way around the circuit, dropping the energy they acquired from photons at a load as shown in Figure
3. The equivalent circuit of the solar cell is shown in Fig. 4.

Figure 3: PV Cell Working Principle

Fig. 4: Solar cell equivant circuit

The current supply Iph represents the electric current generated from the sun beaming on the solar
cell. Rj is the non-linear impedance of the P-N junction. Dj is a P-N junction diode, Rsh and Rs represent
the equivalent lineup with the interior of the materials and connecting resistances in series. Usually in
general analysis, R sh is large, and the value of Rs is small. Therefore in order to simplify the process of
analysis, one can ignore Rsh and Rs. The symbol o R represents the external load. I and V represent the
output current and the voltage of the solar cell, respectively. From the equivalent circuit, and based on the
characteristics of the P-N junction presents the connection between the output current I and the output
voltage V;
  q V   Where np represents the parallel integer of the solar
I = n p I ph − n p I sat  exp 
 kTA n  − 1  , − − − (1 )

  s  
cell; ns represents the series connected integer of the solar cell; q represents the contained electricity in an
electro (1 . 6 × 10 − 19 Columbic ); k is Boltzmann constant (1 . 38 × 10 − 23 j / k ); Tis the temperature of the
solar cell (absolute temperature K °); and A is the ideal factor of the solar cell (A=1 ~ 5). The current Isat
in (1) represents the reversion saturation current of the solar power. Further, Isat can be determined by
using the following formula:
3
T   qE Gap  1 1  Where Tr represents the reference temperature of the
I sat = I rr   exp  
 T − T   ,− − − − ( 2 )

 Tr   kA  r 
solar cell; Irr is the reversion saturation current at the time when the solar cell reaches its temperature Tr;
and EGap is the energy needed for crossing the energy band gap for the semiconductor materials, (the
crystalline Ve EGap ≅).

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From the study we are able to know when the temperature is fixed, the stronger the sunlight is,
the higher the open-circuit voltage and the short-circuit current are. Here we can see the obvious effects of
the short-circuit current by the illumination rather than the open-circuit current. Therefore the solar cell
can provide higher output rate as the sunlight becomes stronger, i.e. solar cell facing the sun.

IV. SYSTEM BLOCK DIAGRAM

The system architecture of the proposed solar tracking control system using microcontroller
MSB430F6438 is shown in Fig. 5. The sun light fed to the solar panel will feed the boost converter
directly which stores the electrical energy temporarily in an inductor and then charges the
battery. The battery then feeds the load during sunlight hours as well as nighttime. The boost
converter is to be operated by a digital controller. The digital controller will be based upon a
microcontroller that monitors the voltage and current levels coming from the solar cell and
controls the boost converter accordingly. Finally, the charge sensor will keep track of the charge
of the battery in order to not overcharge the battery, which may damage some types of
batteries. While not shown, all active components such as the digital controller will be getting its
power from the solar cell.

Fig. 5: System architecture of the solar tracking system.

The array solar tracking system architecture contains two motors to drive the platform,
conducting an approximate hemispheroidal three-dimensional rotation on the array solar generating
power system as shown in Fig. 6. The two motors are decoupled, i.e., the rotation angle of one motor does
not influence that of the other motor, reducing control problems. This implementation minimizes the
system’s power consumption during operation and increases efficiency and the total amount of electricity
generated. The flow chart of the tracking is shown in Fig. 7.

Fig. 6: Sketch of the two-axis array solar cells.

There are two important advantages in the array type mechanism as follows:
(1) High efficiency of light-electricity transformation.

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Since the array solar tracking mechanism has a function of rotating like three-dimensional, the array solar
tracking mechanism can track the sun in real time. Therefore, the system has high efficiency of light-
electricity transformation and has an advantage of large production.
(2) The mechanism is simple and saving power.

Fig. 7: Flow diagram of the solar tracking controller.

The two rotating dimensions of the array solar tracking mechanism are controlled by the two
independent driving sources, which do not have the coupling problem and bear the weight of the other
driving source. At the same time, the rotating inertia of the rotating panels can be reduced. As shown in
the fig. 7. Flow diagram of the solar tracking controller.

The tracking device is composed of two same LDR (Light dependent resistor) light sensitive
resistors, which detect light intensity from eastern, western, southern, and northern directions,
respectively. In every direction, there is a LDR light sensitive resistor with an elevating angle 900 to face a
light source. The two sensors are separated each one. One is using LDR light sensitive resistors to be an
eastward- eastward direction sensor for comparing the light intensity of eastward and westward
directions. When the eastward-westward direction sensor receives different light intensity, the system will
obtain the signal according to the output voltages of the eastward-westward direction sensors. As shown
in the fig. 8.

Fig.8: Motor driver circuit for solar altitude direction

A voltage type analog/digital converter (ADC0804) can read different output voltages of the
sensor and decide which direction has larger light intensity than the other direction. Then, the system will
drive the stepping motors to make the solar panel turn to the decided direction. When the output voltages
of the eastward-westward direction sensor are equal, i.e., the difference between the outputs of the
eastward-westward direction sensors is zero. Then, the motor voltage is also zero. This means that the
tracking process is completed in the eastward-westward direction. Similarly for another southern-northern
direction sensor, it can be analyzed by the same methodology to track the sun in the Southern-northern
direction.

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Fig. 9: Print circuit board of motor driver circuit

Motor driver circuit: This experiment is conducted by the main source of power or motor which
functions both altitude and azimuth directions. Two 12 volt direct circuit motors are employed in the
device. The motor test from head gear indicates that the motor speed is at 8 rpm. This part is split into two
significant parts which are the altitude part and azimuth part. The motor structure is as displayed in the
Fig. 9.

V. EXPERIMENTAL RESULTS

The experimental solar cell panels are shown in the fig.10 (a), (b), (c) and (d) & fig.11. Solar
intensity of the light reaching the Earth is dependent on the sun’s angle of altitude. Solar radiation is
always at highest on a plane that is perpendicular to the sun’s ray. As the horizontal and the altitude angle
change throughout the day and the year, the incidence angle of the solar radiation varies constantly on
given areas. Orienting panels to keep them facing the sun can achieve significant energy gains in
comparison of any fixed position. Gains of 50% during summer and 300% during winter have been
mentioned for a comparison between tracked and horizontal planes. It is interesting to realize that rarely
panels will be installed on horizontal plane. An altitude angle near 30o is normally used in south Indian
area. Despite the fact that percentage gains appear lower during summer than winter, the yield increase is
predominant during the summer period of the year as shown in Fig.10 (b).

Solar trackers may be solo axis or double axis. Solo axis trackers usually use a polar mount for
maximum solar efficiency. Single axis trackers will usually have a manual altitude (axis tilt) adjustment
on a second axis which is adjusted on regular intervals throughout the year. Compared to a fixed amount,
a single axis tracker increases annual output by approximately 30% and a double axis tracker an extra 6%
shown in the fig.12. A tracking device is more expensive than a fixed mounting rack. It requires a
modifiable vertical that can withhold larger wind pressure during storms. It can either be equipped with
an electric drive.
The produce desired output DC voltage and current. Since solar cells are difficult to be produced,
every solar cell panel has its own characteristics. In addition, environmental factors such as dust, clouds,
etc., may cause different voltages and currents in different sets. Another problem is that some sets may be
loads for other sets. In this case, the temperature of set will be risen because of power consumption. When
the internal temperature of a solar cell panel is over 85 C ° ~100 C °, the set will be broken. Furthermore,
all voltage will be applied in the set, when there are some broken sets in the solar cell array. Therefore, a
bypass diode is in a parallel connection to a set for solving the above problem. Thus, a low impedance
path of energy dissipation can be provided for each set to overcome a problem of many sets connection.

209


Fig.10: (a) Completed Solar Tracker Prototypes

Fig.10: (b) and (c) Propose solar tracking set

Fig. 10(d): Difference in irradiance on straight & tracked for sunny days

Fig.11: Solar arrays stationary setup

Fig. 12: The power generation comparison of fixed angle type and tracking systems

VI. FUZZY LOGIC CONTROLLER OF SOLAR ARRAYS
The fuzzy sets concept was proposed by Zadeh in 1965. The fuzzy algorithm can make human
knowledge into the rule base to control a plant with linguistic descriptions. It relies on expert experience
instead of mathematical models. The advantages of fuzzy control include good popularization, high faults
tolerance, and suitable for nonlinear control systems.
A fuzzy controller design has four parts, fuzzification, control rule base, fuzzy inference, and
defuzzification. The block diagram of the fuzzy control system is shown in fig. 13.

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Fig. 13: Block diagram of the fuzzy control.

At first, the sun light illuminates on a LDR light sensitive resistor of the solar tracking device.
Then a feedback analog signal will be produced and transformed into a digital signal through an
analog/digital converter. When the voltage on the eastward-westward direction or the southward-
northward direction is different; the differences will be delivered into the fuzzy controller. Then, the
fuzzy controller produces pulses to motor drivers and the motor drivers produce PWM signals to control
step motors for tuning desired angles. Note that if the differences of sensors are zero, i.e., the sun is
vertical to the solar panel, so the fuzzy controller does not work. Since the sun moves very slow, the fast
rotating speed of the solar tacking device is with high speed rotation not necessary. By fuzzy control,
some advantages such as reducing consumption power of step motors and fast and smooth fixed position
can be achieved. Therefore, the fuzzy control algorithm has enough ability to complete this goal.

Since the corresponding LDR light sensitive resistors can operate independently, it can be seen as
independent control. For one motor control, the error of output voltages of corresponding sensors can be
set as input variables. The rotation time of the stepping motors for clockwise and counterclockwise are
output variables. The membership functions are shown in Figs. 14 (a) and (b). Five fuzzy control rules are
used, as shown in the following.

Fig. 16 shows velocity up after the first movement of the motor on a vertical and horizontal
directions Fig. 17 shows that the variation at motor torque for the period of steady operation on an uneven
road. It can be seen that Fig. 15 and 16 while the vehicle running on uneven rood motor torque is high-
quality adaptive to rood indirectly speed is constant.

Fig.14: (a) & (b) Membership functions of linguistic variables

Fig.15; Motor phase currents after the first movement of the
motor on a vertical and horizontal direction.

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Fig.16: Velocity up curves against to time of the vertical and horizontal direction.

Fig.17: The variation at motor torque for the period of stable operation on a vertical and horizontal
direction.

VII. CONCLUSION

The paper presents a solar tracking power generation system. The tracking controller based on the
fuzzy algorithms uses a MSB430F6438 microcontroller. A solar tracker is designed by employing the
new principle of using small solar cells which functions as self-adjusting light sensors and provides a
variable indication of their relative angle to the sun by detecting their voltage output. The said principle
helps the solar tracker in maintaining a solar array at a sufficiently perpendicular angle to the sun. The
increased power gain over a fixed horizontal array was found to be in excess of 30 to 35%.

ACKNOWLEDGEMENT

We sincerely thank our principal Col Dr. Surendra for his continuous support in PV technology
and for guidance to prepare this paper. We also thank the team of INDNOR Solar project for technical
inputs to complete the content of this research topic.

VIII. REFERENCES

[1] Fahrenburch, A. and Bube, R. 1983, Fundamentals of solar cells, Academic Press, New York.
[2] Partain, L.D. 1995, Sollar Cells and their applications, John Wiley & Sons. New York.
[3] E Weise, R Klockner, R Kniel, Ma Sheng Hong, Qin Jian Ping, “Remote Power Supply Using Wind
and Solar energy – a Sino-German Technical Cooperation Project”, Beijing International Conference on
Wind Energy, Beijing, 1995
[4] Wichert B, Lawrance W, Friese T, First Experiences with a Novel Predictive Control Strategy for PV-
Diesel Hybrid Energy Systems, Solar’99
[5] Duryea S, Syed I, Lawrence W, An Automated Battery Management System for Photovoltaic
Systems, International Journal of Renewable Energy Engineering, Vol 1, No 2, Aug 1999
[6] Twidell J, Weir J, Renewable Energy Systems, Chapman and Hall, 1994
[7] Centre for Resources and Environmental Studies, ANU, Sustainable Energy Systems – Pathways for
Australian Energy Reforms, Cambridge University Press, 1994
[8] Damm, J. Issue #17, June/July 1990. An active solar tracking system, HomeBrew Magazine.
[9] J. Wen, and T. F. Smith, “Absorption of Solar Energy in a Room,” Sol.Energy, vol. 72, no. 4, pp. 283-
297, 2002.
[10] Terasic, http://www.terasic.com.tw
[11] Altera, http://www.altera.com.

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[12] L. A. Zadeh, “Fuzzy sets,” Inform. And contr., vol. 8, pp. 338-353,1965.
[13] L. A. Zadeh, “Fuzzy Algorithms,” Inform. And contr., vol. 12, pp.94-102, 1968.
[14] E. H. Mamdani, “Application of fuzzy algorithms for control of a simple dynamic plant,” in Proc.
Inst. Elect. Eng., vol. 121, pp. 1585-1588, 1974.

IX. ABOUT AUTHORS

1). Babu N. Suraywanshi Working as Associate Professor in Mechanical dept. in
Maharashtra Engg. College Nilanga Latur, (Dist), (M.S) India. He has received B. Tech,
M.Tech. in Thermal Engg. from G.U.G and currently pursuing Ph.D at Rayalseema
University. He is having 16 years of teaching and research experience and published 05
research papers in the International conference & journals.

2). Ibrahim Patel Working as Associate Professor in ECE department, Dr. B.V.Raju
Institute of Technology. Narsapur, Medak, (Dist), Andhra Pradesh India. He has received B.
Tech. (ECE) M. Tech Degree in Biomedical Instrumentation and currently pursuing Ph.D at
Andhra University. He is having 17 years of teaching and research experience and
published 30 research papers in the International conference & journals and His main
research interest includes Voice to sign language. He had received “Best Paper Award” in
ICSCI –International Conference in 2011, & year of the best achievement“Speech processing and
Synthesis” has been accepted for inclusion as one chapter for publication in the book "Speech
Technologies/Book 1" publishing in Dec. 2011 from Vienna, Austria European Union.

3). Prof. Dr. Colonel (Retd.) K. Prabhakar Rao is the Principal of the Institution and he
has vast Administration, Academic and Technical experience spanning 44 years. He is B.E
(Mech.) with 1st Class from Osmania University and Post-Graduation M.E (Machine
Design) with distinction from IISc, Bangalore. He obtained his Doctorate Ph. D (Mech.
Engg) from Dr. Ram Mahonar Lohia Avadh University. He is also the recipient of
Doctorates in Political Science, Strategic Studies, Religious Studies, Mechanical Engineering and
Electrical Engineering from other Universities. He has published 34 Technical Papers and 85 General
Papers in Political Science, Library, Current Affairs and Education. He has published online 720 General
Papers on National & International Affairs, Comparative Religious Studies, Education, History and
Terrorism in US based Websites. He has been the Principal of various Engineering Colleges affiliated to
JNTU for the last 14 years and some of which were developed from inception. He is the recipient of three
National Awards for academic excellence and achievements:

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