Solar arrays through power generation & tracking

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

6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME

203

SOLAR ARRAYS THROUGH POWER GENRATION & TRACKING

Babu Suryawanshi1, Ibrahim Patel

2, Dr. K. Prabhakar Rao

3

(1) Prof and, HOD. of Mechanical Engg., Maharashtra Engg.college Nilanga (M.S)

[email protected]

(2) Assoc. Prof. Dept of ECE Dr. B.V. Raju Inst. of Technology Narsapur Medak (Dist) A. P.

[email protected]

(3) Prof. Dr. Colonel (Retd.) Principal Raja Mahendra college of Engg. Ibrahmpatanam RR (Dist)

[email protected]

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

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET)

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ISSN 0976 – 6359 (Online)

Volume 3, Issue 3, Septmebr - December (2012), pp. 203-213

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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;

)1(,1exp −−−

−

−=

s

satpphpn

V

kTA

qInInI Where np represents the parallel integer of the solar

cell; ns represents the series connected integer of the solar cell; q represents the contained electricity in an

electro );106.1( 19 Columbic−

×k is Boltzmann constant );/1038.1( 23 kj−

× 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:

)2(,11

exp

3

−−−−

−

=

TTkA

qE

T

TII

r

Gap

r

rrsat

Where Tr represents the reference temperature of the

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.



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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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Solar arrays through power generation & tracking