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intercepted by the earth is approximately 1.8*1011
MW, which is many thousands of times larger
than the present consumption rate on the earth from all other in-use commercial energy sources.
The main problem with the solar energy is its dilute nature. Even in the hottest regions on the
earth, the solar radiation flux available rarely exceeds 1 KW/M, which is insufficient for
technological utilization. This problem can be rectified by a device solar tracker which ensures
maximum intensity of sun rays hitting the surface of the panel from sun-rise to sunset.
1.1. Solar geometry and solar angles
The Earth’s orbit about the Sun is almost circular at an average distance of 149.6 million km.
The Earth’s axis of rotation is tilted by an angle Ɛ=23.441o
with respect to the normal to the
plane of the Earth’s orbit (Fig. 1) [1]. The plane of the Earth’s orbit is named as the plane of the
ecliptic. The plane passing through the Earth’s equator is inclined perpendicularly to the plane of
the ecliptic, at an angle Ɛ (angle of obliquity). Based on conservation of angular momentum, the
Earth’s axis of rotation points as a fixed direction in space which means for the same location on
Earth, at a fixed time (for midday as determined by solar time), the altitude of the Sun (the
angular height above the horizon) will vary throughout the year.
Fig. 1.Schematic diagram of earth orbit around sun
[Source: Sproul et al. (2007)]
In order to derive the solar angles, need to define suitable reference frames. Three principal
reference frames will be used, the ecliptic, the equatorial and the horizon reference frames [2].
These reference frames are centered or referenced to the centre of the Earth and the apparent
motion of the Sun is considered for calculations. The Sun and other celestial bodies are assumed
to lay on the celestial sphere (Fig.2) a sphere with a large radius. The daily rotation of the earth is
described by the rotation of the celestial sphere about the polar axis, and the instantaneous
position of the sun is given by the hour angle ω, the angle between the meridian passing through
the sun and the meridian of the site. The celestial sphere is imagined to rotate about the fixed
Earth to depict the daily, apparent motion of the Sun and other celestial bodies (Fig.2) [44].
Fig.2. Celestial sphere geometry of the Sun and Earth
[Source: Sproul et al. (2007)]
1.2. The nomenclature
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1. Declination angle (δ)
It is the angular distance of the sun’s position in north or south of the earth’s equator (Fig.3). The
earth’s axis is tilted 23.34° from the plane of the earth’s orbit around the sun and the earth is in
its annual path around the sun causes the declination angle to vary from 23.45° north on
december 21st (Winter Solstice) to 23.45° south on June 21st (Summer Solstice) [45-47].
Fig.3.Solar angles
2. The altitude angle or elevation angle (α)
It shows how high the sun appears in the sky. The angle is measured between an imaginary line
between the observer and the sun and the horizontal plane the observer is standing on. The
altitude angle is negative when the sun drops below the horizon (Fig.3) [45-47].
3. Solar azimuth angle (ϒs)
It is the angular distance between South and the projection of the line of sight to the sun on the
ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth
angle indicates West of South (Fig.3) [45-47].
The latitude (w)
It is a point or location is the angle made by the radial line joining the location to the center of
the earth with the projection of the line on the equatorial plane. The earth’s axis of rotation
intersects the earth’s surface at 90o
latitude (North Pole) and -90o
latitude (South Pole). Any
location on the surface of the earth then can be defined by the intersection of a longitude angle
and a latitude angle.
2. Components of solar tracking system
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The main mechanism of the solar tracking system consists of the tracking device, the
tracking algorithm, the control unit, the positioning system, the driving mechanism, and the
sensing devices. The tracking algorithm determines the angles which are used to determine the
position of solar tracker. There are two types of algorithms-astronomical algorithms and real
time light intensity algorithms. The astronomical algorithm is a purely mathematical algorithm
based on astronomical references. The real-time light intensity algorithm is based on real-time
light intensity readings. The control unit performs the tracking algorithm and manages the
positioning system and the driving mechanism. The positioning system operates the tracking
device to face the sun at the calculated angles. The positioning system can be electrical or
hydraulic. The driving mechanism is responsible for moving the tracking device to the position
determined by the positioning system. The sensing devices are group of sensors and
measurements that measure the ambient conditions, the light intensity in case of real-time light
intensity algorithms, and the tilt angle of the tracker (by means of an inclinometer or a
combination of limit switches and motor encoder counts) [45].
3. Solar tracking system Vs fixed panel
The amount of output mainly depends on the cosine angle of incidence which is known as the
angle between the sun ray and horizontal surface. The minimum incidence angle gives the
maximum power output. In case of fixed panel except noon time the angle is maximum for the
movement of sun. The efficient solar tracker is which can correct this problem. The first solar
tracker introduced by Finster in 1962, was completely mechanical. One year later, Saavedra
presented a mechanism with an automatic electronic control, which was used to orient an Eppley
pyrheliometer [3]. Anusha et al.[4] compared the fixed PV panel and single axis solar tracking
based on real time clock(RTC) using ARM processor. The experiment is conducted using both
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fixed and tracking system for 6 days. The results show that the solar tracking system increased
the efficiency around 40% and energy received from the sun is improved from 9.00AM to 6.00
PM. Dhanabal et al.[5] compared the efficiencies of static panels and tracking systems of single
axis and dual axis fixed mount. The readings are taken from morning 8 AM to evening 6 PM for
fixed panel, single axis tracker and dual axis tracker for every one hour. The results says the
efficiency of the single axis tracking system over that of the static panel is calculated to be
32.17% and dual axis tracking system over that of the static panel is calculated to be 81.68%.
Tiberiu tudorache et al [6] compared the solar tracking PV panel with a fixed PV panel in terms
of electric energy output and efficiency. The proposed device automatically searches the
optimum PV panel position with respect to the sun by means of a DC motor controlled by an
intelligent drive unit that receives input signals from dedicated light intensity sensors. The solar
tracking PV panel produced more energy than fixed one with about 57.55%. Bione et al. [7]
compared the pumping systems driven by fixed, tracking and tracking with concentration PVs.
The results showed that for a given irradiance, the pumped water flow rate was significantly
different from one another. The fixed PV, the PV with tracker and the concentrating-tracking
systems pumped 4.9, 7.4 and 12.6m3
/day, respectively. Snehal et al. [8] proposed a Field
Programmable Gate Array (FPGA) sensor Based Standalone Solar Tracking System. Sun
tracking system composed of fuzzy logic controller implemented on FPGA sensors, PV panel,
stepper motor, and input-output interface. Xilinx_ISE software is used for coding of FLC for Sun
tracking. The results show that tracking has maximum efficiency than fixed panels.
4. Different types of solar tracking techniques
Fig 4.Solar tracking technologies
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4.1 Based on collectors
4.1.1. Flat plate photovoltaic panel (PV)
In flat-panel photovoltaic applications, trackers are used to minimize the angle of
incidence between the incoming sunlight and a photovoltaic panel. Masakazu Ito et al. [9]
proposed a comparative study of fixed and tracking system of very large-scale PV (VLS-PV)
systems in the world deserts. The work focused on the potential and simulation of the
100MW.Life cycle analysis is applied for the simulation. The potentials are evaluated from
economic viewpoint by LCA method. The results shows that cost reduced by applying tracking
system. Marcel Sur et al. [10] produced solar electricity from fixed-inclined and sun-tracking
crystalline silicon (C-SI) photovoltaic modules in South Africa. The work presents a method to
for estimating the energy output from fixed-mounted and sun-axis tracking flat-plate PV
systems. The simulation uses the solar radiation and temperature time series representing a
historical record of 18 years (1994 to 2011).The Results shows one axis tracker with vertical axis
inclined 30 degrees north typically gains from 15% up to 35% more electricity, compared to
fixed mounting at optimum tilt.Anyaka et al. [11] studied the Improvement of PV Systems
Power Output Using Sun-Tracking Techniques. The work presented the detailed view of sun
tracking systems developed over the past years. The results prove that the applicability of sun
tracking system gives a diverse range of high performance solar-based applications.
4.1.2 Concentrated Photovoltaic (CPV)
The optics in CPV modules accept the direct component of the incoming light to
maximize the energy collected. The tracking functionality in CPV modules is used to orient the
optics such that the incoming light is focused to a photovoltaic collector. Tony Kerzmann et al.
[12] studied the flow rate optimization of a linear concentrating photovoltaic system. The work
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focused on a two dimensional linear concentrated photovoltaic (LCPV) combined with an active
cooling and waste heat recovery system. The results shows that an optimal cooling fluid flow at a
rate of 4 gal/min (2.52×10−4m3
/s) would produce and average of 45.9 kWh of electricity and
15.9 kWh of heat energy. Tripanagnostopoulos et al. [13] proposed the design and performance
aspects for low concentration photovoltaic. The non-uniform distribution of solar radiation on
the PV surface reduces the electrical efficiency and can be rectified by combining the PV with
low concentration devices. The diffuse reflectors are used instead of specular reflectors because
of their low cost. The PV temperature reduction is also a factor so several modes for heat
extraction are applied; using water or air cooled hybrid photovoltaic/thermal (PV/T) solar
systems. Benecke et al. [14] developed the Optical design of low concentrator photovoltaic
modules. This work addresses the necessary procedures that need to be considered when
designing an optical sub-system of low concentrator photovoltaic (LCPV) module. Various
design considerations are taken into account to construct a LCPV module that is characterized
with respect to optical design and electrical performance. Benecke et al. [15] implemented the
design and analysis of a vertical receiver LCPV system. The work presents the design aspects of
the optical and electrical subsystem of LCPV with a geometric concentration ratio of 4.6.An
electrical estimation is conducted by the use of I-V (current-voltage) characteristics obtained
under sun as well as under concentration.
4.1.3Concentrated Solar Power (CSP)
Concentrating solar power or concentrated solar thermal systems use mirrors or lenses to
concentrate a large area of sunlight or solar thermal energy onto a small area. Electrical power is
produced when the concentrated light is converted into heat, which drives a heat engine (usually
a steam turbine) connected to an electrical power generator or powers a thermo chemical
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reaction. Miqdam Tariq et al. [16] studied the effect of design variation on saved energy of
Concentrating Solar Power prototype. The work discussed about the methods to improve the
efficiency of the concentrated solar thermal plant. El jai et al. [17] implemented a modified
model for parabolic trough solar receiver using concentrated solar thermal energy. The work
concentrates on the original mathematical model that describes the heat exchange between the
main components of a thermal solar collector in an integrated solar combined cycle (ISCC) plant.
The solar plant is an integrated combined cycle thermo-solar power plant consists of 256
parabolic trough solar collectors and classified in 64 parallel loops and each loop is 618 meters
long. The use of the solar tracking mechanism is to maintain the incident solar radiation
perpendicular to the reflector and to the focal line of the parabola where a receiver tube contains
the heat transfer fluid. The different simulation results show that both the fluid temperature and
the metal tube temperature grow until reaching a certain equilibrium value.
4.2 Based on the axis
4.2.1. Single axis tracker
Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis
of rotation of single axis trackers is typically aligned along a true North meridian. Rizk et al. [18]
developed solar tracking system with more efficient use of solar panels. This work includes the
potential system benefits of simple tracking solar system of single axis tracker using a stepper
motor and light sensor. This method is increasing power collection efficiency by implementing a
device that tracks the sun to keep the panel at a right angle to sun rays. The power gain is
increased 30% over a fixed horizontal array.
4.2.1.1. Horizontal Single Axis Tracker (HSAT)
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The axis of rotation for horizontal single axis tracker is horizontal with respect to the
ground. Backtracking is one of computing the disposition of panels [48]. Guihua et al. [19]
calculated the optical performance of horizontal single axis tracked solar panels. From the results
it is clear that the east-west placed HSAT is worst to boost the energy while the north-south
placed HSAT increased the efficiency drastically around 36%.
Fig 5.Horizontal Single Axis Tracker
4.2.1.2. Vertical Single Axis Tracker (VSAT)
The axis of rotation for vertical single axis trackers is vertical with respect to the ground. These
trackers rotate from east to west over the course of the day. Lorenzo et al. [20] designed the
tracking of photovoltaic systems with a single vertical axis. The vertical single axis tracking also
called as azimuth tracking is mainly used for the energy gain which can be 40% more compared
to tilted static panels. This research work deals with the design of VSAT photovoltaic plant in
Tudela. The problems of shadowing in E-W direction and also N-S direction and the methods to
rectify are explained in detail. The results clearly specify that VSAT boosted the energy gain
around 40% per annum.
4.2.1.3. Tilted Single Axis Tracker (TSAT)
The tracker with axes of rotation between horizontal and vertical is named as tilted single
axis tracker. Tracker tilt angles are often limited to reduce the wind profile and decrease the
elevated end height. As a module tracks, it sweeps a cylinder that is rotationally symmetric
around the axis of rotation [45].
4.2.1.4. Polar Aligned Single Axis Tracker (PSAT)
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This method is scientifically well known as the standard method of mounting a telescope
support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar
aligned single axis tracker [46].
Fig 6. Polar Aligned Single Axis Tracker
4.2.2 Dual Axis Tracking
Dual axis trackers have two degrees of freedom that act as axes of rotation normal to one
another. The axis that is fixed with respect to the ground is a primary axis. The axis that is
referenced to the primary axis is secondary axis [48].
Fig 7. Dual Axis SolarTracker
4.2.2.1. Tip-Tilt Dual Axis Tracker (TTDAT)
A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a
pole. Normally the east-west movement is driven by rotating the array around the top of the pole.
The vertical azimuth axis is fixed so as to allow great flexibility of the payload connection to the
ground mounted equipment because there is no twisting of the cabling around the pole. Tip-tilt
trackers can make to minimize up-sun shading and therefore maximize the total power being
collected [21-25].
4.2.2.2 Azimuth-Altitude Dual Axis Tracker (AADAT)
An azimuth–altitude dual axis tracker has its primary axis (the azimuth axis) vertical to
the ground and the secondary axis (elevation axis) is normal to the primary axis. The operation is
similar to tip-tilt systems but differ in the way the array is rotated for daily tracking. Instead of
rotating the array around the top of the pole, they use a large ring mounted on the ground with
the array mounted on a series of rollers. The main advantage of this arrangement is the weight of
the array is distributed over a portion of the ring [47]. Liqun Liu et al. [26] discussed about the
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influence factors analysis of the best orientation relative to the sun for dual-axis sun tracking. In
this research work different types of tracking systems are reviewed such as fixed panel, single
axis tracking in east-west, single axis tracking in north-south, and dual axis tracking using both
tip-tilt and altitude-azimuth tracking. The results show the influencing factors are time error,
latitude, and azimuth and tilt angle of the photovoltaic, reflectivity and composite transparent
coefficient. Arbab et al. [27] implemented a computer tracking system of solar dish with two-
axis degree freedoms based on picture processing of bar shadow. The design is based on
computer image processing of a bar shadow to obtain the optimized picture of solar dish
displacements. The system is independent to geographical location of the solar dish and
periodical changes like daily or monthly regulations. Jifeng Song et al. [28] implemented a high
precision dual axis tracking system based on a hybrid strategy designed for concentrated sunlight
transmission via fibers. This system is based on a two-stage tracking process, which consists of a
coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a
specially designed photosensitive sensor. In this design optical fibers are used for the precision
tracking of concentrated sunlight. The advantage of this design is the higher resolution of the sun
sensor because of the use of photosensitive arrays in closer arrangement. From the results it is
clear that system tracked the sun’s focal spot with a position precision of less than 0.3 mm and
the tracking angle precision is 0.1o
. Jay Robert et al. [29] proposed the optimization of a small
scale dual-axis solar tracking system using nano watt technology. The solar module is placed
first in any one direction and the PV array has to search and stop at the highest current gained by
the solar cell. The process is continued for every 30 minutes from 0600H up to 1800H. The
results are measured in these positions for current, voltage and power. An open loop control is
used for controlling the motors. Reis et al. [30] proposed the Modeling the performance of low
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concentration photovoltaic systems. A theoretical model is implemented to study the response of
voltage-through systems in terms of temperature, power output and energy yield using as inputs.
The device is constructed by integrating dual axis system and conventional crystalline Si-
module, named as double sun technology. The results conclude that the double sun technology is
increased the efficiency around 86% compared to fixed panels. Mohammed et al. [31] designed a
parabolic solar cooker with automatic two axes sun tracking system. The solar cooker with
automatic two axes eliminates the standing in the sun for hours to get frequent tracking and
facing the concentrated solar cooker. The results of the continuous test performed for three days
from 8:30 hr to 16:30 hr in the year 2008 and showed that the water temperature inside the
cooker’s tube reached 90o
C in typical summer days for the maximum registered ambient
temperature was 36 o
C. Ahmed Rhif et al. [32] implemented a position control review for a
photovoltaic system dual axis sun tracker. This work presents a sun tracker without using sun
sensors. The sun tracking is performed by changing the solar panel orientation in horizontal and
vertical directions by two motors. The control of these motors is ensured by a microcontroller.
Sliding mode control is used to solve the nonlinear equations. The simulation results conclude
that tracking improves the efficiency around 40% than fixed panel. Okpeki et al. [33] designed
and constructed a bi-directional solar tracking system. This research work includes the design
and fabrication of a bi-directional tracker which can rotate in both azimuth and altitude
directions. The two influencing factors of power output are intensity and wave length of sun
light are addressed in detail. The results conclude that the efficiency is drastically more
compared to fixed panel and the total cost of the tracker is very low. George Bakos et al. [34]
implemented a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency
improvement. Parabolic trough is used with two axis rotation to the sun. The results conclude
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that parabolic collector is increasing the energy than flat collector. Rodiek et al. [35] conducted
solar photovoltaic array tilt angle and tracking performance experiment. Advanced software
models were developed to calculate the change of path by the sun throughout the year and to
predict the optimum angle for the single axis tracker to obtain maximum energy output for the
entire year. Two modeling programs are discussed to predict the optimal angle. For the
experiment five panels are used in a single axis to track azimuthally at the tilt angles of 20º, 25º,
32º (latitude), 40º, and 50º. One more panel is a fixed control panel facing south at latitude tilt.
The results are taken for one year and they conclude that a higher tilted panel (50º) will produce
more power throughout the year compared to modeling from PV Watts that suggests a 32º tilt.
4.3. Based on driver
4.3.1. Active tracker
4.3.1.1. Microcontroller and electro-optical sensor based solar tracker:
Sobuj Kumar Ray et al. [36] presented two ways of rotating freedom solar tracker by
using microcontroller. The work includes the design of a two ways rotating freedom solar tracker
based on microcontroller.PIC16F72 microcontroller is used to activate the motors to get two
ways rotation.LDC sensors are used to get the information about sun radiation. The results are
compared with conventional solar tracker without microcontroller and also with fixed panels.
The difference is almost 37% between fixed panel and tracking system with microcontroller.
Yousif El-Tous et al. [37] studied the thermal evaluation of a sun tracking solar cooker using
microcontroller. The work contains the implementation of tracking system developed for getting
the solar heating using solar cooker. A microcontroller is used for rotating the solar heater with
the movement of the sun. PLC system is used as control system. A comparison between fixed
and sun tracked cooker showed that the use of sun tracking increased the heating temperature by
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36%. Mostefa Ghassoul et al. [38] proposed design of an automatic solar tracking system to
maximize energy extraction. This solar tracking system is controlled by a micro chip PIC
18F452 micro controller. The search mechanism (PILOT) locates the position of the sun and the
intelligent panel mechanism rotates itself with the PILOT to extract the maximum energy. The
main defect in this is the rotation only takes place, if the energy obtained in the new position is
higher than that consumed by the panels during the transition. So one miniature motor is used s
to search the best position for maximum energy extraction. The panel’s mechanism rotates to the
position automatically when energy extraction is optimal. The system is designed in such a way
that panels only follow the sun if that contributes to extra energy extraction and at the same time,
the energy consumed by the panel driving motor is less than that extracted. Jing-Min Wang et al.
[39] proposed the design and implementation of a sun tracker with a dual-axis single motor for
an optical sensor-based photovoltaic system. This work proposes a novel design of a dual-axis
solar tracking PV system which utilizes the feedback control theory along with a four-quadrant
light dependent resistor (LDR) sensor and simple electronic circuits to provide robust system
performance. The proposed system uses a unique dual-axis AC motor and a stand-alone PV
inverter to accomplish solar tracking. Experiment results indicated that the developed system
increased the energy gain up to 28.31% for a partly cloudy day.
4.3.1.2. Auxiliary bifacial solar cell based solar tracker
Bhupendra Gupta et al. [40] explained the design, construction and effectiveness of a
hybrid automatic solar tracking system for amorphous and crystalline solar cells. This work
includes the design a Hybrid solar tracking system implemented by integrating with amorphous
and crystalline solar panel, and microcontroller. The experiment consists of the analysis on the
use of two different material of solar panel like Amorphous and Crystalline in a solar tracking
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system at stationary, single axis, and dual axis and hybrid axis solar tracker. The comparison
shows that the use of the dual-axis tracking system produced 17.87% gain of power output than a
single-axis tracking system. The gain of output power with the hybrid tracking system is further
more (52%) than a stationary system inclined at 23.5o
to the horizontal.
4.3.1.3 Date, time and sensor based
In the date/time and sensor based tracking systems, electronic devices like
microprocessor calculates the sun’s position from basic formulae or algorithms from
geographical information and send signals to the electro motor (Fig.5).
Fig. 8 Position of PV modules in the morning and afternoon
Edwards et al. [41] presented the operation of a computer based sun following system for
parabolic collectors. The computer continuously varies the speed of each collector actuators at
regular intervals throughout the day. The results conclude that for accurate sun following, the
system requires a data output from the central controller of only 500 bit/s for 10,000 collectors
per day.
4.3.2. Passive tracker
The passive trackers use a boiling point from a compressed fluid which moves from one
side to other by the solar heat which creates a gas pressure results the tracker movement [42].
Due to the bad quality of precision orientation, it is unsuitable for certain types of photovoltaic
collectors. In the passive tracker the photovoltaic panels include a hologram behind stripes of
photovoltaic cells so that sunlight reflects [37] on the hologram which allows the cell heat from
behind, thereby increasing the modules’ efficiency. Moreover, the plant need not require moving
while the hologram still reflects sunlight from the needed angle toward the photovoltaic cells.
Jeyaganesh et al.[43] proposed the design and development of a sun tracking mechanism using
the Direct SMA actuation. The Shape Memory Alloy (SMA) element acts as sensor and actuator
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intercepted by the earth is approximately 1.8*1011
MW, which is many thousands of times larger
than the present consumption rate on the earth from all other in-use commercial energy sources.
The main problem with the solar energy is its dilute nature. Even in the hottest regions on the
earth, the solar radiation flux available rarely exceeds 1 KW/M, which is insufficient for
technological utilization. This problem can be rectified by a device solar tracker which ensures
maximum intensity of sun rays hitting the surface of the panel from sun-rise to sunset.
1.1. Solar geometry and solar angles
The Earth’s orbit about the Sun is almost circular at an average distance of 149.6 million km.
The Earth’s axis of rotation is tilted by an angle Ɛ=23.441o
with respect to the normal to the
plane of the Earth’s orbit (Fig. 1) [1]. The plane of the Earth’s orbit is named as the plane of the
ecliptic. The plane passing through the Earth’s equator is inclined perpendicularly to the plane of
the ecliptic, at an angle Ɛ (angle of obliquity). Based on conservation of angular momentum, the
Earth’s axis of rotation points as a fixed direction in space which means for the same location on
Earth, at a fixed time (for midday as determined by solar time), the altitude of the Sun (the
angular height above the horizon) will vary throughout the year.
Fig. 1.Schematic diagram of earth orbit around sun
[Source: Sproul et al. (2007)]
In order to derive the solar angles, need to define suitable reference frames. Three principal
reference frames will be used, the ecliptic, the equatorial and the horizon reference frames [2].
These reference frames are centered or referenced to the centre of the Earth and the apparent
motion of the Sun is considered for calculations. The Sun and other celestial bodies are assumed
to lay on the celestial sphere (Fig.2) a sphere with a large radius. The daily rotation of the earth is
described by the rotation of the celestial sphere about the polar axis, and the instantaneous
position of the sun is given by the hour angle ω, the angle between the meridian passing through
the sun and the meridian of the site. The celestial sphere is imagined to rotate about the fixed
Earth to depict the daily, apparent motion of the Sun and other celestial bodies (Fig.2) [44].
Fig.2. Celestial sphere geometry of the Sun and Earth
[Source: Sproul et al. (2007)]
1.2. The nomenclature
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1. Declination angle (δ)
It is the angular distance of the sun’s position in north or south of the earth’s equator (Fig.3). The
earth’s axis is tilted 23.34° from the plane of the earth’s orbit around the sun and the earth is in
its annual path around the sun causes the declination angle to vary from 23.45° north on
december 21st (Winter Solstice) to 23.45° south on June 21st (Summer Solstice) [45-47].
Fig.3.Solar angles
2. The altitude angle or elevation angle (α)
It shows how high the sun appears in the sky. The angle is measured between an imaginary line
between the observer and the sun and the horizontal plane the observer is standing on. The
altitude angle is negative when the sun drops below the horizon (Fig.3) [45-47].
3. Solar azimuth angle (ϒs)
It is the angular distance between South and the projection of the line of sight to the sun on the
ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth
angle indicates West of South (Fig.3) [45-47].
The latitude (w)
It is a point or location is the angle made by the radial line joining the location to the center of
the earth with the projection of the line on the equatorial plane. The earth’s axis of rotation
intersects the earth’s surface at 90o
latitude (North Pole) and -90o
latitude (South Pole). Any
location on the surface of the earth then can be defined by the intersection of a longitude angle
and a latitude angle.
2. Components of solar tracking system
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The main mechanism of the solar tracking system consists of the tracking device, the
tracking algorithm, the control unit, the positioning system, the driving mechanism, and the
sensing devices. The tracking algorithm determines the angles which are used to determine the
position of solar tracker. There are two types of algorithms-astronomical algorithms and real
time light intensity algorithms. The astronomical algorithm is a purely mathematical algorithm
based on astronomical references. The real-time light intensity algorithm is based on real-time
light intensity readings. The control unit performs the tracking algorithm and manages the
positioning system and the driving mechanism. The positioning system operates the tracking
device to face the sun at the calculated angles. The positioning system can be electrical or
hydraulic. The driving mechanism is responsible for moving the tracking device to the position
determined by the positioning system. The sensing devices are group of sensors and
measurements that measure the ambient conditions, the light intensity in case of real-time light
intensity algorithms, and the tilt angle of the tracker (by means of an inclinometer or a
combination of limit switches and motor encoder counts) [45].
3. Solar tracking system Vs fixed panel
The amount of output mainly depends on the cosine angle of incidence which is known as the
angle between the sun ray and horizontal surface. The minimum incidence angle gives the
maximum power output. In case of fixed panel except noon time the angle is maximum for the
movement of sun. The efficient solar tracker is which can correct this problem. The first solar
tracker introduced by Finster in 1962, was completely mechanical. One year later, Saavedra
presented a mechanism with an automatic electronic control, which was used to orient an Eppley
pyrheliometer [3]. Anusha et al.[4] compared the fixed PV panel and single axis solar tracking
based on real time clock(RTC) using ARM processor. The experiment is conducted using both
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fixed and tracking system for 6 days. The results show that the solar tracking system increased
the efficiency around 40% and energy received from the sun is improved from 9.00AM to 6.00
PM. Dhanabal et al.[5] compared the efficiencies of static panels and tracking systems of single
axis and dual axis fixed mount. The readings are taken from morning 8 AM to evening 6 PM for
fixed panel, single axis tracker and dual axis tracker for every one hour. The results says the
efficiency of the single axis tracking system over that of the static panel is calculated to be
32.17% and dual axis tracking system over that of the static panel is calculated to be 81.68%.
Tiberiu tudorache et al [6] compared the solar tracking PV panel with a fixed PV panel in terms
of electric energy output and efficiency. The proposed device automatically searches the
optimum PV panel position with respect to the sun by means of a DC motor controlled by an
intelligent drive unit that receives input signals from dedicated light intensity sensors. The solar
tracking PV panel produced more energy than fixed one with about 57.55%. Bione et al. [7]
compared the pumping systems driven by fixed, tracking and tracking with concentration PVs.
The results showed that for a given irradiance, the pumped water flow rate was significantly
different from one another. The fixed PV, the PV with tracker and the concentrating-tracking
systems pumped 4.9, 7.4 and 12.6m3
/day, respectively. Snehal et al. [8] proposed a Field
Programmable Gate Array (FPGA) sensor Based Standalone Solar Tracking System. Sun
tracking system composed of fuzzy logic controller implemented on FPGA sensors, PV panel,
stepper motor, and input-output interface. Xilinx_ISE software is used for coding of FLC for Sun
tracking. The results show that tracking has maximum efficiency than fixed panels.
4. Different types of solar tracking techniques
Fig 4.Solar tracking technologies
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4.1 Based on collectors
4.1.1. Flat plate photovoltaic panel (PV)
In flat-panel photovoltaic applications, trackers are used to minimize the angle of
incidence between the incoming sunlight and a photovoltaic panel. Masakazu Ito et al. [9]
proposed a comparative study of fixed and tracking system of very large-scale PV (VLS-PV)
systems in the world deserts. The work focused on the potential and simulation of the
100MW.Life cycle analysis is applied for the simulation. The potentials are evaluated from
economic viewpoint by LCA method. The results shows that cost reduced by applying tracking
system. Marcel Sur et al. [10] produced solar electricity from fixed-inclined and sun-tracking
crystalline silicon (C-SI) photovoltaic modules in South Africa. The work presents a method to
for estimating the energy output from fixed-mounted and sun-axis tracking flat-plate PV
systems. The simulation uses the solar radiation and temperature time series representing a
historical record of 18 years (1994 to 2011).The Results shows one axis tracker with vertical axis
inclined 30 degrees north typically gains from 15% up to 35% more electricity, compared to
fixed mounting at optimum tilt.Anyaka et al. [11] studied the Improvement of PV Systems
Power Output Using Sun-Tracking Techniques. The work presented the detailed view of sun
tracking systems developed over the past years. The results prove that the applicability of sun
tracking system gives a diverse range of high performance solar-based applications.
4.1.2 Concentrated Photovoltaic (CPV)
The optics in CPV modules accept the direct component of the incoming light to
maximize the energy collected. The tracking functionality in CPV modules is used to orient the
optics such that the incoming light is focused to a photovoltaic collector. Tony Kerzmann et al.
[12] studied the flow rate optimization of a linear concentrating photovoltaic system. The work
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focused on a two dimensional linear concentrated photovoltaic (LCPV) combined with an active
cooling and waste heat recovery system. The results shows that an optimal cooling fluid flow at a
rate of 4 gal/min (2.52×10−4m3
/s) would produce and average of 45.9 kWh of electricity and
15.9 kWh of heat energy. Tripanagnostopoulos et al. [13] proposed the design and performance
aspects for low concentration photovoltaic. The non-uniform distribution of solar radiation on
the PV surface reduces the electrical efficiency and can be rectified by combining the PV with
low concentration devices. The diffuse reflectors are used instead of specular reflectors because
of their low cost. The PV temperature reduction is also a factor so several modes for heat
extraction are applied; using water or air cooled hybrid photovoltaic/thermal (PV/T) solar
systems. Benecke et al. [14] developed the Optical design of low concentrator photovoltaic
modules. This work addresses the necessary procedures that need to be considered when
designing an optical sub-system of low concentrator photovoltaic (LCPV) module. Various
design considerations are taken into account to construct a LCPV module that is characterized
with respect to optical design and electrical performance. Benecke et al. [15] implemented the
design and analysis of a vertical receiver LCPV system. The work presents the design aspects of
the optical and electrical subsystem of LCPV with a geometric concentration ratio of 4.6.An
electrical estimation is conducted by the use of I-V (current-voltage) characteristics obtained
under sun as well as under concentration.
4.1.3Concentrated Solar Power (CSP)
Concentrating solar power or concentrated solar thermal systems use mirrors or lenses to
concentrate a large area of sunlight or solar thermal energy onto a small area. Electrical power is
produced when the concentrated light is converted into heat, which drives a heat engine (usually
a steam turbine) connected to an electrical power generator or powers a thermo chemical
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reaction. Miqdam Tariq et al. [16] studied the effect of design variation on saved energy of
Concentrating Solar Power prototype. The work discussed about the methods to improve the
efficiency of the concentrated solar thermal plant. El jai et al. [17] implemented a modified
model for parabolic trough solar receiver using concentrated solar thermal energy. The work
concentrates on the original mathematical model that describes the heat exchange between the
main components of a thermal solar collector in an integrated solar combined cycle (ISCC) plant.
The solar plant is an integrated combined cycle thermo-solar power plant consists of 256
parabolic trough solar collectors and classified in 64 parallel loops and each loop is 618 meters
long. The use of the solar tracking mechanism is to maintain the incident solar radiation
perpendicular to the reflector and to the focal line of the parabola where a receiver tube contains
the heat transfer fluid. The different simulation results show that both the fluid temperature and
the metal tube temperature grow until reaching a certain equilibrium value.
4.2 Based on the axis
4.2.1. Single axis tracker
Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis
of rotation of single axis trackers is typically aligned along a true North meridian. Rizk et al. [18]
developed solar tracking system with more efficient use of solar panels. This work includes the
potential system benefits of simple tracking solar system of single axis tracker using a stepper
motor and light sensor. This method is increasing power collection efficiency by implementing a
device that tracks the sun to keep the panel at a right angle to sun rays. The power gain is
increased 30% over a fixed horizontal array.
4.2.1.1. Horizontal Single Axis Tracker (HSAT)
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The axis of rotation for horizontal single axis tracker is horizontal with respect to the
ground. Backtracking is one of computing the disposition of panels [48]. Guihua et al. [19]
calculated the optical performance of horizontal single axis tracked solar panels. From the results
it is clear that the east-west placed HSAT is worst to boost the energy while the north-south
placed HSAT increased the efficiency drastically around 36%.
Fig 5.Horizontal Single Axis Tracker
4.2.1.2. Vertical Single Axis Tracker (VSAT)
The axis of rotation for vertical single axis trackers is vertical with respect to the ground. These
trackers rotate from east to west over the course of the day. Lorenzo et al. [20] designed the
tracking of photovoltaic systems with a single vertical axis. The vertical single axis tracking also
called as azimuth tracking is mainly used for the energy gain which can be 40% more compared
to tilted static panels. This research work deals with the design of VSAT photovoltaic plant in
Tudela. The problems of shadowing in E-W direction and also N-S direction and the methods to
rectify are explained in detail. The results clearly specify that VSAT boosted the energy gain
around 40% per annum.
4.2.1.3. Tilted Single Axis Tracker (TSAT)
The tracker with axes of rotation between horizontal and vertical is named as tilted single
axis tracker. Tracker tilt angles are often limited to reduce the wind profile and decrease the
elevated end height. As a module tracks, it sweeps a cylinder that is rotationally symmetric
around the axis of rotation [45].
4.2.1.4. Polar Aligned Single Axis Tracker (PSAT)
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This method is scientifically well known as the standard method of mounting a telescope
support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar
aligned single axis tracker [46].
Fig 6. Polar Aligned Single Axis Tracker
4.2.2 Dual Axis Tracking
Dual axis trackers have two degrees of freedom that act as axes of rotation normal to one
another. The axis that is fixed with respect to the ground is a primary axis. The axis that is
referenced to the primary axis is secondary axis [48].
Fig 7. Dual Axis SolarTracker
4.2.2.1. Tip-Tilt Dual Axis Tracker (TTDAT)
A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a
pole. Normally the east-west movement is driven by rotating the array around the top of the pole.
The vertical azimuth axis is fixed so as to allow great flexibility of the payload connection to the
ground mounted equipment because there is no twisting of the cabling around the pole. Tip-tilt
trackers can make to minimize up-sun shading and therefore maximize the total power being
collected [21-25].
4.2.2.2 Azimuth-Altitude Dual Axis Tracker (AADAT)
An azimuth–altitude dual axis tracker has its primary axis (the azimuth axis) vertical to
the ground and the secondary axis (elevation axis) is normal to the primary axis. The operation is
similar to tip-tilt systems but differ in the way the array is rotated for daily tracking. Instead of
rotating the array around the top of the pole, they use a large ring mounted on the ground with
the array mounted on a series of rollers. The main advantage of this arrangement is the weight of
the array is distributed over a portion of the ring [47]. Liqun Liu et al. [26] discussed about the
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influence factors analysis of the best orientation relative to the sun for dual-axis sun tracking. In
this research work different types of tracking systems are reviewed such as fixed panel, single
axis tracking in east-west, single axis tracking in north-south, and dual axis tracking using both
tip-tilt and altitude-azimuth tracking. The results show the influencing factors are time error,
latitude, and azimuth and tilt angle of the photovoltaic, reflectivity and composite transparent
coefficient. Arbab et al. [27] implemented a computer tracking system of solar dish with two-
axis degree freedoms based on picture processing of bar shadow. The design is based on
computer image processing of a bar shadow to obtain the optimized picture of solar dish
displacements. The system is independent to geographical location of the solar dish and
periodical changes like daily or monthly regulations. Jifeng Song et al. [28] implemented a high
precision dual axis tracking system based on a hybrid strategy designed for concentrated sunlight
transmission via fibers. This system is based on a two-stage tracking process, which consists of a
coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a
specially designed photosensitive sensor. In this design optical fibers are used for the precision
tracking of concentrated sunlight. The advantage of this design is the higher resolution of the sun
sensor because of the use of photosensitive arrays in closer arrangement. From the results it is
clear that system tracked the sun’s focal spot with a position precision of less than 0.3 mm and
the tracking angle precision is 0.1o
. Jay Robert et al. [29] proposed the optimization of a small
scale dual-axis solar tracking system using nano watt technology. The solar module is placed
first in any one direction and the PV array has to search and stop at the highest current gained by
the solar cell. The process is continued for every 30 minutes from 0600H up to 1800H. The
results are measured in these positions for current, voltage and power. An open loop control is
used for controlling the motors. Reis et al. [30] proposed the Modeling the performance of low
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concentration photovoltaic systems. A theoretical model is implemented to study the response of
voltage-through systems in terms of temperature, power output and energy yield using as inputs.
The device is constructed by integrating dual axis system and conventional crystalline Si-
module, named as double sun technology. The results conclude that the double sun technology is
increased the efficiency around 86% compared to fixed panels. Mohammed et al. [31] designed a
parabolic solar cooker with automatic two axes sun tracking system. The solar cooker with
automatic two axes eliminates the standing in the sun for hours to get frequent tracking and
facing the concentrated solar cooker. The results of the continuous test performed for three days
from 8:30 hr to 16:30 hr in the year 2008 and showed that the water temperature inside the
cooker’s tube reached 90o
C in typical summer days for the maximum registered ambient
temperature was 36 o
C. Ahmed Rhif et al. [32] implemented a position control review for a
photovoltaic system dual axis sun tracker. This work presents a sun tracker without using sun
sensors. The sun tracking is performed by changing the solar panel orientation in horizontal and
vertical directions by two motors. The control of these motors is ensured by a microcontroller.
Sliding mode control is used to solve the nonlinear equations. The simulation results conclude
that tracking improves the efficiency around 40% than fixed panel. Okpeki et al. [33] designed
and constructed a bi-directional solar tracking system. This research work includes the design
and fabrication of a bi-directional tracker which can rotate in both azimuth and altitude
directions. The two influencing factors of power output are intensity and wave length of sun
light are addressed in detail. The results conclude that the efficiency is drastically more
compared to fixed panel and the total cost of the tracker is very low. George Bakos et al. [34]
implemented a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency
improvement. Parabolic trough is used with two axis rotation to the sun. The results conclude
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that parabolic collector is increasing the energy than flat collector. Rodiek et al. [35] conducted
solar photovoltaic array tilt angle and tracking performance experiment. Advanced software
models were developed to calculate the change of path by the sun throughout the year and to
predict the optimum angle for the single axis tracker to obtain maximum energy output for the
entire year. Two modeling programs are discussed to predict the optimal angle. For the
experiment five panels are used in a single axis to track azimuthally at the tilt angles of 20º, 25º,
32º (latitude), 40º, and 50º. One more panel is a fixed control panel facing south at latitude tilt.
The results are taken for one year and they conclude that a higher tilted panel (50º) will produce
more power throughout the year compared to modeling from PV Watts that suggests a 32º tilt.
4.3. Based on driver
4.3.1. Active tracker
4.3.1.1. Microcontroller and electro-optical sensor based solar tracker:
Sobuj Kumar Ray et al. [36] presented two ways of rotating freedom solar tracker by
using microcontroller. The work includes the design of a two ways rotating freedom solar tracker
based on microcontroller.PIC16F72 microcontroller is used to activate the motors to get two
ways rotation.LDC sensors are used to get the information about sun radiation. The results are
compared with conventional solar tracker without microcontroller and also with fixed panels.
The difference is almost 37% between fixed panel and tracking system with microcontroller.
Yousif El-Tous et al. [37] studied the thermal evaluation of a sun tracking solar cooker using
microcontroller. The work contains the implementation of tracking system developed for getting
the solar heating using solar cooker. A microcontroller is used for rotating the solar heater with
the movement of the sun. PLC system is used as control system. A comparison between fixed
and sun tracked cooker showed that the use of sun tracking increased the heating temperature by
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36%. Mostefa Ghassoul et al. [38] proposed design of an automatic solar tracking system to
maximize energy extraction. This solar tracking system is controlled by a micro chip PIC
18F452 micro controller. The search mechanism (PILOT) locates the position of the sun and the
intelligent panel mechanism rotates itself with the PILOT to extract the maximum energy. The
main defect in this is the rotation only takes place, if the energy obtained in the new position is
higher than that consumed by the panels during the transition. So one miniature motor is used s
to search the best position for maximum energy extraction. The panel’s mechanism rotates to the
position automatically when energy extraction is optimal. The system is designed in such a way
that panels only follow the sun if that contributes to extra energy extraction and at the same time,
the energy consumed by the panel driving motor is less than that extracted. Jing-Min Wang et al.
[39] proposed the design and implementation of a sun tracker with a dual-axis single motor for
an optical sensor-based photovoltaic system. This work proposes a novel design of a dual-axis
solar tracking PV system which utilizes the feedback control theory along with a four-quadrant
light dependent resistor (LDR) sensor and simple electronic circuits to provide robust system
performance. The proposed system uses a unique dual-axis AC motor and a stand-alone PV
inverter to accomplish solar tracking. Experiment results indicated that the developed system
increased the energy gain up to 28.31% for a partly cloudy day.
4.3.1.2. Auxiliary bifacial solar cell based solar tracker
Bhupendra Gupta et al. [40] explained the design, construction and effectiveness of a
hybrid automatic solar tracking system for amorphous and crystalline solar cells. This work
includes the design a Hybrid solar tracking system implemented by integrating with amorphous
and crystalline solar panel, and microcontroller. The experiment consists of the analysis on the
use of two different material of solar panel like Amorphous and Crystalline in a solar tracking
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system at stationary, single axis, and dual axis and hybrid axis solar tracker. The comparison
shows that the use of the dual-axis tracking system produced 17.87% gain of power output than a
single-axis tracking system. The gain of output power with the hybrid tracking system is further
more (52%) than a stationary system inclined at 23.5o
to the horizontal.
4.3.1.3 Date, time and sensor based
In the date/time and sensor based tracking systems, electronic devices like
microprocessor calculates the sun’s position from basic formulae or algorithms from
geographical information and send signals to the electro motor (Fig.5).
Fig. 8 Position of PV modules in the morning and afternoon
Edwards et al. [41] presented the operation of a computer based sun following system for
parabolic collectors. The computer continuously varies the speed of each collector actuators at
regular intervals throughout the day. The results conclude that for accurate sun following, the
system requires a data output from the central controller of only 500 bit/s for 10,000 collectors
per day.
4.3.2. Passive tracker
The passive trackers use a boiling point from a compressed fluid which moves from one
side to other by the solar heat which creates a gas pressure results the tracker movement [42].
Due to the bad quality of precision orientation, it is unsuitable for certain types of photovoltaic
collectors. In the passive tracker the photovoltaic panels include a hologram behind stripes of
photovoltaic cells so that sunlight reflects [37] on the hologram which allows the cell heat from
behind, thereby increasing the modules’ efficiency. Moreover, the plant need not require moving
while the hologram still reflects sunlight from the needed angle toward the photovoltaic cells.
Jeyaganesh et al.[43] proposed the design and development of a sun tracking mechanism using
the Direct SMA actuation. The Shape Memory Alloy (SMA) element acts as sensor and actuator
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Solartracking review
- 1. See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/312067334 SOLAR TRACKING SYSTEM- A REVIEW Article in International Journal of Sustainable Engineering · January 2016 DOI: 10.1080/19397038.2016.1267816 CITATIONS 48 READS 56,005 1 author: Some of the authors of this publication are also working on these related projects: Biofuels View project Numerical analysis of heat transfer characteristics with triangular cut twisted tape inserts View project RAJAN K Dr.MGR Educational and Research Institute 94 PUBLICATIONS 902 CITATIONS SEE PROFILE All content following this page was uploaded by RAJAN K on 17 January 2018. The user has requested enhancement of the downloaded file.
- 2. F o r P e e r R e v i e w O n l y Solar Tracking System-A review Journal: International Journal of Sustainable Engineering Manuscript ID TSUE-2014-0050.R2 Manuscript Type: Review Paper Date Submitted by the Author: 12-Oct-2015 Complete List of Authors: krishna, sunitha; st.peters university, mechanical K, Rajan; DR.M.G.R university, Mechanical Keywords: Green engineering, Renewable energy, Renewable energy technologies User-Supplied Keywords: solar energy, photovoltaic, solar tracking system, Azimuth, Passive actuator URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering
- 3. F o r P e e r R e v i e w O n l y Solar Tracking System-A review Suneetha Racharla1* , K Rajan2 1* Department of mechanical engineering, Research scholar in St.Peter’s university. 2 Department of mechanical engineering, Dr.M.G.R University, Chennai 1* suneetha 220@gmail.com, 2 krajanmech@gmail.com Abstract The generation of power from the reduction of fossil fuels is the biggest challenge for the next half century. The idea of converting solar energy into electrical energy using photovoltaic panels holds its place in the front row compared to other renewable sources. But the continuous change in the relative angle of the sun with reference to the earth reduces the watts delivered by solar panel. In this context solar tracking system is the best alternative to increase the efficiency of the photovoltaic panel. Solar trackers move the payload towards the sun throughout the day. In this paper different types of tracking systems are reviewed and their pros and cons are discussed in detail. The results presented in this review confirm that the azimuth and altitude dual axis tracking system is more efficient compared to other tracking systems. However in cost and flexibility point of view single axis tracking system is more feasible than dual axis tracking system. KEYWORDS: Solar energy, Photovoltaic panel, solar tracker, Azimuth, passive actuator,latitude. 1. Introduction Nowadays the energy deficiency problems faced by the world, more especially the third world countries, are urging researchers to find an alternative energy source that would complement the conventional fossil fuel. The alternative energy sources include solar, nuclear and wind. Solar energy is the energy generated by harnessing the power of the solar radiation. It is the cleanest source of energy which can pollute the climate the least. The power from the sun Page 1 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 4. F o r P e e r R e v i e w O n l y intercepted by the earth is approximately 1.8*1011 MW, which is many thousands of times larger than the present consumption rate on the earth from all other in-use commercial energy sources. The main problem with the solar energy is its dilute nature. Even in the hottest regions on the earth, the solar radiation flux available rarely exceeds 1 KW/M, which is insufficient for technological utilization. This problem can be rectified by a device solar tracker which ensures maximum intensity of sun rays hitting the surface of the panel from sun-rise to sunset. 1.1. Solar geometry and solar angles The Earth’s orbit about the Sun is almost circular at an average distance of 149.6 million km. The Earth’s axis of rotation is tilted by an angle Ɛ=23.441o with respect to the normal to the plane of the Earth’s orbit (Fig. 1) [1]. The plane of the Earth’s orbit is named as the plane of the ecliptic. The plane passing through the Earth’s equator is inclined perpendicularly to the plane of the ecliptic, at an angle Ɛ (angle of obliquity). Based on conservation of angular momentum, the Earth’s axis of rotation points as a fixed direction in space which means for the same location on Earth, at a fixed time (for midday as determined by solar time), the altitude of the Sun (the angular height above the horizon) will vary throughout the year. Fig. 1.Schematic diagram of earth orbit around sun [Source: Sproul et al. (2007)] In order to derive the solar angles, need to define suitable reference frames. Three principal reference frames will be used, the ecliptic, the equatorial and the horizon reference frames [2]. These reference frames are centered or referenced to the centre of the Earth and the apparent motion of the Sun is considered for calculations. The Sun and other celestial bodies are assumed to lay on the celestial sphere (Fig.2) a sphere with a large radius. The daily rotation of the earth is described by the rotation of the celestial sphere about the polar axis, and the instantaneous position of the sun is given by the hour angle ω, the angle between the meridian passing through the sun and the meridian of the site. The celestial sphere is imagined to rotate about the fixed Earth to depict the daily, apparent motion of the Sun and other celestial bodies (Fig.2) [44]. Fig.2. Celestial sphere geometry of the Sun and Earth [Source: Sproul et al. (2007)] 1.2. The nomenclature Page 2 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 5. F o r P e e r R e v i e w O n l y 1. Declination angle (δ) It is the angular distance of the sun’s position in north or south of the earth’s equator (Fig.3). The earth’s axis is tilted 23.34° from the plane of the earth’s orbit around the sun and the earth is in its annual path around the sun causes the declination angle to vary from 23.45° north on december 21st (Winter Solstice) to 23.45° south on June 21st (Summer Solstice) [45-47]. Fig.3.Solar angles 2. The altitude angle or elevation angle (α) It shows how high the sun appears in the sky. The angle is measured between an imaginary line between the observer and the sun and the horizontal plane the observer is standing on. The altitude angle is negative when the sun drops below the horizon (Fig.3) [45-47]. 3. Solar azimuth angle (ϒs) It is the angular distance between South and the projection of the line of sight to the sun on the ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth angle indicates West of South (Fig.3) [45-47]. The latitude (w) It is a point or location is the angle made by the radial line joining the location to the center of the earth with the projection of the line on the equatorial plane. The earth’s axis of rotation intersects the earth’s surface at 90o latitude (North Pole) and -90o latitude (South Pole). Any location on the surface of the earth then can be defined by the intersection of a longitude angle and a latitude angle. 2. Components of solar tracking system Page 3 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 6. F o r P e e r R e v i e w O n l y The main mechanism of the solar tracking system consists of the tracking device, the tracking algorithm, the control unit, the positioning system, the driving mechanism, and the sensing devices. The tracking algorithm determines the angles which are used to determine the position of solar tracker. There are two types of algorithms-astronomical algorithms and real time light intensity algorithms. The astronomical algorithm is a purely mathematical algorithm based on astronomical references. The real-time light intensity algorithm is based on real-time light intensity readings. The control unit performs the tracking algorithm and manages the positioning system and the driving mechanism. The positioning system operates the tracking device to face the sun at the calculated angles. The positioning system can be electrical or hydraulic. The driving mechanism is responsible for moving the tracking device to the position determined by the positioning system. The sensing devices are group of sensors and measurements that measure the ambient conditions, the light intensity in case of real-time light intensity algorithms, and the tilt angle of the tracker (by means of an inclinometer or a combination of limit switches and motor encoder counts) [45]. 3. Solar tracking system Vs fixed panel The amount of output mainly depends on the cosine angle of incidence which is known as the angle between the sun ray and horizontal surface. The minimum incidence angle gives the maximum power output. In case of fixed panel except noon time the angle is maximum for the movement of sun. The efficient solar tracker is which can correct this problem. The first solar tracker introduced by Finster in 1962, was completely mechanical. One year later, Saavedra presented a mechanism with an automatic electronic control, which was used to orient an Eppley pyrheliometer [3]. Anusha et al.[4] compared the fixed PV panel and single axis solar tracking based on real time clock(RTC) using ARM processor. The experiment is conducted using both Page 4 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 7. F o r P e e r R e v i e w O n l y fixed and tracking system for 6 days. The results show that the solar tracking system increased the efficiency around 40% and energy received from the sun is improved from 9.00AM to 6.00 PM. Dhanabal et al.[5] compared the efficiencies of static panels and tracking systems of single axis and dual axis fixed mount. The readings are taken from morning 8 AM to evening 6 PM for fixed panel, single axis tracker and dual axis tracker for every one hour. The results says the efficiency of the single axis tracking system over that of the static panel is calculated to be 32.17% and dual axis tracking system over that of the static panel is calculated to be 81.68%. Tiberiu tudorache et al [6] compared the solar tracking PV panel with a fixed PV panel in terms of electric energy output and efficiency. The proposed device automatically searches the optimum PV panel position with respect to the sun by means of a DC motor controlled by an intelligent drive unit that receives input signals from dedicated light intensity sensors. The solar tracking PV panel produced more energy than fixed one with about 57.55%. Bione et al. [7] compared the pumping systems driven by fixed, tracking and tracking with concentration PVs. The results showed that for a given irradiance, the pumped water flow rate was significantly different from one another. The fixed PV, the PV with tracker and the concentrating-tracking systems pumped 4.9, 7.4 and 12.6m3 /day, respectively. Snehal et al. [8] proposed a Field Programmable Gate Array (FPGA) sensor Based Standalone Solar Tracking System. Sun tracking system composed of fuzzy logic controller implemented on FPGA sensors, PV panel, stepper motor, and input-output interface. Xilinx_ISE software is used for coding of FLC for Sun tracking. The results show that tracking has maximum efficiency than fixed panels. 4. Different types of solar tracking techniques Fig 4.Solar tracking technologies Page 5 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 8. F o r P e e r R e v i e w O n l y 4.1 Based on collectors 4.1.1. Flat plate photovoltaic panel (PV) In flat-panel photovoltaic applications, trackers are used to minimize the angle of incidence between the incoming sunlight and a photovoltaic panel. Masakazu Ito et al. [9] proposed a comparative study of fixed and tracking system of very large-scale PV (VLS-PV) systems in the world deserts. The work focused on the potential and simulation of the 100MW.Life cycle analysis is applied for the simulation. The potentials are evaluated from economic viewpoint by LCA method. The results shows that cost reduced by applying tracking system. Marcel Sur et al. [10] produced solar electricity from fixed-inclined and sun-tracking crystalline silicon (C-SI) photovoltaic modules in South Africa. The work presents a method to for estimating the energy output from fixed-mounted and sun-axis tracking flat-plate PV systems. The simulation uses the solar radiation and temperature time series representing a historical record of 18 years (1994 to 2011).The Results shows one axis tracker with vertical axis inclined 30 degrees north typically gains from 15% up to 35% more electricity, compared to fixed mounting at optimum tilt.Anyaka et al. [11] studied the Improvement of PV Systems Power Output Using Sun-Tracking Techniques. The work presented the detailed view of sun tracking systems developed over the past years. The results prove that the applicability of sun tracking system gives a diverse range of high performance solar-based applications. 4.1.2 Concentrated Photovoltaic (CPV) The optics in CPV modules accept the direct component of the incoming light to maximize the energy collected. The tracking functionality in CPV modules is used to orient the optics such that the incoming light is focused to a photovoltaic collector. Tony Kerzmann et al. [12] studied the flow rate optimization of a linear concentrating photovoltaic system. The work Page 6 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 9. F o r P e e r R e v i e w O n l y focused on a two dimensional linear concentrated photovoltaic (LCPV) combined with an active cooling and waste heat recovery system. The results shows that an optimal cooling fluid flow at a rate of 4 gal/min (2.52×10−4m3 /s) would produce and average of 45.9 kWh of electricity and 15.9 kWh of heat energy. Tripanagnostopoulos et al. [13] proposed the design and performance aspects for low concentration photovoltaic. The non-uniform distribution of solar radiation on the PV surface reduces the electrical efficiency and can be rectified by combining the PV with low concentration devices. The diffuse reflectors are used instead of specular reflectors because of their low cost. The PV temperature reduction is also a factor so several modes for heat extraction are applied; using water or air cooled hybrid photovoltaic/thermal (PV/T) solar systems. Benecke et al. [14] developed the Optical design of low concentrator photovoltaic modules. This work addresses the necessary procedures that need to be considered when designing an optical sub-system of low concentrator photovoltaic (LCPV) module. Various design considerations are taken into account to construct a LCPV module that is characterized with respect to optical design and electrical performance. Benecke et al. [15] implemented the design and analysis of a vertical receiver LCPV system. The work presents the design aspects of the optical and electrical subsystem of LCPV with a geometric concentration ratio of 4.6.An electrical estimation is conducted by the use of I-V (current-voltage) characteristics obtained under sun as well as under concentration. 4.1.3Concentrated Solar Power (CSP) Concentrating solar power or concentrated solar thermal systems use mirrors or lenses to concentrate a large area of sunlight or solar thermal energy onto a small area. Electrical power is produced when the concentrated light is converted into heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator or powers a thermo chemical Page 7 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 10. F o r P e e r R e v i e w O n l y reaction. Miqdam Tariq et al. [16] studied the effect of design variation on saved energy of Concentrating Solar Power prototype. The work discussed about the methods to improve the efficiency of the concentrated solar thermal plant. El jai et al. [17] implemented a modified model for parabolic trough solar receiver using concentrated solar thermal energy. The work concentrates on the original mathematical model that describes the heat exchange between the main components of a thermal solar collector in an integrated solar combined cycle (ISCC) plant. The solar plant is an integrated combined cycle thermo-solar power plant consists of 256 parabolic trough solar collectors and classified in 64 parallel loops and each loop is 618 meters long. The use of the solar tracking mechanism is to maintain the incident solar radiation perpendicular to the reflector and to the focal line of the parabola where a receiver tube contains the heat transfer fluid. The different simulation results show that both the fluid temperature and the metal tube temperature grow until reaching a certain equilibrium value. 4.2 Based on the axis 4.2.1. Single axis tracker Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of rotation of single axis trackers is typically aligned along a true North meridian. Rizk et al. [18] developed solar tracking system with more efficient use of solar panels. This work includes the potential system benefits of simple tracking solar system of single axis tracker using a stepper motor and light sensor. This method is increasing power collection efficiency by implementing a device that tracks the sun to keep the panel at a right angle to sun rays. The power gain is increased 30% over a fixed horizontal array. 4.2.1.1. Horizontal Single Axis Tracker (HSAT) Page 8 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 11. F o r P e e r R e v i e w O n l y The axis of rotation for horizontal single axis tracker is horizontal with respect to the ground. Backtracking is one of computing the disposition of panels [48]. Guihua et al. [19] calculated the optical performance of horizontal single axis tracked solar panels. From the results it is clear that the east-west placed HSAT is worst to boost the energy while the north-south placed HSAT increased the efficiency drastically around 36%. Fig 5.Horizontal Single Axis Tracker 4.2.1.2. Vertical Single Axis Tracker (VSAT) The axis of rotation for vertical single axis trackers is vertical with respect to the ground. These trackers rotate from east to west over the course of the day. Lorenzo et al. [20] designed the tracking of photovoltaic systems with a single vertical axis. The vertical single axis tracking also called as azimuth tracking is mainly used for the energy gain which can be 40% more compared to tilted static panels. This research work deals with the design of VSAT photovoltaic plant in Tudela. The problems of shadowing in E-W direction and also N-S direction and the methods to rectify are explained in detail. The results clearly specify that VSAT boosted the energy gain around 40% per annum. 4.2.1.3. Tilted Single Axis Tracker (TSAT) The tracker with axes of rotation between horizontal and vertical is named as tilted single axis tracker. Tracker tilt angles are often limited to reduce the wind profile and decrease the elevated end height. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation [45]. 4.2.1.4. Polar Aligned Single Axis Tracker (PSAT) Page 9 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 12. F o r P e e r R e v i e w O n l y This method is scientifically well known as the standard method of mounting a telescope support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar aligned single axis tracker [46]. Fig 6. Polar Aligned Single Axis Tracker 4.2.2 Dual Axis Tracking Dual axis trackers have two degrees of freedom that act as axes of rotation normal to one another. The axis that is fixed with respect to the ground is a primary axis. The axis that is referenced to the primary axis is secondary axis [48]. Fig 7. Dual Axis SolarTracker 4.2.2.1. Tip-Tilt Dual Axis Tracker (TTDAT) A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a pole. Normally the east-west movement is driven by rotating the array around the top of the pole. The vertical azimuth axis is fixed so as to allow great flexibility of the payload connection to the ground mounted equipment because there is no twisting of the cabling around the pole. Tip-tilt trackers can make to minimize up-sun shading and therefore maximize the total power being collected [21-25]. 4.2.2.2 Azimuth-Altitude Dual Axis Tracker (AADAT) An azimuth–altitude dual axis tracker has its primary axis (the azimuth axis) vertical to the ground and the secondary axis (elevation axis) is normal to the primary axis. The operation is similar to tip-tilt systems but differ in the way the array is rotated for daily tracking. Instead of rotating the array around the top of the pole, they use a large ring mounted on the ground with the array mounted on a series of rollers. The main advantage of this arrangement is the weight of the array is distributed over a portion of the ring [47]. Liqun Liu et al. [26] discussed about the Page 10 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 13. F o r P e e r R e v i e w O n l y influence factors analysis of the best orientation relative to the sun for dual-axis sun tracking. In this research work different types of tracking systems are reviewed such as fixed panel, single axis tracking in east-west, single axis tracking in north-south, and dual axis tracking using both tip-tilt and altitude-azimuth tracking. The results show the influencing factors are time error, latitude, and azimuth and tilt angle of the photovoltaic, reflectivity and composite transparent coefficient. Arbab et al. [27] implemented a computer tracking system of solar dish with two- axis degree freedoms based on picture processing of bar shadow. The design is based on computer image processing of a bar shadow to obtain the optimized picture of solar dish displacements. The system is independent to geographical location of the solar dish and periodical changes like daily or monthly regulations. Jifeng Song et al. [28] implemented a high precision dual axis tracking system based on a hybrid strategy designed for concentrated sunlight transmission via fibers. This system is based on a two-stage tracking process, which consists of a coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a specially designed photosensitive sensor. In this design optical fibers are used for the precision tracking of concentrated sunlight. The advantage of this design is the higher resolution of the sun sensor because of the use of photosensitive arrays in closer arrangement. From the results it is clear that system tracked the sun’s focal spot with a position precision of less than 0.3 mm and the tracking angle precision is 0.1o . Jay Robert et al. [29] proposed the optimization of a small scale dual-axis solar tracking system using nano watt technology. The solar module is placed first in any one direction and the PV array has to search and stop at the highest current gained by the solar cell. The process is continued for every 30 minutes from 0600H up to 1800H. The results are measured in these positions for current, voltage and power. An open loop control is used for controlling the motors. Reis et al. [30] proposed the Modeling the performance of low Page 11 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 14. F o r P e e r R e v i e w O n l y concentration photovoltaic systems. A theoretical model is implemented to study the response of voltage-through systems in terms of temperature, power output and energy yield using as inputs. The device is constructed by integrating dual axis system and conventional crystalline Si- module, named as double sun technology. The results conclude that the double sun technology is increased the efficiency around 86% compared to fixed panels. Mohammed et al. [31] designed a parabolic solar cooker with automatic two axes sun tracking system. The solar cooker with automatic two axes eliminates the standing in the sun for hours to get frequent tracking and facing the concentrated solar cooker. The results of the continuous test performed for three days from 8:30 hr to 16:30 hr in the year 2008 and showed that the water temperature inside the cooker’s tube reached 90o C in typical summer days for the maximum registered ambient temperature was 36 o C. Ahmed Rhif et al. [32] implemented a position control review for a photovoltaic system dual axis sun tracker. This work presents a sun tracker without using sun sensors. The sun tracking is performed by changing the solar panel orientation in horizontal and vertical directions by two motors. The control of these motors is ensured by a microcontroller. Sliding mode control is used to solve the nonlinear equations. The simulation results conclude that tracking improves the efficiency around 40% than fixed panel. Okpeki et al. [33] designed and constructed a bi-directional solar tracking system. This research work includes the design and fabrication of a bi-directional tracker which can rotate in both azimuth and altitude directions. The two influencing factors of power output are intensity and wave length of sun light are addressed in detail. The results conclude that the efficiency is drastically more compared to fixed panel and the total cost of the tracker is very low. George Bakos et al. [34] implemented a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement. Parabolic trough is used with two axis rotation to the sun. The results conclude Page 12 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 15. F o r P e e r R e v i e w O n l y that parabolic collector is increasing the energy than flat collector. Rodiek et al. [35] conducted solar photovoltaic array tilt angle and tracking performance experiment. Advanced software models were developed to calculate the change of path by the sun throughout the year and to predict the optimum angle for the single axis tracker to obtain maximum energy output for the entire year. Two modeling programs are discussed to predict the optimal angle. For the experiment five panels are used in a single axis to track azimuthally at the tilt angles of 20º, 25º, 32º (latitude), 40º, and 50º. One more panel is a fixed control panel facing south at latitude tilt. The results are taken for one year and they conclude that a higher tilted panel (50º) will produce more power throughout the year compared to modeling from PV Watts that suggests a 32º tilt. 4.3. Based on driver 4.3.1. Active tracker 4.3.1.1. Microcontroller and electro-optical sensor based solar tracker: Sobuj Kumar Ray et al. [36] presented two ways of rotating freedom solar tracker by using microcontroller. The work includes the design of a two ways rotating freedom solar tracker based on microcontroller.PIC16F72 microcontroller is used to activate the motors to get two ways rotation.LDC sensors are used to get the information about sun radiation. The results are compared with conventional solar tracker without microcontroller and also with fixed panels. The difference is almost 37% between fixed panel and tracking system with microcontroller. Yousif El-Tous et al. [37] studied the thermal evaluation of a sun tracking solar cooker using microcontroller. The work contains the implementation of tracking system developed for getting the solar heating using solar cooker. A microcontroller is used for rotating the solar heater with the movement of the sun. PLC system is used as control system. A comparison between fixed and sun tracked cooker showed that the use of sun tracking increased the heating temperature by Page 13 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 16. F o r P e e r R e v i e w O n l y 36%. Mostefa Ghassoul et al. [38] proposed design of an automatic solar tracking system to maximize energy extraction. This solar tracking system is controlled by a micro chip PIC 18F452 micro controller. The search mechanism (PILOT) locates the position of the sun and the intelligent panel mechanism rotates itself with the PILOT to extract the maximum energy. The main defect in this is the rotation only takes place, if the energy obtained in the new position is higher than that consumed by the panels during the transition. So one miniature motor is used s to search the best position for maximum energy extraction. The panel’s mechanism rotates to the position automatically when energy extraction is optimal. The system is designed in such a way that panels only follow the sun if that contributes to extra energy extraction and at the same time, the energy consumed by the panel driving motor is less than that extracted. Jing-Min Wang et al. [39] proposed the design and implementation of a sun tracker with a dual-axis single motor for an optical sensor-based photovoltaic system. This work proposes a novel design of a dual-axis solar tracking PV system which utilizes the feedback control theory along with a four-quadrant light dependent resistor (LDR) sensor and simple electronic circuits to provide robust system performance. The proposed system uses a unique dual-axis AC motor and a stand-alone PV inverter to accomplish solar tracking. Experiment results indicated that the developed system increased the energy gain up to 28.31% for a partly cloudy day. 4.3.1.2. Auxiliary bifacial solar cell based solar tracker Bhupendra Gupta et al. [40] explained the design, construction and effectiveness of a hybrid automatic solar tracking system for amorphous and crystalline solar cells. This work includes the design a Hybrid solar tracking system implemented by integrating with amorphous and crystalline solar panel, and microcontroller. The experiment consists of the analysis on the use of two different material of solar panel like Amorphous and Crystalline in a solar tracking Page 14 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 17. F o r P e e r R e v i e w O n l y system at stationary, single axis, and dual axis and hybrid axis solar tracker. The comparison shows that the use of the dual-axis tracking system produced 17.87% gain of power output than a single-axis tracking system. The gain of output power with the hybrid tracking system is further more (52%) than a stationary system inclined at 23.5o to the horizontal. 4.3.1.3 Date, time and sensor based In the date/time and sensor based tracking systems, electronic devices like microprocessor calculates the sun’s position from basic formulae or algorithms from geographical information and send signals to the electro motor (Fig.5). Fig. 8 Position of PV modules in the morning and afternoon Edwards et al. [41] presented the operation of a computer based sun following system for parabolic collectors. The computer continuously varies the speed of each collector actuators at regular intervals throughout the day. The results conclude that for accurate sun following, the system requires a data output from the central controller of only 500 bit/s for 10,000 collectors per day. 4.3.2. Passive tracker The passive trackers use a boiling point from a compressed fluid which moves from one side to other by the solar heat which creates a gas pressure results the tracker movement [42]. Due to the bad quality of precision orientation, it is unsuitable for certain types of photovoltaic collectors. In the passive tracker the photovoltaic panels include a hologram behind stripes of photovoltaic cells so that sunlight reflects [37] on the hologram which allows the cell heat from behind, thereby increasing the modules’ efficiency. Moreover, the plant need not require moving while the hologram still reflects sunlight from the needed angle toward the photovoltaic cells. Jeyaganesh et al.[43] proposed the design and development of a sun tracking mechanism using the Direct SMA actuation. The Shape Memory Alloy (SMA) element acts as sensor and actuator Page 15 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 18. F o r P e e r R e v i e w O n l y position the solar receptor tilted appropriately to face the sun directly at all times during the day. The thermal stimulus required to activate the SMA element is provided by the concentration and direct focusing of the incident sun rays on to the SMA element. The results show the possibility of the design and development of a sun tracking mechanism using SMA that directly uses sunlight without the need for any additional external power source. Table.1.Comparision table for different tracking systems Table.2. Comparision table on cost and payback for different tracking systems 5. Conclusion The innovative designs in sun tracking systems have enabled the development of many solar thermal and photovoltaic systems for a diverse variety of applications in recent years compared to the traditional fixed panels. Solar systems which track the changes in the sun’s trajectory over the course of the day collect a far greater amount of solar energy, and therefore generate a significantly higher output power. This paper has presented a review of the major types of sun tracking systems developed over the past 20 years. It has been shown that these sun tracking systems can be broadly classified as single axis and dual axis, depending on their mode of rotation. Further it can be classified as active and passive tracker depending on the actuator. The sub division and their basic principles of each method have been reviewed. Overall, the results presented in this review confirm that the azimuth and altitude dual axis tracking system is more efficient compared to other tracking systems. However in cost and flexibility point of view single axis tracking system is more feasible than dual axis. In future the present paper details will be useful in selecting an accurate and particular tracker with respect to region, available space and estimated cost. The present work may be useful to improve the design characteristics of different types of solar tracking systems to improve performance. Page 16 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 19. F o r P e e r R e v i e w O n l y 6. References: 1. Mitton S, 1977.The Cambridge encyclopedia of astronomy. London: 1st ed. 2. Alistair,B.sproul. 2007. “Derivation of solar geometric relationships using vector analysis.” Renewable energy 32: 1187-1205 3. Roth,p.georgiev., Boudinov.A., and Cheap.H. 2005. “Two axis sun following device.” Energy conservation and management 46:1179-92. 4. Anusha.K., Chandra.S., and Mohan Reddy. 2013. “Design and development of real time clock based efficient solar tracking system.” International journal of Engineering Research and Applications (IJERA) 3:1219-1223. 5. Dhanabal.R., Bharathi.V., Ranjitha.R., Ponni.A., Deepthi.S., and Mageshkannan.P. 2013. “Comparison of efficiencies of solar tracker systems with static panel single axis tracking system and dual axis tracking system with fixed mount.” International Journal of Engineering and Technology (IJET) 5:1925-1933. 6. Tiberiu tudorache., Constantin daniel oancea., and Lliviu kreindler. 2012. “Performance evaluation of a solar tracking PV panel.” U.P.B. Sci. Bull series C 74:3-10. 7. Bione.J., Vilela.OC., and Fraidenraich.N. 2004. “Comparison of the performance of PV water pumping systems driven by fixed, tracking and V-trough generators.” Solar energy 76:703-11. 8. Snehal Hon.P., Kolte.M.T. 2013. “FPGA Based Standalone Solar Tracking System.” International Journal of Scientific and Research Publications l3:1-5. 9. Masakazu Ito., Kazuhiko Kato., Keiichi Komoto., Tetsuo Kichimi., Hiroyuki Sugihara., and Kosuke Kurokawa. 2003. “Comparative study of fixed and tracking system of very large-scale PV (VLS-PV) systems in the world deserts.” Proceedings of 3rd WCPEC 3O:A2-01. Page 17 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 20. F o r P e e r R e v i e w O n l y 10. Marcel Suri., Tomas Cebecauer., Artur Skoczek and Juraj Betak. 2012. “Solar electricity production from fixed-inclined and sun-tracking c-si photovoltaic modules in South Africa.” 1st Southern African Solar Energy Conference (SASEC ):1-8. 11. Anyaka.B.O., Ahiabuike.D.C., and Mbunwe. M. J. 2013. “Improvement of PV Systems Power Output Using Sun-Tracking Techniques.” International Journal of Computational Engineering Research 3:80-98 12. Tony kerzmann., laura Schaefer. 2013. “Flow Rate Optimization Of A Linear Concentrating photovoltaic System.” Journal of solar energy engineering 135:10-14. 13. Tripanagnostopoulos.Y., Souliotis.M., Tselepis.S., Dimitriou.V., and Makris.Th. 2005. “Design and Performance Aspects for low concentration photovoltaics.” 20th European Photovoltaic Solar Energy Conference and Exhibition, Barcelona, Spain. 14. Benecke. M.A., van Dyk. E. E., Vorster.F.J., 2013. “Optical design of low concentrator photovoltaic modules.” Journal of energy in South Africa 24:4-9. 15. Benecke. M.A., van Dyk. E. E., Vorster.F.J., 2013. “The design and analysis of a vertical receiver LCPV system.” journal of energy in south Africa 20:16-19. 16 Miqdam Tariq. C., Khalil. I. A., Hussein. A. K., Feras Hasoon., Hakim Sultan Aljibori. S., Ali Alwaeli. A.K., Firas Raheem. S., and Ali Alwaeli. H. A., 2012. “Effect of Design Variation on Saved Energy of Concentrating Solar Power Prototype.” Proceedings of the World Congress on Engineering 3:1-6. 17 Eljai. M.C., Chalqi. F.Z. 2013. “A modified model for parabolic trough solar receiver.” American Journal of Engineering Research (AJER) 2:200-211. 18. Rizk. J., Chaiko.Y. 2008. “Solar Tracking System- More Efficient Use of Solar Panels.” World Academy of Science, Engineering and Technology 17:313-315. Page 18 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 21. F o r P e e r R e v i e w O n l y 19 Guihua. Li., Runsheng Tang., and Hao Zhang. 2012. “Optical Performance Of Horizontal Single Axis tracked Solar Panels:2012.” International Conference on Future Energy, Environment and materials 16:1744-1752. 20. Lorenzo. E., Perez. M.,.Ezpeleta.A., and Acedo. J. 2002. “Design of Tracking Photovoltaic Systems with a Single Vertical Axis.” Progress in photovoltaic: research and applications 10:533-543. 21. Mehleri. E., Zervas. P., Sarimveis. H., Palyvos. J., and Markatos. N. 2010. “Determination of the optimal tilt angle and orientation for solar photovoltaic arrays.” Renewable Energy 2; 24-69. 22. Al Mohamad.A. 2004. “Efficiency improvements of photo-voltaic panels using a Sun-tracking system.” Applied Energy 79:345–54. 23. Batayneh. W., Owais. A. and Nairoukh. M. 2013. “An intelligent fuzzy based tracking controller for a dual-axis solar PV system.” Automatic in Construction 29: 100-106. 24. Alata. M., Al-Nimr .M. A. and Qaroush.Y. 2005. “Developing a multipurpose sun tracking system using fuzzy control.” Energy Conversion & Management 46:1229-1245. 25. Al-Naima.F.M., Yaghobian,N.A. 1990. “Design and construction of a solar tracking system.” Solar Wind Technol 7: 611-617. 26. Liqun Liu., Han Xiaoqing., Chunxia Liu and Jing Wang. 2013. “The influence factors analysis of the best orientation relative to the sun for dual-axis sun tracking system.” Journal of Vibration and Control: 1-7. 27. Arbab.H., Jazi. B., and Rezagholizadeh.M. 2009. “A computer tracking system of solar dish with two- axis degree freedoms based on picture processing of bar shadow.” Renewable Energy 34: 1114–1118. Page 19 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 22. F o r P e e r R e v i e w O n l y 28. Jifeng Song., Yongping Yang., Yong Zhu., and Zhou Jin. 2013. “A high precision tracking system based on a hybrid strategy designed for concentrated sunlight transmission via fibers.” Renewable energy 57:12-19. 29. Jay Robert.B., del Rosario., Reggie. C.G., and Elmer Dadios.P. 2014. “Optimization of A Small Scale Dual-Axis Solar Tracking System Using Nanowatt Technology.” Journal of Automation and Control Engineering 2:134-137. 30. Reis. F., Brito. M.C., Corregidor. V., Wemans .J., and Sorasio.G. 2010. “Modeling the performance of low concentration photovoltaic systems.” Solar energy materials and solar cells 1:1-5. 31. Mohammed.S., Al-Soud., Essam Abdallah., Ali Akayleh., Salah Abdallah., and Salah Abdallah. 2010. “A parabolic solar cooker with automatic two axes sun tracking system.” Applied energy 87:463-470. 32. Ahmed Rhif.A., 2013. “Position Control Review for a Photovoltaic System-Dual axis sun tracker.” IETE Technical Review 28:478-485. 33. Okpeki.U.K., Otuagoma.S.O. 2013.“Design and Construction of a Bi–Directional Solar Tracking system.” International Journal of Engineering and science 2:32-38. 34. George Bakos.c. 2013. “Design and construction of a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement.” Solar energy materials and solar cells 3:2-7. 35. Julie A. Rodiek., Steve R. Best., and Casey Still. 2010. “Auburn University’s Solar Photovoltaic Array Tilt Angle and Tracking Performance Experiment.” American Institute of Aeronautics and Astronautics : 1-5 Page 20 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 23. F o r P e e r R e v i e w O n l y 36. Sobuj Kumar Ray., Abul Bashar.Md., Maruf Ahmad. and Fahad Bin. 2012. “Two Ways of rotating Freedom Solar Tracker by Using ADC of Microcontroller.” Global Journal of Researches in engineering 12:29-34. 37. Yousif El.Tous., Omar Badran. O., and Anwar Al Mofleh. 2012. “Thermal evaluation of a sun tracking solar cooker.” International journal of energy and environment:3:83-90. 38. Mostefa Ghassoul. 2013. “Design of an Automatic Solar Tracking System to Maximize Energy Extraction.” International Journal of Emerging Technology and Advanced Engineering 3:453- 460. 39. Jing Min Wang., Chia Liang Lu. 2013. “Design and Implementation of a Sun Tracker with a Dual-Axis Single Motor for an optical Sensor-Based Photovoltaic System.” sensors 13:3175- 3168. 40 Bhupendra Gupta,, Neha Sonkar., Brahman Singh Bhalavi., and Pankaj Edla.J. 2013. “Design, Construction and Effectiveness Analysis of Hybrid Automatic Solar Tracking System for Amorphous and Crystalline Solar Cells.”: American journal of engineering research 2:221-228. 41. Edwards. B.P.1978. “Computer based sun following system.” Solar Energy 21:491–496. 42. Semma.R.P., Imamura M.S. 1980. “Sun tracking controller for multi kW photovoltaic concentrator system.” In Proceedings of the 3rd International Photovoltaic Sol Energy Conf, Cannes, France: 27-31. 43. Jeya Ganesh.N., Maniprakash.S., Chandrasekaran.L., Srinivasan.S.M., and Srinivasa.A.R. (2011). “Design and Development of a Sun Tracking mechanism using the Direct SMA actuation.” Journal of mechanical design 133: 1-14. 42. McFee R.H. 1975. Power collection reduction by mirror surface non flatness and tracking error for a central receiver solar power system 14: 1493-502. Page 21 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 24. F o r P e e r R e v i e w O n l y 44. Alistair Sproul.B. 2007. “Derivation of the solar geometric relationships using vector analysis.” Renewable Energy 32: 1187-1205. 45. Rockwell Automation 2009. “Solar Tracking Application.” A Rockwell Automation White Paper: 1-8. 46. http://personal.cityu.edu.hk/~bsapplec/solar1.htm. 47. http://en.wikipedia.org/wiki/Solar_zenith_angle. 48. http://en.wikipedia.org/wiki/Solar_azimuth_angle. 49. http://en.wikipedia.org/wiki/Solar_tracker. Page 22 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 25. F o r P e e r R e v i e w O n l y Fig. 1.Schematic diagram of earth orbit around sun Fig.2. Celestial sphere geometry of the Sun and Earth Fig.3.Solar angles Page 23 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 26. F o r P e e r R e v i e w O n l y Fig 4.Solar tracking technologies Fig 5.Horizontal Single Axis Tracker Page 24 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 27. F o r P e e r R e v i e w O n l y Fig 6. Polar Aligned Single Axis Tracker Fig 7. Dual Axis SolarTracker Fig. 8 Position of PV modules in the morning and afternoon Page 25 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 28. F o r P e e r R e v i e w O n l y Table.1.Comparision table for different tracking systems Type of solar system performance capabilities Number of axis Possible manufactures Technical restrictions Single axis solar tracking system Horizontal single axis tracker (HSAT) 68% compared to fixed panel Less complicated, less expensive, rigid and stable. less likely to be damaged during storms 1 ARRAY Technlogies inc,U.S.A. SAHAJ SOLAR, India WUXI HAOSOLAR Technology co.,Ltd, China. DEGE Renergie GmbH, Germany Occupy lot of space because there are tobe arranged horizontally Vertical single axis tracker (VSAT) 62% compared to fixed panel when loss due to wind force taken into account Less complicated, less expensive, 1 ARRAY Technlogies inc,U.S.A WUXI HAOSOLAR Technology co.,Ltd, China. DEGE Renergie GmbH, Germany Easily affected by wind force. so support should be taken care Tilted single axis tracker (TSAT) 69% compared to fixed panel More suitable for smaller Latitudes i.e places which are close to equator 1 ARRAY Technlogies inc,U.S.A WUXI HAOSOLAR Technology co.,Ltd, China. DEGE Renergie GmbH, Germany The inclination should be calculated very accurately to avoid shading and wind loss Polar aligned single axis trackers (PASAT) Still experiments are going on. More suitable for larger latitudes i.e places which are far from equator 1 ARRAY Technlogies inc,U.S.A WUXI HAOSOLAR Technology co.,Ltd, China. DEGE Renergie GmbH, Germany Still experiments are going on this. Pros and cons has to be studied. Dual axis solar tracking system Tip–tilt dual axis tracker (TTDAT 78% compared to fixed panel without considering the extra manufacturing cost of dual axis Able to track the sun in both directions (east-west as well as north- south). & Able to minimize the up-sun shading. 2 ARRAY Technologies inc, U.S.A. ALL EARTH RENEWABLES,U.S.A. TITAN TRACKERS, Europe DEGE Renergie GmbH, Germany Should be attached on a long pole so wind forces will be very high Azimuth- altitude dual axis tracker (AADAT) 82% compared to fixed panel without considering the extra manufacturing More suitable for greater latitude where substantial seasonal variation in 2 ARRAY Technlogies inc,U.S.A. OPEL SOLAR, Canada DEGE Renergie GmbH, Germany It’s pivoting mechanism rests on the ground so occupies a large space and these are Page 26 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 29. F o r P e e r R e v i e w O n l y cost of dual axis sun’s height and arc. & The weight of the array is distributed over a portion of the ring not suitable for northern climates with snow build up. Passive tracking system 40% compared to fixed panel With the help of passive materials like SMA (shape memory alloy),the additional parts can be eliminated. -- ZOOMWORKS,U.S.A cost of the materials acting as actuators ll be very high and availability of some materials ll be difficult. Also sluggish in moving cold temperature Table.2. Comparision table on cost and payback for different tracking systems Type of solar tracker Cost per watt power Projected pay-back Fixed solar panel $2-2.4/ watt depending on the panel size and region. 1.5 to 3.5 ye ars for crystalline silicon PV systems. 1 to 1.5 years for thin film technologies Single axis solar tracking system $1.17/watt premium with respect to efficiency 3.0 years of payback on tracker investment Dual axis solar tracking system $0.36 /watt premium with respect to efficiency 3.5 to 5 years of payback cost on tracker investment Passive tracking system $1.2-2 /watt depending on the tracker size and features Approximately 5 years of payback cost Page 27 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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- 36. F o r P e e r R e v i e w O n l y Solar Tracking System-A review Suneetha Racharla1* , K Rajan2 1* Department of mechanical engineering, Research scholar in St.Peter’s university. 2 Department of mechanical engineering, Dr.M.G.R University, Chennai 1* suneetha 220@gmail.com, 2 krajanmech@gmail.com Abstract The generation of power from the reduction of fossil fuels is the biggest challenge for the next half century. The idea of converting solar energy into electrical energy using photovoltaic panels holds its place in the front row compared to other renewable sources. But the continuous change in the relative angle of the sun with reference to the earth reduces the watts delivered by solar panel. In this context solar tracking system is the best alternative to increase the efficiency of the photovoltaic panel. Solar trackers move the payload towards the sun throughout the day. In this paper different types of tracking systems are reviewed and their pros and cons are discussed in detail. The results presented in this review confirm that the azimuth and altitude dual axis tracking system is more efficient compared to other tracking systems. However in cost and flexibility point of view single axis tracking system is more feasible than dual axis tracking system. KEYWORDS: Solar energy, Photovoltaic panel, solar tracker, Azimuth, passive actuator,latitude. 1. Introduction Nowadays the energy deficiency problems faced by the world, more especially the third world countries, are urging researchers to find an alternative energy source that would complement the conventional fossil fuel. The alternative energy sources include solar, nuclear and wind. Solar energy is the energy generated by harnessing the power of the solar radiation. It is the cleanest source of energy which can pollute the climate the least. The power from the sun Page 34 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 37. F o r P e e r R e v i e w O n l y intercepted by the earth is approximately 1.8*1011 MW, which is many thousands of times larger than the present consumption rate on the earth from all other in-use commercial energy sources. The main problem with the solar energy is its dilute nature. Even in the hottest regions on the earth, the solar radiation flux available rarely exceeds 1 KW/M, which is insufficient for technological utilization. This problem can be rectified by a device solar tracker which ensures maximum intensity of sun rays hitting the surface of the panel from sun-rise to sunset. 1.1. Solar geometry and solar angles The Earth’s orbit about the Sun is almost circular at an average distance of 149.6 million km. The Earth’s axis of rotation is tilted by an angle Ɛ=23.441o with respect to the normal to the plane of the Earth’s orbit (Fig. 1) [1]. The plane of the Earth’s orbit is named as the plane of the ecliptic. The plane passing through the Earth’s equator is inclined perpendicularly to the plane of the ecliptic, at an angle Ɛ (angle of obliquity). Based on conservation of angular momentum, the Earth’s axis of rotation points as a fixed direction in space which means for the same location on Earth, at a fixed time (for midday as determined by solar time), the altitude of the Sun (the angular height above the horizon) will vary throughout the year. Fig. 1.Schematic diagram of earth orbit around sun [Source: Sproul et al. (2007)] In order to derive the solar angles, need to define suitable reference frames. Three principal reference frames will be used, the ecliptic, the equatorial and the horizon reference frames [2]. These reference frames are centered or referenced to the centre of the Earth and the apparent motion of the Sun is considered for calculations. The Sun and other celestial bodies are assumed to lay on the celestial sphere (Fig.2) a sphere with a large radius. The daily rotation of the earth is described by the rotation of the celestial sphere about the polar axis, and the instantaneous position of the sun is given by the hour angle ω, the angle between the meridian passing through the sun and the meridian of the site. The celestial sphere is imagined to rotate about the fixed Earth to depict the daily, apparent motion of the Sun and other celestial bodies (Fig.2) [44]. Fig.2. Celestial sphere geometry of the Sun and Earth [Source: Sproul et al. (2007)] 1.2. The nomenclature Page 35 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 38. F o r P e e r R e v i e w O n l y 1. Declination angle (δ) It is the angular distance of the sun’s position in north or south of the earth’s equator (Fig.3). The earth’s axis is tilted 23.34° from the plane of the earth’s orbit around the sun and the earth is in its annual path around the sun causes the declination angle to vary from 23.45° north on december 21st (Winter Solstice) to 23.45° south on June 21st (Summer Solstice) [45-47]. Fig.3.Solar angles 2. The altitude angle or elevation angle (α) It shows how high the sun appears in the sky. The angle is measured between an imaginary line between the observer and the sun and the horizontal plane the observer is standing on. The altitude angle is negative when the sun drops below the horizon (Fig.3) [45-47]. 3. Solar azimuth angle (ϒs) It is the angular distance between South and the projection of the line of sight to the sun on the ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth angle indicates West of South (Fig.3) [45-47]. The latitude (w) It is a point or location is the angle made by the radial line joining the location to the center of the earth with the projection of the line on the equatorial plane. The earth’s axis of rotation intersects the earth’s surface at 90o latitude (North Pole) and -90o latitude (South Pole). Any location on the surface of the earth then can be defined by the intersection of a longitude angle and a latitude angle. 2. Components of solar tracking system Page 36 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 39. F o r P e e r R e v i e w O n l y The main mechanism of the solar tracking system consists of the tracking device, the tracking algorithm, the control unit, the positioning system, the driving mechanism, and the sensing devices. The tracking algorithm determines the angles which are used to determine the position of solar tracker. There are two types of algorithms-astronomical algorithms and real time light intensity algorithms. The astronomical algorithm is a purely mathematical algorithm based on astronomical references. The real-time light intensity algorithm is based on real-time light intensity readings. The control unit performs the tracking algorithm and manages the positioning system and the driving mechanism. The positioning system operates the tracking device to face the sun at the calculated angles. The positioning system can be electrical or hydraulic. The driving mechanism is responsible for moving the tracking device to the position determined by the positioning system. The sensing devices are group of sensors and measurements that measure the ambient conditions, the light intensity in case of real-time light intensity algorithms, and the tilt angle of the tracker (by means of an inclinometer or a combination of limit switches and motor encoder counts) [45]. 3. Solar tracking system Vs fixed panel The amount of output mainly depends on the cosine angle of incidence which is known as the angle between the sun ray and horizontal surface. The minimum incidence angle gives the maximum power output. In case of fixed panel except noon time the angle is maximum for the movement of sun. The efficient solar tracker is which can correct this problem. The first solar tracker introduced by Finster in 1962, was completely mechanical. One year later, Saavedra presented a mechanism with an automatic electronic control, which was used to orient an Eppley pyrheliometer [3]. Anusha et al.[4] compared the fixed PV panel and single axis solar tracking based on real time clock(RTC) using ARM processor. The experiment is conducted using both Page 37 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 40. F o r P e e r R e v i e w O n l y fixed and tracking system for 6 days. The results show that the solar tracking system increased the efficiency around 40% and energy received from the sun is improved from 9.00AM to 6.00 PM. Dhanabal et al.[5] compared the efficiencies of static panels and tracking systems of single axis and dual axis fixed mount. The readings are taken from morning 8 AM to evening 6 PM for fixed panel, single axis tracker and dual axis tracker for every one hour. The results says the efficiency of the single axis tracking system over that of the static panel is calculated to be 32.17% and dual axis tracking system over that of the static panel is calculated to be 81.68%. Tiberiu tudorache et al [6] compared the solar tracking PV panel with a fixed PV panel in terms of electric energy output and efficiency. The proposed device automatically searches the optimum PV panel position with respect to the sun by means of a DC motor controlled by an intelligent drive unit that receives input signals from dedicated light intensity sensors. The solar tracking PV panel produced more energy than fixed one with about 57.55%. Bione et al. [7] compared the pumping systems driven by fixed, tracking and tracking with concentration PVs. The results showed that for a given irradiance, the pumped water flow rate was significantly different from one another. The fixed PV, the PV with tracker and the concentrating-tracking systems pumped 4.9, 7.4 and 12.6m3 /day, respectively. Snehal et al. [8] proposed a Field Programmable Gate Array (FPGA) sensor Based Standalone Solar Tracking System. Sun tracking system composed of fuzzy logic controller implemented on FPGA sensors, PV panel, stepper motor, and input-output interface. Xilinx_ISE software is used for coding of FLC for Sun tracking. The results show that tracking has maximum efficiency than fixed panels. 4. Different types of solar tracking techniques Fig 4.Solar tracking technologies Page 38 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 41. F o r P e e r R e v i e w O n l y 4.1 Based on collectors 4.1.1. Flat plate photovoltaic panel (PV) In flat-panel photovoltaic applications, trackers are used to minimize the angle of incidence between the incoming sunlight and a photovoltaic panel. Masakazu Ito et al. [9] proposed a comparative study of fixed and tracking system of very large-scale PV (VLS-PV) systems in the world deserts. The work focused on the potential and simulation of the 100MW.Life cycle analysis is applied for the simulation. The potentials are evaluated from economic viewpoint by LCA method. The results shows that cost reduced by applying tracking system. Marcel Sur et al. [10] produced solar electricity from fixed-inclined and sun-tracking crystalline silicon (C-SI) photovoltaic modules in South Africa. The work presents a method to for estimating the energy output from fixed-mounted and sun-axis tracking flat-plate PV systems. The simulation uses the solar radiation and temperature time series representing a historical record of 18 years (1994 to 2011).The Results shows one axis tracker with vertical axis inclined 30 degrees north typically gains from 15% up to 35% more electricity, compared to fixed mounting at optimum tilt.Anyaka et al. [11] studied the Improvement of PV Systems Power Output Using Sun-Tracking Techniques. The work presented the detailed view of sun tracking systems developed over the past years. The results prove that the applicability of sun tracking system gives a diverse range of high performance solar-based applications. 4.1.2 Concentrated Photovoltaic (CPV) The optics in CPV modules accept the direct component of the incoming light to maximize the energy collected. The tracking functionality in CPV modules is used to orient the optics such that the incoming light is focused to a photovoltaic collector. Tony Kerzmann et al. [12] studied the flow rate optimization of a linear concentrating photovoltaic system. The work Page 39 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 42. F o r P e e r R e v i e w O n l y focused on a two dimensional linear concentrated photovoltaic (LCPV) combined with an active cooling and waste heat recovery system. The results shows that an optimal cooling fluid flow at a rate of 4 gal/min (2.52×10−4m3 /s) would produce and average of 45.9 kWh of electricity and 15.9 kWh of heat energy. Tripanagnostopoulos et al. [13] proposed the design and performance aspects for low concentration photovoltaic. The non-uniform distribution of solar radiation on the PV surface reduces the electrical efficiency and can be rectified by combining the PV with low concentration devices. The diffuse reflectors are used instead of specular reflectors because of their low cost. The PV temperature reduction is also a factor so several modes for heat extraction are applied; using water or air cooled hybrid photovoltaic/thermal (PV/T) solar systems. Benecke et al. [14] developed the Optical design of low concentrator photovoltaic modules. This work addresses the necessary procedures that need to be considered when designing an optical sub-system of low concentrator photovoltaic (LCPV) module. Various design considerations are taken into account to construct a LCPV module that is characterized with respect to optical design and electrical performance. Benecke et al. [15] implemented the design and analysis of a vertical receiver LCPV system. The work presents the design aspects of the optical and electrical subsystem of LCPV with a geometric concentration ratio of 4.6.An electrical estimation is conducted by the use of I-V (current-voltage) characteristics obtained under sun as well as under concentration. 4.1.3Concentrated Solar Power (CSP) Concentrating solar power or concentrated solar thermal systems use mirrors or lenses to concentrate a large area of sunlight or solar thermal energy onto a small area. Electrical power is produced when the concentrated light is converted into heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator or powers a thermo chemical Page 40 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 43. F o r P e e r R e v i e w O n l y reaction. Miqdam Tariq et al. [16] studied the effect of design variation on saved energy of Concentrating Solar Power prototype. The work discussed about the methods to improve the efficiency of the concentrated solar thermal plant. El jai et al. [17] implemented a modified model for parabolic trough solar receiver using concentrated solar thermal energy. The work concentrates on the original mathematical model that describes the heat exchange between the main components of a thermal solar collector in an integrated solar combined cycle (ISCC) plant. The solar plant is an integrated combined cycle thermo-solar power plant consists of 256 parabolic trough solar collectors and classified in 64 parallel loops and each loop is 618 meters long. The use of the solar tracking mechanism is to maintain the incident solar radiation perpendicular to the reflector and to the focal line of the parabola where a receiver tube contains the heat transfer fluid. The different simulation results show that both the fluid temperature and the metal tube temperature grow until reaching a certain equilibrium value. 4.2 Based on the axis 4.2.1. Single axis tracker Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of rotation of single axis trackers is typically aligned along a true North meridian. Rizk et al. [18] developed solar tracking system with more efficient use of solar panels. This work includes the potential system benefits of simple tracking solar system of single axis tracker using a stepper motor and light sensor. This method is increasing power collection efficiency by implementing a device that tracks the sun to keep the panel at a right angle to sun rays. The power gain is increased 30% over a fixed horizontal array. 4.2.1.1. Horizontal Single Axis Tracker (HSAT) Page 41 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 44. F o r P e e r R e v i e w O n l y The axis of rotation for horizontal single axis tracker is horizontal with respect to the ground. Backtracking is one of computing the disposition of panels [48]. Guihua et al. [19] calculated the optical performance of horizontal single axis tracked solar panels. From the results it is clear that the east-west placed HSAT is worst to boost the energy while the north-south placed HSAT increased the efficiency drastically around 36%. Fig 5.Horizontal Single Axis Tracker 4.2.1.2. Vertical Single Axis Tracker (VSAT) The axis of rotation for vertical single axis trackers is vertical with respect to the ground. These trackers rotate from east to west over the course of the day. Lorenzo et al. [20] designed the tracking of photovoltaic systems with a single vertical axis. The vertical single axis tracking also called as azimuth tracking is mainly used for the energy gain which can be 40% more compared to tilted static panels. This research work deals with the design of VSAT photovoltaic plant in Tudela. The problems of shadowing in E-W direction and also N-S direction and the methods to rectify are explained in detail. The results clearly specify that VSAT boosted the energy gain around 40% per annum. 4.2.1.3. Tilted Single Axis Tracker (TSAT) The tracker with axes of rotation between horizontal and vertical is named as tilted single axis tracker. Tracker tilt angles are often limited to reduce the wind profile and decrease the elevated end height. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation [45]. 4.2.1.4. Polar Aligned Single Axis Tracker (PSAT) Page 42 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 45. F o r P e e r R e v i e w O n l y This method is scientifically well known as the standard method of mounting a telescope support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar aligned single axis tracker [46]. Fig 6. Polar Aligned Single Axis Tracker 4.2.2 Dual Axis Tracking Dual axis trackers have two degrees of freedom that act as axes of rotation normal to one another. The axis that is fixed with respect to the ground is a primary axis. The axis that is referenced to the primary axis is secondary axis [48]. Fig 7. Dual Axis SolarTracker 4.2.2.1. Tip-Tilt Dual Axis Tracker (TTDAT) A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a pole. Normally the east-west movement is driven by rotating the array around the top of the pole. The vertical azimuth axis is fixed so as to allow great flexibility of the payload connection to the ground mounted equipment because there is no twisting of the cabling around the pole. Tip-tilt trackers can make to minimize up-sun shading and therefore maximize the total power being collected [21-25]. 4.2.2.2 Azimuth-Altitude Dual Axis Tracker (AADAT) An azimuth–altitude dual axis tracker has its primary axis (the azimuth axis) vertical to the ground and the secondary axis (elevation axis) is normal to the primary axis. The operation is similar to tip-tilt systems but differ in the way the array is rotated for daily tracking. Instead of rotating the array around the top of the pole, they use a large ring mounted on the ground with the array mounted on a series of rollers. The main advantage of this arrangement is the weight of the array is distributed over a portion of the ring [47]. Liqun Liu et al. [26] discussed about the Page 43 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 46. F o r P e e r R e v i e w O n l y influence factors analysis of the best orientation relative to the sun for dual-axis sun tracking. In this research work different types of tracking systems are reviewed such as fixed panel, single axis tracking in east-west, single axis tracking in north-south, and dual axis tracking using both tip-tilt and altitude-azimuth tracking. The results show the influencing factors are time error, latitude, and azimuth and tilt angle of the photovoltaic, reflectivity and composite transparent coefficient. Arbab et al. [27] implemented a computer tracking system of solar dish with two- axis degree freedoms based on picture processing of bar shadow. The design is based on computer image processing of a bar shadow to obtain the optimized picture of solar dish displacements. The system is independent to geographical location of the solar dish and periodical changes like daily or monthly regulations. Jifeng Song et al. [28] implemented a high precision dual axis tracking system based on a hybrid strategy designed for concentrated sunlight transmission via fibers. This system is based on a two-stage tracking process, which consists of a coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a specially designed photosensitive sensor. In this design optical fibers are used for the precision tracking of concentrated sunlight. The advantage of this design is the higher resolution of the sun sensor because of the use of photosensitive arrays in closer arrangement. From the results it is clear that system tracked the sun’s focal spot with a position precision of less than 0.3 mm and the tracking angle precision is 0.1o . Jay Robert et al. [29] proposed the optimization of a small scale dual-axis solar tracking system using nano watt technology. The solar module is placed first in any one direction and the PV array has to search and stop at the highest current gained by the solar cell. The process is continued for every 30 minutes from 0600H up to 1800H. The results are measured in these positions for current, voltage and power. An open loop control is used for controlling the motors. Reis et al. [30] proposed the Modeling the performance of low Page 44 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 47. F o r P e e r R e v i e w O n l y concentration photovoltaic systems. A theoretical model is implemented to study the response of voltage-through systems in terms of temperature, power output and energy yield using as inputs. The device is constructed by integrating dual axis system and conventional crystalline Si- module, named as double sun technology. The results conclude that the double sun technology is increased the efficiency around 86% compared to fixed panels. Mohammed et al. [31] designed a parabolic solar cooker with automatic two axes sun tracking system. The solar cooker with automatic two axes eliminates the standing in the sun for hours to get frequent tracking and facing the concentrated solar cooker. The results of the continuous test performed for three days from 8:30 hr to 16:30 hr in the year 2008 and showed that the water temperature inside the cooker’s tube reached 90o C in typical summer days for the maximum registered ambient temperature was 36 o C. Ahmed Rhif et al. [32] implemented a position control review for a photovoltaic system dual axis sun tracker. This work presents a sun tracker without using sun sensors. The sun tracking is performed by changing the solar panel orientation in horizontal and vertical directions by two motors. The control of these motors is ensured by a microcontroller. Sliding mode control is used to solve the nonlinear equations. The simulation results conclude that tracking improves the efficiency around 40% than fixed panel. Okpeki et al. [33] designed and constructed a bi-directional solar tracking system. This research work includes the design and fabrication of a bi-directional tracker which can rotate in both azimuth and altitude directions. The two influencing factors of power output are intensity and wave length of sun light are addressed in detail. The results conclude that the efficiency is drastically more compared to fixed panel and the total cost of the tracker is very low. George Bakos et al. [34] implemented a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement. Parabolic trough is used with two axis rotation to the sun. The results conclude Page 45 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 48. F o r P e e r R e v i e w O n l y that parabolic collector is increasing the energy than flat collector. Rodiek et al. [35] conducted solar photovoltaic array tilt angle and tracking performance experiment. Advanced software models were developed to calculate the change of path by the sun throughout the year and to predict the optimum angle for the single axis tracker to obtain maximum energy output for the entire year. Two modeling programs are discussed to predict the optimal angle. For the experiment five panels are used in a single axis to track azimuthally at the tilt angles of 20º, 25º, 32º (latitude), 40º, and 50º. One more panel is a fixed control panel facing south at latitude tilt. The results are taken for one year and they conclude that a higher tilted panel (50º) will produce more power throughout the year compared to modeling from PV Watts that suggests a 32º tilt. 4.3. Based on driver 4.3.1. Active tracker 4.3.1.1. Microcontroller and electro-optical sensor based solar tracker: Sobuj Kumar Ray et al. [36] presented two ways of rotating freedom solar tracker by using microcontroller. The work includes the design of a two ways rotating freedom solar tracker based on microcontroller.PIC16F72 microcontroller is used to activate the motors to get two ways rotation.LDC sensors are used to get the information about sun radiation. The results are compared with conventional solar tracker without microcontroller and also with fixed panels. The difference is almost 37% between fixed panel and tracking system with microcontroller. Yousif El-Tous et al. [37] studied the thermal evaluation of a sun tracking solar cooker using microcontroller. The work contains the implementation of tracking system developed for getting the solar heating using solar cooker. A microcontroller is used for rotating the solar heater with the movement of the sun. PLC system is used as control system. A comparison between fixed and sun tracked cooker showed that the use of sun tracking increased the heating temperature by Page 46 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 49. F o r P e e r R e v i e w O n l y 36%. Mostefa Ghassoul et al. [38] proposed design of an automatic solar tracking system to maximize energy extraction. This solar tracking system is controlled by a micro chip PIC 18F452 micro controller. The search mechanism (PILOT) locates the position of the sun and the intelligent panel mechanism rotates itself with the PILOT to extract the maximum energy. The main defect in this is the rotation only takes place, if the energy obtained in the new position is higher than that consumed by the panels during the transition. So one miniature motor is used s to search the best position for maximum energy extraction. The panel’s mechanism rotates to the position automatically when energy extraction is optimal. The system is designed in such a way that panels only follow the sun if that contributes to extra energy extraction and at the same time, the energy consumed by the panel driving motor is less than that extracted. Jing-Min Wang et al. [39] proposed the design and implementation of a sun tracker with a dual-axis single motor for an optical sensor-based photovoltaic system. This work proposes a novel design of a dual-axis solar tracking PV system which utilizes the feedback control theory along with a four-quadrant light dependent resistor (LDR) sensor and simple electronic circuits to provide robust system performance. The proposed system uses a unique dual-axis AC motor and a stand-alone PV inverter to accomplish solar tracking. Experiment results indicated that the developed system increased the energy gain up to 28.31% for a partly cloudy day. 4.3.1.2. Auxiliary bifacial solar cell based solar tracker Bhupendra Gupta et al. [40] explained the design, construction and effectiveness of a hybrid automatic solar tracking system for amorphous and crystalline solar cells. This work includes the design a Hybrid solar tracking system implemented by integrating with amorphous and crystalline solar panel, and microcontroller. The experiment consists of the analysis on the use of two different material of solar panel like Amorphous and Crystalline in a solar tracking Page 47 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 50. F o r P e e r R e v i e w O n l y system at stationary, single axis, and dual axis and hybrid axis solar tracker. The comparison shows that the use of the dual-axis tracking system produced 17.87% gain of power output than a single-axis tracking system. The gain of output power with the hybrid tracking system is further more (52%) than a stationary system inclined at 23.5o to the horizontal. 4.3.1.3 Date, time and sensor based In the date/time and sensor based tracking systems, electronic devices like microprocessor calculates the sun’s position from basic formulae or algorithms from geographical information and send signals to the electro motor (Fig.5). Fig. 8 Position of PV modules in the morning and afternoon Edwards et al. [41] presented the operation of a computer based sun following system for parabolic collectors. The computer continuously varies the speed of each collector actuators at regular intervals throughout the day. The results conclude that for accurate sun following, the system requires a data output from the central controller of only 500 bit/s for 10,000 collectors per day. 4.3.2. Passive tracker The passive trackers use a boiling point from a compressed fluid which moves from one side to other by the solar heat which creates a gas pressure results the tracker movement [42]. Due to the bad quality of precision orientation, it is unsuitable for certain types of photovoltaic collectors. In the passive tracker the photovoltaic panels include a hologram behind stripes of photovoltaic cells so that sunlight reflects [37] on the hologram which allows the cell heat from behind, thereby increasing the modules’ efficiency. Moreover, the plant need not require moving while the hologram still reflects sunlight from the needed angle toward the photovoltaic cells. Jeyaganesh et al.[43] proposed the design and development of a sun tracking mechanism using the Direct SMA actuation. The Shape Memory Alloy (SMA) element acts as sensor and actuator Page 48 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
- 51. F o r P e e r R e v i e w O n l y position the solar receptor tilted appropriately to face the sun directly at all times during the day. The thermal stimulus required to activate the SMA element is provided by the concentration and direct focusing of the incident sun rays on to the SMA element. The results show the possibility of the design and development of a sun tracking mechanism using SMA that directly uses sunlight without the need for any additional external power source. Table.1.Comparision table for different tracking systems Table.2. Comparision table on cost and payback for different tracking systems 5. Conclusion The innovative designs in sun tracking systems have enabled the development of many solar thermal and photovoltaic systems for a diverse variety of applications in recent years compared to the traditional fixed panels. Solar systems which track the changes in the sun’s trajectory over the course of the day collect a far greater amount of solar energy, and therefore generate a significantly higher output power. This paper has presented a review of the major types of sun tracking systems developed over the past 20 years. It has been shown that these sun tracking systems can be broadly classified as single axis and dual axis, depending on their mode of rotation. Further it can be classified as active and passive tracker depending on the actuator. The sub division and their basic principles of each method have been reviewed. Overall, the results presented in this review confirm that the azimuth and altitude dual axis tracking system is more efficient compared to other tracking systems. However in cost and flexibility point of view single axis tracking system is more feasible than dual axis. In future the present paper details will be useful in selecting an accurate and particular tracker with respect to region, available space and estimated cost. The present work may be useful to improve the design characteristics of different types of solar tracking systems to improve performance. Page 49 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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- 58. F o r P e e r R e v i e w O n l y Response to the reviewer comments: We are very thankful to reviewers for their valuable suggestions. It surely helped us to improve the quality of the paper. (1 Please substitute the "Wikipedia" references (page 23), for other references that are more adequate for a scientific journal. This must be checked and changed. ANS: The references have been changed to be adequate for a scientific journal. Page 56 of 56 URL: http:/mc.manuscriptcentral.com/tsue International Journal of Sustainable Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 View publication stats View publication stats