The document discusses solar tracking systems which orient photovoltaic panels, reflectors, or other devices toward the sun for maximum exposure. It describes several types of solar trackers, including single-axis and dual-axis models. Single-axis trackers rotate around one axis, while dual-axis trackers rotate around two perpendicular axes for improved sun-following. The document also covers types of drives, controls, and algorithms used in solar tracking systems.

1. Solar Energy Tracking System
Introduction
Concept
Photovoltaic’s (PV) is a method of generating electrical power by converting solar
radiation into direct current electricity using semiconductors that exhibit the
photovoltaic effect.
Materials
Materials presently used for photovoltaic’s include monocrystalline silicon,
polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium
selenide/sulfide.
Photovoltaic effect & Photoelectric effect
The photovoltaic effect is the creation of a voltage (or a corresponding electric
current) in a material upon exposure to light. Though the photovoltaic effect is
directly related to the photoelectric effect, the two processes are different and
should be distinguished. In the photoelectric effect, electrons are ejected from a
material's surface upon exposure to radiation of sufficient energy. The
photovoltaic effect is different in that the generated electrons are transferred
between different bands (i.e., from the valence to conduction bands) within the
material, resulting in the buildup of a voltage between two electrodes.
Solar Tracker
A solar tracker is a generic term used to describe devices that orient various
payloads toward the sun. The optics in concentrated solar applications accepts
the direct component of sunlight light and therefore must be oriented
appropriately to collect energy. Tracking systems are found in all concentrator
applications because such systems do not produce energy unless oriented closely
toward the sun.

2. Payloads
Payloads can be photovoltaic panels, reflectors, lenses or other optical devices
Tracker Types
Photovoltaic trackers can be grouped into classes by the number and orientation
of the tracker’s axes. Compared to a fixed amount, a single axis tracker increases
annual output by approximately 30% and a dual axis tracker an additional 6%.
Single Axis Trackers
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. It is possible to align them in any cardinal direction with advanced
tracking algorithms.
There are several common implementations of single axis trackers. These include
Horizontal Single Axis Trackers, Vertical Single Axis Trackers, and Tilted Single Axis
Trackers. The orientation of the module with respect to the tracker axis is
important when modeling performance.
Horizontal Single Axis Tracker (HSAT)
The axis of rotation for Horizontal Single Axis Tracker is horizontal with respect to
the ground. The posts at either end of the axis of rotation of a Horizontal Single
Axis Tracker can be shared between trackers to lower the installation cost.
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. Such
trackers are more effective at high latitudes than are horizontal axis trackers.

3. Tilted Single Axis Tracker (TSAT)
All trackers with axes of rotation between horizontal and vertical are considered
Tilted Single Axis Trackers. Tracker tilt angles are often limited to reduce the wind
profile and decrease the elevated end’s height off the ground.
Polar Aligned Single Axis Trackers (PASAT)
One scientifically interesting variation of a Tilted Single Axis Tracker is a Polar
Aligned Single Axis Trackers (PASAT). In this particular implementation of a Tilted
Single Axis Tracker the tilt angle is equal to the latitude of the installation. This
aligns the tracker axis of rotation with the earth’s axis of rotation. These are rarely
deployed because of their high wind profile.
Dual Axis Trackers
Tip – Tilt Dual Axis Tracker (TTDAT)
A Tip – Tilt Dual Axis Tracker has its primary axis horizontal to the ground. The
secondary axis is then typically normal to the primary axis. The posts at either end
of the primary axis of rotation of a Tip – Tilt Dual Axis Tracker can be shared
between trackers to lower installation costs.
Field layouts with Tip – Tilt Dual Axis Trackers are very flexible. The simple
geometry means that keeping the axes of rotation parallel to one another is all
that is required for appropriately positioning the trackers with respect to one
another.
Azimuth-Altitude Dual Axis Tracker (AADAT)
An Azimuth – Altitude Dual Axis Tracker has its primary axis vertical to the ground.
The secondary axis is then typically normal to the primary axis.
Field layouts must consider shading to avoid unnecessary energy losses and to
optimize land utilization. Also optimization for dense packing is limited due to the
nature of the shading over the course of a year.

4. This mount is used as a large telescope mount owing to its structure and
dimensions. One axis is a vertical pivot shaft or horizontal ring mount, that allows
the device to be swung to a compass point. The second axis is a horizontal
elevation pivot mounted upon the azimuth platform. By using combinations of
the two axis, any location in the upward hemisphere may be pointed. Such
systems may be operated under computer control according to the expected
solar orientation, or may use a tracking sensor to control motor drives that orient
the panels toward the sun. This type of mount is also used to orient parabolic
reflectors that mount a Stirling engine to produce electricity at the device.[
Drive types
Active tracker
Active trackers use motors and gear trains to direct the tracker as commanded by
a controller responding to the solar direction.
In order to control and manage the movement of these massive structures special
slewing drives are designed and rigorously tested.
Active two-axis trackers are also used to orient heliostats - movable mirrors that
reflect sunlight toward the absorber of a central power station. As each mirror in
a large field will have an individual orientation these are controlled
programmatically through a central computer system, which also allows the
system to be shut down when necessary.
Passive tracker
Passive trackers use a low boiling point compressed gas fluid that is driven to one
side or the other (by solar heat creating gas pressure) to cause the tracker to
move in response to an imbalance. As this is a non-precision orientation it is
unsuitable for certain types of concentrating photovoltaic collectors but works
fine for common PV panel types. These will have viscous dampers to prevent
excessive motion in response to wind gusts.

5. Shader/reflectors are used to reflect early morning sunlight to "wake up" the
panel and tilt it toward the sun, which can take nearly an hour. The time to do this
can be greatly reduced by adding a self-releasing tie down that positions the
panel slightly past the zenith (so that the fluid does not have to overcome gravity)
and using the tie down in the evening. (A slack-pulling spring will prevent release
in windy overnight conditions.)
Chronological tracker
A chronological tracker counteracts the Earth's rotation by turning at an equal
rate as the earth, but in the opposite direction. Actually the rates aren't quite
equal, because as the earth goes around the sun, the position of the sun changes
with respect to the earth by 360° every year or 365.24 days. A chronological
tracker is a very simple yet potentially a very accurate solar tracker specifically for
use with a polar mount (see above). The drive method may be as simple as a gear
motor that rotates at a very slow average rate of one revolution per day (15
degrees per hour). In theory the tracker may rotate completely, assuming there is
enough clearance for a complete rotation, and assuming that twisting wires are
not an issue.
Sun tracking control system
A control circuit for tracking of a heat radiation source which functions to
maintain heat collection structure in optimum alignment with the source thereby
to enable maximum efficiency of heat collection; the control circuit includes a
threshold circuit for sensing ambient light level to provide enablement control to
A-C power circuitry which energizes the heat collector orienting drive system, and
the threshold circuit also functions to automatically invert the heat collector to a
protected position upon detection of insufficient threshold voltage; and, the
circuit further comprises a tracking section energized by a radiation sensor to
cause intermittent energization of the drive system to further enable intermittent
bi-directional tracking movement of the heat collector, such tracking circuitry
being enabled by detection of sufficient threshold voltage.

6. Automatic guidance system for radiation-responsive systems
The invention concerns a guidance, or tracking, arrangement which automatically
adjusts the alignment of a radiation responsive system in accordance with the
position of a movable radiation source.
The arrangement utilizes two bodies able to transmit heat expansion forces into
linear movements to rotate a rocker about an axis perpendicular to the path
plane of the source. The bodies are partially shaded such that exposure to the
radiation source controls the extent to which the bodies rotate the rocker.
Resilient support means compensate the arrangement for undue forces arising
from expansions of the bodies.
Photovoltaic array with two-axis power maximization tracking
A control system for maximizing the power supplied by an array of solar cells
senses the current and voltage produced and multiplies these to determine the
instantaneous power. The array is tilted slightly in a first direction and the effect
on the instantaneous power is noted. If an increase in power was produced, a
further movement in the same direction is executed; but if the first movement
produced a reduction in power, a movement in the opposite direction is
executed. The process continues until no increase in power is obtained in either
direction. Thereafter, the same process is carried out with respect to a second
axis of the solar array.

7. Advantages
• Solar tracking systems continually orient photovoltaic panels towards the
sun and can help maximize your investment in your PV system.
• One time investment, which provides higher efficiency & flexibility on
dependency.
• Tracking systems can help reducing emissions and can contribute some
help against global warming.
• Bulk implementations of tracking systems help reduced consumption of
power by other sources.
• It enhances the clean and emission free power production.
Disadvantages
• Initial investment is high.
• It’s a bit of difficult for servicing, as the systems are not quite popular
regionally.
• Moving parts and gears which will require regular maintenance.
• May require repair or replacement of broken parts over a long run.
• It has to be built reliably, against damages caused by heavy rains
Conclusion
• With Global Warming constantly affecting the world in numerous ways, it is
essential we begin taking care of our environment in whatever way
possible.
• Present day technologies stresses on everything to be clean & green.
• Being environmentally friendly, solar power generators and panels are
reasonably easy, safe, and convenient to install.
• A life cycle analysis proves that solar cells are cleaner than conventional
fossil fuel power generation.
• With Global Warming constantly knocking on our door, solar energy takes a
step in the right direction by emitting no waste products whatsoever.
• Hence enhancing the solar powered systems with advanced intelligent
trackers proves to be optimal and grab every possible opportunity to gain
advantage of the solar power

8. References
http://www.solarpoweristhefuture.com
http://www.scientificamerican.com
http://www.linak.com/products
http://www.thesolarguide.com
http://www.patentstorm.us
http://www.free-power.org
http://en.wikipedia.org