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1. Abstract on solar energy tracking system — Document
Transcript
1. Solar Energy Tracking SystemIntroductionConceptPhotovoltaic’s (PV) is a method of
generating electrical power by converting solarradiation into direct current electricity
using semiconductors that exhibit thephotovoltaic effect.MaterialsMaterials presently
used for photovoltaic’s include monocrystalline silicon,polycrystalline silicon,
amorphous silicon, cadmium telluride, and copper indiumselenide/sulfide.Photovoltaic
effect & Photoelectric effectThe photovoltaic effect is the creation of a voltage (or a
corresponding electriccurrent) in a material upon exposure to light. Though the
photovoltaic effect isdirectly related to the photoelectric effect, the two processes are
different andshould be distinguished. In the photoelectric effect, electrons are ejected
from amaterials surface upon exposure to radiation of sufficient energy. Thephotovoltaic
effect is different in that the generated electrons are transferredbetween different bands
(i.e., from the valence to conduction bands) within thematerial, resulting in the buildup of
a voltage between two electrodes.Solar TrackerA solar tracker is a generic term used to
describe devices that orient variouspayloads toward the sun. The optics in concentrated
solar applications acceptsthe direct component of sunlight light and therefore must be
orientedappropriately to collect energy. Tracking systems are found in all
concentratorapplications because such systems do not produce energy unless oriented
closelytoward the sun.
2. PayloadsPayloads can be photovoltaic panels, reflectors, lenses or other optical
devicesTracker TypesPhotovoltaic trackers can be grouped into classes by the number
and orientationof the tracker’s axes. Compared to a fixed amount, a single axis tracker
increasesannual output by approximately 30% and a dual axis tracker an additional
6%.Single Axis TrackersSingle 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
Northmeridian. It is possible to align them in any cardinal direction with
advancedtracking algorithms.There are several common implementations of single axis
trackers. These includeHorizontal Single Axis Trackers, Vertical Single Axis Trackers,
and Tilted Single AxisTrackers. The orientation of the module with respect to the tracker
axis isimportant when modeling performance.Horizontal Single Axis Tracker
(HSAT)The axis of rotation for Horizontal Single Axis Tracker is horizontal with respect
tothe ground. The posts at either end of the axis of rotation of a Horizontal SingleAxis
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 theground. These trackers rotate from East to West over the course of the day.
Suchtrackers 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 consideredTilted Single Axis Trackers. Tracker tilt angles are often
limited to reduce the windprofile 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 PolarAligned Single Axis Trackers
(PASAT). In this particular implementation of a TiltedSingle Axis Tracker the tilt angle
is equal to the latitude of the installation. Thisaligns the tracker axis of rotation with the

2. earth’s axis of rotation. These are rarelydeployed because of their high wind profile.Dual
Axis TrackersTip – Tilt Dual Axis Tracker (TTDAT)A Tip – Tilt Dual Axis Tracker has
its primary axis horizontal to the ground. Thesecondary axis is then typically normal to
the primary axis. The posts at either endof the primary axis of rotation of a Tip – Tilt
Dual Axis Tracker can be sharedbetween trackers to lower installation costs.Field layouts
with Tip – Tilt Dual Axis Trackers are very flexible. The simplegeometry means that
keeping the axes of rotation parallel to one another is allthat is required for appropriately
positioning the trackers with respect to oneanother.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 tooptimize land utilization. Also
optimization for dense packing is limited due to thenature of the shading over the course
of a year.
4. This mount is used as a large telescope mount owing to its structure anddimensions. One
axis is a vertical pivot shaft or horizontal ring mount, that allowsthe device to be swung
to a compass point. The second axis is a horizontalelevation pivot mounted upon the
azimuth platform. By using combinations ofthe two axis, any location in the upward
hemisphere may be pointed. Suchsystems may be operated under computer control
according to the expectedsolar orientation, or may use a tracking sensor to control motor
drives that orientthe panels toward the sun. This type of mount is also used to orient
parabolicreflectors that mount a Stirling engine to produce electricity at the device.[Drive
typesActive trackerActive trackers use motors and gear trains to direct the tracker as
commanded bya controller responding to the solar direction.In order to control and
manage the movement of these massive structures specialslewing drives are designed and
rigorously tested.Active two-axis trackers are also used to orient heliostats - movable
mirrors thatreflect sunlight toward the absorber of a central power station. As each mirror
ina large field will have an individual orientation these are controlledprogrammatically
through a central computer system, which also allows thesystem to be shut down when
necessary.Passive trackerPassive trackers use a low boiling point compressed gas fluid
that is driven to oneside or the other (by solar heat creating gas pressure) to cause the
tracker tomove in response to an imbalance. As this is a non-precision orientation it
isunsuitable for certain types of concentrating photovoltaic collectors but worksfine for
common PV panel types. These will have viscous dampers to preventexcessive motion in
response to wind gusts.
5. Shader/reflectors are used to reflect early morning sunlight to "wake up" thepanel and tilt
it toward the sun, which can take nearly an hour. The time to do thiscan be greatly
reduced by adding a self-releasing tie down that positions thepanel 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 releasein windy overnight
conditions.)Chronological trackerA chronological tracker counteracts the Earths rotation
by turning at an equalrate as the earth, but in the opposite direction. Actually the rates
arent quiteequal, because as the earth goes around the sun, the position of the sun
changeswith respect to the earth by 360° every year or 365.24 days. A
chronologicaltracker is a very simple yet potentially a very accurate solar tracker
specifically foruse with a polar mount (see above). The drive method may be as simple as
a gearmotor that rotates at a very slow average rate of one revolution per day (15degrees

3. per hour). In theory the tracker may rotate completely, assuming there isenough clearance
for a complete rotation, and assuming that twisting wires arenot an issue.Sun tracking
control systemA control circuit for tracking of a heat radiation source which functions
tomaintain heat collection structure in optimum alignment with the source therebyto
enable maximum efficiency of heat collection; the control circuit includes athreshold
circuit for sensing ambient light level to provide enablement control toA-C power
circuitry which energizes the heat collector orienting drive system, andthe threshold
circuit also functions to automatically invert the heat collector to aprotected position upon
detection of insufficient threshold voltage; and, thecircuit further comprises a tracking
section energized by a radiation sensor tocause intermittent energization of the drive
system to further enable intermittentbi-directional tracking movement of the heat
collector, such tracking circuitrybeing enabled by detection of sufficient threshold
voltage.
6. Automatic guidance system for radiation-responsive systemsThe invention concerns a
guidance, or tracking, arrangement which automaticallyadjusts the alignment of a
radiation responsive system in accordance with theposition of a movable radiation
source.The arrangement utilizes two bodies able to transmit heat expansion forces
intolinear movements to rotate a rocker about an axis perpendicular to the pathplane of
the source. The bodies are partially shaded such that exposure to theradiation source
controls the extent to which the bodies rotate the rocker.Resilient support means
compensate the arrangement for undue forces arisingfrom expansions of the
bodies.Photovoltaic array with two-axis power maximization trackingA control system
for maximizing the power supplied by an array of solar cellssenses the current and
voltage produced and multiplies these to determine theinstantaneous power. The array is
tilted slightly in a first direction and the effecton the instantaneous power is noted. If an
increase in power was produced, afurther movement in the same direction is executed;
but if the first movementproduced a reduction in power, a movement in the opposite
direction isexecuted. The process continues until no increase in power is obtained in
eitherdirection. Thereafter, the same process is carried out with respect to a secondaxis 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 rainsConclusion • 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

4. 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
SolarEnergyTrackingSystemIntroductionConceptPhotovoltaic’s(PV)isamethodofgeneratingelectricalpowe
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ffect