Solar energy has the greatest potency of all the beginnings of renewable energy and if merely a little sum of this signifier of energy is used, it will be one of the most of import supplies of energy particularly when other beginnings in the state have depleted. Energy comes to the Earth from the Sun. This energy keeps the temperature of the Earth above that in colder infinite, causes current in the ambiance and in ocean, causes the H2O rhythm and generates photosynthesis in workss.
Solar power provides electrical coevals by agencies of heat engines or photovoltaic cells. Once converted, its utilizations are limited merely by human incompetency.
1.1 Applications of Solar Energy:
Heating and chilling of residential edifices
Solar H2O warming
Solar drying of agricultural and carnal merchandises
Salt production by vaporization of saltwater
Solar photovoltaic cells
Solar Electric Power coevals by: –
Reflectors with lenses and pipes for fluid circulation
1.2 Active and Passive Solar Heating
Solar engineerings are mistily characterized as either inactive solar or active solar. This categorization is based on the manner they capture, convert and distribute sunshine. Active solar techniques include:
The usage of photovoltaic panels and
Solar thermic aggregators ( with electrical or mechanical equipment ) to change over sunshine into utile end products.
Passive solar techniques include
Orienting a edifice to the Sun,
Choosing stuffs with favourable thermic or light scattering belongingss,
Planing infinites that of course circulate air.
1.3 Concentrated Solar power ( CSP )
Concentrating Solar Power ( CSP ) systems uses lenses, mirrors and tracking systems to concentrate a big country of sunshine into a little beam. This focussed visible radiation is so used as the heat beginning for a conventional power works or is concentrated onto photovoltaic surfaces.
1.4 Concentrating solar thermal ( CST )
Concentrating solar thermic systems usually use lenses or mirrors or extremely brooding metals like aluminum and tracking systems to concentrate a big country of sunshine into a little beam. This concentrated visible radiation is so used as heat beginning for a conventional power works ( solar thermoelectricity ) .
A broad scope of concentrating engineerings exists such as the Parabolic Trough, Dish Stirling, Concentrating Linear Fresnel Reflector, Solar chimney and tower. Each of this concentration method is capable of bring forthing high temperatures and correspondingly high thermodynamic efficiencies, but they vary in the manner that they do the trailing of the Sun and concentrating visible radiation. Recently, concentrating solar thermal is being more and more cost-efficient.
A parabolic trough is normally made of a additive parabolic reflector that focuses and dressed ores light onto a receiving system positioned along the reflector ‘s focal line. The receiving system is a tubing located right above the center of the parabolic mirror and is filled with a working fluid. The reflector follows the Sun during the daytime hours utilizing a individual axis tracker. A on the job fluid ( e.g. run salt ) is heated to 150-350 A°C as it flows through the receiving system and is so used as a heat beginning for a power coevals system. Trough systems are the most developed CSP engineering.
Solar Thermal Electric Power Generation
In general, the transition of solar energy into electricity by manner of thermal or heat energy is what is known as Solar Thermal Electric power coevals. Heat can be converted straight by thermionic or solar cell or thermo- electric methods. The most practical thermal electric process is to use solar energy to heat a on the job fluid. The heat energy is so converted into mechanical energy in a turbine and eventually into electrical energy by agencies of a conventional generator coupled to the turbine.
Solar thermic power coevals employs power rhythms which are loosely classified as low, medium, high temperature rhythms.
Low temperature rhythms by and large use level home base aggregators.
Medium temperature rhythms work at maximal temperature runing from 150-300 grades
High temperature rhythms work at temperatures above 300 grades.
For the low and average temperature ranges, the thermodynamic rhythms preferred are the rankine rhythm. For the high temperature scope, apart from the Rankine, Brayton and Stirling rhythms are besides considered.
For efficient transition of heat energy into mechanical energy and hence into electricity, the working fluid should be supplied to the turbine at high temperature. To obtain such temperatures requires the usage of concentrating aggregators. This is done by two ways:
Central receiving system system
Distributed aggregator system
Central receiving system system is preferred for the big scale coevals of power.
On the other manus, distributed aggregator design possibly more suited for power workss of smaller electrical capacity.
Sun tracker is a term used to depict devices that orient assorted equipments like photovoltaic panels, reflectors, lenses etc.
Broadly the angle of incidence between incoming visible radiation and photovoltaic panel is minimized thereby increasing the sum of energy produced from a fixed sum of installed power bring forthing capacity.
There are two different types of trackers:
3.1 Concentrated photovoltaic ( CPV ) and Concentrated Solar thermal ( CSP )
These Concentrated Solar applications should be oriented suitably to roll up energy to accept the direct constituent of sunshine. Tracking systems are really indispensable since systems can non bring forth energy unless it is decently oriented towards the Sun.
Now these tracker types can be farther classified harmonizing to a figure of factors such as:
Number and orientation of their axes
And foundation type.
3.2 Standard Photovoltaic ( PV ) Trackers
Photovoltaic panels accept both direct and diffuse visible radiation
Light being blocked by the clouds or reflecting off of other objects is known as diffuse visible radiation from the sky.
The panels on these specific trackers ever gather direct visible radiation.
The map of these standard photovoltaic trackers is to minimise the incident angle between incoming visible radiation and the panel. This increases the sum of energy gathered from the direct sunshine.
3.3 Concentrated Photovoltaic ( CPV ) Trackers
Along with the capturing of the direct visible radiation, it besides captures a part of diffuse visible radiation when in low concentration.
The map in such faculties is to point the optics in such a manner that the entrance visible radiation is focused to a photovoltaic aggregator.
A Sun tracker is equipment for pointing devices like twenty-four hours illuming reflector, photovoltaic panel, concentrated solar reflector or lens etc.
The place of the Sun in the sky is different at different seasons and different clip of the twenty-four hours due to the uninterrupted motion of Sun across the sky.
Equipment such as the 1s described above shows its maximal power when pointed at or near the Sun. So the effectivity of such equipment can be increased over a fixed place.
A well known type of Sun tracker is the heliostat. A heliostat is a movable mirror through which the traveling Sun is reflected towards a fixed location.
Tracker Mount Types
Solar trackers can be divided into four:
A polar saddle horse is used by individual axis trackers for maximal efficiency. These type of trackers usually have an lift accommodation on a 2nd axis which is adjusted throughout the twelvemonth at regular intervals. A individual axis tracker can increase its end product by around 30 % and a double axis tracker can increase an extra 36 % .
Now double Axis Trackers can be farther classified into:
These types of trackers have an axis aligned parallel to the axis of rotary motion of Earth around the North and south poles. This is why it is named Polar trackers. These trackers should be angled towards the North and the angle between this axis and perpendicular should be equal to your latitude.
Since strong afternoon is peculiarly desirable for photovoltaic systems ( as production rate at afternoon is straight relative to the demand particularly due to summer season air conditioning ) , individual axis tracking system combined with clip of usage metering is used.
4.1 Angle of decline:
There is another accommodation along a 2nd axis called the angle of decline which is seen in the simple polar trackers with individual axis tracking system.
This is used to angle the panel to confront the Sun at its highest ( summer ) and lowest places ( winter ) in the sky.
Now this can be manually or automatically operated as per desired. The angle of decline is set to zero grades as default confronting your panel straight out perpendicular to the polar axis.
It should be kept in head that when making manual accommodations for angle of decline, it should be done at least twice a twelvemonth, i.e, one time at winter solstice and one time at summer solstice.
At the clip of winter solstice ( minimal decline ) , the Sun ‘s beams would be -23.5o South of the Earth ‘s equator and at the clip of summer solstice, the Sun ‘s beams would be +23.5o North of the Earth ‘s equator.
The suns decline would be zero at the equinoxes ( Latin word: equal darks ) .So as illustration U can take 15o or 20o as an optimum solution for the summer months.
4.3 Horizontal axle:
Single axis horizontal trackers can besides be made available oriented by either active or inactive mechanisms.
A horizontal long tubing is mounted upon frames the axis of which is on a north – south line.
Upon the tubing, the panels are mounted and it rotates on its ain axis to track the gesture of Sun. They are non that effectual during winter noon since these tubings do non lean towards the equator. On the other manus they provide a significant sum of productiveness during the spring and summer seasons.
They do give much end product at higher heights. The simpleness of the mechanism is a chief advantage along with the rigidness of the construction.
4.4 Vertical axle:
Apart from horizontal individual axis trackers there are perpendicular individual axis.
It has its panels either perpendicular, at a fixed, adjustable or tracked lift angle.
Unlike horizontal axles, these perpendicular axles are ideal for high latitudes particularly the long yearss in summer with the Sun going through a long discharge.
This is a type of mounting which helps in back uping the weight of the whole tracker and allows it to travel in double waies for turn uping a individual mark.
Out of the two axes, one axis of support is called height which is horizontal and helps the telescope in traveling up or down,
The other axis is perpendicular called the AZ leting the telescope to swing in a radial way.
A computing machine is required to track a complicated object such as Earth.
Different Methods of Tracking
5.1 Drive Types
5.1.1 Active tracker
These trackers use motors and gear trains in directing the tracker as commanded by a accountant reacting to the solar way. Active two axis trackers are used to orient heliostats.
Light feeling type of trackers has two exposure detectors, photodiodes, configured differentially so that they end product a nothing when having the same light flux.
They are supposed to be level and are 90o grades apart. Since the motors consume energy, utilize them merely when necessary.
Now if the visible radiation is below some threshold degree, there may non b adequate power available for reorientation.
Precaution should be taken so as non blow energy during cloudy yearss when there is non adequate visible radiation.
5.1.2 Passive tracker
This type of tracker plants on the rule of making a gas force per unit area by utilizing a low BP compressed gas fluid.
This fluid is so driven to one side or the other due to solar warming therefore making gas force per unit area.
This causes the tracker to travel in response to an instability.
These sorts of trackers are provided with Syrupy Dampers to forestall inordinate gesture in response to weave blasts and Shader or Reflectors to reflect the early forenoon visible radiation to get down the panel tilting towards the Sun.
5.2 Chronological tracker
A chronological tracker helps in antagonizing the Earth ‘s rotary motion by turning at an equal rate as the Earth but in the opposite way. These types of trackers are seen with a polar saddle horse on it. A gear motor revolving at a really slow norm rate of 1 revolution per twenty-four hours is used as the driver here. In theory the tracker possibly able to revolve wholly one time in a twenty-four hours and any other issues can be avoided by resetting the tracker every twenty-four hours.
5.3 Algorithms for Sun Tracking
Time Based Algorithm
In Time Based Algorithm, Panels are tracked harmonizing to tome. So a construction must be fixed to a specific place to track Sun right. Harmonizing to this technique, Sun informations way is stored in signifiers of tabular array ‘s w.r.t clip and the panel ‘s place is adjusted consequently.
5.4 Peturb and Observe:
Now this is the most normally used algorithm. The fig below shows the P v/s V curve of a PV array which has its upper limit at MPP.
If the operating electromotive force of the PV array is perturbed in a given way and dP/dV & gt ; 0, it is known that the disturbance moved the array ‘s operating point toward the MPP.
The algorithm would so go on to unhinge the PV array electromotive force in the same way.
If dP/dV & lt ; 0, so it moves the PV array off from the MPP, and the P & A ; O algorithm reverses the way of the disturbance.
A disadvantage in utilizing P & A ; O is that it oscillates around the MPP in steady province operation. It can besides track in the incorrect way, off from the MPP, under quickly increasing or diminishing irradiance degrees.
Power ( W )
Voltage ( V )
Figure Power v/s Voltage
Construction of a Solar Tracker:
A exposure resistance or light dependent resistance or Cd sulphide cell is one whose opposition decreases with increasing incident visible radiation strength. It is besides known as photoconductor.
It is made up of a high opposition semiconducting material.
A high frequence set of light falling on the device excited the negatrons and they jump into the conductivity set. The ensuing free negatron and holes conduct electricity.
A photoelectric device can be either intrinsic or extrinsic type.
Intrinsic semiconducting materials are non efficient since they have their ain charge bearers. E.g. : Silicon. In this sort, the photon must hold high plenty energy to excite the negatron across the full set spread from valency set to conductivity set.
On the other manus, extrinsic devices possess drosss called dopants.In extrinsic, due to doping the energy spread is low doing the negatrons easier to leap to the conductivity set. If a sample of Si has some of its atoms replaced by Ph atoms ( drosss ) , there will be excess negatrons for conductivity.
It is a type of exposure sensor capable of change overing visible radiation into either current or electromotive force.
They are similar to regular rectifying tubes except that they may be either exposed or packaged with a window or optical fibre connexion to let visible radiation to make the sensitive portion of the device.
A PIN junction is preferred compared to a PN junction.
Photon of high energy on striking a rectifying tube excites the negatron, thereby making an negatron and a antielectron ( hole ) .
A depletion part is created and if the soaking up occurs in it, these negatrons and antielectrons are swept off from the junction due to the constitutional field of the depletion part. This makes the holes move toward the anode and negatrons toward the cathode thereby bring forthing a photocurrent.
6.1.3 PV Cells
This is the chief device which converts sunshine straight into electricity by the photovoltaic consequence.
Large assemblies of solar cells are combined to do solar panel, solar faculties etc. The energy generated this manner is an illustration for solar energy.
Difference between Solar cells and PV cells is that while the former is reserved for devices intended specifically to capture energy from sunshine, the latter is used when no light beginning is specified.
Automated Sun tracking System
In desert countries and topographic points where H2O is non available in surplus, Sun plays a major function in bring forthing electricity utilizing solar cells. Now the end product of solar cells depends wholly on the strength of sunshine and angle of incidence. The solar panels must confront the Sun the whole twenty-four hours in order to acquire maximal efficiency. But due to the rotary motion of Earth, these panels ca n’t keep their place ever in forepart of Sun, therefore ensuing in lessening of efficiency. Therefore to acquire a changeless end product, Automated Sun Tracking System is introduced to invariably revolve the solar panel along with the Earth ‘s rotary motion. The most dramatic characteristic of this system is that it takes Sun as a mention or steering beginning alternatively of earth therefore doing it possible for its detectors to supervise the sunshine and revolve the panel consequently to acquire the maximal sunshine.
Decisions and Future Work
Study of solar system and Sun trailing in item.
Understanding assorted maps of Sun trackers and its different types.
Understanding the demand for solar thermal electric power coevals.
Detailed survey of Automatic Sun tracking System.
8.2 Future Work:
In deepness survey about the ASTS.
Construction of a concentrated type solar aggregator.
Use a Sun tracker to mensurate the twenty-four hours dark differences.
Analysis of the fluctuation of the sunshine utilizing a tracking device.