solar power plant
TRANSCRIPT
SUMMARY SOLAR POWER SOLAR COLLECTORS
* FLAT PLATE COLLECTORS * FOCUSSING COLLECTORS
SOLAR THERMAL POWER GENERATION
* Low temperature cycle
* Medium temperature cycle
* High temperature cycle
PHOTO VOLTAIC
SOLAR POWER
The sun gives out 3.7 X watts of energy in to space, out of which earth intercepts only 5Xth part of it
The portion of the incident solar radiation which comes directly from the apparent solar disc is called Direct or Beam Radiation.
The solar radiation received from the sun after reflection and scattering by the atmosphere is called Diffuse radiation.
Total radiation=diffused radiation + direct radiation
ADVANTAGE Non-polluting
nature Inexhaustable
source Can be readily
harnessed without affecting the environment
DISADVANTGENon availability
during nights and during periods of cold weather
USES Operate enginesTo power refrigeratorsTo heat water To heat and cool buildings To run pumps Sewage treatment plants Powers cars, ovens, water stills, furnaces,
distillation equipments , crop driers
SOLAR COLLECTORS
In most of the devices utilising solar energy, the solar energy in the radiant energy form is converted in to heat energy using mechanical devices known as solar collector. The solar collector absorbs incident solar radiation and transfer the energy to a fluid passing in contact with it.
FLAT PLATE COLLECTOR
In flat-plate collectors there is no optical concentration of sunlight and they are generally stationary . In addition to this their outlet temperature capability is below 100 °C
A flat plate collector is basically a black surface that is placed at a convenient path of the sun. And a typical flat plate collector is a metal box with a glass or plastic cover (called glazing) on top and a dark-colored absorber plate on the bottom. The sides and bottom of the collector are usually insulated to minimize heat loss
Flat plate collectors
Based on type of heat transfer fluid used it is divided in to two Liquid heating collectors employ water
or other non freezing solutions as working fluid
Air or gas heating collectors employ air or gas as the working fluid
Components of a typical flat plate collector Absorber plate:
It is usually made of copper , steel or plastic. The surface is covered with a flat black material of high absorbance. If copper or steel is used it is possible to apply a selective coating that maximizes the absorbance of solar energy and minimizes the radiation emitted by plate.
Flow passages:
The flow passages conduct the working fluid through the collector. If the working fluid is a liquid , the flow passage is usually a tube that is attached to or is a part of absorber plate. If the working fluid is air , the flow passage should be below the absorber plate to minimize heat lssues.
Cover plate: To reduce convective and radiative heat losses from
the absorber , one or two transparent covers are generally placed above the absorber plate. They usually be made from glass or plastic.
Insulation: These are some materials such as fiberglass and
they are placed at the back and sides of the collector to reduce heat losses.
Enclosure: A box that the collector is enclosed in holds the
components together, protect them from weather, facilitates installation of the collector on a roof or appropriate frame.
Cross section of a basic flat-plate solar collector
Flat plate collectors used for heating buildings
Flat-plate collectors used for heating swimming pools
FOCUSSING COLLECTORSIn concentrating solar collectors the incident solar energy is reflected and made to concentrate at a convenient point.
They are classified by According to type of reflecting medium:
parabolic, spherical or flat concentrators
According to the optics : point focus system, line focus system
Parabolic concentrating collector Spherical concentrating collector
Flat concentrating collector
Point focusing system
Line Focusing collector
Solar thermal power generation Low temperature cycle :
use flat plate collectors. Maximum temperature limit is up to 100°C
Medium temperature cycle:
works at temperature range 150 to 300°C
High temperature cycle:
works at temperature range above 300°C
Low temperature system
Solar colle
ctor
Heat
exc
hanger
Turbine ~
Condenser
pump
Organic fluids like ammonia, freon, etc which evaporates at lower temperature is utilised to run the turbine
Medium temperature system
Utilises cylindrical or parabolic solar concentrators which can easily give temperature up to 300°C. In this system steam is directly generated in the concentrators and is used to drive the turbine
High temperature system
Photo Voltaic
Photo voltaic effect (PV) effect is defined as the generation of an electromotive force as a result of the absorption of ionising radiation
Solar cell are usually made of a single crystal silicon, gallium arsenide is another solar cells material.
n-type semiconductor
p-type semiconductor
+ + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - -
Physics of Photovoltaic Generation
Depletion Zone
It needs little maintenance, it is long lived, its energy source is unlimited and it can be made from raw materials which are available in huge quantities. Produce very little power at very high cost. Output is not constant and it varies with the time of the day
Photovoltaic System
Typical output of a module (~30 cells) is ≈ 15 V, with 1.5 A current
APPLICATIONS OF SOLAR ENERGY
SOLAR WATER HEATER SOLAR COOKER
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