INTRODUCTION.pptx

INTRODUCTION
• SOLAR CELL is the photovoltaicdevice that convert the light energy(from the sun) into electrical energy.
• This device works on the principle of photovoltaic effect.
PRINCIPLE OF SOLAR CELL
PHOTOELECTRIC EFFECT
The phenomenonof emissionof electrons from metal surfaces when exposed to light energy is called
photoelectric effect.
The device based on this effect is called photovoltaicdevice

CONSTRUCTION OF SOLAR CELL
It consist of n-type semiconductor (emitter) layer
and p-type semiconductor (base).
These two layers are sand wiched and hence there
is a formation of PN junction.
The surface is coated with anti-reflection coating
to avoid the loss of incident light energy due to
reflection.
A proper metal contacts are made on the n-type
and p-type side of the semiconductor for electrical
connection.

WORKING OF SOLAR CELL
• When a solar panel is exposed to sunlight,the
light energies are absorbed by a semiconductor
material.
• Due to this absorbed energy the electrons are
liberated and produce external DC current which
is then convereted into 240 volt AC current using
an inverter for different applications.

TYPES OF SOLAR CELLS
Solar Cells are classified as
• Monocrystalline silicon cells
• Polycrystallinesilicon cells
• Amorphous silicon cells
MONOCRYSTALLINE SILICON CELLS
It is produced from pure silicon
It is a single crystal and efficiency of this cell will be
higher.
POLYCRYSTALLINE SILICON CELLS
It consist of severalcrystals of siliconin a single PV
cell .
AMORPHOUS SILICON CELLS
Amorphous Si is a non-crystallineallotropic form of
silicon.
It can be deposited on a thin flim at very low
temperatureonto a substrate.
Three amorphous Si layers – P layer,I layer, N layer
are fromed consecutivelyon a glass substrate.

• This PIN junction corresponds to PN junction of
single crystal silicon solar cell.
• In the process of this junction formation a
number of solar cells are formed in series on a
substrate at one time which leads to generate a
desired voltage.
ADVANTAGES OF SOLAR CELL
• It is clean and non-polluting.
• It is a renewable energy.
• They require little maintenance and has high
durability.
• There are no fuel costs or fuel supply problems.
DISADVANTAGES OF SOLAR CELL
They are expensive
They need large land to produce efficient power
Sun does not shine consistently.

APPLICATIONS OF SOLAR CELLS
• Domestic power supply.
• Dryingagricultural products
• Water Heating
• Generatingelectrical power

SOLAR PHOTOVOLTAIC SYSTEM
• A photovoltaic system is able to supply electrical energy to a given load by directly converting solar
energy through photovoltaic effect.
• PV modules are the main building blocks and they can be arranged in arrays to increase the electrical
production.

TYPES OF PV SYSTEM
• There are three types of solar PV systems
• Grid-tied,
• Off-grid (also called stand-alone)
• Hybrid solar PV system
• Grid-tied PV System
• The grid-tied solar PV system is a PV system that is
connected to the utility grid.
• It is the cheapest PV system as its main components include
only the PV modules and the inverter.
• It provides a quick payback period and greater return on
investment especially for businesses that operate only
during the day.

OFF-GRID (ALSO CALLED STAND-
ALONE) PV System
The Off-grid also called stand-alone is an
autonomous system.
It is the most expensive PV system because
it includes an energy storage system that
stores electricity and supply it at night or
when it is cloudy.
Its payback period is longer because of the
additional cost of energy storage.
It is suitable for homes or businesses
located in rural or isolated regions or in
urban regions with unreliable and expensive
grid electricity.

Hybrid solar PV system
The hybrid solar PV system is a PV that
is connected to the grid and at the
same time has an energy storage
system.
It is less expensive than the off-grid
system because the size of the energy
storage system can be reduced and the
additional power back-up needed can
be supplied from the grid or utility
when there is no sun.
It is suitable for homes or businesses
located in urban regions with unstable,
unreliable, and expensive grid
electricity.

SOLAR COLLECTORS
• A solar collector is a device for collecting solar radiation and transfer the energy to a fluid passing in contact with it
• There are two main types of solar collectors
a)Non-Concentrating or flat plate collectors
b)Concentrating or focusing type collectors
Non-Concentrating or flat plate collectors
• The flat plate solar collector is a type of solar thermal panel whose objective is to transform solar power
into thermal energy.
• The operationof a flat plate collector is based on heat transfer.
• Solar radiation falls on the heat-absorbingplate of the collector.
• When incident solar radiationhits the absorbingplate surface, part of its energyis converted into heat.
Consequently,the temperature of the solar collector increases.
• If we pass a fluid inside the collector, the fluid temperature rises because part of the absorbingplate heat
is transferred to the liquid.
• The fluid transportsthe heat from the collector to heat exchangers to supply the energysystem.

Components of a Flat Plate Collector
A typicalflat-platecollector is madeup of the followingelements:
1. Absorbing Plate
• The absorbing plate is the element that intercepts solar radiation
inside the collector and is responsible for transforming solar
energy into thermalenergy.
• The absorbing plate is usually formed by a metallic foil, usually
copper (an excellent thermal conductor), that darkens. Dark, matte
bodies capture solar radiationbetter than any other color.
There are two ways to darken the absorbing plate:
• First, a thin film of heat black paint resists high temperatures.
• Selective treatment is based on electrochemical depositions or
paints with metallic oxides with high absorption of solar radiation
and low heat emissivity.
• The absorbing plate incorporates a grid of conduits through which
the heat transfer fluid will circulate.
2. Glazing Cover
• The glazing cover has the function of isolating the solar collector from
external environmental conditions and allowing solar radiation to pass
through. This cover is what causes the greenhouse effect.
• It is usually made up of a single sheet of solid
glass approximately 4mmthick.
• This part is only present in glazed flat plate solar
collectors, designedto minimizeheat loss.
3. Isolation
• The insulation reduces heat losses from the inside
of the collector - specifically from the absorbing
plate - to the outside.
• It is usually made up of synthetic foam sheets
(polyurethane, cyanides, fiberglass, etc.) located on
the sides and the back of the solar panel.
• 4. Housing
• The housing serves to house the rest of the
components of the solar collector.
• This closure is typically formed by an aluminum
profile that guarantees a resistance of the
assembly, even under extreme working conditions.
• In addition, the casing has perforations for draining
condensates in the lower part.

TYPESOF FLAT PLATE COLLECTORS
Flat plate collectors are broadly classified into two
types
a)Water or Liquid Heaters
b)Air Heaters
Water or Liquid Heaters
An liquid based collector is a type of solar collector in
which liquid is used as the medium for heat transfer .

Air Heaters
An air-based collector is a type of solar collector in
which air is is used as the medium for heat transfer
instead of a liquid.
Solar FPCs can be used to heat air or other gases,
with satisfactory performance.
Because of the low heat transfer
coefficients between absorber and air, some type
of extended surface geometry is needed to
counteract this problem.

ADVANTAGE OF FLAT PLATE COLLECTOR
Flat plate collector have the following advantages:
(i) Absorb direct, diffuse and reflected components
o solar radiation,
(ii) Are fixed in tilt and orientation and thus, there is
no needed of tracking the Sun,
(iii) Are easy to make and are low in cost,
(iv)Have comparatively low maintenance cost and
Long life
(v)Operate at comparativelyhigh efficiency.

CONCENTRATING /FOCUSSING SOLAR COLLECTORS
• A solar collector that uses reflective surfaces to concentrate sunlight onto a small area, where it is
absorbed and converted to heat or, in the case of solar photovoltaic (PV) devices, into electricity.
• Concentrators can increase the power flux of sunlight hundreds of times.
• Various types of concentrating solar collectors are:
a)Parabolictrough collector.
b)Mirror Strip reflector
c)Fresnellens collector.
d)Flat plate collectors with adjustable mirrors
e)CompoundParabolic Concentrator(CPC)
f)Parabolic dish collector.
g)Heliostat collector.

Parabolic Trough Collector
• It is a line focusing type collector.
• In this type of collector, the solar radiations falling on the
area of the parabolic reflector are concentrated at the
focus of the parabola.
• When the reflector is manufactured in the form of a
trough with the parabolic cross-section, the solar
radiations gets focused along a line.
• An absorber pipe is placed along this line and a working
fluid (usually synthetic oil or water) flows through it. When
the focused solar radiations fall on the absorber pipe, it
heats the fluid to a high temperature. Then the heat
absorbed by the working fluid is transferred to water for
producing steam.
• The focus of solar radiations changes with the change in
sun’s elevation. In order to focus the solar radiations on the
absorber pipe, either the trough or the collector pipe is
rotated continuously about the axis of the absorber pipe.

Mirror Strip reflector
• It is also called line type focusing solar collector.
• A number of plane or slightly curved (concave)mirror
strips are mounted on a flat base.
• The angle of the individual mirrors is such that they reflect
solar radiation from a special direction on the same focal
line where the absorber pipe is placed.
• The collector pipe is rotates so that the reflected ray on the
absorber remains focused with respect to change in suns
elevations.
• The collector pipe is rotates so that the reflected ray on the
absorber remains focused with respect to change in suns
elevations.

Fresnel lens collector
• In this collector a Fresnel lens which consist of fine liner
grooves on the surface of refracting material of optical
quality on one side and flat on the other side is used.
• The angle of each groove is designed that the optical
behaviors of Fresnel lens is similar to that of spherical
lens.
• The solar radiation which falls normal to the lens are
refracted by the lens and are focused on a line where
absorbed tube is places to absorb solarradiation.
• Fresnel Collector –acrylic sheet -4.7 cm X 0.005 cm width.

Flat plate collectors with adjustable mirrors
• A flat-plate collector with adjustable mirrors.
• It consist of a flat-plate collector facing south, with mirrors
attached to its north and south edges.
• If the mirrors are set at the proper angle, they reflect solar
radiation on the absorber plate.
• Thus the latter receives reflected radiation in addition to that
normally falling on it. In order to make the mirror effective, the
angles should be adjusted continuously as the sun’s altitude
changes.

Compound Parabolic Concentrator(CPC)
• It is a trough like arrangement of two facing parabolic
mirrors.
• It is non-focussing but solar radiation from many
directions is reflected toward the bottom of the trough.
• Due to this, a large proportion of solar radiation including
diffused radiation is collected in the concentrate area.
• The absorber plate of CPC reflectors can be designed with
any of the following shape:
Flat one sided absorber
Flat two sided absorber (fin)
Wedge like absorber
Tubular absorber

Parabolic dish collector.
It is a point focussing collector which brings solar radiation to
a focus at a point .
A dish 6.6 m in diameter has been made up of 200 curved
mirror segments forming a paraboloidal surface.
The absorber located at the focus is a cavity made of a
zirconium copper alloy with a black chrome selective coating.
The heat transport fluid flows into and out of the absorber
cavity.
The dish can be turned automatically about two axes so that
the sun is always kept in a line with focus and base of the
paraboloidal dish.
Thus sun can be fully tracked essentially at all times.
Concentration ratio is very high which finds its applications
where high temperature are required.

Heliostat collector
• In this collector, the receiver is located at the top of the
tower.
• It has a large number of independently-moving flat
mirrors (heliostats) spread over a large area of ground to
focus the reflected solar radiations on the receiver.
• The heliostats are installed all around the central tower.
• Each heliostat is rotated into two directions so as to track
the sun.
• The solar radiations reflected from heliostats are
absorbed by the receiver mounted on a tower of about 500
m height.
• The tower supports a bundle of vertical tubes containing
the working fluid.
• The working fluid in the absorber receiver is converted
into the high-temperature steam of about 600oC – 700oC.
• This steam is supplied to a conventional steam power
plant coupled to an electric generator to generate electric
power .

APPLICATIONS OF SOLAR ENERGY SYSTEM
SOLAR POND
• A Natural or artificial body of water for collecting and absorbing solar radiation energy and storing it as a heat.
TYPES OF SOLAR POND
CONVECTIVE SOLAR POND
It reduces heat loss by hindering evaporation with a cover over the surface of the pond.
NON-CONVECTIVE SOLAR POND
It reduces heat loss by preventing convection from occurring with in the pond.

CONVECTIVE SOLAR POND
• It is very shallow about 5 – 10 cm deep
with a radiation absorbing (black
plastic) at the bottom.
• A curved cover made of transparent
fibre glass over the pond permits entry
of solar radiation but redues losses by
radiationand convection.
• The water in such a pond would heat
upto only a few degree and soon
acquire uniform temperature in such
away that heat is absorbed at the
bottom.
• Due to the occurrence of natural
convection current which transfer the
heat from the bottom to surface of the
water.

NON-CONVECTIVE SOLAR POND
• This pond contain salt water at the bottom with a layer
of fresh water at the bottom.
• Because of this salt content the solar pond bottom
water is more dense than the cooler fresh water at the
top and hence it does not tend to rise.
• Thus a relatively stable layer of heated salt water is
thus produced at the bottom of the pond with a lighter
layer of cooler fresh water.
• Dissolved salts of sodium chloride, magnesium
chloride etc. are used to create layer of water with
different densities.
• No membrane is used at the top of the pond.
• The salt concentrationsteadily increases with depth.
• The diffusion of salt automatically creates a
continuous gradient through the non convective
layer.
• • Difficult to maintain the density gradient for a long
and therefore concentrated brine is added
periodically to the Bottom.
Thus a solar pond has three zones
i)Surface convective zone (0.3 – 0.5 m)salinity <5%
ii)Non- Convective zone (1 -1.5 m) salinity increase with
depth
iii)Lower convective zone (1.5- 2 m)salinity approximately
20%

CHARACTERISTICS OF SALT USED IN SOLAR POND
• It must have high value of solubility
• Its solution must be transparent to solar radiation
• It must be available in abudance near site
• It must be expensive.
APPLICATION OF SOLAR POND
• Heating and cooling of building
• Production of power
• Industrial process heat
• Heat for biomass conversion ,drying corps on farms.

SOLAR REFRIGERATON
• Refrigeration is a process in which work is done to
move heat from one location to another.
SOLAR REFRIGERATION
• Refrigerator which runs on electricity provided by
Solar Energy is known as solar Refrigeration.
• Solar-powered refrigerators may be most commonly
used in the future generation.
TYPES OF SOLAR REFRIGERATION:
 Photovoltaic Operated Refrigeration Cycle
 Solar Mechanical Refrigeration
 AbsorptionRefrigeration
PHOTOVOLTAIC OPERATED REFRIGERATION CYCLE
• In this system, solar radiation is directly converted to
direct current electricity using semiconducting
materials.
• The operation of a PV-powered solar refrigeration
cycle is simple.
• Solar photovoltaic panels produce DC electrical power
that can be used to operate a DC motor, which is
coupled to the compressor of a vapour compression
refrigeration system.
• The process that makes the refrigeration possible is the
conversion of sunlight into DC electrical power, achieved
by the PV panel.
• The DC electrical power drives the compressor to circulate
refrigerant through a vapour compression refrigeration
loop that extracts heat from an insulated enclosure.
• This enclosure includes the thermal reservoir and a phase
change material
.

SOLAR MECHANICAL REFRIGERATION
• In this type of refrigeration system, required
compressor power to drive the compressor in
refrigeration cycle is provided by a solar Rankine
cycle.
• Sunlight strikes the solar panel which drives a
Rankine cycle and produces work in the turbine.
• This work is then utilized to run the compressor of the
vapour compressionrefrigeration system.
SOLAR ABSORPTION REFRIGERATION SYSTEM
• In this system, low grade energy as heat from solar
panel is used as input for chilling purpose.
• Basic components of such refrigeration system are
absorber, generator, solar panel, condenser, expansion
valve, evaporator, DC battery and fan.
• The compressor in the vapour compression system is
replaced by a generator, absorber and pump.

• Refrigerant (NH3) in the evaporator
absorbs the heat from the refrigerated
space and gets evaporated.
• It is then passed to absorber where it
is dissolved with absorbent (H2O) and
pumped to generator.
• Electrical energy from solar panel is
utilized for heating in the generator
and the refrigerant enters into
condenser.
• The refrigerant is converted to liquid in
the condenser and the pressure of the
liquid refrigerant is dropped to the
evaporator pressure with the help of an
expansiondevice (ED).
• The main advantage of absorption system is compression of
liquid instead of vapour which results in less mechanical work
requirement as input.
• But the system is much expansive compared to compression
refrigeration system.
• Other than ammonia-water combination, few more refrigerant -
absorber pairs have been tried which are listed in table

CENTRAL RECEIVER POWER GENERATION [SOLAR TOWER]
Basic operation
SE--- HE-----ME--EE
COMPONENTS
• Receiver subsystem
• Heat Transport System
• Heat Storage System
• Heliostat

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