1. UNIT II SOLAR ENERGY
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Solar Radiation – Measurements of Solar
Radiation - Flat Plate and Concentrating
Collectors – Solar direct Thermal Applications
– Solar thermal Power Generation -
Fundamentals of Solar Photo Voltaic
Conversion – Solar Cells – Solar PV Power
Generation – Solar PV Applications.
3. 3
Solar energy
Solar energy comes from the light of the sun, which means it is a
renewable source of energy. We can use the sun light to create
pollution free electricity
The solar cell is the system used to convert the sunlight energy
into electrical energy
4. Disadvantages
• Solar panels are
expensive.
• When it is cloudy or at
night there is not enough
light.
• Some people don’t like
the look of solar panels.
What is it?
• Solar power
uses energy
from the
Sun.
• Solar panels
transfer the
Suns energy
to heat
water.
Advantages
• The energy from the Sun
is free.
• The sun does not produce
greenhouse gases.
• The sun will always be
there during our lifetime.
5. • Solar energy is the most readily available
source of energy.
• It is free.
• It is also the most important of the non-
conventional sources of energy because it is
non-polluting.
Solar Energy
6.
7. Energy from the sun
• About half the incoming solar energy reaches the Earth's surface.
• The Earth receives 174 petawatts (PW) (1015 watts) of incoming solar
radiation at the upper atmosphere. Approximately 30% is reflected back to
space while the rest is absorbed by clouds, oceans and land masses.
• Earth's land surface, oceans and atmosphere absorb solar radiation, and this
raises their temperature. Sunlight absorbed by the oceans and land masses
keeps the surface at an average temperature of 14 °C.
• By photosynthesis green plants convert solar energy into chemical energy,
which produces food, wood and the biomass from which fossil fuels are
derived.
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8. PH 0101 Unit-5 Lecture -1 8
Areas of the world with high Solar radiation
• The basic resource for all solar energy systems is the
sun.
• Knowledge of the quantity and quality of solar energy
available at a specific location is of prime importance
for the design of any solar energy system
9. PH 0101 Unit-5 Lecture -1 9
• Although the solar radiation is relatively constant outside
the earth's atmosphere, local climate influences can cause
wide variations in available radiation on the earth’s surface
from site to site.
• In addition, the relative motion of the sun with respect to
the earth will allow surfaces with different orientations to
intercept different amounts of solar energy.
• It is the primary task of the solar energy system designer
to determine the amount, quality and timing of the solar
energy available at the site selected for installing a solar
energy conversion system.
19. Thermal Collector Mechanics
Solar energy is
absorbed,
transformed, and
concentrated in a
solar thermal
collector over a
time or spatial
gradient to produce
usable energy
20. Thermal Collector Technologies
• Solar Cookers
• Parabolic Troughs
• Parabolic Dish
• Central Receiver
System
• Solar Chimney
• Solar Distillers
• Solar Water Heaters
22. Parabolic Trough
• A parabolic trough concentrates sunlight along
a spatial gradient into a linear focal point
• A fluid acts as a thermal sink as it passes
through tubes along the focal point
• Parabolic troughs are used to generate
electricity but are susceptible to seasonal
changes
24. Parabolic Dish
• A parabolic dish or solar furnace is a large
reflector that concentrates thermal energy into
a single focal point
• The focal point can contain a Stirling Engine
to generate electricity or the energy can be
focused and used in industrial processes
• On a small scale, a reactor can be used in the
same way a solar oven is used
37. Solar Cookers
• Solar cookers or ovens are primarily used in
developing nations as a primary method for
cooking using passive solar heat to cook
primary meals
• Insulated box that collects solar radiation
enhanced by reflectors attached to each side
• Helps combat deforestation
39. Solar Distiller
• Solar radiation heats up the contaminated
water and allows the water to evaporate,
leaving the contaminant behind
• System design collects distilled water for use
• Technology purifies water and can serve from
one person to a community depending on the
size of system installed
43. Solar Chimney
A solar chimney is a technology that can be used to enhance the
ventilation of a residential or commercial structure.
44. Solar Water Heater - Overview
• A solar water heater concentrates solar energy
over a time gradient
• Common usage ranges from pool heaters to hot
water for showering and domestic use
• The most popular solar collector
• Heavily used in Florida until World War 2
increased the demand for copper
45. Solar Water Heater - Components
• Conductive thermal collectors
(painted black to aide absorption)
• Transparent cover to capture solar
radiation
• Pipes for water flow
• Insulation
• Water body
46. Solar Water Heater - Passive Design
• Passive design uses thermal convection to
circulate heat in the water system
• The water body needs to be above the solar
collector
• As water heats up it rises into the water body
pushing cold water down
48. Solar Water Heater - Active Design
• Uses pumps to circulate
hot water
• Spends electricity
lowering the energy
savings
49. Applying Solar Water Heating
• The solar collector should be placed facing South
and at an angle equal to that of the latitude
• For increased efficiency angle should be increase
by 15 degrees during the winter season and
decreased by 15 degrees in the summer
• This makes the angle to the sun closest to 90
degrees during seasonal changes
50. 50
What are Solar Cells?
• Solar cells are devices which convert solar light energy directly
into electricity
• Sunlight contains packets of energy called photons that can be
converted directly into electrical energy.
• This is referred to as the photovoltaic effect.
• Photo- means light and -voltaic means electrical current;
• A solar cell provides direct current (DC) electricity, similar to
batteries.
• Batteries however use electrochemical reaction.
51. 51
Atoms
An atom is composed of three different particles:
• Nucleus- Center of the atom:
1. Protons (P+)-- positively charged.
-- equal to the number of
electrons.
2 Neutrons -- no charge.
3. Electrons (e-) -- negatively charged.
-- orbit the nucleus.
The outermost electrons of an atom
determine its chemical and electrical
properties
Protons (P+)
Neutrons
(e-)
52. 52
Semiconductor Doping
• How can we change the electrical properties of the pure Semiconductor
material?
• By adding foreign material to it, called dopants. (impurities)
• Boron, phosphorus, arsenic are common dopants.
• Rate of low :1 every 100,000,000 atoms
high: 1 every 10,000 atoms
Silicon (Si) with Phosphorus (P2,8,5) dopant : n-type
(extra valence electrons are added)
Silicon (Si) with Boron (B2,3) dopant = p-type
(missing fourth valence electron, holes)
53. 53
Photon Hits the Atom of a “Semi” Material
.
www.altensol.comph/solal-photovoltaic
Hole is the “empty space” left behind as a result of the movement of the
free electron. Holes have + charge.
54. Disadvantages
• Solar cells are
expensive.
• They take up lots of
space.
• They only work in Sun
light
What is it?
• Solar cells
use energy
from the Sun.
• Solar panels
transfer the
Suns energy
directly into
electricity.
Advantages
• The energy from the Sun
is free.
• The sun does not produce
greenhouse gases.
• The sun will always be
there during our lifetime.
56. 56
. Sunlight is made of photons, small particles of energy.
These photons are absorbed by and pass through the material of a solar cell or
solar PV panel. The photons 'agitate' the electrons found in the material of the
photovoltaic cell.
As they begin to move (or are dislodged), these are 'routed' into a current. This,
technically, is electricity - the movement of electrons along a path.
www.altensol.com.ph/solar_photovoltaic_philip
The Process
57. 57
So, How does it work?
• Light breaks silicon bonds and creates “free” electrons
and holes, “missing electrons”
• Holes are positive charges
• Built-in field separates electrons and holes
Step 1. Photogeneration of charge carriers,
electron (negative) and hole (positive).
Step 2. Separation of the charge carriers
through the medium.
58. Solar Photo voltaic (SPV)
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• In photovoltaic conversion, Solar radiation
falls on semi-conductor devices called solar
cells which convert the sunlight directly into
electricity.
• When a bright light shines on a cell, energy
from the light (photons) enables electrons to
break free from the junction between them.
This is called photo electric effect.
59. Solar Photo voltaic (SPV)
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• N-Type – Excess electrons
• N- Type- doping with phosphorous or arsenic
• P- Type – Shortage of electrons
• P Type – doping silicon with boron
• When cell is connected to a load, Electron flow
from n-type to p-type
• The ratio of the maximum useful power to the
ideal power is called fill factor(k). K=0.65 to0.80
