This document summarizes the process of converting solar energy into electricity using photovoltaic cells. It discusses key concepts like the photoelectric effect, photovoltaic effect, intrinsic and extrinsic semiconductors, n-type and p-type doping, and the construction and working of solar cells. It also provides details on the performance parameters of solar cells including efficiency, fill factor and their calculation. Finally, it discusses some common applications of solar photovoltaic technology like solar lanterns, street lights, fencing systems, and water pumping systems.

1. Md. I. A. Ansari
Department of Agricultural Engineering
(e-mail: irfan26200@yahoo.com)
Renewable Energy and Green Technology

2. Conversion of Solar Energy into Electricity

3. Photoelectric Effect
• The photoelectric effect is the emission
of electrons when solar radiation strikes
on the surface of certain metals.
• Electrons emitted are called
photoelectrons.
• These free electrons flow through a circuit
built into solar cell which form electric
current.

4. Photovoltaic Effect
• The effect due to which light energy is
converted into electrical energy in
certain semiconductors is known
as photovoltaic effect.
• The photovoltaic effect is the basic
process in which a solar cell converts
solar energy into electrical energy .

5. • A solar cell is a semiconductor made of
crystalline silicon or other materials
which when exposed to sunlight,
generates electricity through the
photovoltaic effect.
• The conductivity of semiconductor
materials lies between conductors and
insulators.

6. • A pure silicon crystal or germanium crystal
is known as an intrinsic semiconductor.
• There are not enough free electrons and
holes in an intrinsic semi-conductor to
produce a usable current.
• Therefore, electrical properties of intrinsic
semi-conductor can be modified by doping
which is a process of adding impurity atoms
to a crystal to increase either the number of
free electrons or holes.

7. When a crystal is doped, it is called an
extrinsic semi-conductor.
Types of semiconductor:
• n-type semiconductor
• p-type semiconductor

8. Doping of Semiconductors
• The addition of a small percentage of
foreign atoms in the regular crystal
lattice of silicon or germanium produces
dramatic changes in their electrical
properties, producing n-type and p-type
semiconductors.
• A silicon atom has 4 valence electrons,
which makes bond to adjacent atoms.

9. • P-type semiconductor: When the
trivalent impurity is added to
an intrinsic or pure
semiconductor (silicon or germanium),
then it is called p-type semiconductor.
This doping creates excess holes.
• Trivalent impurities such as Boron (B),
Gallium (G), Indium(In), Aluminium (Al)
etc are called acceptor impurity.

10. • N-type semiconductor: When
pentavalent impurity is added to
an intrinsic or pure
semiconductor (silicon or germanium),
then it is called n-type semiconductor.
This doping creates extra electrons.
• Pentavalent impurities such as
phosphorus, arsenic, antimony etc are
called donor impurity.

12. PV Cell Construction
• The most common type of
semiconductor currently in use is silicon
crystal.
• Silicon crystals are laminated into n-type
and p-type layers, stacked on top of
each other.

13. PV Cell Construction
1) Low iron glass
2) Polymer layer ( ethylene
vinyl acetate)
3) Anti-reflective coating
4) PV Cell consisting of
a) Front electrical contact
b) Emitter (n-type Silicon)
c) Base (p-type Silicon)
d) Back electrical contact
5) Back polymer layer
1
2
3
a
n-type Silicon
b
p-type Silicon
c
d
5
- - - - - - - - - - - -
+ + + + + + + + + + + +

15. • Solar cells are made up of extremely
thin silicon wafers (about 300 micron
m) and to protect cells from damage,
cells are hermetically sealed between a
layer of toughened glass and layers of
ethyl vinyl acetate (EVA).
• When connected by an external circuit,
electrons flow from the n-side to p-side
to create electricity.

16. Working Principle of Solar Cell
• When solar radiation strikes a photovoltaic
cell, the solar cell absorbs solar radiation.
• When the solar radiation interacts with the
silicon cell, electrons begin to move, creating
a flow of electric current which is direct
current (DC) .
• The metallic wires capture and feed this
current electricity to a battery or can be used
immediately .
• An inverter is used to convert direct current
into alternating current (AC) because some of
the appliances require AC supply for their
work.

19. Basic types of silicon solar cells are:
1. Mono crystalline silicon solar cells
2. Poly crystalline silicon solar cells
3. Thin film or Amorphous silicon solar cells.

20. Mono Crystalline Silicon Solar Cells
• A monocrystalline solar cell is made from
a single crystal of silicon.
• The conversion efficiency for single-
silicon commercial modules ranges
between 15-25%.
• Costlier

22. • Poly crystalline silicon solar cells: The
energy conversion efficiency for a
commercial module made of
polycrystalline silicon ranges between
10 to 20%.
• Less expensive to produce due to
simpler manufacturing process.

24. Thin-film Solar Cells
• The thin film cells are produced from
amorphous silicon.
• The efficiency is 5 to 8%.
• These are very cheap to manufacture.

26. • The magnitude of the electric current
generated depends on the intensity of
the solar radiation, exposed area of the
solar cell, the type of the materials used
in fabricating the solar cell and
temperature.
• Photovoltaic cells come in different sizes, but
most common is 10 cm by 10 cm and
generate about 0.5 V and 1 W.
• The different combinations of cells are
used for increasing the output.
• There are three possible ways of
combining the PV cells.

27. Series Combination of PV Cells
If more than two cells are connected in
series with each other, then the output
current of the cell remains same, and their
voltage becomes doubles.

28. Parallel Combination of PV cells
• In the parallel combination of the cells,
the voltage remains same, and the
magnitude of current becomes double.

29. Series-Parallel Combination of PV cells
• In the series-parallel combination of cells
the magnitude of both the voltage and
current increases.

30. • The power output of a solar cell can be
increased by using tracking mechanism to
keep the PV device directly facing the sun or
by concentrating the sunlight using lenses or
mirror.
• PV cells are bundled together in modules or
panels or array to produce higher voltage and
increased power.
• One unit of electricity=1kWh
1 kWh= 36 x 105 J= 3.6 MJ

32. A SPV system normally consists of:
A SPV array
Charge controller needed to prevent
overcharging and deep discharging
A power storage system (batteries)
An inverter for converting the DC to AC
power
Backup power supplies (generators)

34. Performance of Solar Cells
• The main parameters that are used to
characterize the performance of solar cells
are:
• Peak power
• Fill factor (FF)
• Solar cell conversion efficiency

35. • Peak power: The peak output power from a
PV cells is defined as the maximum power
output that the PV cells could deliver under
standard test conditions (1000 W/m2 solar
radiation intensity at 25 oC and 1.5 AM (air
mass).
• The wattage output of a PV module is rated
in peak watt (Wp).

36. • Short-circuit current: The short-circuit
current is the current that flows through the
external circuit when the electrodes of the
solar cell are short circuited.
• Open circuit voltage: Voltage available from
a power source in an open circuit, I = 0.
• Maximum power point (MPP): The point on
a power (I-V) curve that has the highest
value of the product of its corresponding
voltage and current, or the highest power
output.

38. • Fill Factor: This is the ratio of the maximum
power generated by a solar cell to the
product of the open circuit voltage and short
circuit current.
• Fill factor=Maximum Power/ (ISC x VOC)
=(Impp x Vmpp)/ (ISC x VOC)
• mpp: maximum power point
• VOC: Open circuit voltage
• ISC: Short circuit current

39. • Higher fill factor is desirable .
• As a general rule, commercial PV cells
will have a fill factor greater than 0.7.
• Cells with factor less than this are not
recommended for practical application
in larger electricity generation projects.

40. At the maximum power output of a solar
panel, the voltage and current are 18 V and
5.56 A respectively. If the open circuit
voltage and short circuit current of the
same solar panel are 21.6 V and 6.11 A
respectively, the fill factor of the panel
(round off to 2 decimal places) is
_________. [GATE (AG) 2020]

41. Solution:
Fill factor=Maximum power/ISC x VOC
=(Impp x Vmpp)/ ISC x VOC
=[18 x 5.56]/[21.6 x 6.11]=0.7583 Ans.

42. • Solar cell efficiency: It is defined as the
ratio of power output from solar cell,
module, or array to the incident power.
• Solar cell conversion efficiency=[maximum
power generated x 100]/incident power
• Incident power= Area x Solar radiation
intensity

43. The conversion efficiency of a solar cell is
12%. For a maximum power output of 9×10-3
W at an incident solar radiation of 250 Wm-2,
the required surface area of the solar cell in
mm2 will be ________. [GATE (AG) 2015]
Solution: Conversion efficiency of a solar
cell=Power output (W) x 100/Power input (W)
Or, 0.12=9×10-3/(250 x A)
Or, A=9×10-3/(250 x 0.12) m2=(9×10-3x 1000 x
1000)/(250 x 0.12) mm2=300 mm2 Ans.

44. A solar cell having an area of 25 cm2 gives
a current of 0.85 A and voltage of 0.55 V at
maximum power point. The input power is
1000 W/m2. Calculate the solar cell
conversion efficiency.
Solution:
Solar cell conversion efficiency=[maximum
power generated x 100]/incident power
=[0.85 x 0.55 x 100]/[1000 x25 x 10-4]
=18.7 % Ans.

45. • The area of a solar cell is 100 cm2 and
input power is 400 W/m2. The solar cell
conversion efficiency is 16 %. Calculate
the output power of solar cell.
• Solution: Solar cell conversion
efficiency=[maximum power generated x
100]/incident power
• Maximum power generated=400 x 100 x
10-4 x 0.16=0.64 W Ans.

46. Advantages of Photovoltaic Cells
Absence of moving parts.
 Direct conversion of solar energy into
electrical energy
Low maintenance cost.
No environmental pollution.
Very long life.
Highly reliable.

47. Limitations of Photovoltaic cells
Manufacture of silicon crystals is labour and
energy intensive.
The principle limitation is high cost.
The insolation is unreliable and therefore
storage batteries are needed.
Solar power plants require very large land areas.
Electrical generation cost is very high.
Manufacturing cost of solar cells is very high.
The initial cost of the plant is very high

48. Application of Solar Photovoltaic Systems

49. Solar Lantern

50. Solar Lantern
A solar lantern is a simple application of solar
photovoltaic technology which has found good
acceptance in rural regions for various
purposes where the power supply is irregular
and scarce.
Solar lantern is made of five main components:
Solar PV panel, the storage battery, charge
controller, casing and the lamp (CFL) or
LED).

51. The casing of a solar lantern may be made
of either metal, plastic or fibre glass.
There are a plug point, charging indication
and discharging indication on the casing.
Green LED light indicates the charging of
the battery.
The charge controller controls excessive
charging or deep discharging of the battery.
The measure of a battery capacity is
ampere hour (AH).
A single charge can operate the lamp for
about 4-5 hours.

52. • The solar PV module used for charging
solar lantern ranges from 8 Watts peak
to 14 Watts peak.
• Normally battery capacity of a solar
lantern is 12 V, 7 AH.
• The CFL lamp used in this system is
normally of either 5W or 7W.

53. Solar Street Light

54. Solar Street Light
 Solar street lighting system is designed for
outdoor lighting used to illuminate a street or
open areas, campus, etc.
 Solar street lights operates from sunset to
sunrise i.e., the lamp automatically switches
ON after the sunset and switches OFF after
sunrise.
 The system is provided with battery storage
backup sufficient to operate the light for 10-11
hours daily.

55. Street lighting system consists of SPV
module, charge controller unit, battery,
luminary, interconnecting cables and
pole.
The system is provided with automatic
ON/OFF time switch for sunset to
sunrise operation and overcharge /deep
discharge prevention cut-off with LED
indicators.

56. • The SPV module produces suitable voltage
and current, which is used to charge the
battery inside the battery box which is fixed
on to the pole at a suitable height from the
ground for easy maintenance and
replacement.
• The Charge Controller Unit (CCU) is the heart
of the system, which controls the charging
and discharging of the battery and thereby
increase the battery life.
• The energy stored in the battery is used to
light up the lamp (LED lamp or CFL lamp)
during night time.

57. • The solar street light system comprise of :
a) 74 Wp Solar PV Module
b) 12 V, 75 AH Tubular plate battery with battery
box
c) Charge Controller cum inverter
d) 11 Watt CFL Lamp with fixtures
ON/OFF time switch for dusk to down operation
Overcharge/deep discharge prevention cut off with
LED indicators
e) 4 m mild steel lamp post above ground level with
weather proof paint and mounting hardware.
• Life: 15-20 yrs

60. Solar Fencing System
• The solar fence is scientific fence and works
on solar energy with backup facility to run
uninterruptedly during the nights as well as
cloudy days.
The basic building blocks of a solar fence
are:
Solar panel, battery, energizer, earthing
(grounding system) and fence system.

61. Working Principle of Solar Fencing System
• The solar panel generates DC and charges
the battery.
• The output of the charged battery reaches
the controller or fencer or charger or
energizer.
• The energizer is the heart of solar fence.

62. • When powered, the energizer produces
pulses of nearly 8000 volts at regular
intervals that are sharp and short-lived.
• These pulses are passed through the wires
of the fencing system at a rate of around 1
pulse every 1-1.5 second with every pulse
lasting for nearly 3 ms, thus ensuring that
no physical harm is caused to the intruder
who attempts to come in contact with the
solar fence.

63. • The live wire of the energizer is connected
to the fence wire and the earth terminal to
the earth system.
• Animal / Intruder touching the live wire
creates a path for the current through its
body to the ground and back to the
energizer via the earth system and
completes the circuit.
• Thus the intruder receives a shock.

66. Features of a solar fence:
• Low maintenance cost
• No physical harm caused to human
beings or animals
• Cost-effective
• Makes use of solar energy
• Generally, comes with a centralized
alarm system

67. Areas of Application
• Domestic applications such as at residential
homes
• Industrial applications such as at factories
• Agricultural applications such as in farms
and forests
• Parks & Zoos
• Military stations & police stations
• Schools & hospitals

68. Solar Water Pumping System
• Normally water pump is operated by diesel or
electricity.
• Day by day, the cost of diesel and electricity is rising.
• To overcome this problem, a solar water pump is the
best solution for drawing water from the pond, bore
well, open well, canal, etc. for irrigation, drinking,
etc.
• The solar water pumping system is a stand-alone
system operating on power generated using solar PV
(photovoltaic) system.

69. Working principle of solar pump: The
system of solar water pump works on the
photovoltaic principle which converts the
solar energy into electricity to run the water
pump.
• The pumps draw the water from the pond,
bore well, open well, canal, etc.
• These pumps are used in small scale for
farmers, horticulture farms, cattle feeding,
irrigation, gardens, etc.

70. The solar water pumping system is
provided with:
• 1800 W solar PV panel (24 nos. X 75
Wp)
• 2 HP centrifugal DC mono-block / AC
submersible with inverter.
• The average water delivery of 2 HP
solar pump is around 1.38 to 1.40 lakh
litre per day.

73. Advantages of solar pumps:
 No fuel cost as it uses solar energy
 No conventional grid electricity required
 Long operating life
 Highly reliable
 Easy to operate and maintain
 Eco-friendly
 Saving of diesel
• Less operating cost
• Less maintenance

74. Disadvantages of solar pumps:
• It is costly.
• It needs a battery.
• It is expensive.
• The output of the panel will depend on the
weather.

75. Top Five Solar Power Plants In India
• Solar power in India is a fast developing
industry.
• India stands third in Asia and fourth in the
world in terms of solar power production.
• The country's solar installed capacity reached
37.627 GW as of 31 March 2020.

76. 1. Bhadla Solar Park (World’s largest solar park),
Rajasthan – 2,250MW
2. Shakti Sthala solar power project, Karnataka –
2,050MW
3. Ultra Mega Solar Park, Andhra Pradesh – 1,000
MW
4. Rewa Solar Power Project, Madhya Pradesh –
750MW
5. Kamuthi solar power plant, Tamil Nadu – 648MW

77. Solar Park, Rajasthan

78. Solar Park

79. Solar Park

80. Solar Cell Producing Country
Japan
China
Germany
Taiwan
Australia
USA
Italy

81. Future of Photovoltaic Cells
• PV cell is cost-effective for providing electricity in
remote areas and in other applications.
• As the costs of fossil fuels and electricity increase is
increasing, PV cell is becoming more cost-effective
compared to electricity generated from conventional
sources.
• The market for photovoltaic cells is increasing at
rapid pace and cost is declining continuously due to
advancement in technologies and mass production.