This document discusses solar photovoltaics (PV) and includes the following key points: 1. PV systems use electronic components to convert solar radiation into electricity, with greater intensity of sunlight producing greater electricity flow. 2. The photovoltaic effect was first observed in 1839, and silicon semiconductor cells that could convert light to electricity with 4-6% efficiency were developed by Bell Labs in 1954. 3. There are three main types of PV cell materials - mono-crystalline, polycrystalline, and amorphous thin-film - which have different efficiencies, costs, and appearances.

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Lecture #4
uzair@neduet.edu.pk
Dr. Muhammad Uzair
Assistant Professor
Mechanical Engineering Department
NED University of Engineering & Technology
DICE Lab (MED, NED)
+99261261 (Ext. 2206)
uzair@neduet.edu.pk
uzair@neduet.edu.pk
Report:
“Solar energy, radiant light and heat from the sun,
has been harnessed by humans since ancient
times using a range of ever-evolving technologies.
Solar energy technologies include solar heating,
solar photovoltaics, solar thermal electricity and
solar architecture, which can make considerable
contributions to solving some of the most urgent
problems the world now faces.”
From "Solar Energy Perspectives: Executive
Summary“ - International Energy Agency (2011)
What is photovoltaic (PV) ?
• PV systems use electronic
component to convert
solar radiation into
electricity.
• Greater the intensity of
sunlight, greater is the
flow of electricity.
Photovoltaic (PV) = Photo (Light) + Voltaic (Volts)

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History of PV effect
• Certain materials would produce
small amount of electric current
when exposed to light.
E.B. Alexandre, 1839
• A Silicon semiconductor was able to convert
light into electricity with 4-6% efficiency
Bell Labs, 1954
Electricity generation through PV
Semiconductor materials: They have the
properties of an insulator, but when exposed to
light or heat, they become conductor.
Electricity generation through PV Electricity generation through PV

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Types of cell materials Types of cell materials
Mono-crystalline
A crystal of silicon is grown from
highly pure molten silicon
• Efficiency:
15-18%
• Power/Area:
135-170 W/sq.m
• Very expansive
• Uniform dark blue, circle or cut-
square shape.
Types of cell materials
Polycrystalline
Silicon is heated to high temperature and cooled
under controlled conditions in a mold (casting
process).
As the molten silicon sets, an irregular poly- or
multi-crystal is formed.
• Efficiency:
12-14%
• Power/Area:
120-150 W/sq.m
• Less expansive than mono-crystalline type.
• Different blue shades, square shape.
Types of cell materials
Amorphous Si/Thin-film
• Silicon, CIS or CdTe is deposited as gas on a
glass, aluminium or plastic surface.
• Layer (thin film) of semiconductor material is
only 0.5-2.0 µm thick.
• Less semiconductor raw material is used.
• Less sensitive to the effects of shade and high
temperatures.
• Efficiency:
5-6%
• Power/Area:
60-80 W/sq.m
• Very cheap compared to above
• Any color, looks like thin film.

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Comparison of different cell types Production of cells
Silica Sand
Silicon Blocks
Mon-crystalline
Wafers
Basic Terms Basic Terms

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Basic Terms Types of Solar PV Systems
• Grid-tied (On Grid) systems
• Off-grid systems
• Solar parks
Types of Solar PV Systems
Electricity is fed directly into the power supply.
Excess electricity being sold to energy companies
using grid.
Grid-tied Systems
Types of Solar PV Systems
Grid-tied Systems

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Types of Solar PV Systems
Electricity is generated
and
stored in batteries for use
locally.
Off-grid Systems
Types of Solar PV Systems
Off-grid Systems
Types of Solar PV Systems
A photovoltaic power station is called solar park.
Solar parks
Types of Solar PV Systems
Solar parks
Olmedilla PhotovoltaicPark, La Mancha, Spain
60 MW, 384 million euros, World’s biggest park!

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Electrical characteristics of PV cells Electrical characteristics of PV cells
Module or panel specifications
• Cell type and its efficiency
• Warranty of linear power output (years)
• Mechanical data (dimensions, area and weight)
• Rated power (Wp or Pmax) in Watts at
Standard Test Conditions (STC), also known as
name-plate rating. STC: Irradiance 1000
Watts/m2 at 25 °C.
• Temperature coefficients for power, voltage
and current (in -%/°C)
• Electrical data at STC
Module specification sheet

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Models comparison Market trends
Module
prices and
system costs
are
decreasing
continuously!
Solar energy in Pakistan
Pakistan:
3.5 to 7
kWh/m²/day
Germany:
2.5–3.2
kWh/m²/day
Solar energy in Pakistan: Applications

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Ambient influences on cells and
modules
Ambient influences on cells and
modules
Ambient influences on cells and
modules
Ambient influences on cells and
modules

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Ambient influences on cells and
modules
Ambient influences on cells and
modules
Ambient influences on cells and
modules
PV cell interconnection and module
design

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PV cell interconnection and module
design
Module interconnection and array
design
Module interconnection and array
design
Module interconnection and array
design

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Module interconnection and array
design
Module interconnection and array
design
Module interconnection and array
design
Solar PV system components
• Batteries
• Charge controllers
• Inverters
• Cables and connectors
• Mounting systems