The document discusses solar photovoltaics (PV), which directly convert sunlight into electricity using solar cells. It provides a history of PV development and describes the basic physical principles, including how doping silicon creates p-type and n-type semiconductors which form a p-n junction in solar cells. When photons interact with the junction, electrons are excited and electricity is generated. The document outlines different PV technologies like monocrystalline, polycrystalline, and thin film solar cells as well as their manufacturing processes and comparisons. It also briefly discusses the balance of system components needed for a complete solar PV system.

1. CIVE 685: Environmental Sustainable Renewable Energy Resources
Solar Energy II :
Solar Photovoltaics
Rana A. Bilbeisi
October 07, 2020
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2. Outline
• Introduction and history
• Basic physical and chemical principles of
PVs
• Innovative and Emerging PV technologies
• Application
• Remote power supply
• Grids
• Large power plants
• Environmental impact and future prospective
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3. Largest private PV system in Lebanon - 2015
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http://www.solarserver.com/solar-magazine/solar-news/archive-2015

4. Introduction and history
• Photovoltaics:
(Greek for light) (units of potential diff in an electric field)
Describes a DIRECT method of generating electricity from solar
radiation commonly known as solar cells.
Conversion of solar radiation to electricity through the use of solid state
devices (best energy conversion devices)
Various model scales:
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Small scale: Hand watches
and calculators
Large scale: International
space station with a
combined output of 130 kW
Medium scale: Radio
transmitter

5. History
1839
1877
1883
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1958
2000-
2010
Discovery: Edmond Bacquerel through his work on “wet cell batteries”.
He observed in the voltage of the battery upon subjecting it to light.
Reporting first PV effect: Day & Adams reporting the electrical
properties of selenium, when exposed to light.
Construction of first selenium solar cell: Charles Fritts reporting the
construction of the first solar cell with a 1% efficiency.
Modern Higher efficiency: Chapin-Fuller-Pearson group researched
the effect of light on semiconductors. Solar conversion increased to 6%
1950 upon using doped silicon
Use of PVs to power small radio transmitters.
Increased installation of PVs to more than 20 folds with the
improvement of lost effectiveness (increased efficiency up to 25%).

6. Global cumlative PV installed capacity (MW)
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https://phlebasblog.files.wordpress.com/2014/09/oecd_pv-global-cumulative-capacity.jpg

7. Basic physical and chemical principles of PVs
Albert Einstein received, in 1921, the Nobel Prize
for discovering the laws of photoelectric effect
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Emission of electrons or other free
carriers when light hits a material

8. Photovoltaic material:
Elements in Semiconductors
Metalloids:
Silicon is a metalloid.
Silicon is one of a small group of
elements that occupy a ‘staircase’
diagonal line on the periodic table,
where the elements chemical
properties fit neither description
completely. Some metalloids are
semiconductors.
Silicon is one of the most abundant elements on earth
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9. Semiconductors
• Silicon is part of a class of materials called semiconductors
that is to say, that it isn’t a conductor nor an insulator
• It has electrical resistivity that is somewhere in between a
conductor and an insulator
• In its regular state, silicon isn’t all that conductive, as none
of its electrons can move (and movement of electrons is
essential for conductivity); the electrons are locked into the
crystalline structure – each atom sharing electrons with its
neighbour
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10. Silicon
10

11. Doping Silicon
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• We can control and enhance this semiconducting property by
adding other elements to change the way silicon behaves.
• This is known as “doping“ since silicon is “doped” with a
small quantity of a different element.
• By introducing free electrons, or creating gaps into which free
electrons can go, we can create useful devices.
P-type semiconductor N-type semiconductor
Free electrons and holes are considered carriers; a carrier which is a
charged particle can move about creating current

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p – n junctions and the PV effect
• The two types of doped silicon have slightly different electrical
properties, and we can take advantage of this by creating a
“junction”.
• We are joining a piece of “P-Type” silicon and a piece of “N-
Type” silicon; so the junction we create is known as a “PN
junction”.
• Those of you who are familiar with electronics, will recognise
that a “PN junction” is effectively a diode – our photovoltaic cell
is effectively a large, planar diode with a big surface area.

13. Pn junction

15. Reminder: Light, photon energy and band gap
Compare the energy (eV) associated
with photons of the blue light
(wavelength of ~410 nm) with that of
infrared radiation (wavelength of 820
nm).
Answer: 3 eV vs 1.5 eV
Energy levels are important for understanding two mechanisms that determine the
efficiency of PVs:
1. In order to promote an electron from the valence band to the conduction band, it
has to get energy from a photon of light with an energy greater than the bad gap
of a particular semiconductor.
2. Useful electrical energy that contributed to the solar cell is equal to the band
gap. Surplus of energy will be dissipated as heat.

16. PV Cell and Light Interactions
Four possible interactions with incident photons:
1. Photon with an energy equal to the band gap.
2. Photon with an energy greater than the band gap.
3. Photon with an energy smaller than the band gap.
4. Photos reflected from the front surface of the cell, or somehow blocked from
reaching the crystal

17. Solar Panel Manufacturing Technologies
• Solar Panel is an indispensable component of this system, it is responsible for collecting solar
radiations and transform them into electrical energy
• Solar Panel is an array of several solar cells (Photovoltaic cells)
• The arrays can be formed by connecting them in parallel or series connection depending upon the
energy required 14

18. Solar Panel Manufacturing Technologies
 The most common solar technology is crystalline Si. Its two types
are: Mono- Si and Poly- Si
 Mono-Si: Crystal Lattice of entire sample is continuous.
 Poly-Si: Composed of many crystallites of varying size and
orientation.
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19. Monocrystalline Silicon cells
• Silicon is “tetravalent”, four electrons available in the outer shell
form ‘covalent’ bonds.
• The natural tendency to achieve full outer shells with eight electrons
by forming bonds with other elements, silicon form four covalent
bonds to achieve a full outer shell.
• Silicon forms a regular crystalline structure. This is to say that the
forces between the atoms of silicon are such that they arrange
themselves in the most compact pattern that the forces between
atoms will allow.
Crystalline Silicon (3D representation)
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20. Monocrystalline Silicon cells
Mono-Si Solar Panels
Mono-Si is manufactured by
Czochralski process:
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21. 21
Solar Panel Manufacturing Technologies
Mono- Solar Panels: Since they are cut from single crystal, they give the module a
uniform appearance.
• Advantages:
Highest efficient module till now with efficiency of between 13 to 21%.
Commonly available in the market.
Greater heat resistance.
Acquire small area where ever placed.
• Disadvantages:
More expensive to produce.
High amount of Silicon.
High embodied energy (total energy required to produce).

22. Solar Panel Manufacturing Technologies
• Poly-Si Solar Panels:
Polycrystalline (or multicrystalline) modules are composed of a number of different crystals,
fused together to make a single cell.
Poly-Si solar panels have a non-uniform texture due to visible crystal grain present due to
manufacturing process.
• Advantages:
Good efficiency between 14 to 16%.
Cost effective manufacture.
Commonly available in the market.
• Disadvantages:
Not as efficient as Mono-Si.
Large amount of Si.
High embodied energy
Visible crystal grain in poly-Si
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23. Amorphous Silicon
• Amorphous silicon is a ‘thin film’ device
• It is not a “crystalline” form of silicon
• Rather than the tetrahedral crystalline structure carrying on
over a long range, amorphous silicon is disordered, with
‘dangling bonds’.
• These dangling bonds can be “passivated” by bonding hydrogen to
them
• This is known as a-Si:H, hydrogenated amorphous silicon
• This hydrogen reduces the number of “dangling bonds” by several
orders of magnitude. However, it also leads to light-induced
degradation over time, know as the Staebler-Wronski effect
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24. Solar Panel Manufacturing Technologies
• Amorphous-Si Panels:
Non-crystalline allotrope of Si with no definite arrangement of atoms.
• Advantages:
Partially shade tolerant
More effective in hotter climate
Uses less silicon - low embodied energy
No aluminum frame - low embodied energy
• Disadvantages:
Less efficient with efficiency between 6 to 12%
Less popular - harder to replace
Takes up more space for same output
New technology - less proven reliability
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25. Solar Panel Manufacturing Technologies
• Thin Film Solar Panels:
 Made by depositing one or more thin layers
(thin film) of photovoltaic material on a
substrate.
 Thin film technology depends on the type
of material used to dope the substrate.
 Cadmium telluride (CdTe), copper indium
gallium selenide (CIGS) and amorphous
silicon (A-Si) are three thin-film technologies
often used as outdoor photovoltaic solar
power production.
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26. 26
Comparison of Mono-Si, Poly-Si and Thin film Panels
Mono-Si Panels Poly-Si Panels Thin Film Panels
1. Most efficient with max.
efficiency of 21%.
1. Less efficient with
efficiency of 16% (max.)
1. Least efficient with max.
efficiency of 12%.
2. Manufactured from single
Si crystal.
2. Manufactured by fusing
different crystals of Si.
2. Manufactured by
depositing 1 or more layers of
PV material on substrate.
3. Performance best at
standard temperature.
3. Performance best at
moderately high temperature.
3. Performance best at high
temperatures.
4. Requires least area for a
given power.
4. Requires less area for a
given power.
4. Requires large area for a
given power.
5. Large amount of Si hence,
high embodied energy.
5. Large amount of Si hence,
high embodied energy.
5. Low amount of Si used
hence, low embodied energy.
6. Performance degrades in
low-sunlight conditions.
6. Performance degrades in
low-sunlight conditions.
6. Performance less affected
by low-sunlight conditions.
7. Cost/watt: 1.589 USD 7. 1.418 USD 7. 0.67 USD
8. Largest Manufacturer:
Sunpower (USA)
8. Suntech (China) 8. First Solar (USA)

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Balance of System
• A solar PV system consists of :
1. Solar panels
2. Power conditioning regulator:
- Converts the DC current coming from PV system to an AC current
- Regulates the power (maintaining almost constant voltage)
- Surge protector (from voltage spikes)
3. Backup battery, saving energy at high supply to be provided at
lower supply times of the day

28. 28
Classification of Solar PV systems
• Distributed System:- This system is much more
successful and unique. Can be further classified into three
types:
1) Stand-alone System
2) Hybrid Solar PV System (Consumer applications)
3) Grid-Interactive System
• Central Power Station System:- These are conceptually
similar to any other conventional power station. They feed
power to the grid to meet day time peak loads. The capital
costs are high.

29. Stand-alone PV Solar System
- PV technology is not connected to a grid or any energy backup system
- Located at the load center
- Dedicated to meet electrical loads of a village/community or a specific
set of loads
- Used remote or rural areas (developing countries, where grid do not
exist) which have no access to grid supply
- Examples: (a) PV parking meter, (b) Navigation Buoy and (c) Mobile health
clinics (mainly used in Africa to transportmedication).
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30. Hybrid Solar PV System
- Larger scale more economic energy generation
- These systems are meant for low energy consumer devices
- Designed for indoor applications
- Usually backed up by another form of energy, fossil fuel or renewables
(mostly wind energy)
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A Hybrid energy system usually consists of two or more renewable energy sources
used together, providing increased system efficiency as well as greater balance in
energy supply
http://www.ecoplanetenergy.com/all-about-eco-energy/overview/hybrid/

31. Grid-Interactive System
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- It is connected to utility grid with two-way metering system
- A relatively bigger system, that can be used for a whole village or
community
- The grid can absorb surplus PV power, making it available for other
customers’ use
- The grid provide energy backup from conventional sources at night or
during cloudy days
These grid interactive power systems
are connected to:
(1) A “synchronous inverter” that
transforms the direct current power
for the PV array to an alternating
current AC at a frequency and
voltage accepted by the grid.
(2) A “Credit and “ debit” meter
measuring the amount of power
sold to or bought from the utility –
“Feed-in Tariffs”.

32. Components of a PV system
In the case of homes connected to
the utility grid, PV can produce
electricity (converted to AC by a power
conditioner) during the day. The extra
electricity can then be sold to the utility
during the day, and the utility can in
turn provide electricity at night or
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during poor weather
Components of a PV system to get the power generated to the load (in
this example, a house).:
The stand-alone PV system, uses
battery storage to provide dependable
DC electricity day and night.

33. Central Power Station System: Grid Connected PV
Power Plants
48 MW, Nivada, USA
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- Large, multi-megawatt scale, centralized PV power systems
- Used to supply power to local and regional grids
- Produced electricity will be distributed (rather than being used onsite), which
involve transmission losses
- Expensive to implement and requires large area of land (in some cases, they
are implemented on wasted land, along a motor way)
PV array in low value land,
Switzerland 1 MW, Sun Farm, UK
Other examples:
- Prescott Airport Location: Arizona; Public service; Configuration: 1,450 KWp
- SGS Solar Location: Arizona; Tucson Electric Power Co; Configuration: 3,200 KWp
Hybrid systems

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Environmental Impact
Harnessing solar energy through PV systems is:
• Clean
• Sustainable
• Free (after return on investment)
• Provide electricity to remote areas
Some of its disadvantages include:
• Relatively low efficiency relative to how costly the system’s
equipment are
• Intermittency problems
• Reliability depends on the location
• Environmental impact of PV cell production and disposal

35. Conclusion: Solar Energy
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- There is little price difference between photovoltaic and solar thermal energy
- Photovoltaics may become more affordable as more photovoltaics move to utility
scale installations
- Solar thermal power, however, still has the advantage that it can store power
- Solar technologies are currently much more expensive than other sources of
renewable energy, ie. solar energy is not a cost-effective power generation
system
Relative costs of renewable energy. This figure indicates that both types of solar cost roughly the
same and are approximately 2 times more expensive than any other form of renewable energy.
"2009 Renewable Energy Data Book," U.S. Dept. of Energy, August 2010.

36. Solar PV cost:

37. Examples of Solar PVs
https://www.businessinsider.com/china-panda-shaped-solar-energy-farms-project-2018
6?utm_content=buffer71324&utm_medium=social&utm_source=facebook.com&utm_campaign=bu
ffer-ti&fbclid=IwAR0ujgazSXnbBRFaoxESbg2gIL9Oxp6AFpLYnfRFcY9QS-u4SaiqL2a8VZ8#the-100-
megawatt-52-million-solar-farm-stretches-248-acres-4
Panda Power Plant was completed in
Guigang, Guangxi, in October 2017.
It has an installed capacity of 60
megawatts, enough to accommodate
6,000 homes per year.
The 100-megawatt, $52 million solar
farm stretches 248 acres. Capable of
generating power for more than 10,000
households annually, the plant was
connected to Datong's electricity grid in
June 2017.

38. Solar Concentrator
•These 25-kW Solar Systems dishes installed in Hawthorn, Australia
•The concentrators use an array of mirrors to focus sunlight onto high
efficiency silicon solar cells
• Four supports hold the cells in front of the mirrors
• The supports also supply cooling water and electrical connections
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39. References
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• Godfrey ed. (2012). Renewable Energy: Power for a Sustainable
Future, 3rd Edition (chapter 3).
• McConnell and Fthenakis (2012) "Third Generation
Photovoltaics", ISBN 978-953-51-0304-2, (chapter 7).
• "Annual Energy Outlook 2010," U.S. Energy Information
Administration, DOE/EIA-0383 (2010), April 2011.
• R. Laleman, J. Albrecht, and J. Dewulf, "Life Cycle Analysis to Estimate the
Environmental Impact of Residential Photovoltaic Systems in Regions with a
Low Solar Irradiation," Renewable and Sustainable Energy Reviews 15, 267
(2011).
• Links:
• http://www.solarserver.com/solar-magazine/solar-news/archive-2015
• https://phlebasblog.files.wordpress.com/2014/09/oecd_pv-global-
cumulative-capacity