Photovoltaic Energy
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Transcript of Photovoltaic Energy
Photovoltaic Energy
Paolo Abagar, Mario Miguel Celdran, Arjan Delos Santos, Keno Hibaya, Kevin Richard Miraflores, Lovely Jane Vallinas
EE 147
Energy Conversion EECE Department
Mindanao State University – Iligan Institute of Technology Iligan City, Philippines
I. INTRODUCTION
The term "photovoltaic" has two parts: ‘φῶς
(phōs)’ a Greek word meaning light, and ‘volt’, a word
coined in honour of the inventor of the electric battery,
Alessandro Volta ( 1745-1827). It is produced when
sunlight is converted into energy with the use of solar
cells or semiconductors.
-Photovoltaics is the field of technology and
research related to the practical application of
photovoltaic cells in producing electricity from light,
though it is often used specifically to refer to the
generation of electricity from sunlight.
Photovoltaics (PV) is a method of generating
electrical power by converting solar
radiation into direct current electricity using
semiconductors that exhibit the photovoltaic effect.
Photovoltaic power generation employs solar
panels composed of a number of solar cells containing a
photovoltaic material. Materials presently used for
photovoltaics include monocrystalline
silicon, polycrystalline silicon, amorphous
silicon, cadmium telluride, and copper indium gallium
selenide/sulfide. Due to the increased demand
for renewable energy sources, the manufacturing of
solar cells and photovoltaic arrays has advanced
considerably in recent years .
II. HISTORY
Photovoltaic energy has been discovered for
almost two centuries. Photovoltaic effect was first
discovered by a 19 year old French experimental
physicist named Edmund Becquerel while he is
experimenting with an electrolytic cell made up of two
metal electrodes. Until in 1954, Bell Labs researchers
Pearson, Chapin, and Fuller reported their discovery of
4.5% efficient silicon solar cells. Then in 1964 the
Nimbus spacecraft was launched with a 470-W PV
array which was its first practical application.
However, it was not until 1940 that the first
modern solar cell manufacturing began. This used
silicon as the semiconductor material, patented by the
American inventor, Rusell Ohl. In 1955, the American
utility, Western Electric, began to market solar cell
arrays.
The first practical applications for these
devices were in artificial satellites. They were an
efficient way of providing electricity to remote bodies.
Vanguard 1 thus became the first satellite to use a
photovoltaic module to feed the transmitter, which
consumed a mere 5 milliwatts. By the mid-70's,
photovoltaic modules began to be used in different
terrestrial applications. These included clocks, games
and calculators.
Over recent decades, photovoltaic technology
has continued to advance, leading to the development
of photovoltaic systems connected to networks. This
has triggered an industry whose main objective is to
supply modules for large photovoltaic farms to generate
electricity on a quite different scale. In this market, T-
Solar has become the byword for excellence.
III. PROCESS
Photovoltaic (PV) cells are made up of at least
2 semi-conductor layers. One layer containing a
positive charge, the other a negative charge.
The photovoltaic process converts sunlight,
which is the most abundant energy source on the planet,
directly into electricity. The sun emits photons (light),
which generate electricity when they strike a
photovoltaic cell. So in the same way a photovoltaic
cell, made from a semi-conducting material, is a device
that converts light into electricity.
Sunlight consists of little particles of solar
energy called photons. As a PV cell is exposed to this
sunlight, many of the photons are reflected, pass right
through, or absorbed by the solar cell.
When sunlight strikes the solar cell, electrons
are knocked loose and move toward the treated front
surface of the solar cell. This creates an electron
imbalance between the front and back of the cell and
causes electricity to flow – the greater the intensity of
light, the greater the flow of electricity.
Solar cells are made of silicon, a special type
of melted sand, consisting of two or more thin layers of
semi-conducting material, usually silicon. The layers
are given opposite charges – one positive, one negative.
When enough photons are absorbed by the
negative layer of the photovoltaic cell, electrons are
freed from the negative semiconductor material. Due to
the manufacturing process of the positive layer, these
freed electrons naturally migrate to the positive layer
creating a voltage differential, similar to a household
battery.
When the 2 layers are connected to an external
load, the electrons flow through the circuit creating
electricity. Each individual solar energy cell produces
only 1-2 watts. To increase power output, cells are
combined in a weather-tight package called a solar
module. These modules (from one to several thousand)
are then wired up in serial and/or parallel with one
another, into what's called a solar array, to create the
desired voltage and amperage output required by the
given project.
Due to the natural abundance of silicon, the
semi-conductor material that PV cells are primarily
made of, and the practically unlimited resource in the
sun, solar power cells are very environmentally
friendly. They burn no fuel and have absolutely no
moving parts which makes them virtually maintenance
free, clean, and silent.
Illustrations:
Photovoltaic effect was first observed by
French physicist A. E. Bacquerel in 1839. Photovoltaic
effect is directly related to the photoelectric
effect.When the sunlight or any other light is incident
upon a material surface, the electrons present in
the valence band absorb energy and, being excited,
jump to the conduction band and become free.
Illustration:
These highly excited, non-thermal electrons
diffuse, and some reach a junction where they are
accelerated into a different material by a built-in
potential. This generates an electromotive force, and
thus some of the light energy is converted into electric
energy.
IV. TYPES OF PV CELLS
Monocrystalline Silicon Cells
These are made using cells sliced from a single
cylindrical crystal of silicon, this is the most efficient
photovoltaic technology, typically converting around
15% of the sun's energy into electricity. The
manufacturing process required to produce
monocrystalline silicon is complicated, resulting in
slightly higher costs than other technologies.
Polycrystalline Silicon Cells
Also sometimes known as multicrystalline cells, these
are made from cells cut from an ingot of melted and
recrystallised silicon. The ingots are then saw-cut into
very thin wafers and assembled into complete cells;
they are generally cheaper to produce than
monocrystalline cells, due to the simpler manufacturing
process, but they tend to be slightly less efficient, with
average efficiencies of around 12%.
Thick-film Silicon
This is a variant on multicrystalline technology where the
silicon is deposited in a continuous process onto a base
material giving a fine grained, sparkling appearance. Like
all crystalline PV, it is normally encapsulated in a
transparent insulating polymer with a tempered glass
cover and then bound into a metal framed module.
Other Thin Films
A number of other materials such as cadmium telluride
(CdTe) and copper indium diselenide (CIS) are now being
used for PV modules. The attraction of these technologies
is that they can be manufactured by relatively inexpensive
industrial processes, certainly in comparison to crystalline
silicon technologies, yet they typically offer higher
module efficiencies than amorphous silicon. Most offer a
slightly lower efficiency: CIS is typically 10-13%
efficient and CdTe around 8 or 9%. A potential
disadvantage is the use of highly toxic metals such as
Cadmium with the need for carefully controlled
manufacturing and end of life disposal, although a typical
CdTe module contains only 0.1% Cadmium which is
reported to be a lower quantity of the metal than is found
in a single AA-sized NiCad battery.
V. ADVANTAGES
1. Available nearly everywhere
2. Inexhaustible and abundant
3. Clean energy
Solar power is clean energy with little
environmental impact, and does not release air
pollutants or noise while it is being generated.
Compared to other means of generating power
(hydraulic, nuclear, thermal), it demands little in
terms of installation condition or scale. The
distance between the point where the energy is
generated and consumed is therefore short and
keeps power loss minimal during supply. With few
moving parts in its system it has no mechanical
corrosion and long life. Above all, it benefits from
an infinite source of energy.
4. Production end-wastes and emissions are
manageable
5. Noise Free
6. Less transmission/distribution losses
7. protects against rising energy prices
8. Excess heat can be used for co-generation
9. There is room for improvement
10. Long-lasting
11. Maintenance and operating expenses are low
Solar Energy systems are virtually maintenance
free and will last for decades. Once installed, there
are no recurring costs. They operate silently, have
no moving parts, do not release offensive smells and do not require you to add any fuel.
12. Get paid
13. Solar energy systems are now designed for
particular needs. For instance, you can convert
your outdoor lighting to solar. The solar cells are
directly on the lights and can’t be seen by anyone.
At the same time, you eliminate all costs associated
with running your outdoor lighting.
VI. DISADVANTAGES
1. Expensive
This is due to its installation, any regulatory fees,
semi-conducting material used, and infancy.
2. Lack of consistency and reliability
We know that this system relies on the steady
absorption of sunlight. But there are factors that
limit the availability of sunlight:
Latitude – efficacy falls as the distance
from the equator increases.
Clouds/Weather
Night
3. Takes up a lot of space
4. Solar panels consume land, as power generation per
unit square is low
5. Panel deterioration
6. Environmental pollutants - A few of the more
notorious substances contained in panels and associated equipment include:
Cadmium.
Lead
7. Only areas of the world with lots of sunlight and
very low heat are suitable for solar power generation
8. When there is no solar energy to be collected you'll
have to have adequate battery backup to get you
through the nights and rainy days.
9. It takes a considerable amount of solar panels
depending on your location to produce the same amount of electricity
10. Current devices which utilize solar energy are
expensive.
11. Solar panels require quite a large area for installation to achieve a good level of efficiency.
12. Heat degrades the system faster and also degrades in time
VII. APPLICATIONS
1. Power Stations
As of July 2012, the largest photovoltaic (PV)
power plant in the world is the Agua Caliente Solar
Project in USA (247 MW).
Agua Caliente Solar Project
Some use innovative tracking systems that
follow the sun's daily path across the sky to
generate more electricity than conventional fixed-
mounted systems and there are no fuel costs or
emissions during operation of the power stations.
CEPALCO’S 1mwp Photovoltaic Power Plant
From the start of its commercial operations on
September 26, 2004, the PV plant has exported to
CEPALCO a total of 4,169,100 kWh or an average
of 1,389,700kWh annually
CEPALCO’s 1MWp plant, with installed costs
close to 5.3 Million US Dollars, uses 6,500 solar
panels on 2 hectares of land
2. In Buildings (Building-Integrated Photovoltaics
(BIPV)) and Rural Electrification
Photovoltaic arrays are often associated with
buildings or houses: usually mounted on top of the existing roof structure or on the existing walls.
Building-integrated photovoltaics (BIPV) are
increasingly incorporated into new domestic and
industrial buildings as a principal or ancillary source of electrical power.
A 2011 study using thermal imaging has
shown that solar panels, provided there is an open
gap in which air can circulate between them and
the roof, provide a passive cooling effect on
buildings during the day and also keep accumulated heat in at night.
3. In Transport
PV has traditionally been used for electric
power in space. It is being used increasingly to
provide auxiliary power in boats and cars. A self-
contained solar vehicle would have limited power
and low utility, but a solar-charged vehicle would allow use of solar power for transportation.
SINAG is the Philippines’ first entry to the
World Solar Challenge
4. Standalone devices
PV was used frequently to power calculators
and novelty devices.
Solar powered remote fixed devices have seen
increasing use recently in locations where significant
connection cost makes grid power prohibitively
expensive.
VIII. REFERENCES
[1.] http://www.solarenergy.net/Articles/how-
photovoltaic-cells-work.aspx
[2.] https://en.wikipedia.org/wiki/Photovoltaic_system
[3.] http://pveducation.org/pvcdrom/solar-cell-
operation/photovoltaic-effect
[4.] http://www.triplepundit.com/2012/04/solar-
photovoltaics-pros-cons/
[5.] http://www.triplepundit.com/2012/04/solar-
photovoltaics-pros-cons/
[6.] http://www.solarguide.co.uk/solar-pv
[7.] http://www.solarpowerplanetville.com/photovolta
ic-solar-panels-advantages-and-disadvantages
[8.] http://www.renewableenergyworld.com/rea/blog/
post/2012/12/advantages-and-disadvantages-of-
solar-photovoltaic-quick-pros-and-cons-of-solar-
pv
[9.] http://www.nef.org.uk/greencompany/active-pv-
cells.htm
[10.] http://www.tsolar.com/en/portal.do?IDM=242&N
M=2
[11.] http://www.powersourcesolar.com/5151/