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DESCRIPTIONOverview of Photovoltaic Energy and its uses.
Paolo Abagar, Mario Miguel Celdran, Arjan Delos Santos, Keno Hibaya, Kevin Richard Miraflores, Lovely Jane Vallinas
Energy Conversion EECE Department
Mindanao State University Iligan Institute of Technology Iligan City, Philippines
The term "photovoltaic" has two parts: (phs) 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 .
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
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
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.
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
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
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.
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.
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
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%.
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.
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.