Basics of Photovoltaic cell

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Photovoltaic or Solar Cell
Contents:
•Definition
•Construction of Photovoltaic Cell
•Working of Photovoltaic Cell
•Combination of PV Cells
Series Combination
Parallel Combination
Series-Parallel Combination
•Advantages
•Disadvantages
•Applications
Dr. M V Raghavendra,
Dept of Electronics & Communication

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Definition:
•The Photovoltaic cell is the semiconductor device that converts the light into
electrical energy.
•The voltage induced by the PV cell depends on the intensity of light incident
on it.
•The name Photovoltaic is because of their voltage producing capability from
light (Photons).
•The electrons of the semiconductor material are joined together by the
covalent bond.
•The Light energy is made of small energy particles called photons.
• When the photons incident on the semiconductor material, then the
electrons are energized and starts emitting.
•The energized electron are known as the Photoelectrons.
•And the phenomenon of emission of electrons is known as the
photoelectric effect.
•The working of the Photovoltaic cell depends on the photoelectric effect.
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•The semiconductor materials like arsenide, indium, cadmium, silicon, selenium
and gallium are used for making the PV cells.
•Mostly silicon and selenium are used for making the cell.
•Consider the figure below shows the constructions of the silicon photovoltaic
cell.
•The upper surface of the cell is made of the thin layer of the n-type material so
that the light can easily enter into the material.
•Two metal contacts at p-type and n-type material which acts as their positive
and negative output terminals respectively.
•The multi-crystalline or mono-crystalline semiconductor material make the
single unit of the PV cell.
•The output voltage and current obtained from the single unit of the cell is very
less.
•The magnitude of the output voltage is 0.6v for a single cell.
Construction of Photovoltaic Cell
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Construction of Photovoltaic Cell
Note:
Always
Photovoltaic Cell
is connected in
reverse bias
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Working of PV cell
•The PV cell is made of the semiconductor material which is neither a
complete conductor nor an insulator.
•The light incident on the semiconductor material may pass through it.
•This property of semiconductor material makes it more efficient for
converting the light energy into electric energy.
•When the semiconductor material absorbs light, the electrons of the
material starts emitting.
•This happens because the light consists small energized particles called
photons. When the electrons absorb the photons, they become energized
and starts moving into the material.
•Because of the effect of an electric field, the particles move only in the one
direction and develops current.
•The semiconductor materials have the metallic electrodes through which the
current goes out of it.
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•Consider the figure below shows the PV cell made of silicon and the resistive load is
connected across it.
•The PV cell consists the P and N-type layer of semiconductor material.
•These layers are joined together to form the PN junction.
•The junction is the interface between the p-type and n-type material.
•When the light fall on the junction the electrons starts moving from one region to
another.
Working of PV cell
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The different combinations of cells are used for increasing the
output efficiency.
There are three possible ways of combining the PV cells.
• Series Combination
• Parallel Combination
• Series-Parallel Combination
Combination of PV Cells
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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 input voltage becomes doubles.
•The graph below shows the output characteristic of the PV cells when connected in
series.
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Parallel Combination of PV cells
In the parallel combination of the cells, the voltage remains same, and the
magnitude of current becomes double.
The characteristic curve of the parallel combination of cells is represented below.
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Series-Parallel Combination of PV cells
In the series-parallel combination of cells the magnitude of both the voltage and
current increases.
Thereby, the solar panels are made by using the series-parallel combination of the
cells.
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Solar Module & Solar Panel
The solar module is constructed by connecting the single solar cells.
And the combination of the solar modules together is known as the solar panel.
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Advantages of Photovoltaic Cells:
Environmental Sustainability: Photovoltaic cells generate clean and green energy as
no harmful gases such as Co2, NO2 etc are emitted. Also, they produce no noise
pollution which makes them ideal for application in residential areas.
Economically Viable: Operation and maintenance cost of cells are very low. The cost
of solar panel incurred is only the initial cost i.e., purchase and installation.
Accessible: Solar panels are easy to set up and can be made accessible in remote
locations or sparsely inhabited areas at a lesser cost as compared to conventional
transmission lines. They are easy to install without any interference to the residential
lifestyle.
Renewable: Energy is free and abundant in nature.
Cost: Solar panels have no mechanically moving parts except in some highly advanced
sunlight tracking mechanical bases.
Consequently, the solar panel price for maintenance and repair is negligible.
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Disadvantages of Photovoltaic Cells:
•The efficiency of solar panels is low compared to other renewable sources of
energy.
•Energy from the sun is intermittent and unpredictable and can only be
harnessed in the presence of sunlight. Also, the power generated gets reduced
during cloudy weather.
•Long range transmission of solar energy is inefficient and difficult to carry.
•The current produced is DC in nature and the conversion of DC current to AC
current involves the use of additional equipments such as inverters.
•Photovoltaic panels are fragile and can be damaged relatively easily.
•Additional insurance costs are required to ensure a safeguard to the
investments.
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Applications of Photovoltaic Cells:
•Solar Water Heating
•Solar-distillation
•Solar-pumping
•Solar Drying of Agricultural and Animal Products
•Solar Cooking
•Solar Electric Power Generation
•Solar Thermal Power Production
•Solar cars,
•solar trams,
•solar buses and
•Street lights also seen to operate with the help of solar energy.
•Small gadgets that involve little energy, such as calculators, watches.
• Nano-technology
•Satellite Communication
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