solar cells and its applications
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Solar C
ells
&Its
Applicatio
ns
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The Solar Cell• The most common type of solar cells are Photovoltaic
Cells (PV cells)• Converts sunlight directly into electricity• Cells are made of a semiconductor material (eg. silicon)• Light strikes the PV cell, and a certain portion is
absorbed• The light energy (in the form of photons) knocks
electrons loose, allowing them to flow freely, forming a current
• Metal contacts on the top and bottom of PV cell draws off the current to use externally as power
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Why Use Solar Cells?• Low maintenance, long lasting sources of energy• Provides cost-effective power supplies for people
remote from the main electricity grid• Non-polluting and silent sources of electricity• Convenient and flexible source of small amounts
of power• Renewable and sustainable power, as a means to
reduce global warming
• In 2002, the global market for photovoltaic panels and equipment was valued at 3.5 billion dollars
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The Single Crystalline Silicon Solar Cell• Pure silicon is a poor
conductor of electricity• “Doping” of silicon with
phosphorus and boron is necessary to create n-type and p-type regions
• This allows presence of free electrons and electron-free ‘holes’
• The p-n junction generates an electric field that acts as a diode, pushing electrons to flow from the P side to the N side
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The Solar Cell
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When Light Hits the Cell
• Light energy (photons) ionizes the atoms in the silicon and the internal field produced by the junction separates some of the positive charges (holes) from the negative charges (electrons)
• The holes are swept into the p-layer and the electrons are swept into the n-layer
• The charges can only recombine by passing through an external circuit outside the material
• Power is produced since the free electrons have to pass through the load to recombine with the positive holes
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Efficiency of Solar Cells• The amount of power available from a PV device
is determined by– Type and area of the material– The intensity of the sunlight– The wavelength of the sunlight
• Single crystalline solar cells 25% efficency• Polycrystalline silicon solar cells less than
20%• Amorphous silicon solar cells less than 10%
• Cells are connected in series to form a panel to provide larger voltages and an increased current
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Arrays and Systems
• Panels of solar cells can be linked together to form a larger system – an array
(a) a PV panel array, ranging from two to many hundreds of panels;(b) a control panel, to regulate the power from the panels;(c) a power storage system, generally comprising of a number of specially designed batteries;(d) an inverter, for converting the DC to AC power (eg 240 V AC)(e) backup power supplies such as diesel startup generators (optional)(f) framework and housing for the system(g) trackers and sensors (optional);
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Solar Cells are used in a wide variety of
applications• Toys, watches, calculators
• Electric fences
• Remote lighting systems
• Water pumping
• Water treatment
• Emergency power
• Portable power supplies
• Satellites
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Future Applications
• Looks like denim
• Can be draped over any shape
• No rigid, silicon base
• Made of thousands of flexible, inexpensive solar beads between two layers of aluminum foil
• Each bead functions as a tiny solar cell
The Flexible Solar Cell
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Future Applications
• Based on photosynthesis in plants• Use of light-sensitive dyes• Cost of manufacture is decreased by
60%
Organic Solar Cells
New Alloys
• Indium, gallium, and Nitrogen
• Converts full spectrum of sunlight from near-infrared to far-ultraviolet
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Future Applications• Tiny rods are embedded
in a semi-conducting plastic layer sandwiched between two electrodes
• Rods act like wires, absorbing light to create an electric current
Nano Solar Cells
Tetrapod Nanocrystals
• May double the efficiency of plastic solar cells
• Made of cadmium, tellurium
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Thank you all…!!!
Devendra.J