Page 162 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

The incident light breaks the thermal equilibrium condition of the junction. The free electrons in the depletion
region can quickly come to the n-type side of the junction. Similarly, the holes in the depletion can quickly come
to the p-type side of the junction. Once, the newly created free electrons come to the n-type side, cannot further
cross the junction because of barrier potential of the junction. Similarly, the newly created holes Nonrenewable, or
“dirty,” energy includes fossil fuels such as oil, gas, and coal. Nonrenewable sources of energy centration of holes
becomes more in another side, i.e. the p-type side of the junction, the p-n junction will behave like a small battery
cell. A voltage is set up which is known as photo voltage. If we connect a small load across the junction, there will
be a tiny current flowing through it. Commonly used materials are-Silicon, GaAs, CdTe etc.
Criteria for Materials to be Used in Solar Cell
1 Must have band gap from 1ev to 1.8ev

2 It must have high optical absorption.
3 It must have high electrical conductivity.
4 The raw material must be available in abundance and the cost Of the material must be low.
Basic of Photo voltaic cell

A solar cell (also known as a photovoltaic cell or PV cell) is defined as an electrical device that converts light
energy into electrical energy through the photovoltaic effect. A solar cell is basically a p-n junction diode. Solar
cells are a form of photoelectric cell, defined as a device whose electrical characteristics – such as current,
voltage, or resistance vary when exposed to light.
Individual solar cells can be combined to form modules commonly known as solar panels The common single
junction silicon solar cell can produce a maximum open- circuit voltage of approximately 0.5 to 0.6 volts. By itself
this isn’t much but remember these solar cells are tiny. When combined into a large solar panel, considerable,
amounts of renewable energy can be generated.
Construction of Solar Cell
A solar cell is basically a junction diode, although its construction it is little bit different from conventional p-n
junction diodes. A very thin layer of p-type semiconductor is grown on a relatively thicker n-type semiconductor.
We then apply a few finer electrodes on the top of the p-type semiconductor layer. These electrodes do not
obstruct light to reach the thin p-type layer. Just below the p- type layer there is a p-n junction. We also provide
a current collecting electrode at the bottom of the n-type layer. We encapsulate the entire assembly by thin glass
to protect
Module Panel and Array

A solar cell is the basic building block of a solar module. Each cell produces approximately 1/2 a volt and a solar
module can have any number of solar cells. A solar module designed for charging a 12 volt battery will typically
have 36 solar cells while the typical residential grid connected system uses solar modules with 60 solar cells. For
large commercial and utility scale solar systems, solar modules will have typically 72 solar cells. By increasing
the number of solar cells the module voltage and wattage increases.
Most solar cells manufactured today are approximately 6″ by 6″. Small custom solar modules will contain solar
cells that are cut to smaller sizes. For example if a full size solar cell produces 10 amps and it is cut in half it will
now only produce 5A. As the solar cell is cut in half, its typical voltage remains unchanged at 1/2 a volt.
Factor that influence the output of a PV Module

The major that affect the output of module are load resistance ,sunlight intensity (module direction and tilt ), cell
temperature, shading soiling , module mismatch , invertor conversion losses and solar cell structure.

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CITS : E & H - Electronics Mechanic - Lesson 90 - 93