Transcript SOLAR ENERGY The Law of Conservation of Energy: •Energy can only change from one form to another. •Energy can not be created.

SOLAR ENERGY
The Law of Conservation of Energy:
•Energy can only change from one form to another.
•Energy can not be created or destroyed.
We have always used solar energy as far back as humans have existed
on this planet.
We use the solar energy every day in many different ways.
1. When we hang laundry outside to dry in the sun, we are using the
solar heat to do work, drying our clothes.
2. Plants use the solar light to make food. Animals eat plants for food.
3. decaying plants hundreds of millions of years ago produced the
coal, oil and natural gas that we use today.
4. Even nuclear energy comes from a star because the uranium atoms
used in nuclear energy were created in the fury of a nova - a star
exploding.
Photovoltaic materials produce electrical power from sunlight.
The basic component of photovoltaic power conversion is the
solar cell.
The history of photovoltaic materials goes back to 1839 when
Edmund Becquerel discovered the photo galvanic effect:
where electric currents were produced from light induced
chemical reactions.
However it was not until 1954 that the first solar cell was
developed with an efficiency of 6%: efficiency = power
output/available solar power.
Solar cells found their first use in powering satellites, however
their use for terrestrial power production has been growing
rapidly.
1. A solar cell is a device that converts the energy of sunlight directly
into electricity by the photovoltaic effect.
• The word Photovoltaic is a combination of the Greek
word for Light and the name of the physicist
Allesandro Volta.
• It identifies the direct conversion of sunlight into
energy by means of solar cells.
• The photoelectric effect discovered by Alexander
Bequerel in 1839.
• The photoelectric effect describes the release of
positive and negative charge carriers in a solid state
when light strikes its surface.
2. Solar cells are composed of various semi-conducting materials.
Semiconductors are materials, which become electrically conductive
when supplied with light or heat, but which operate as insulators at
low temperatures.
Over 95% of all the solar cells produced worldwide are composed of the
semiconductor material Silicon (Si).
As the second most abundant element in earth`s crust, silicon has the
advantage, of being available in sufficient quantities, and additionally
processing the material does not burden the environment.
To produce a solar cell, the semiconductor is contaminated or "doped".
"Doping" is the intentional introduction of chemical elements, with
which one can obtain a surplus of either positive charge carriers (pconducting semiconductor layer) or negative charge carriers (nconducting semiconductor layer) from the semiconductor material.
If two differently contaminated semiconductor layers are combined, then
a so-called p-n-junction results on the boundary of the layers.