Civil Engineering Reference
In-Depth Information
the increased current coming from parallel connections, although the cell
voltage is not sensitive to light intensity, the current is affected. This struc-
ture enables a variety of voltage and current options to be available depen-
ding on the user's requirements. The steps (Table 12.1) of the process that
is undertaken in the cell are highlighted below but it needs to be noted that
when sunlight hits the panel not all energy is directly converted to direct
current (DC) electricity, as the light can either be absorbed, refl ected or
move straight through the cell.
A common assumption by many is that this principle will only work on
sunny days. This is incorrect; solar power works to its maximum when there
are no clouds in the sky and the sun is in its optimum position, but it will
also operate without maximum sun, albeit slightly less effi ciently. Out of the
many renewable energy technologies, it is suspected that solar power could
have the brightest future, not only because of potential advancements in
materials and production methods but also because of some basic enginee-
ring principles embedded in the technology. PV cells currently produce
approximately 1.5 W, dependent on size, so when they are placed together
in a matrix form on a frame covered in glass, this is referred to as a module
raising possible output. Several modules can be furthermore connected
together in an array to provide any power combination required; hence in
this confi guration output power is not an issue. As with all innovations, PVs
have positive and negative points as outlined in Table 12.2; however, resear-
Table 12.1
Steps in producing electricity from the sun
Step
Description
1
Solar panel is struck by photons contained in sunlight
2
In the semiconductor material, negative electrons are knocked
loose from their atoms
3
Enabling movement in a single direction in the material
4
Creating the possibility of an electric circuit from the electrons
5
Provided the negative and positive of the cell are connected,
then DC electricity is generated
Table 12.2
Photovoltaic advantages and disadvantages
Advantages
Disadvantages
No moving parts
High costs
Operates quietly
Low effi ciency
No operating emissions
More expensive than fossil fuels
Long term use
Limited-maintenance
Modular - enabling gradual expansion
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