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How Solar Power Works - the Basics
The sun has been providing heat and light to the earth since the
beginning of time. Humans have been using the sunís energy to heat
homes for thousands of years but it wasnít until the last century
that we discovered how solar
power works to generate electricity directly from solar
radiation. In the next few decades, solar technology will progress
to the point where we can cost-effectively transform our society
from fossil fuels to one based on the free energy of the sun.
Solar radiation can be harnessed in two ways, to produce
electricity and to produce heat.
Solar Power - Photovoltaic
Photovoltaic cells (PV cells or solar cells)
convert sunlight directly into electricity. When sunlight strikes the cell,
it causes electrons to flow from one side of semiconductor material, through
an external circuit and then back to another side of the PV cell. This
direct current (DC) can be used to charge batteries or inverted to create
alternating current (AC) to run household appliances.
The efficiency of existing solar panels is around 20 ≠ 30 %. The
remaining solar energy (70 ≠ 80%) is turned into heat rather than
electricity. Since the amount of generated current is still quite
low, solar panels are relatively expensive compared to other
generation technology (i.e. hydro, coal, nuclear). As the efficiency
of solar cells increase and manufacturing techniques improve, they
will become cheaper for the average residential household and become
more widely used.
The warmth of the sun can be used to generate heated air that can
be distributed throughout a building. The easiest application is to
allow sunlight to stream threw a window where radiant heat warms the
indoor air (passive heating). More sophisticated heaters use solar
collectors such as walls, roofs and panels to gather the sunís heat
and transfer it to a heat-collecting fluid (i.e. water, ethylene glycol).
In an active solar heater, a machine such as a ceiling fan is
used to move the warm air from the collector and to other parts
of the building. More elaborate and efficient methods use fluid
systems in which a pump and tubes transport the warmed liquid
to radiators. For large buildings, storage tanks collect the
heated fluid throughout the day for later use.
Advantages of Solar Power
- Sunlight is plentiful, clean and free. No pollution is created.
- When away from the power grid, solar power
can provide cost-effective electricity for small applications.
- Although solar equipment has a large initial cost, it requires very little
maintenance after installation.
Disadvantages of Solar Power
- Solar power is only generated during daylight hours and when there
is no cloud cover.
- The best locations for producing solar power are arid, uninhabited
locations which may not be close to where the power is needed.
Transmission lines are costly to install.
- The intensity of the sun changes from season to season and the
effect is more pronounced the further away from the equator. This
energy fluctuation may not satisfy the local energy requirement.
- Solar power generators are expensive to build (large amount of
land and expensive equipment). Even passive solar collectors (i.e.
more windows) add to the construction cost of new buildings.
Retrofits are expensive.
The type of solar generator and how solar power works for your
application depends on location, time of year and the amount of
energy required. Since the space needed for solar panels is
large, energy conservation may help reduce the energy requirement
to within the amount of heat and power produced.