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 sun's energy to heat
homes for thousands of years but it wasn't until the last century
that we discovered how solar
to generate electricity directly from solar
radiation. In the next few decades, solar technology will continue
to progress, hopefully until the point where we can cost-effectively
transform our society from a dependency on fossil fuels to one based
on free energy from the sun.
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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
currently averages around 20 - 30% (this has been steadily increasing - see article mentioned
above). The remaining solar energy 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,
will become more affordable for the average residential homeowner and thus 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 sun's 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 traveling, away from the power grid, or during a blackout, solar power
can provide cost-effective electricity for small applications. It can also be
used to heat homes,
heat pools, heat water,
and power all sorts of household and garden items like
birdbaths, garden fountains,
Christmas lights, and many others too.
In Amsterdam, there's even a solar bike path!
- Although solar equipment has a large initial cost, it requires minimal
maintenance after installation.
Disadvantages of Solar Power
- Solar power is only generated during daylight hours and when there
is no cloud cover.
- Although maintenance requirements are minimal, maintenance is important --
shadows falling over the solar panel, or any sort of debris or snow
covering the solar panels, can dramatically affect its efficiency.
- 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.