Types of Solar Power and How They Work by zsg11761


									Types of Solar Power and How They Work                work because the silicon substrate has a weak
                                                      grip on its electrons. The cells are made of two
The term "solar energy" usually refers to ways        layers of silicon, one with too many electrons
the sun's energy can be used as heat, lighting,       (the n-layer) and one with too few (the p-layer).
and electricity.                                      When light hits the first layer, electrons are
                                                      knocked loose. As they flow toward the layer
One simple, obvious use of sunlight is to light       with too few electrons, they pass through an
our buildings. The sun can also affect a              electric circuit, the current from which can be
building's heating and cooling costs: If properly     used to power equipment and devices.
designed, a building can capture the sun's heat in
the winter and reject it in the summer, while         In the 1970s, a serious effort began to produce
using daylight year round for lighting.               photovoltaic panels that could provide cheaper
                                                      solar power. Experimenting with new materials
Solar Energy Collectors/ConcentratorsBesides          and production techniques, solar manufacturers
using design features to maximize use of the sun,     cut costs for solar cells rapidly, as the following
some buildings have active systems to gather and      graph shows.
store solar energy. Solar collectors sit on the
rooftops of buildings to collect solar energy for     Many solar panels are used today to power
space heating, water heating, and space cooling.      cellular phone transmitters, road signs, and water
Most solar collectors are large flat boxes, painted   pumps, as well as millions of solar watches and
black on the inside, with glass covers. In the        calculators. But most of the market for solar
most common design, pipes in the box carry            electric is concentrated in off-grid homes, in the
liquids that take the heat from the box and bring     villages of developing countries and the vacation
it into the building. This heated liquid, usually a   homes of industrial countries. Developing
water-alcohol mixture to prevent winter freezing,     nations see PV as a way to avoid building long
is used to heat water in a tank or is put through     and expensive power lines to remote areas.
radiators to heat the air.
                                                      Recently, even utilities in developed countries
Oddly enough, because of the cooling effect           have been attaching photovoltaics to their power
moist air has when it evaporates, solar heat can      grids. In some locations, it is less costly and
also drive a cooling system. Such systems are         politically difficult to install distributed solar
currently at work in humid southeastern               panels than to upgrade the transmission and
climates, like that of Florida.                       distribution system needed to meet ever-growing
                                                      electricity demand.
By using mirrors and lenses to concentrate the
rays of the sun, solar thermal systems produce        This distributed-generation approach provides a
high temperatures that can be used to heat water      new model for the utility systems of the future.
for producing steam to drive an electric turbine      Small generators, spread out in a city and
or for industrial applications, like boiling water    controlled by computers, could replace the large
to sterilize soup cans.                               coal and nuclear plants that dominate now.

Solar concentrators come in three main designs:       As the cost of photovoltaic systems continues to
parabolic troughs, parabolic dishes and central       decline, they will find increasingly larger niches.
receivers. The most common is parabolic               No other electrical generator is as easy to install
troughs—long, curved mirrors that concentrate         or maintain. Even among the various types of
sunlight on a liquid inside a tube that runs          renewable energy, photovoltaics have great
parallel to the mirror. Parabolic dish                potential. The cells are made of silicon, one of
concentrators and central receivers can produce       the most plentiful materials on earth, and they
much higher temperatures and produce                  draw power from the everlasting sun, so they
electricity more efficiently but are more             will never run into the problem of fuel scarcity.
complicated and are not in common use.                As PV prices continue to fall, solar power will
                                                      become a significant source of electricity in the
Solar Energy – Photovoltaics (PV)In 1839,             21st century.
French scientist Edmund Becquerel discovered
that certain materials would give off a spark of
electricity when struck with sunlight. Solar cells

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