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Thermal Technology
What is thermal
technology?
BY JANE MCGRATH
Whenever
the cost of gas starts burning holes in our wallets, we start paying
closer attention to the development of alternative energy technology.
Right
now, one of those up-and-coming technologies is thermal
technology, which uses one of the most common forms of energy: heat.
To
understand the technology, we have to know a little about thermodynamics, which is the study of the
laws that govern the movement of heat.
Although
the word may seem intimidating, we already understand the basics of
thermodynamics through common sense.
For
instance, we know that if we were to put a hot cup of coffee in a
freezer, it wouldn't take long for the coffee to cool down. This is because
heat travels from hot things to cold things.
The
heat travels from the hot coffee and escapes into the freezing cold air and
will continue until the air and the coffee are the same temperature.
The
term thermal technology can be a confusing one because people use it so
broadly.
Generally,
when people use the term "thermal technology," they mean the ways we
can use heat to do what we want.
For
instance, some people use the term thermal technology to refer to climate
control -- for example, stopping the movement of heat with insulation, or
changing the temperature in a room.
Because
heat always wants to travel from hot to cold, it's difficult to make it go in
the other direction. In fact, it's impossible according to the laws of
thermodynamics.
Air
conditioning units, however, use special fluids that can work within these laws
to make a room colder.
Some
electronics, such as thermal fax machines are also said to use thermal
technology.
These
electronics use heat to do their job, as opposed to climate control units,
which move heat around to do their jobs.
A
thermal fax machine, for example, generates heat from electricity in its
print head. Then, it applies this heat to special thermal paper or through a
transfer ribbon to print faxes.
This
method makes for a simple, durable fax machine that doesn't even need ink
cartridges to work.
Turning
heat into useful energy is difficult, but advancements in the field of thermal
technology have made it more possible than ever before.
Perhaps
the most exciting application of thermal technology has to do with capturing
the sun’s heat to produce electricity.
Next,
we'll find out how this is possible and why some believe it's the energy of the
future.
Scientists
have known for a long time that the sun’s beams carry an enormous amount of
energy down to earth in the forms of light and heat.
However,
it's been a challenge to tap this energy and efficiently convert it into usable
electricity.
Photovoltaic
(PV) panels, for instance, can convert the
sun's light into electricity to power a household or building to some extent,
but remain comparatively expensive or inefficient.
Some
believe that solar thermal technology, however, is the Holy Grail for cheap,
clean, renewable energy.
Whereas
fossil fuels may lead to global climate change and are becoming more expensive,
solar thermal energy is clean and might soon become competitively priced.
By
converting the sun's heat into usable electricity, this technology could help
wean countries off fossil fuels.
Solar
thermal power doesn't convert solar energy directly to electricity like PV
panels do.
Instead
it does so indirectly -- often using heat to turn water to steam.
And,
much like in fossil-fueled power plants, this steam can turn a turbine that
powers an electric generator.
A
few different systems can collect solar heat:
·
Solar tower: When surrounded by heliostats,
which are special mirrors that track the sun, a solar tower can collect the
sun's energy.
The centralreceiver at the top of the tower
collects and stores heat in special liquid salts that are transported from the
tower to a steam generator.
·
Parabolic troughs: This kind of system uses the shape of parabola to
intensify heat and collect it from the sun no matter what time of day.
Tubes filled with
a special fluid run through this system. As the special fluid travels by, it
warms up and essentially "collects" the heat.
The fluid then carries its heat to the water, which
converts to steam. What's special about the fluid is that it is an oil that can
reach temperatures of 750 degrees Fahrenheit (400 degrees Celsius) [source: Biello].
Molten salts can store extra heat for use when the sun
isn't available.
·
Fresnal reflector: Instead of heating fluid, this mechanism heats water
directly. It can do this efficiently by increasing the atmospheric pressure.
This steam can then go on to power a turbine.
· Solar dish:
These move with the sun to collect heat all day. Using mirrors, they reflect
sunlight onto a focal point.
They then convert this heat to
mechanical power by heating a compressed fluid. Then, expanding that hot
compressed fluid can operate a piston and create useful energy.
The California Mojave
Desert is home to power plants that use parabolic troughs as well as solar towers. Various countries, such as Spain, Morocco and Israel, are building or planning to build solar thermal power plants as well [source: Wald].
Desert is home to power plants that use parabolic troughs as well as solar towers. Various countries, such as Spain, Morocco and Israel, are building or planning to build solar thermal power plants as well [source: Wald].
How
can plants like these help countries that don't get much sun?
Some
say it's quite feasible to install a system of transmission lines that would
carry high-voltage direct current long distances.
This
way, countries rich with sun could erect solar thermal power plants and send
this power to places that don't get as much sun.
As
the technology develops, some believe it will soon become cheap enough to
compete with fossil fuels, especially with the help of high taxes on carbon
emissions. Specifically, this might work if the price of solar thermal power
comes down to about 10 cents per kilowatt-hour [source: Biello].
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