Solar Thermal Technology
Solar thermal technology is
one of the two methods used to harness solar energy for
domestic and commercial use. The other technology currently
in use is photovoltaics. Solar thermal technology harvests
sunlight and uses it directly without converting it into any
other form.
This
technology uses solar energy as heat and does not rely on
batteries for storage. This results in cost benefits as
compared with solar photovoltaic technology. It costs far more
to store electricity than to store
heat.
How does solar
thermal technology harness sunlight to enable us to use it to
power our appliances and systems? Basically, this technology
uses large parabolic mirrors or reflectors to focus sunlight in
order to generate heat. This in turn heats oil contained in
glass tubes to roughly 370 degrees centigrade. The hot oil is
then used to convert water into steam. This steam powers
turbines that produce electricity using the method of
electromagnetic induction.
The devices
used to concentrate the sun’s rays are also known as
collectors. These collectors come in low, medium and high
temperature versions. Depending on the temperature capacity,
collectors serve specific purposes. For example, low
temperature collectors are usually in the form of flat plates
and are used to heat swimming pools. Medium temperature
collectors, which are often in flat plate form as well, are
employed in water heating systems for residential and
commercial purposes. It is, however, the high temperature
collectors, which are normally used to produce electric power
for general use.
Popular
consumer applications, which use solar thermal technology, are
solar cookers and water heaters. Solar water heaters are now
considered cost effective and convenient substitutes for
electric water heaters. They are economical, safe and simple to
use and reliable.
Solar thermal
technology produces clean power. Unlike conventional
electricity generation, this system does not produce
environmentally degrading carbon
emissions.
While this
method of generating power is currently expensive, efforts are
on to reduce production costs thereby making it a viable
alternative to non – renewable energy sources. Currently, it is
cheaper to produce electricity using coal than
sunlight.
Concentrated
solar power technology or CSP can prove to be viable if applied
efficiently. This technology uses parabolic mirrors shaped to
resemble very long troughs, which focus sunlight onto tubes
that contain molten salt. These salts in turn store heat, which
is used in thermal power plants. Modern thermal plants are
working towards bring down electricity costs to Rs.4 per unit.
With properly implemented technological improvements, CSP
plants can eventually generate electricity at competitive
prices. The major drawback of solar thermal technology is that
it requires immediate and direct sunlight. Cloudy conditions
render this method ineffective. Similarly, no power can be
produced after sundown. Solar thermal power companies are
working on developing viable and cost – effective storage
solutions to store heat for use in the absence of direct
sunlight.
The Indian
Government is actively encouraging and assisting the setting up
of solar thermal power plants. According to Government
estimates, around 50, 000 MW of power can be sourced from
renewable energy alternatives. Private sector companies engaged
in producing power from renewable energy sources are given tax
incentives. A mega 35MW solar thermal plant is being set up in
Rajasthan with a view to demonstrate that solar thermal power
production using the parabolic trough method is functionally
doable and to focus on the development of this technology in
order to reduce costs. Also, this is an eco – friendly
technology and contributes to the reduction of greenhouse gas
emissions in the long run. The effectiveness and overall
success of this project would, it is anticipated, lead to the
use of this technology in other parts of the country and
gradually minimise our dependence on polluting fossil
fuels.
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