| SOLAR
THERMAL POWER PLANTS TECHNOLOGIES (DEMONSTRATION UNITS)
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The
scenario has thrown new fears on renewable energy resources
like solar, wind, Biogas etc. Renewable technologies promise
not only energy security at affordable cost but can speed
up the development of rural areas. Among renewable resources
Concentrating Solar Power Plants is one of the best suited
technologies to help, in an affordable way, mitigate climate
change as well as reduce the consumption of fossil fuels.
There are two types of Solar Thermal Technologies that are
mature and are being installed in many developed places
such as USA, Spain, Israel, Greece, and developing countries
like Mexico, Morocco, India and Egypt. These technologies
are as follows: |
Solar
Dish Stirling Engine Technology: |
A
solar dish/engine system utilizes solar energy as the source
energy to heat the working fluid of a Stirling engine which
drives an electric generator. Essentially the system consists
of parabolic solar concentrator, tracking system, receiver
and Stirling engine with generator. The compactness of the
system makes it well suited for remote operations. The power-generating
equipment, i.e. solar heat exchanger/ receiver and Stirling
engine, is mounted at the focal point of the solar dish.
The engine converts heat to mechanical power by compressing
the working fluid (Helium or Hydrogen) when it is cold,
heating the compressed working fluid, and then expanding
the fluid with a piston to produce work. The engine is coupled
to an electric generator to convert the mechanical power
to electric power. The capacity of a single unit is typically
from 5 to 25 kW. These are ideal for stand alone and or
other decentralised application.
Fig-1
|
Solar
Parabolic Trough Technology: |
This
system also utilizes solar energy as a heat source to generate
steam which in turn runs a steam turbine which is used to
generate electricity. Essentially the system consists of
collectors, the fluid transfer pumps, the power generating
system, the natural gas auxiliary subsystem, and the controls.
In this system solar radiation incident on the parabolic
trough is reflected on to a receiver tube in which flows
the working fluid. This fluid is heated up to 300 ºC.
This hot fluid is then used to produce steam to run the
steam turbine. Steam cycle power plants up to 80 MW capacity
using parabolic trough collectors have been in commercial
operation for more than 15 years. Nine plants with a total
of 354 MW of installed power are feeding the California
electric grid with 800-million kWh/ year at a cost of about
10-12 cents/kWh.
Fig-2
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Advantages
of the Technology: |
 |
The potential life cycle of the Stirling engine is
extraordinarily high since there is no internal pollution
of the piston & bearing due to combustion of fuels. |
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Parabolic trough concentrator can be used for utility
scale generation of solar steam for process heat application
and solar power generation. |
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Both the dish and parabolic trough technologies can
be additionally be powered by fossil or bio-mass (i.e.
biogas). Thus the system is also available to operate
during the cloudy or night-time. |
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The systems fulfill all the requirements that can
be demanded from a future-oriented, environmentally
friendly energy system. |
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Tracking system of the dish/collectors is controlled
by sun sensors to meet the peak power demands during
summer time and its sales bring greatest revenue. |
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Thermal
storage for at least 3 hours further reduces the cost
of delivered energy. |
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Reduce
dependence on the fossil fuels. |
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