A solar
turbine power plant uses the energy in solar radiation captured by
so-called solar collectors. Solar power is a renewable source of
energy. The solar radiant energy reaching the earth's surface is around 1.783*1014 KJ
or 1.353kJ/s per square meter. Solar plants provide energy ranging from a
few kilowatts to a few megawatts. The constraints associated with solar plants
are size, space, high capital cost, and the inevitable fluctuations in the
daily supply of solar radiant energy.
Concentrating
solar power (CSP) is a utility-scale renewable energy option for generating
electricity that is receiving considerable attention in the southwestern United
States and other sunbelts worldwide.
Although
many people think of photovoltaic (PV) cells when thinking about solar power,
CSP technologies that concentrate sunlight to create heat that can be used to
generate electricity are also becoming more popular. While there are some PV
cells that utilize concentration, the focus of this article and most CSP
applications is on technologies where concentrated solar energy heats a fluid,
gas, or solid which is then used to generate electricity using steam.
CSP
technologies use mirrors to reflect and concentrate sunlight onto receivers
that collect the solar energy and convert it to heat. The thermal energy can
then be used to produce electricity via a steam turbine or heat engine driving
a generator. CSP systems can be classified by how they collect solar energy: 1)
power tower systems, 2) linear concentrator systems, and 3) dish/engine
systems.
1)
Power Tower system
Power
tower systems consist of numerous large, flat,
sun-tracking mirrors, known as heliostats that focus sunlight onto a receiver
at the top of a tower. The heated fluid in the receiver is used to generate
steam, which powers a turbine and a generator to produce electricity. Some
power towers use water/steam as the heat-transfer fluid. Individual commercial
plants can be sized to produce up to 200 megawatts of electricity.
2) Linear concentrator system
Linear
concentrator systems capture the sun's energy with large
mirrors that reflect and focus the sunlight onto a linear receiver tube. The
receiver contains a fluid that is heated by the sunlight and then used to
create steam that spins a turbine generator to produce electricity. Alternatively,
steam can be generated directly in the solar field, eliminating the need for
costly heat exchangers. Currently, individual systems can generate about 80
megawatts of electricity.
3) Dish/engine system
Dish/engine
systems use parabolic dishes of mirrors to direct and
concentrate sunlight onto a central engine that produces electricity. The
dish/engine system produces relatively small amounts of electricity compared to
other CSP technologies-typically in the range of 3 to 25 kilowatts.
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