Beam down Solar Power Tower Concept and the Ways to make it

The power tower is a concentrating solar power concept capable of
generating high temperatures. In this concept, there is a central tower
surrounded by a heliostat field. The heliostats reflect the solar rays on
to a central receiver atop the central tower. It is also known as the
central receiver concept. Usually the receiver employs a heat transfer
fluid like molten salt to absorb solar thermal energy which in turn
transfers it to a steam generator to produce high temperature and high
pressure steam. The steam generated is then passed to a turbo-generator as
in the traditional Rankine cycle to produce electricity. The concept has
several applications including high efficiency electric power generation,
material processing, thermo-chemical hydrogen production and process heat
applications. Traditionally, the solar power tower is a beam up design and
there are several power plants already in operation worldwide based on
this concept.

In beam down design also, the central tower is surrounded by heliostats
which reflects the solar rays on to a hyperboloid mirror atop the tower
which in turn reflects back the solar beam to a ground based receiver
system. Beam down concept retains all the advantages of the beam up
design. The beam down system has the additional advantage that only the
hyperboloid mirror is atop the central tower making it lighter and
reducing its cost. It also enables design of natural circulation based
molten salt as well as steam generating system which eliminates molten
salt pumps, the associated maintenance issues and the flow control
required to suit the diurnal variation of solar insolation. In addition,
it also helps in collection of the spillage as well as reduction of
thermal losses. Further it is easy to integrate high efficiency
supercritical CO2 based Brayton cycle power conversion system. With beam
down concept, it is also possible to design an integral receiver cum
storage cum steam generating system which eliminates molten salt piping
and significantly reduces steam piping. The above can make beam down solar
power tower concept cheaper than solar PV.