Page 153 - Design of Solar Thermal Power Plants

138 3. GENERAL DESIGN OF A SOLAR THERMAL POWER PLANT

For a 100 MW-level power tower plant, area of the concentration field is
about 1 million square meters. The last row of heliostats is 2 km away
from the tower.
T ¼ expð bLÞ¼ expð 0:02 2Þ¼ 0:96

3.2.6 Heat Losses of Power Tower Cavity Receiver
Receiver is the device in the CSP generation system that converts solar
energy into thermal energy. Receiver of the power tower generation system
is normally mounted at the top of the receiver tower. There are mainly two
types of receivers, cavity type and cylinder type receivers. The cavity
receiver is used to absorb the solar radiation collected by the concentration
field arranged in northern sectors (Fig. 3.10A and C), whereas the cylinder
receiver is used to receive solar radiation collected by the concentration
field arranged in circles surrounding the receiver tower (Fig. 3.10B).
Absorber of the cavity receiver is mounted within a cavity structure
insulating thermal from outside; opening area of the cavity is less than the
surface area of the absorber, which is able to effectively reduce heat loss of
the absorber. A cylinder receiver is made by welding a large amount of
straight tubes that are vertically parallel to each other on the instrument in
order to create strip receiver plates, and put together the receiver plates in
order to create an approximate cylinder. Bottom and top of the cylinder
have been designed with heat-transfer fluid header for providing cold and
hot transfer fluid to the receiver and collecting the thermal transfer fluid.
According to different heat-transfer fluid inside the absorber, receivers for
the power tower generation system can be categorized into synthetic oil
receiver, water/steam receiver, molten-salt receiver, air receiver, liquid
metal receiver, solid particle receiver, etc. According to different features of
solar radiation absorption process inside the receiver, receivers for the
power tower generation system can be categorized into volumetric receiver
and tubular receiver. The volumetric receiver’s absorber is normally made
of honeycomb ceramics, foam ceramics, metal gauze, foam metal and other

FIGURE 3.10 Various kinds of concentration fields and receivers.