Page 273 - Design of Solar Thermal Power Plants

4.3 DESIGN OF THE SOLAR TOWER POWER PLANT 255

suggested that airflow measurements should be used for estimating
surface heat flux conditions and the control of heliostat actions.
a. A sealed glass window fault or sudden stoppage of the air
compressor will cause the pressurized air receiver’s air resistance
to drop suddenly. In such an event, the heliostats must be moved
away immediately to prevent the receiver from being burnt up.
The heliostats and flow-resistance measurement system inside
the receiver shall be designed with a linkage device.
b. In the event of fan failure of a nonpressurized air receiver, the
receiver temperature rises sharply or the flow rate becomes zero.
In this case, the heliostat field must be immediately stopped. The
flowmeter should be placed behind the receiver to measure
receiver airflow or can be placed at the outlet of an induced draft
fan; due to multistage heat exchange and storage, air temperature
at this point will already be comparatively low.
8. In the event of freezing blockage inside the transmission pipeline of
a molten-salt receiver, the molten salt will not flow into the receiver
and the surface temperature of the heat absorber will rise. Based on
the surface temperature of the absorber, heliostat actions can be
controlled based on absorber surface temperature and through the
flow of molten salt. As a molten-salt flowmeter is easy to break
down, flowmeter failure diagnosis can be made by combining the
heat-absorbing surface temperature and molten-salt flow rate of the
receiver. When either one occurs, the heliostats can be moved away
to a safe position.
9. Before receiver startup, pipelines shall be preheated. Before heliostats
project energy into the receiver, the receiver shall first be filled with
heat-transfer fluid to avoid dry burning of the receiver. The fluid
temperature shall be close to the heat absorber temperature that
corresponds to the same time. If the receiver contains a superheated
section, focus must be placed on monitoring the temperature the
superheated section and adjusting it according to input energy
directions from the heliostat field. The difference between the
temperature of the superheated section of the receiver and that of the

water-cooled wall of the receiver shall not exceed 100 C [20].
a. For a molten-salt receiver, the heat absorber’s surface
temperature shall exceed the freezing point of molten salt by over

50 C. Heliostats shall be controlled in groups and their
concentrated beams gradually moved to corresponding positions
on the heat-absorbing surface one by one so that the temperature
of the heat absorber can rise accordingly. All heliostats must be
moved to normal working positions within 60 min. A molten-salt
system should be circulated 24 hours a day to achieve an
antifreezing effect. Such circulation shall be conducted through