Page 243 - Design of Solar Thermal Power Plants

226 4. DESIGN OF THE CONCENTRATION SYSTEM

thermocouples; temperatures of various heat-absorbing surfaces can be
determined, however, through the infrared camera monitoring method.
Fig. 4.1 shows a thermal image of a receiver at work in a solar tower
power plant. According to the color distribution, the temperature distri-
bution of the heat-absorbing surface inside the cavity receiver can be
detected. In the event that the absorber’s surface temperature exceeds the
upper limit, the relevant heliostats should be moved so that temperature
increases of the corresponding part can be restrained.

4.1.3 Modes of Concentration Field Control

Due to the large land coverage of the solar-concentrating field, the
concentrator should be locally controlled during regular work. A host
computer can only monitor the relevant status and give “start/stop” com-
mands; if possible, centralized control should also be applied. The control
system of the concentrating solar heat collection system is connected to the
distributed control system (DCS) of the power plant through a fieldbus. The
solar collector field functions under control of the concentrating field
supervisory controller (CFSC), as a whole or by sector. The CFSC is a
computer system located in the central control room that is capable of
communicating both with the control unit of each concentrator and with the
DCS. The CFSC collects and supervises the status and position information
of various concentrators and receives instructions from the DCS, as well as
giving general control instructions tothe concentrating field. During the day
and when the power plant is well prepared for it, the CFSC gives starting
instructions; at night and in the event of strong winds, the CFSC gives
stopping instructions including shutoff of the concentrators.

FIGURE 4.1 Thermogram of the receiver at Badaling power tower plant [20].