Page 211 - Design of Solar Thermal Power Plants

3.7 CALCULATION OF ANNUAL POWER GENERATION 195

concentration field area based on the capacity requirement proposed by
the owner. Annual power generation of the power plant is related to solar
to electricity conversion efficiency at the design point, concentration field
area, and solar irradiation resources. The specific calculation process has
been explained in details as follows.

3.7.1 Calculation by Applying the Design Point Method

In annual power generation calculation, except for such invariable
factors as solar irradiation resources and weather, others are all variables.
The key point for annual power generation calculation is to determine
the collector field power, which includes the concentration field area and
receiver power. The concentration process, thermal receiver, thermal
storage, and heat exchange are coupled to power generation, which shall
be calculated by using multiple factors simultaneously on the basis of
system energy balance. At a typical time point, such as the design point,
the concentration field area depends on the rated input of steam turbine,
rated input of thermal storage, and operating mode of power plant cor-
responding to the design point. It is normally required that at the design
point, the concentration field provides energy to the receiver, output
power of which shall be not less than the sum of rated input of steam
turbine and rated input of thermal storage. At this moment, the power
plant is basically able to ensure the full-load power generation during the
day and several hours of power generation during the night. In this case,
the rated input power of thermal storage shall be the ratio of the capacity
of thermal storage to its thermal-charging operation hours.
Fig. 3.45 shows the annual power generation calculation process.
Firstly, irradiation and meteorological conditions shall be determined;
then, a concentration field area shall be assumed. When considering the
output of concentration field as the input of receiver, the output power of
receiver shall be equivalent to the sum of required input power of steam
turbine and thermal storage. In case of the condition not being satisfied, it
is necessary to reassume the concentration field area until the request is
satisfied.
After determining the concentration field area, the system efficiency
can be calculated based on the concentrating efficiency, receiver efficiency,
generating efficiency, etc. Then, annual power generation of the system
can be calculated.
Thus the basic idea for calculating the annual power generation is that
under specified geographic location, meteorological conditions, solar
irradiation conditions, steam turbine capacity and thermal storage
capacity, the concentration field area and the annual mean generating
efficiency of CSP generation system can be determined.