Page 226 - Design of Solar Thermal Power Plants

3.7 CALCULATION OF ANNUAL POWER GENERATION 209

Feed water design parameters of point 7 at deaerator outlet are as
follows:

p 7 ¼ 0:12 MPa; T 7 ¼ 104:0 C; h 7 ¼ 435:99 kJ=kg; s 7 ¼ 1:352 kJ=ðkg$KÞ
Steam turbine final outlet exhaust at point 3 in Fig. 3.48 enters into the
condenser and experiences the 3-4 constant-pressure cooling process in
the condenser, in which steam is cooled and completely condensed into
saturation water through phase change while discharging thermal; water
from the environment is used as the refrigerant. From the above, ther-
modynamic parameters of point 4 in Fig. 3.48 are as follows:

p 4 ¼ 0:0073 MPa; T 4 ¼ 39:78 C; h 4 ¼ 166:64 kJ=kg
So far, the entire thermodynamic process has been successfully simu-
lated. From the above, by applying this thermodynamics-based method,
calculation of the annual generating capacity can be accomplished.
Furthermore, other parameter groups that are comparatively compre-
hensive can be obtained as well. Whereas by applying the design point
method, only system energy parameters corresponding to one time point
can be calculated, and the mathematical model is steady state model.

3.7.5 Influences of Location on Calculation of Parabolic
Trough Collector Efficiency
Two definitions of transient efficiency of parabolic trough collector:

Q _
h DNI ¼
DNI A
Q _
h Gbp ¼
G bp A
Efficiencies calculated based on these two definitions vary significantly.
Considering cosine influences, h Gbp is used in order to precisely reflect the
actual thermal energy.
A calculation example on the efficiency of parabolic trough collector
has been provided in this section by selecting three locations:
Badaling, Beijing (40 22 N, 115 56 E);
0

0

Sanya, Hainan (18 15 N, 109 30 E);

0
0

Hohhot, Inner Mongolia (41 N, 111 45 E)

0
Annual mean efficiencies of parabolic trough collector in above areas
can be calculated, from which, it can be concluded that different
geographic locations have resulted in different incidence angles; in-
fluences of latitude on the efficiency can also be seen. The local solar hour
is assumed to be 8:00e16:00 and the annual mean DNI of three locations is