Page 231 - Design of Solar Thermal Power Plants

214 3. GENERAL DESIGN OF A SOLAR THERMAL POWER PLANT

Then

f
h DNI ¼ h Gbp cosðqÞ 1 tanðqÞ ¼ 0:6 0:7971 ¼ 0:4782
L
Badaling is close to Hohhot in latitude, thus the respective
calculation results are almost the same.

3.8 DETERMINATION OF THERMAL
STORAGE RESERVE

Thermal storage mainly aims at guaranteeing the stable and contin-
uous operation of power plant, so as to satisfy the request of power grid
and achieve the maximum economy.

3.8.1 Principles of Selecting Thermal Storage Capacity

Determination of thermal storage mainly depends on the distribution of
feed-in tariff against time and the requirement of power grid on peak
modulation. Duration of thermal storage shall be merely determined by the
full-load generating hours in sunless intervals and economy of power price.
As great investments are involved, it must be calculated on a prudent basis.
Step I: Preliminary determination of thermal storage period according
to the feed-in tariff and time difference of sunset.
Fig. 3.61 has indicated that time interval with high power price after
sunset is more or less 6 h. Thus thermal storage period can be preliminarily
set as 6 h.
However, due to the application of thermal storage system, initial
investment may be increased, and the generating cost of power plant
may grow. Thus it is necessary to conduct Step II.

1.6 Feed-in tariff 1000 90 100 80
Feed-in tariff/[yuan/(kWh)] 1.2 1 700 Solar irradiation /(W/m 2 ) 70 60 50 40 Grid- connection volume load rate /%
900
Solar irradiance
1.4
Grid-connection load rate
800
600
500
0.8
400
0.6
0.4
200
0.2 300 30 20
100 10
0 0 0
1 3 5 7 9 11 13 15 17 19 21 23
Time/h
FIGURE 3.61 Determination of thermal storage period.