Page 69 - Design of Solar Thermal Power Plants

2.5 DISTRIBUTION OF THE SOLAR RESOURCE IN SEVERAL 61

2.5.1 The Solar Resource in Beijing

0
00
00
The coordinates of Beijing are 115 23 17 E, 39 54 27 N, which is based

0
on the geographic coordinates of Tiananmen Square; the elevation of
Tiananmen Square is 44.4 m. Declination of the axis line of Beijing is 6 17 00

by west. The city starts at 39 28 N in the south and reaches 41 05 N in the
0

0

north; and starts at 115 25 E in the west and reaches 117 30 E in the east by

0

0
striding across latitude 1 37 from north to south and longitude 2 05 from
0

0
west to east. As Beijing is located in the middle latitude zone, the city
features an obvious warm temperate zone with a semihumid continental
monsoon climate, which has had profound impacts on Beijing’s other
natural factors.
2.5.1.1 Solar Altitude Sunrise Time, and Sunset Time of Beijing
Beijing is located near 40 N and enjoys a solar altitude change of

46 52 during the year. Around midday, the solar altitude changes from
0

0
0
26 34 on the winter solstice (December 22) to 73 26 on the summer

solstice (June 21), while sunshine duration changes from 9 h 20 min to
15 h 1 min. Solar radiation varies greatly during the year and serves as
the foundation for the temperature alternation and division of the four
seasons in Beijing.
Sunrise and sunset times are determined by the position of the sun in
the sky. The sun rises latest and sets earliest on the winter solstice;
conversely, the sun rises earliest and sets latest on the summer solstice;
sunrise and sunset times during spring and autumn fall between these
times.
2.5.1.2 Solar Radiation in Beijing
Monthly solar radiation for Beijing is shown in Table 2.2. From January,
monthly global radiation starts to increase, enjoys a large increase from
March to May, reaches its maximum levels in May and June, and de-
creases after June. Because July belongs to a rainy season, the monthly
global radiation drops quite quickly, followed by decreases from
September through November, reaching the bottom in December.
2
Beijing’s global annual radiation is 4702e5707 MJ/m . The two high-
value areas are in the Badaling Basin and around the northeastern sec-
tion from Tanghekou to Gubeikou, with global annual radiation as high as
2
5707 MJ/m ; a low-value area is located around Xiayunling in the Fang-
2
shan District, with global annual radiation of 4702 MJ/m . For the year,
the variation of solar global radiation shows a unimodal distribution.
From January to May, along with an increase in solar altitude and daytime
hours, monthly global radiation gradually increases, reaching its
maximum by May; from June to December, it decreases along with
monthly reductions in solar altitude and daytime hours, reaching its