Page 89 - Design of Solar Thermal Power Plants

78 2. THE SOLAR RESOURCE AND METEOROLOGICAL PARAMETERS

Hainan has a tropical marine monsoon climate in which summer is
long and winter is not significant; sunshine is sufficient and temperature
is high with abundant rainfall; the eastern area is wet, western area is dry,
southern area is warm, northern area is cold, and photosynthetic poten-
tials are great. It is warm all year with abundant rainfall and distinctive
dry and wet seasons; the wind is normally strong with tropical storms and
typhoons occurring frequently; and climatic resources are diversified.
Basic characteristics of the region are four indistinctive seasons with no
intensive thermal in summer and no severe cold in winter; the annual
temperature range is small, and the annual mean temperature is high; the
dry and rainy seasons are clearly distinguished from each other with a
dry winter and spring and rainy summer and autumn; there are many
tropical cyclones; light, thermal, and water resources are abundant; wind,
aridity, cold, and similar climatic disasters occur frequently [12,13].

2.5.7.1 Solar Radiation and Sunshine Duration of Hainan
2
The annual global solar radiation in Hainan is 4500e5800 MJ/m ;
variation in global radiation days is not significant. Hainan is located
south of the Tropic of Cancer, and various areas of Hainan enjoy long
sunshine durations with annual sunshine durations of 1750e2650 h and
illumination ratios of 50%e60%. The sunshine duration in the west
coastal area can be as high as 2650 h, whereas in the central mountainous
areas it may be as low as 1750 h due to more clouds and mist. The seasonal
distribution of sunshine durations indicates that summer (JuneeAugust)
has the longest sunshine duration followed by spring (March) and
autumn (SeptembereNovember); winter has the shortest sunshine
duration.
2.5.7.2 Thermal Characteristics of Hainan
Annual mean temperatures of various areas in Hainan fall in the range

of 22.8e25.0 C, a bit lower in central mountainous areas and higher in the
southwest. There is no winter season, and January and February are the
coldest months with a mean temperature between 16 and 24 C and a

mean extreme minimum temperature of over 5 C at most times. Summer

is from the middle 10 days of March to the first 10 days of November; July
and August have the highest mean temperatures at 25 and 29 C. Thermal

characteristics of various meteorological stations throughout the province
during the 1971e2005 period are shown in Table 2.11.
2.5.7.3 Precipitation Conditions in Hainan
Most areas of Hainan have sufficient precipitation. The annual mean
precipitation for the entire province is above 1500 mm. Influenced by
monsoon and terrain, precipitation varies significantly in terms of time
and space. Annual precipitation has a circular distribution with an east