(1) Class I region
The annual sunshine time is 3 200~3 300h, and the total amount of solar radiation received per square meter in one year is 6680~8400MJ, which is equivalent to the heat emitted by the combustion of 225~285kg of standard coal. It mainly includes northern Ningxia, northern Gansu, southeastern Xinjiang, western Qinghai and western Tibet. It is the region with the most abundant solar energy resources in China, which is comparable to that of India and northern Pakistan. In particular, the western part of Tibet has the most abundant solar energy resources. The annual sunshine time is 2900~3400h, and the annual total radiation is as high as 7000~8000MJ/m2, second only to the Sahara Desert, ranking second in the world.
(2) Class II region
The annual sunshine time is 3000~3200h, and the total amount of solar radiation received per square meter in one year is 5852-6680 MJ, which is equivalent to the heat emitted by the combustion of 200~225kg of standard coal. It mainly includes northwestern Hebei, northern Shanxi, southern Inner Mongolia, southern Ningxia, central Gansu, eastern Qinghai, southeastern Tibet and southern Xinjiang. It is an area rich in solar energy resources in China. The equivalent of Jakarta in Indonesia.
(3) Class III region
The annual sunshine time is 2200~3000h, and the total amount of solar radiation received per square meter in one year is 5016~5852MJ, which is equivalent to the heat emitted by the combustion of 170~200kg of standard coal. Mainly include southeastern Shandong, southeastern Henan, southeastern Hebei, southern Shanxi, northern Xinjiang, Jilin, Jiangning, Yunnan, northern Shaanxi, southeastern Gansu, southern Guangdong, southern Fujian, northern Jiangsu, northern Anhui, Tianjin, Beijing and southwestern Taiwan. It is a medium type area of solar energy resources in China. Equivalent to the Washington area of the United States.
(4) Class IV region
The annual sunshine time is 1400~2 200h, and the total amount of solar radiation received per square meter in one year is 4190~5016 MJ, which is equivalent to the heat emitted by the combustion of 140~170kg of standard coal. It mainly includes Hunan, Hubei, Guangxi, Jiangxi, Zhejiang, northern Fujian, northern Guangdong, southern Shaanxi, southern Jiangsu, southern Anhui, Heilongjiang, and northeastern Taiwan. It is an area with poor solar energy resources in China. Equivalent to the Milan region of Italy.
(5) Class V region
The annual sunshine time is 1000~1400h, and the total amount of solar radiation received per square meter in one year is 3344~4190 MJ, which is equivalent to the heat emitted by the combustion of 115~140kg of standard coal. It mainly includes Sichuan Basin (including present-day Chongqing) and Guizhou. This area is the area with the least solar energy resources in China. Equivalent to most of Europe.
The class I, class II and class III regions, the annual sunshine time is more than 2 200h, and the total annual solar radiation is higher than 5016MJ/m2. They are areas with rich or relatively rich solar energy resources in China, with a large area, accounting for about 2/3 of the country’s total area. As mentioned above, it has favorable conditions for utilizing solar energy. In the class IV and class V regions, although the conditions of solar energy resources are relatively poor, they also have certain utilization value, and some of them may be developed and utilized. In short, from the national point of view, China is a country rich in solar energy resources, and has unique conditions for the development of solar energy utilization. As long as we work hard, solar energy utilization in China has broad prospects for development.
The research and calculation of solar energy resources cannot be done once and for all. In recent years, studies have found that with the increase of air pollution, the amount of solar radiation in various places shows a downward trend. The above distribution of solar energy resources in China is mainly calculated based on the data before the 1980s, so its representativeness has been reduced. To this end, the Chinese Academy of Meteorological Sciences recalculated the distribution of China’s solar energy resources based on the latest research data at the end of the 20th century.