16-17 Solar Energy Resource Calculation
Author: Source: Datetime: 2016-12-24 13:53:55
It should be pointed out that there are many meteorological elements that affect solar radiation, such as cloudiness, cloudiness, transparency, etc. In addition, altitude, geographical latitude, season, time and other factors can not be ignored. Cloudiness, cloudiness and atmospheric transparency can be said to be variable, difficult to measure. Therefore, most of the calculation methods are also limited to sunny, practical value has been limited. The methods discussed below are limited to multi-year averages, ie, annual or monthly mean exposures H in the climatological sense.
There are many kinds of methods for calculating the total radiation exposures, which can be expressed as
H = H0f (s1, n) (1-10)
H0 based on the total radiation exposure value, f (s1, n),as a function of the degree of shielding the sky; s1 is the percentage of sunshine; n is the amount of cloud.
In the formula (1-10), s1 and n may be either one or may be used together.H0 selection can be divided into three.
① astronomical radiation. Astronomical radiation refers to the sun at the upper limit of the atmosphere. Since there is no air in the upper bound of the atmosphere, there is no scattering, and in fact only direct solar radiation is present and only varies with latitude and time. Since astronomical radiation does not respond to different altitudes, it is not conducive to the settlement of such vast areas as China, undulating terrain obvious situation.
② sunny radiation. In order to obtain this value, it is necessary to plot the multi-year measured data of each solar site day by day to plot the date as the abscissa, and then plot the contours of all points, and then calculate the response time (month) Under the area, that is, within the month sunny exposure volume. This is not only the workload of large, and the outline of the representative of the atmosphere is often in the case of extreme transparency of the exposure amount of radiation, the value of partial high. In addition, because the measured site is scarce and unevenly distributed, the result can not be taken into account at different altitudes and latitudes.
(3) the total radiation exposure in the ideal atmosphere. The exposing volume has the following advantages: a. Can be calculated accurately, without finishing a large number of limited sites of the original measured data; b. Can be different altitude and latitude distribution values. The so-called ideal atmosphere, also known as dry clean atmosphere, as its name suggests, in terms of its composition, in addition to no water vapor and aerosols, and - the atmosphere is no different. This eliminates uncertainties in the atmosphere and allows calculation of the scattering and absorption of atmospheric fixation components to solar radiation.
As for the specific expression of f (s1, n) , a large number of studies at home and abroad are now clear, with the effect of sunshine percentage is better than the use of cloud. This is not difficult to understand, because the sunshine percentage is, after all, the result of continuous recording, while the amount of cloud by the visual, and only one day 4 observations, which also includes a night recording [its solar terms, meaningless The currently accepted form of the best expression is
H = H0f (a + bs1) (1-11)
Where, a and b for the regression coefficient, according to the measured data obtained using the least squares method.
Wang Bingzhong calculated the distribution of the national solar energy resources, but provided only the overall trend of China's solar energy resources distribution. As the work is limited to the whole country, the characteristics of individual regions may be considered inappropriate. To understand the details of a particular region, there is no need to sort out the original observation data, optional formula to start, the general can refer to the provincial meteorological department to find the desired file results.
However, it should be pointed out that the work of solar energy resources is not a once and for all work. In recent years, the study found that with the increase of air pollution, solar radiation around the general decline. And Wang Bingzhong and other resources are mainly based on the distribution of the 20th century, 80 years before the data, so its representation has decreased. In addition, in recent years, the widespread use of meteorological satellite data to carry out the rescue of solar energy resources, which is the future direction we should work hard.
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