Before investing in the construction of photovoltaic power stations, the owner usually conducts income measurement and decides whether to carry out follow-up work based on the measured results. An important basis for revenue estimation is to estimate the power generation capacity at the site to be selected. At this stage, there are three sources of data for solar energy resources. One is satellite data, the other is climatological method projection data, and the third is actual measurement data.
NASA data has become the first choice of many homeowners because of its free and quick data. It is the solar radiation data with a resolution of 3Km~110km obtained by NASA through inversion of satellite observation data. It is found through our comparative analysis in our country. There are different degrees of high or low deviations in different regions, especially in areas with more rainy days in the eastern and central China, where NASA data are higher than 10% of measured data. In such regions, if NASA data are used for profit estimation, it is very important. The result may be overly optimistic.
The following takes a 10MW photovoltaic power station project in the eastern part of China as an example, and uses NASA data and weather station observation data to make profit calculations.
I. Comparison of NASA data and weather station observation data
Figure 1: Comparison of NASA Data and Weather Station Observations
NASA data averaged 4865MJ/m2 of solar radiation for many years, which was 12.7% higher than the 4317MJ/m2 observed by the weather station. The monthly deviation was different. From November to February, NASA data was higher than 25% above the weather station in March. ~NAS NASA data is 3%~15% higher than weather stations. The monthly variation trend during the year was basically the same, all gradually rising from January. Affected by the rainy season in the eastern part of the country, it dropped slightly in June. After reaching the highest value in July, it gradually fell back.
Second, the calculation of power generation results
Under the same premise of calculation, NASA data and observational data of weather stations were used to calculate the on-grid electricity respectively. The on-grid electricity calculated by NASA data was about 100 hours higher than the observation data of the weather station. The comparison results are as follows.
Table 1: Comparison of NASA Data and Weather Station Observation Data Calculation
From the above table, we can see that the results calculated by NASA data not only generate high power, but also calculate the optimal tilt angle of the PV module by 5°.
III. Comparing the results of photovoltaic power station revenue measurement
Under the premise of the same measurement, the estimated net income calculated from NASA data and weather station observation data is used to measure the project income. The pre-tax, projected investment tax, and post-capital tax internal rate of return calculated by NASA data for project financing need to be calculated. It is 21.41%, 21.14%, and 58.02% higher than the weather station observation data. The investment profit rate and total investment return rate were higher by 34.73% and 22.09%.
Table 2: NASA Data and Meteorological Station Observation Data Income Measured Difference Table
Summary: When the photovoltaic power plant project is selected and the development decision is made at the early stage, if the NASA data alone may cause a relatively large deviation, if the actual measurement data cannot be obtained, appropriate corrections should be made according to the actual situation of the project site.
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