According to the "Design Specification for Photovoltaic Power Stations" (GB50797-2012), the calculation of the spacing of photovoltaic arrays is based on the goal of "guaranteing that the solar array will have 6 hours of sunshine per day during the winter solstice". (That is, 6 hours of sunshine during the winter solstice is guaranteed, hereinafter: the sunshine duration of the photovoltaic array for the winter solstice is referred to as: sunshine duration).
At present, the ground photovoltaic power stations constructed at different latitudes in China have completed the calculation of the spacing of photovoltaic arrays according to this specification, without considering the reduction in radiation and power generation caused by the change in the distance of the photovoltaic array due to differences in latitude and sunshine duration; This change caused differences in the area and investment of photovoltaic power plants.
This article will conduct research on the above situation, and analyze the relationship between the loss of power generation and investment changes caused by this, and propose the recommended duration of sunshine in different latitudes of photovoltaic power plants. Calculate the distance according to the classic formula, the following formula:
This paper first calculates the period of time that the photovoltaic array is blocked throughout the year under different conditions of sunshine duration based on the above formula, and can calculate the radiation received by the horizontal ground throughout the year. Therefore, the available radiation rate of the inclined surface of the photovoltaic array (ie: the rate of power generation) can be obtained.
At the same time, according to the above formula, the spacing of the photovoltaic array under the above constraints can be obtained, so as to obtain the unit area of ​​photovoltaic power plant per MWp. Changes in the area of ​​land will cause changes in the investment of some materials of photovoltaic power plants (for example: cable investment), changes in land costs, etc.
In order to simplify the calculation of investment changes, the principles for the value of the cost of photovoltaic power plants are as follows:
1) Except for changes in equipment and materials investment caused by land occupation, other investments remain unchanged;
2) The unit price of photovoltaic modules is 4.5 yuan / Wp, and the unit price of inverter is 0.5 yuan / Wp. The prices of other materials refer to the fixed electricity price;
3) Do not consider investment changes caused by terrain changes;
4) Land acquisition is calculated in two ways: paid and unpaid, and the land price is 5,000 yuan / mu.
Combining Table 1 and Figures 1 to 2 and analyzing the above calculation results, the following conclusions can be drawn:
1) Under different conditions of sunshine duration, the ratio of the available radiation value and the ratio of the amount of power generation of power stations in low-latitude areas change significantly. However, the proportion of the available radiation value and the proportion of the power generation of the power station in the high-latitude area did not change significantly. Moreover, the difference in power station investment in low-latitude regions is small; while the difference in power station investment in high-latitude regions is significant. It can be seen that as the latitude increases, the area of ​​the power station increases, resulting in a significant increase in power station investment.
2) Under the same conditions of sunshine duration, the proportion of power generation in high latitude areas is higher than that in low latitude areas. The proportion of power generation capacity of the power station is positively correlated with latitude.
3) When the latitude is lower than 25 °, the increase in the proportion of power generation is higher than the increase in the investment ratio; conversely, when the latitude is higher than 30 °, the increase in the proportion of investment is higher than the increase in the proportion of power generation. Therefore, it is recommended to increase the sunshine duration of photovoltaic power plants in low latitude areas to 7-8 hours, and reduce the sunshine duration in high latitude areas to less than 6 hours.
4) When the latitude is between 25 ° and 30 °, when the sunshine duration is 6 to 7 hours, the increase in the investment rate is basically the same as the increase in the power generation rate. Therefore, it is recommended to take 6-7 hours of sunshine hours at this time.
5) From the analysis of Figure 2, it is known that as the duration of sunshine increases, the intersection point of the proportion curve of the electricity generation capacity and the investment proportion curve shifts to a low latitude. From this, the optimal sunshine duration curve for each latitude is obtained, as shown in Figure 3.
According to the above conclusion: take the photovoltaic power station built at latitude 40 ° as an example, the duration of sunshine is 6 hours: theoretically, the power generation rate of the power station is 99.19%, and the power station occupies an area of ​​28.47 acres; as shown in FIG. The power generation rate of the upper power station is 99.67%, and the power station covers an area of ​​25.58 mu. The power generation rate of the power station is reduced by 0.48%, and the area of ​​the power station is reduced by 2.89 mu (10.15%). According to the cost principle mentioned above, the power station will reduce investment by approximately 85,700 yuan (10.13%) and 71,300 yuan (10.13%) in a paid and unpaid manner respectively. It can be seen that the photovoltaic plant has significant benefits after selecting the best sunshine duration.
In summary: the calculation of the spacing of photovoltaic power plant arrays should be analyzed and demonstrated based on the difference in latitude and investment level. If there is actual measured light resource data in this area, it should also be combined with the light resource data for analysis in order to achieve the purpose of saving land, controlling investment, and increasing the profit of the power station.
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