As we all know, in order to get good power generation effect, the PV array should face due south and the inclination angle should be a little lower than the local geographical latitude angle, which is often said to be the best inclination angle. In the best orientation and tilt angle of the photovoltaic array to obtain good power generation effect.
But there are a lot of site roof or site often can not meet the array accurately facing south or roof tilt can not meet the best tilt angle requirements. These problems can bring a lot of trouble to the power plant designers or constructors. We will discuss this issue below.
If we do not consider the influence of the atmosphere on the solar radiation, the tilt angle of the PV array with a fixed tilt angle should be equal to the local geographical latitude angle to obtain the maximum solar radiation, that is, the maximum power generation.
But because the atmospheric quality varies greatly, when sunlight penetrates the atmosphere, a large part is converted into diffuse reflection by water molecules, carbon dioxide and other gases in the atmosphere, to get more direct radiation should be designed to the tilt angle of the array to the local latitude angle, and to get more scattered radiation should be placed in a horizontal position, that is, the tilt angle is 0.
And to get more direct solar radiation and scattered radiation at the same time. To obtain more direct and scattered solar radiation at the same time, the tilt angle has to be modified according to the distribution of direct and scattered solar radiation in each location. This is the so-called tilt angle optimization.
Although we can theoretically optimize the tilt angle of the PV array, we may encounter many problems or difficulties when implementing commercial and industrial rooftop PV.
Many buildings do not necessarily face due south, and the structure and slope of the building roof do not always fully meet the requirements of optimal orientation and tilt angle.
In this case, will our PV system still generate enough power as ideal? How much does the change in orientation and tilt of the PV array affect the power generation?
Scientific calculations and analyses of the variation of solar radiation obtained by the change of inclination and orientation of PV arrays across the country were carried out.
The results of the analysis showed that:
01 ：For most areas in China, the impact of 10 degrees deviation in the orientation of the PV array is less than 1%, and the impact of 20 degrees deviation in the orientation is less than 2%.
And the lower the latitude of the region, the smaller the impact. For example, the Sanya area, the best inclination should be about 18 degrees, and if the array inclination is 8 degrees, its solar radiation will be only about 0.4% less than the best inclination surface, and if the best inclination is maintained, but the orientation deviates east or west 10 degrees, the amount of solar radiation obtained is not much difference.
02 ：The positive deviation of the inclination angle of the PV array has a large impact on PV power generation, while the negative deviation of the inclination angle has a smaller impact. Negative deviation of 10 degrees has an impact of less than 2% in most areas.
03 ：for the radiation resources of good areas, because the share of direct radiation is larger, tilt angle on the impact of radiation is much greater than the radiation resources of relatively poor areas (these areas scattered radiation share is larger).
For example, Jiuquan area, the best inclination angle should be about 40 degrees, and if the inclination angle is 30 degrees, its solar radiation will be reduced by about 1.2% than the best inclination surface, while if the best inclination angle is maintained, but facing east or 10 degrees, the amount of solar radiation obtained will be reduced by about 0.3%.
04 ：The effect of inclination on radiation is higher at high latitudes than at low latitudes.
05 ：It should be noted that although a small change in inclination angle has little effect on the total amount of electricity generated throughout the year, it can have a large effect on the amount of electricity generated in different seasons.
For example, a negative deviation in tilt angle will lead to an increase in power generation in summer, while power generation will drop significantly in winter.
For commercial rooftop photovoltaic systems that are mainly self-generated and self-used, you should not only consider the annual power generation, but also fully consider the relationship between power generation and electricity load in each quarter, and design or adjust the tilt angle of the array as much as possible, so that your photovoltaic power generation system can serve you better.
The optimization of the tilt angle of PV power generation array is not only a result of scientific calculation, but also needs to be adjusted and amended according to the actual situation on site.
Especially for PV power generation systems integrated with buildings, the aesthetics of the buildings, urban management and planning requirements and other factors should be fully considered, and the commercial and industrial and household PV systems should be made according to the local conditions.