The influence of azimuth and tilt angle on the power generation of solar panels

1. Azimuth

The azimuth of the solar array is the angle between the vertical plane of the array and the south direction (negative angle is set for the east, positive angle is set for the west). In general, when the array faces south (that is, the angle between the vertical plane of the array and the south is 0°), the solar cell generates the most electricity. When it deviates from the south (northern hemisphere) by 30°, the array's power generation will decrease by about 10% to 15%; when it deviates from the south (northern hemisphere) by 60°, the array's power generation will decrease by about 20% to 30%. However, in a clear summer, the maximum solar radiation energy is a little later in the afternoon, so when the array's orientation is slightly to the west, the maximum power generation can be obtained in the afternoon. In different seasons, the solar array can generate the most electricity when it is slightly to the east or west. The location of the array is subject to many conditions, such as the azimuth of the land when it is set on the ground, the azimuth of the roof when it is set on the roof, or the azimuth when it is to avoid the sun's shadow, as well as many factors such as layout planning, power generation efficiency, design planning, and construction purpose. If you want to adjust the azimuth to coincide with the peak load time of the day, please refer to the following formula. As for the occasion of grid-connected power generation, it is hoped that the azimuth will be selected by comprehensively considering the above aspects.

Azimuth = (peak load time of the day (24-hour system) - 12) × 15 + (longitude - 116) The relationship curve between solar radiation and time when the solar array in Beijing is at different azimuths on October 9. In different seasons, the peak time of solar radiation in each azimuth is different.

2. Tilt angle

The tilt angle is the angle between the plane of the solar array and the horizontal ground, and it is hoped that this angle is the optimal tilt angle when the array generates the maximum power in a year. The optimal tilt angle in a year is related to the local geographical latitude. When the latitude is high, the corresponding tilt angle is also large. However, like the azimuth angle, the design should also take into account the restrictions such as the tilt angle of the roof and the tilt angle of snow sliding down (slope greater than 50%-60%). For the tilt angle of snow sliding down, even if the power generation is small during the snow accumulation period, the annual total power generation will increase. Therefore, especially in the grid-connected power generation system, the sliding of snow is not necessarily given priority. In addition, other factors should be further considered. For the south (azimuth angle of 0°), when the tilt angle gradually transitions from the horizontal (tilt angle of 0°) to the optimal tilt angle, the solar radiation increases continuously until the maximum value, and then the solar radiation decreases continuously when the tilt angle is increased. Especially after the tilt angle is greater than 50°~60°, the solar radiation drops sharply until the power generation drops to the minimum when it is placed vertically at the end. There are actual examples of arrays placed vertically or tilted at 10° to 20°. For situations where the azimuth is not 0°, the value of the slope solar radiation is generally low, and the maximum solar radiation value is near the tilt angle close to the horizontal plane. The above is the relationship between the azimuth angle, tilt angle and power generation. For the specific design of a certain array, the azimuth angle and tilt angle should be further considered in combination with the actual situation.

3. Impact of shadows on power generation

Generally, when calculating the power generation, it is obtained under the premise that there is no shadow on the array surface. Therefore, if the solar cell cannot be directly illuminated by sunlight, only scattered light is used to generate electricity, and the power generation at this time is about 10% to 20% less than that without shadow. In view of this situation, we need to correct the theoretical calculation value. Usually, when there are buildings and mountains around the array, there will be shadows around the buildings and mountains after the sun comes out, so when choosing a place to lay the array, you should try to avoid the shadow. If it is really impossible to avoid it, you should also solve it from the wiring method of the solar cell to minimize the impact of the shadow on the power generation. In addition, if the array is placed front and back, when the distance between the rear array and the front array is close, the shadow of the front array will affect the power generation of the rear array. There is a bamboo pole with a height of L1, and the length of its shadow in the north-south direction is L2. The height (elevation angle) of the sun is A. When the azimuth is B, assuming that the shadow ratio is R, then: R = L2/L1 = ctgA×cosB This formula should be calculated on the day of the winter solstice, because the shadow on that day is the longest. For example, the height of the upper edge of the square array is h1, and the height of the lower edge is h2, then: the distance between the square arrays a = (h1-h2)×R. When the latitude is higher, the distance between the square arrays increases, and the area of ​​the setting place will also increase accordingly. For square arrays with anti-snow measures, their inclination angle is large, so the height of the square array is increased. In order to avoid the influence of shadows, the distance between the square arrays will also be increased accordingly. Usually, when arranging square arrays, the structural dimensions of each square array should be selected separately, and its height should be adjusted to an appropriate value, so as to use its height difference to adjust the distance between the square arrays to the minimum. When designing a solar array, comprehensive considerations should be taken into account while reasonably determining the azimuth and tilt angles to ensure that the array is in optimal condition.