Reasons for Tilt Solar Panels

You may have noticed that most solar panels around us are tilted, whether on rooftops or streetlights. The tilt angle of solar panels is related to the local geographic location and latitude. Let's analyze why solar panels should be tilted.

I. Reasons for Tilt Solar Panels

Solar panels primarily absorb sunlight and convert solar radiation energy directly or indirectly into electricity through the photoelectric effect or photochemical effect. In other words, the more solar radiation a solar panel receives, the more electricity it can convert. Therefore, the output power of a solar panel depends on factors such as solar irradiance and solar cell temperature.

Our country is located in the Northern Hemisphere, and most areas are at high latitudes. Sunlight is tilted at an angle. Only by tilting solar panels in the opposite direction can the light-receiving surface of the panel be as perpendicular to the sunlight as possible, achieving maximum efficiency. Currently, there are fully automatic solar panels that continuously adjust their horizontal angle as the angle of the sun changes, ensuring that the panel is perpendicular to the sunlight from morning to night. Sunlight is generally best between 10 a.m. and 3 p.m., so solar panels should be tilted southeast, preferably at an angle of 30° to 60°. As long as the angle is within ±20° of due south, power generation will not be significantly affected. If conditions permit, the angle should be tilted within 20° southwest, so that peak solar power generation occurs slightly after noon. This helps increase power generation in winter.

I. Solar Panel Tilt Angle Calculation

1. Azimuth Calculation

The azimuth of a solar array is the angle between the vertical plane of the array and due south (eastward is set as a negative angle, westward is set as a positive angle). Generally, solar power generation is maximized when the array is facing due south (i.e., the angle between the vertical plane and due south is 0°). A deviation of 30° from due south (in the northern hemisphere) reduces power generation by approximately 10% to 15%. A deviation of 60° from due south (in the northern hemisphere) reduces power generation by approximately 20% to 30%. On a clear summer day, solar radiation reaches its peak late in the afternoon. Therefore, aligning the array slightly to the west can yield maximum power generation in the late afternoon. Depending on the season, aligning the solar array slightly to the east or west can also yield peak power generation.

To adjust the azimuth angle to align peak load and peak power generation, refer to the following formula: Azimuth angle = (peak load time (24-hour system) - 12) x 15 + (longitude - 116). Peak solar radiation occurs at different times of the year at different locations.

2. Tilt Angle Calculation

The tilt angle is the angle between the plane of the solar array and the horizontal ground. It is intended to be the tilt angle of the array during the year when power generation is at its peak. The annual tilt angle is related to the local latitude, with higher latitudes resulting in a greater tilt angle. However, as with azimuth, design constraints must also be considered, such as the roof's inclination angle and the slope angle for snowfall (slope greater than 50%-60%).

For a south-facing roof (azimuth of 0°), as the inclination angle gradually transitions from horizontal (0°) to the vertical, insolation increases continuously until it reaches a maximum value. Then, as the inclination angle increases, insolation decreases steadily. Especially after the inclination angle exceeds 50°-60°, insolation decreases sharply until, when the roof is positioned vertically, the power generation capacity reaches a minimum. For roofs with an azimuth angle other than 0°, insolation values ​​on inclined surfaces are generally lower, with values ​​near horizontal.

3. Impact of Shaded Area

If solar cells are not directly exposed to sunlight, only diffuse light is used for power generation, resulting in a power generation capacity reduction of approximately 10%-20% compared to unshaded roofs. To address this situation, the theoretical calculated values ​​must be corrected. Typically, when surrounding solar arrays, such as buildings or mountains, shadows will be cast when the sun comes out. Therefore, the location for the solar array should be avoided as much as possible. If avoidance is unavoidable, the solar cell wiring method should be adjusted to minimize the impact of shadows on power generation.

In addition, if solar arrays are placed in a front-to-back arrangement, the shadow cast by the front array will affect the power generation of the rear array if the distance between the rear array and the front array is close. At higher latitudes, the distance between arrays increases, and the installation area also increases accordingly. For solar arrays with snow protection measures, the steeper the tilt angle, the higher the array height. To avoid shadows, the distance between arrays must also be increased.

In summary, solar panels generate electricity by receiving solar radiation. The more radiation they receive, the greater the power generation. Therefore, multiple factors should be considered in advance when designing the solar panel installation angle.

Keywords：

Sun Earth Solar, Ningbo Sun Earth, Sun-Earth, Sun Earth, solar panels