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Solar panel tilt angle
refers to the angle between the plane of the solar panel and the horizontal plane.
This topic is widely discussed in the technical community. The tilt angle is determined based on geographical location
(like latitude), aiming for the front of the solar panel to face the sun
(or slightly west of due south) so that the tilt coincides with the local latitude.
Solar energy is a clean energy source, and its application is rapidly growing worldwide. Utilizing sunlight to generate electricity is one way to harness solar energy. However, the cost of building a solar power system remains high. Currently, the cost of solar power generation in Bitpott accounts for approximately
60 to 70%, so how to choose the azimuth and tilt angles of the solar array is a crucial issue for optimizing solar energy use.
1. Azimuth angle
The azimuth angle of the solar array is the angle between the vertical plane of the array and due south (where an east deviation is negative, and a west deviation is positive). Generally, when the array faces directly south
(with an angle of
0°), the solar panels generate maximum output. At a deviation of
30° east of due south, the output decreases by about
10 to 15%. At a deviation of
60° east of due south, the output decrease is approximately
20% to 30%. However, during clear summer days, solar radiation peaks shortly after noon, so a slight westward tilt of the array can increase afternoon power generation.
Different seasons may provide opportunities for higher energy production with slight adjustments to the azimuth angle, either east or west. The placement of the array can be influenced by many factors, such as soil orientation for ground installations or roof angles for rooftop setups, and even shading from surrounding buildings. For matching peak electricity load times to peak power generation times, the following formula can be applied. In grid-connected generation scenarios, it’s advisable to consider all these factors when selecting the azimuth angle.
Azimuth angle
= (Peak load time of the day (in 24-hour format) – 12) × 15 + (Longitude – 116).
2. Tilt angle
The tilt angle is the angle between the solar panel’s plane and the horizontal ground, ideally aligned to maximize yearly energy output. The appropriate tilt angle varies with local geographical latitude, with higher latitudes requiring steeper tilt angles. However, like the azimuth angle, roof pitch and snow slide angles must also be considered in the design.
Regarding snow slide angles, even during snow periods, total annual energy generation can still increase. Hence, especially in grid-connected systems, snow sliding may not be an initial concern, but other factors should be evaluated. For panels facing directly south (azimuth angle of
0°), the tilt angle starts from horizontal (0°) and gradually increases, leading to enhanced solar radiation until reaching a peak, after which increased tilt causes a decline in radiation. Particularly, when the tilt exceeds
50° to 60°, solar input sharply decreases until it reaches a vertical position, where generation falls to a minimum. There are practical examples of arrays positioned from vertical to tilts of
10° to 20°. For azimuth angles not equal to
0°, the solar radiation values are generally lower, close to angles near horizontal. The relationships between azimuth angle, tilt angle, and energy generation should be combined with practical conditions for specific designs.
3. Impact of shadows on energy generation
Generally, energy generation calculations assume that the panel array is free of shadows. If the solar panels are not directly exposed to sunlight, then only scattered light can be harnessed, resulting in a yield that is about
10% to 20% less than when unshaded. Adjustments to theoretical calculations are necessary in these situations.
When there are buildings or mountains near the array, shadows may obstruct sunlight after sunrise. Thus, it’s important to avoid shaded locations during installation. If avoiding shadows is impossible, then mitigation strategies in wiring or the placement distance between front and back arrays can reduce shadow impacts on generation.
For instance, consider a pole of height
L1, with a shadow length of
L2 in the north-south direction. If the sun’s altitude is
A and the azimuth angle is
B, the shadow ratio can be defined as
R = L2/L1 = ctgA × cosB.
This calculation should be based on the winter solstice when shadows are at their longest. If the upper edge height of the array is
h1 and the lower edge height is
h2, then the distance between arrays
a = (h1-h2) × R. For higher latitudes, increased distances between arrays lead to larger areas needed for installation. For arrays designed with snow prevention measures, a greater tilt necessitates increased height, thereby increasing distance between arrays. Typically, the configuration of the array should consider the dimensions of each panel, optimizing height differentials to minimize spacing. In designing solar panel arrays, determining the azimuth and tilt angles must also integrate practical considerations to ensure optimal performance.
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