Altitude vs solar panel angle
In the Northern Hemisphere, the approximate solar altitude is 90 degrees minus the latitude year-round. In summer, this angle decreases by 23.5 degrees, making it flatter, and in winter, it increases by 23.5 degrees. For optimal efficiency, solar panels should be positioned perpendicular to the solar rays, which would be at an angle of 90 degrees minus the solar altitude. However, the general guideline suggests tilting the panels at an angle of latitude + 15 degrees in summer and latitude - 15 degrees in winter. Why is this adjustment recommended in the calculations?
For instance, at a latitude of 40 degrees, the summer solar altitude would be calculated as 90 - 40 + 23.5 = 73.5 degrees. However, the recommended tilt angle for solar panels is calculated as 40 - 15 = 25 degrees, why not 90 - 73.5 = 16.5 degrees?
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Firstly, let me correct some assumptions.
Altitude at solar noon = 90 – latitude (Equinox)
Altitude at solar noon = 90 – latitude + 23.5 (Summer)
Altitude at solar noon = 90 – latitude – 23.5 (Winter)
Active solar panel optimized year around = latitude degree.
Active solar panel optimized for winter only = latitude + 15 degree.
Active solar panel optimized for summer only = latitude - 15 degree.
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Thank you Haytham for the clarification.
The concept of "solar noon" really helped clarify things for me. Here's my takeaway: the optimal angle for solar panels relative to latitude is determined by how sunlight exposure varies over time. At the peak of summer during solar noon, the ideal angle for a photovoltaic (PV) panel is essentially latitude - 23.5 degrees for maximum efficiency. Yet, to ensure the best performance across the entire day and throughout the summer season, adjusting the panel angle to latitude - 15 degrees provides a more effective solution, optimizing energy production over a prolonged period.
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PV panel tilt depends on latitude as you mentioned, for max efficacy you need to tilt the panel toward the sun. That means, when the sun is high in the summer flatten the panel by 15 degree, so the optimal sun angle is Latitude – 15 degree. The opposite is true in winter as the sun is low, steepen it by 15 degree. If you have a fixed panel the optimize year around performance is latitude angle to collect the south sun.
I think 15 degree is the key and that angle has been tested and recommended by specialist.
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