Tilt and azimuth

The position of the sun in the sky for any place on the planet depends on the time of the day and the time of the year. It is important to have a good understanding of the sun's position throughout the year in order to properly position a PV system to maximize the production of a PV system. The earth is at all times rotating around its own axis (completing a full rotation approximately every 24 hours) and orbiting around the sun (completing a full orbit appxoimately every 365 days). The daily rotation causes the strength of the sun to vary throughout the day as it rises in the East and sets in the West each day. The yearly orbit of the earth around the sun accounts for the variation in the strength of the sun in different areas between the seasons.

The earth rotates around its own axis at an angle of roughly 23.5°, which creates seasonal variation as the angle of the sun's rays striking any location on earth varies depending upon the position of the earth in its orbit around the sun. Sunlight is strongest when it strikes a surface perpendicularly or a 90° angle. Additionally, this change in the angle leads to longer days in the summer time and shorter days in the winter time.

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  Left: June 21 - The Northern hemisphere is tilted towards the sun and therefore receives stronger stronger sunlight for a longer period each day than the Southern hemisphere which has its winter solstice. Right: December 21 - The Southern hemisphere is tilted towards the sun and has its summer solstice while the Northern hemisphere has its winter solstice.

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  The Earth orbits the sun in a nearly perfect circle once each year. The angle of the axis of the earth does not vary as it moves around the sun, which creates variations throughout the year.

Orientation

The sun arcs through the sky from East to West each day. The sun will reach the top of its arc each day around noon, at which point it should be directly to the North (0°) in the Southern hemisphere and directly to the South in the Northern hemisphere. If a PV array is facing directly West, it will be unable to capture much sunlight when the sun is in the East and vice-versa, therefore it is ideal to position PV modules to face directly North in the Southern hemisphere and directly South in the Northern hemisphere.

Southern hemisphere: A PV module on a fixed mounting structure will maximize yearly production by facing directly towards the North:

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  June 21, 9:00 in Mozambique: The sun rises in the East.

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  June 21, 15:00 in Mozambique: The sun descends in the West.

Northern hemisphere: A PV module on a fixed mounting sturcture will maximize yearly production by facing directly towards the South:

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  June 21, 9:00 in Mozambique: The sun rises in the East.

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  June 21, 15:00 in Mozambique: The sun descends in the West.

The earth makes a complete rotation about its own axis approximately every 24 hours. As the earth rotates the sun moves through the sky each day, rising in the East and setting in the West.

The earth rotates around the sun in a nearly perfect circle one time every 365 days. Better color/image simulator for graphics https://ccnmtl.github.io/astro-simulations/sun-motion-simulator/#

Original https://astro.unl.edu/naap/motion3/animations/sunmotions.html