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Solar Panel Orientation

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It's obvious that solar panels produce most power when they are pointed directly at the sun. So, any installation needs to provide maximum sunlight onto their surfaces. Ideally, even in winter, they should receive full sun from  about 9am to 3pm.  Remarkably, there is still a wide range of elevations and orientation that will provide useful output.  It is possible to try passive tracking or even reflectors to enhance light falling on them.  If you are considering a DIY solar project, you need to look carefully at how you orientate your panels.

In the Northern Hemisphere, solar panels should always face true south.
In the Southern Hemisphere, they should face north.

The question is, at what angle from horizontal should the panels be tilted?   The usual advice suggests panel tilt should be equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer.  It turns out that you can do better than this - about 4% better especially in winter.

Optimum Tilt for Winter
The winter season has the least sun, so you need to maximise your capture rate. To calculate the best angle of tilt in the winter, take your latitude, multiply by 0.9, and add 29 degrees. The result is the angle from the horizontal at which the panel should be tilted.

The amount of power your panels put out is directly proportional to power received from the sun and will vary throughout the day and varies over the year will vary in line with the monthlysun hours .  Since this varies not only during the day, but as the seasons progress, solar systems are often rated as an average of the output energy from the peak sun hours and is usually given as a monthly average.  

Not only are solar systems affected by the quality of sunlight throughout the day, any shading will also affect their output.  Trees, buildings and high structures can throw shadows that affect part of an array.  Not that not only will those cells not work as efficiently, but nearby cells are affected by this (it is effectively resistance in the circuit) and cells may overheat, reducing their effectiveness.  Even higher hills on the horizon can limit the "sun hours"  in early morning or late afternoon.

One other problem can be, that if a panel or array is not protected by a blocking or bypass diode, when a panel stops producing power either due to shade, clouds or night, current can flow out of and drain your batteries.  Don't forget that the distance your panels or array are from the controller or storage must also be taken into consideration.  Long cable runs can be affected by the simple resistance of the wire and there will be power loss between the array and the batteries. 

Solar Pathfinder™
gives an entire year’s solar potential for a given site in just seconds.
This non-electronic instrument is ready-to-use upon receipt of shipment.

Solar Pathfinder

  • a powerful non-electronic instrument that includes:
  • Printed Manual (online version also available)
  • Sunpath Diagrams (latitude & application specific)
  • Angle estimator (for determining altitude and azimuth)
  • White marking pen with extra leads
  • Tool box specifically designed for the Pathfinder™
Solar Pathfinder Assistant is companion software that generates monthly sunpaths for each specific site latitude instead of relying on the stock latitude band diagrams. It includes weather data for North America, Central America, Europe, and Southwest Pacific.
Click here to learn more


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