Recommended height for solar panels
I am laying out a roof plan, looking at shading. I made a good scale drawing and now need to assume a mounting height in order to finalize the shaded no go areas. I suppose there are different opinion...
Forum Discussion
Panel height and no go areas? It depends on the latitude, time of the year (shades are longer in winter), and height of superstructures on the roof.
Like others said, the simplest way is to lay out a piece of cardboard the size of the panel, and see how much shading is there at different times. Lift the cardboard by, say, 3" as the panel frame thickness is ~2" and you need some clearance under the frame.
Empirically, for a flat panel (i.e. surface 3" above the roof) most users are trying to stay 14-18" from the A/C unit and 10-12" from lower structures. Structures that are less than 3" above the roof don't matter, naturally.
If you prefer using your brains, there is indeed a formula that BFL13 has seen somewhere - I think he saw that formula in high school course of trigonometry :)... Or in the 1st semester of the very 1st college course.
Tan S = H/L, where S is the angle of sun over the horizon, H - height of the structure creating the shade, and L - horizontal distance to that structure.
The biggest unknown, as you can see, is the sun altitude over horizon because it varies with time of the year and latitude, and with time of the day. But you can find the sun altitude at noon for your most frequent latitudes.
Keep in mind that H is the height of the structure above the panel surface, not above the roof.
In the end, if you can't clear the shades to your satisfaction, you have 2 choices:
1) wire in parallel (if there is more than 1 panel), or
2) let it be. Like that serial killer said in Mentalist series, "You win some, you lose some".
Like others said, the simplest way is to lay out a piece of cardboard the size of the panel, and see how much shading is there at different times. Lift the cardboard by, say, 3" as the panel frame thickness is ~2" and you need some clearance under the frame.
Empirically, for a flat panel (i.e. surface 3" above the roof) most users are trying to stay 14-18" from the A/C unit and 10-12" from lower structures. Structures that are less than 3" above the roof don't matter, naturally.
If you prefer using your brains, there is indeed a formula that BFL13 has seen somewhere - I think he saw that formula in high school course of trigonometry :)... Or in the 1st semester of the very 1st college course.
Tan S = H/L, where S is the angle of sun over the horizon, H - height of the structure creating the shade, and L - horizontal distance to that structure.
The biggest unknown, as you can see, is the sun altitude over horizon because it varies with time of the year and latitude, and with time of the day. But you can find the sun altitude at noon for your most frequent latitudes.
Keep in mind that H is the height of the structure above the panel surface, not above the roof.
In the end, if you can't clear the shades to your satisfaction, you have 2 choices:
1) wire in parallel (if there is more than 1 panel), or
2) let it be. Like that serial killer said in Mentalist series, "You win some, you lose some".
