Impact on output if I can't mount panels level to the ground

[sensij]

Agreed - I am looking at doing that as an option too. I actually went out and measure the slope of the ground - it sits at about 27%-30%.

I can sketch this out... but it that right? Do you mean the slope is facing west, and has a 27-30 deg slope? If that is true, you might be better off just installing the array flush to the slope with a few extra panels, and forget about the extra work to add the southerly tilt. If you keep the south tilt, there will be self-shading if the rows are too close together. If you mean 27-30% as the tangent, so about 16 deg slope, that would be better.

[tandrup]

I can sketch this out... but it that right? Do you mean the slope is facing west, and has a 27-30 deg slope? If that is true, you might be better off just installing the array flush to the slope with a few extra panels, and forget about the extra work to add the southerly tilt. If you keep the south tilt, there will be self-shading if the rows are too close together.

Hi Sensij - the slope is 27%-30% - so roughly 15-17 degrees. Maybe I just go with that slope - and tilt the panels slightly to the South so I end up with an effective SW azimuth and tilt that seems reasonable. I was trying to be scientific about it - but maybe the approach of adding a few more panels make sense.

[sensij]

OK, with a 16 deg west slope, if you mount parallel to the slope you might get 1412 kWh / kW.

Now, let's say you keep the south edge of the panels parallel to the ground (16 deg slope to the west), and elevate the north edge 32 deg to create some southerly tilt. The end result is an array with an azimuth of about 24 deg west of south (180 + 23.8 = 203.8), and a tilt of about 35.4 deg. That array might produce 1581 kWh / kW, about 12% more than the flush array.

[Naptown]

Can you face the array parallel to the ground and face slightly 20d or so toward the east to correct.

[tandrup]

OK, with a 16 deg west slope, if you mount parallel to the slope you might get 1412 kWh / kW.

Now, let's say you keep the south edge of the panels parallel to the ground (16 deg slope to the west), and elevate the north edge 32 deg to create some southerly tilt. The end result is an array with an azimuth of about 24 deg west of south (180 + 23.8 = 203.8), and a tilt of about 35.4 deg. That array might produce 1581 kWh / kW, about 12% more than the flush array.

Awesome - just what I was looking for. Can you show me how you get the 23.8 degrees and the effective tilt?

Thanks,
Lars

[sensij]

3D modeling.

CompundTilt.GIF

[foo1bar]

3D modeling.

This is assuming the bottom of the array follows the slope of the hill.

If the OP is doing a system like http://www.snapnrack.com/residential-ground-mount or http://www.ironridge.com/products/gr...nting/overview

then I don't think that will be the case.
From what I can tell those are setup to be used with all the footings (or all the pipes) at one grade.

As for self-shading with a stair-step design - the solution is easy - just have the lower ones slightly forward. If the top-to-bottom horizontal distance of the panel is 2 feet, and the lower panel's middle is at the same elevation as the upper panel's bottom, move the lower panels forward 1 foot. Then they're all in 1 plane, even though the footings are slightly different from one stairstep to the next.

If you put a extra space between the panels for each step you can be less precise and the shadows will still be minimal

[tandrup]

3D modeling.

[ATTACH=CONFIG]7771[/ATTACH]

Very cool - thanks!

[tandrup]

FWIW - I found a tool online from Solmetric - free basic tool that can model a based slope + a tilt system on top of that. Pretty easy to use. Thanks everyone!