South facing panels on a north facing roof?

[moose1949]

I am trying to find the best place to put panels to maximize solar in the winter. We have lots of trees that produce shading when the Sun is low in the southern sky in winter. The rest of the year looks good. Based on PVWATTS for my location, south facing panels produce about 40% more AC energy than either east or west facing panels in December and January. We have one location on our lot, our shop, where it faces south and gets decent sun in the winter and plan to put 6-8 panels on the south facing part of the roof of that shop. Putting panels on the North facing part of that shop roof facing north does next to nothing in the winter based on PVWATTS. Is it a bad idea to try to position the panels on the north facing part of the roof so that the panels face south as shown in the attached drawing? I know wind loads have to be considered but it seems that if ground mounts can do this it could be done on a roof. If it is not a bad idea, does anyone have a good design for mounting panels like that? Thank you.

 

[zanydroid]

I’ve seen them installed; the mounting cost more and require engineering in the permit package, vs the cheapest type of solar mount and exempted from package for flat/parallel mounted panels. I don’t know the design but risers are available in many racking systems that offer in house engineering support for a fee

It comes down to a space and cost benefit comparison. If you get 40% with suboptimal facing you would need to slightly scale up battery storage and 2.5x the solar panels / standard tier racking / forgo paying extra engineering fee.

If hiring out the work you may also have harder time getting an installer to do less conventional racking

 

[zanydroid]

For your shading situation you might want to run Aurora shading simulator as an extra check against your manual azimuth/orientation plotting against the ephemeris track. In case one or the other methodology is done wrong.

I combined Aurora from a vendor estimate with manually using an ephemeris app to project sun track and using a drone’s IMU/orientation sensors to measure angles

 

[robbob2112]

The major problem with mounting panels as you diagram is that they will act as a sail and the uplift force can be pretty extreme. This is why it takes professional engineering to see if it is doable at all.

 

[littleharbor2]

I built a cedar, Dog-eared fence to help mitigate the uplift problem on my flat roof. Been through 3 big tropical storms and various other major wind events in the last 10 years. No problem.