Panels to the rain roof advice

[jbatx]

Hey peeps,
I have 20 t250 panels on make shift "ground mounts"... scrap lumber, rocks, laying on the ground. It's time to get them moved up to my rain collection roof for a variety of reasons - pv production, safety being the top two.

My rain roof is 20×30' and only about a 4-5 degree slope. There's ample room up there for 25 of these panels.

The roof is built over a 20' connex and two 2700g water tanks. There is no need to consider heat under the roof.

The roof is made from 12×3 ribbed aluminum roof panels on an over built treated lumber 2x6 structure with rafters 20" apart and perpendicular support for the panel. I have no concern for the roof supporting the roughly 820lb of panels.

I priced out laying unistrut rails and hardware for this project and it's going to run me about $1100 from Lowes... ouch.

My questions are...

1. In this case how much gap do you recommend between the roof panels and the pv panels?

2. Got any less expensive ideas?

 

[Samcat]

It is nice to have about 0.5 meters space between 2 or 3 rows of panels for maintenance and cleaning. Especially when laying down and working on wiring or connectors issues. Also good space for blowing leafs if they accumulated between roof and solar panels. Space between roof and panels should be enough so you can work on this things mentioned above, if there is need for repairs or maintenance.
Good luck.

 

[fromport]

My questions are...

1. In this case how much gap do you recommend between the roof panels and the pv panels?

2. Got any less expensive ideas?

As you know panels generate less power at high temps so any kind of ventilation underneath the panels helps.
1)
I think 4" raised from the roof is a good reference.
2)
I recently bought some unistrut and a local "bolts & nuts place" was about 40% cheaper than the local lowes/HD.
Check it out

 

[jbatx]

As you know panels generate less power at high temps so any kind of ventilation underneath the panels helps.
1)
I think 4" raised from the roof is a good reference.
2)
I recently bought some unistrut and a local "bolts & nuts place" was about 40% cheaper than the local lowes/HD.
Check it out

Thanks for the pro-tip. I'll ship around

 

[BradCagle]

You should toss a few panels up there, and experiment with height to raise them. You might not need a lot of air flow on that type of roof considering it's all open.

I use the cone nuts to mount to Unistrut, so I just leave enough space to get under to tighten.

 

[jbatx]

I have some left over 2x2 steel tubing that I could use for stand offs.

 

[rplarry]

I helped a friend mount his panels to a metal roof and we used aluminum angle of the side of the panels and down onto the metal and spaced them so we screwed into the wood supports under the metal roof. Not very expensive for the angle and easy to cut into short lengths.

 

[jbatx]

I helped a friend mount his panels to a metal roof and we used aluminum angle of the side of the panels and down onto the metal and spaced them so we screwed into the wood supports under the metal roof. Not very expensive for the angle and easy to cut into short lengths.

I'm having trouble picturing this

 

[rplarry]

I took some 2x2" alum angle and cut it into 4" lengths and screwed it to the sides of the solar panels. Then screwed down through the angle and into the roof to secure the panel to the roof.

 

[BobT]

You might want to look into the mini-rail system at Signature Solar. They are relatively inexpensive and easy to install on a metal roof like you have on your rainwater collection system. We are in the process of installing 16 100W panels (4S4P) on the off grid cabin I'm building. I do agree with others that it is a good idea to leave some working space between the rows of panel for maintenance, I didn't do this and it complicates maneuvering around, especially on a 6/12 pitch. I can only attest to the physical benefits of the mini-rail system, I haven't powered it up yet to see how it functions operationally.