Panel Racking

[gmcmurry]

Is this the correct place to discuss various racking ideas?

Greg

[bcroe]

Racking

Is this the correct place to discuss various racking ideas? Greg

Sure, it's all very expensive. Some of us have used aluminum angle, steel, treated wood,
stainless steel connectors, or a combination of them. Bruce Roe

[gmcmurry]

I am working on a ballasted racking idea for my flat roof at 34 degrees in Southern California. It seems I have the perfect location for many many panels. My house gets really warm, as it is pounded by the sun. When this project is completed, I will even appreciate the extra insulation I will get by having a major portion of my roof double insulated by a layer of solar panels.

My current design will use a Unistrut frame mounted on concrete ballasts. Wind is not a problem in my area.

My question is (I am sure this is the first of many) if I am mounting my panels in "landscape" mode, is there any reason I cannot clamp them to my horizontally run Unistrut on the ends? This would be two conventional clamps on the short ends. My panels will be about 6' 5" X 3' 3". I would have the clamps about 28" apart on the 3' 3" (39") side.

Almost every illustration I have seen, shows panels attached on the long side when in "landscape" position.

I need most of my power in the Summer, I am thinking of 15 degree tilt, direct facing South and rows 24 inches apart.

I would appreciate any comment.

140611 Racking Prototype 02_s.jpg

I have included this picture of my prototype racking. Of course, it is only one section and there will be many more pieces like this. I am looking to build a section that holds 9 horizontally mounted 250W panels. There would be a minimum of 12 concrete weights. Only 2 are shown. 4 ballast weights across and 3 deep supporting an array of 3 panels wide by 3 deep.

The wood 2X3 represents the short side of one of the 77" X 39" panels. Adjacent panels would share clamps in the horizontally run Unistrut

I am planning on using micro-inverters for my electrical connection.

Greg

[J.P.M.]

I am working on a ballasted racking idea for my flat roof at 34 degrees in Southern California. It seems I have the perfect location for many many panels. My house gets really warm, as it is pounded by the sun. When this project is completed, I will even appreciate the extra insulation I will get by having a major portion of my roof double insulated by a layer of solar panels.

My current design will use a Unistrut frame mounted on concrete ballasts. Wind is not a problem in my area.

My question is (I am sure this is the first of many) if I am mounting my panels in "landscape" mode, is there any reason I cannot clamp them to my horizontally run Unistrut on the ends? This would be two conventional clamps on the short ends. My panels will be about 6' 5" X 3' 3". I would have the clamps about 28" apart on the 3' 3" (39") side.

Almost every illustration I have seen, shows panels attached on the long side when in "landscape" position.

I need most of my power in the Summer, I am thinking of 15 degree tilt, direct facing South and rows 24 inches apart.

I would appreciate any comment.

[ATTACH=CONFIG]4341[/ATTACH]

I have included this picture of my prototype racking. Of course, it is only one section and there will be many more pieces like this. I am looking to build a section that holds 9 horizontally mounted 250W panels. There would be a minimum of 12 concrete weights. Only 2 are shown. 4 ballast weights across and 3 deep supporting an array of 3 panels wide by 3 deep.

The wood 2X3 represents the short side of one of the 77" X 39" panels. Adjacent panels would share clamps in the horizontally run Unistrut

I am planning on using micro-inverters for my electrical connection.

Greg

Sounds like you're doing this yourself ?

If so, and none of my business but, I'd respectfully suggest you stop now.

Starters:

Will the roof take the loads ?

Wind is always a consideration. A lot or a little. As are seismic considerations.

What happens to a ballasted system on a slope or horizontal surface in a seismic event ?

Solar electric panels are not meant as insulation. Poor idea for a lot of reasons.

Any thoughts as to building permits/plan check/design review ?

Lots more.

[gmcmurry]

Did you notice this was a DIY section? (smile)

All of your thoughts are appreciated and will be taken into consideration. There are many ballasted installations in my area, so this is nothing new. Its simply an engineering issue.

It is far safer, on a flat roof, to make no penetrations. When I say flat, I mean zero pitch. You must have roofs like that in San Diego.

As for insulation -- If 1/3 of your roof is covered by solar panels, that is 1/3 the amount of solar heat being absorbed by your roof. In my case, I have no insulation on my roof. My roof is simply hot mop, paper and gravel covered T&G 2X6s. I will definitely get an insulation benefit by installing solar panels. That much less heat through the roof, that much less air conditioning, that much more benefit from having roof mounted solar panels.

Greg

[bcroe]

I have included this picture of my prototype racking. Of course, it is only one section and there will be many more pieces like this. I am looking to build a section that holds 9 horizontally mounted 250W panels. There would be a minimum of 12 concrete weights. Only 2 are shown. 4 ballast weights across and 3 deep supporting an array of 3 panels wide by 3 deep.

The wood 2X3 represents the short side of one of the 77" X 39" panels. Adjacent panels would share clamps in the horizontally run Unistrut. Greg

I don't see any triangle braces. That 4 sided figure could pivot or "rock" at the corners.
Bruce Roe

[russ]

All of your thoughts are appreciated and will be taken into consideration. There are many ballasted installations in my area, so this is nothing new. Its simply an engineering issue. But is your roof designed for the load?

It is far safer, on a flat roof, to make no penetrations. When I say flat, I mean zero pitch. You must have roofs like that in San Diego.

As for insulation - There is a big difference between shading a roof and having insulation. It will help yes - actual insulation would help far more.

Comments in bold within the text.

[gmcmurry]

I don't see any triangle braces. That 4 sided figure could pivot or "rock" at the corners.
Bruce Roe

Good point - a few carefully placed diagonals will be added to the structure. THANKS

[J.P.M.]

Did you notice this was a DIY section? (smile)

All of your thoughts are appreciated and will be taken into consideration. There are many ballasted installations in my area, so this is nothing new. Its simply an engineering issue.

It is far safer, on a flat roof, to make no penetrations. When I say flat, I mean zero pitch. You must have roofs like that in San Diego.

As for insulation -- If 1/3 of your roof is covered by solar panels, that is 1/3 the amount of solar heat being absorbed by your roof. In my case, I have no insulation on my roof. My roof is simply hot mop, paper and gravel covered T&G 2X6s. I will definitely get an insulation benefit by installing solar panels. That much less heat through the roof, that much less air conditioning, that much more benefit from having roof mounted solar panels.

Greg

To answer your question: Yes. Simply confirming before I continued. Where's the harm in that ?

Take my thoughts as your needs dictate. Scrap the rest.
As for the rest:

Ballasted systems have been around for a long time for many applications. I've even designed a few for some non solar applications back in the day.

From what you write, it seems we have different ideas of how the engineering design process works and what's considered safe, appropriate and fit for purpose.

For example, I'm not sure the design feature of no penetrations on a flat roof is "far safer" than not considering wind loadings which are always a design consideration requiring some analysis more than" Wind is not a problem in my area", or safer than the possibility of a collapse failure caused by failure to check all design loading conditions against roof strength, or array movement caused by wind, seismic or other external sources that would impact the design.

FWIW, my understanding is that shading an area is not quite the same as insulating an area. For starters, shading prevents energy from reaching a surface. Insulation usually slows the transfer of energy (in this case heat) through the roof/wall/structure. The two are not the same.

Contrary to what you may think or write, unless you put the panels directly on the roof surface you will definitely get no insulation benefit by installing solar panels. That you may think that is so does not increase my confidence in the rest of your design capabilities.

I wish you luck with your venture.

[gmcmurry]

To answer your question: Yes. Simply confirming before I continued. Where's the harm in that ?

Take my thoughts as your needs dictate. Scrap the rest.
As for the rest:

Ballasted systems have been around for a long time for many applications. I've even designed a few for some non solar applications back in the day.

From what you write, it seems we have different ideas of how the engineering design process works and what's considered safe, appropriate and fit for purpose.

For example, I'm not sure the design feature of no penetrations on a flat roof is "far safer" than not considering wind loadings which are always a design consideration requiring some analysis more than" Wind is not a problem in my area", or safer than the possibility of a collapse failure caused by failure to check all design loading conditions against roof strength, or array movement caused by wind, seismic or other external sources that would impact the design.

FWIW, my understanding is that shading an area is not quite the same as insulating an area. For starters, shading prevents energy from reaching a surface. Insulation usually slows the transfer of energy (in this case heat) through the roof/wall/structure. The two are not the same.

Contrary to what you may think or write, unless you put the panels directly on the roof surface you will definitely get no insulation benefit by installing solar panels. That you may think that is so does not increase my confidence in the rest of your design capabilities.

I wish you luck with your venture.

This is a tough room...

[J.P.M.]

This is a tough room...

I've always tried (with limited success) to remember to not take my self too seriously. However, I always took my engineering very seriously.

An uninformed, cavalier attitude about the things of which you write is, first of all, possibly unsafe. IMO, you're out of your league in the design dept.

For my part, I'll take your remark about a tough room as a positive one. For your part, I'd respectfully and sincerely suggest you take what you need and leave the rest as your needs dictate.

[gmcmurry]

Those that find the need to constantly remind everyone that they are speaking respectfully, never are.

[inetdog]

Those that find the need to constantly remind everyone that they are speaking respectfully, never are.

And those who are quick to take offense will often do so even when none is offered.
'Nuff said?

[J.P.M.]

And those who are quick to take offense will often do so even when none is offered.
'Nuff said?

Amen.

[Shockah]

gmcmurry, this a FREE forum where PRICELESS advice has already been shared.
However, there is no satisfaction guarantee.

I actually enjoyed the first part of this DIY thread... as I am a DIY advocate.
That pesky word "insulation" had to come in the room and ruin things.
Basically, you are shielding your roof-top from the sun... but not insulating your structure from the heat.
I agree with you though, that the interior should be cooler just from the shielding.
I once shielded a concrete roof-top office with a layer of corrugated steel 12"' above.
The results were noticeable.

Two things caught my eye- Your ballasts look good,,, and your workshop floor clean.

However, if you "needed" the suggestion to gusset the corners, then you might want to humble down a bit and realize you may be a bit over your head on this project.

Check out this flat roof install where all it took was a gust of wind to tear the array into pieces. ... <<< and this was a professional install.

Also, I have to concur that concrete ballasts do move under the slightest seismics.
If you can't penetrate the roof for anchors, then at least mount tethers on opposite fascias to keep the ballasts from sliding off the roof.

Good luck with your project. Please post photos of your progress.