Solar Array Mounting

Toonces · September 2013

I have a question about mounting my future solar array. Here's my requirements:

1. I need the system to be expandable.
2. Location: SE Ohio latitude 40; 3.5 solar insolation
3. Immediate array size: (2) 300w(roughly) GT panels
4. Future array size: unknown, but this is for a tiny cabin used 10 times a year at most.
5. Array location: hillside w/possible rock ledges =posssible poor depth of holes.
6. Equipment: compact excavator and hand mixing of concrete

I'm trying to decide if I want to do a single top of pole mount, or a multi-pier ground rack system.

The top of pole mount would allow me much easier access to pivot the panels for the different seasons and times of day (when I'm there ofcourse).
The ground rack would probably be fixed in place, but possibly easier to install due to rock ledges?

I guess I'm not sure if I would even bother to pivot the panels at all. I would love to get some opinions on this if possible.

BB. · September 2013

Re: Solar Array Mounting

Regarding seasonal/1-axis/2-axis tracking... Try PV Watts with different configurations. Using Erie Penn as being closer to you, and a 1,000 watts of panels (1kW is minimum PV Watts will accept) with 0.52 derating:

At 42 Degrees from horizontal:

Month    Solar Radiation (kWh/m 2/day)    AC Energy (kWh)
1      2.19          35   
2      3.23          48   
3      4.20          67   
4      5.02          75   
5      5.55          83   
6      5.55          78   
7      5.76          82   
8      5.52          79   
9      5.02          71   
10      3.89          58   
11      2.07          29   
12      1.94          29   
Year      4.17          734

Vs a full 2-axis tracker (best you can do):

Month    Solar Radiation (kWh/m 2/day)    AC Energy (kWh)
1      2.43          39   
2      3.71          56   
3      5.01          81   
4      6.59          101   
5      7.81          120   
6      8.14          118   
7      8.33          122   
8      7.43          110   
9      6.38          92   
10      4.61          70   
11      2.29          32   
12      2.14          33   
Year      5.41

You can see there would be some improvement with full 2-axis tracking--But the costs of tracking (or making an adjustable array) vs just getting one or two more panels may not be worth the added expense/costs. And, of course, 10% more power in the dead of winter is only ~3-4kWH over a month (1 kW of panels) or ~0.1 kWH per day--A backup generator is probably going to be needed in any case.

If you will be using the cabin in winter and/or you have heavy snow falls where mounting the panels vertical can shed snow and even pickup reflections from the snow field--May be worth it.

Otherwise, I am not a big fan of single pole mounts. You need a huge amount of concrete at the base to prevent the array from over turning in high winds. Vs the simplicity and rigidity of a rack mount with multiple points of ground contact.

Another think to think about is theft/damage... Many times, mounting the panels on an (relatively) inaccessible roof can be worth the security/installation hassles too.

-Bill

jtdiesel65 · September 2013

Re: Solar Array Mounting

I have two poles with 12 panels on each. Pictures of early versions when they were only 8 panels per pole.

http://forum.solar-electric.com/showthread.php?2462-PV-pole-rack-movement-and-wind.

They have since been welded and longer horizontal bars installed to accomodate 4 more panels.

Unless you build the rack for future panels (meaning build a rack that holds 8 panels, but only put 2 on it for now), upgrade is a pain.

I used to pivot my panels 5 or 6 times a year. Now I only pivot once in fall and once in spring. Unless you are pushing the envelope and need every single watt, it doesn't make sense to move the panels. I move mine into summer position only because it gives me more juice to dump into running two AC units and a dehumidifier (usually still with unused juice). I'm not sure I really even have to move them, but it's fairly simple to do. Where I am, there is a full 5 hour peak difference in day length between summer and winter.

The thing with the tracker is it does almost nothing in winter. So you kinda have to size your array for winter or live off a generator. In summer, the tracker increases performance but if your array is sized for winter or even fall, the performance increase is not needed. I've done the numbers multiple times and could never get the expense of a tracker to work out. It always made more sense to buy more panels. Especially now with low panel prices.

One thing to keep in mind is snow removal. You need to be able to get at them.

jcheil · September 2013

Re: Solar Array Mounting

Attachment not found.Attachment not found.Attachment not found.Here are some pictures of the mounts I built. They are 1-axis adjustable and since it only takes me about 10 minutes to adjust them I do it 4 times per year.

Being in Florida we have tropical storm force winds frequently. The 4x6 posts are 5' in the ground with (3) 80-lb bags of concrete in each with anchors. If you were able to get down to rock, I would simply drill some anchors into the rock and attach them to the 4x6 posts. This design is very rigid vs a single pole with a top-heavy platform. I know my setup has seen frequent 60+ mph winds and has had minimal movement.

Total cost for everything needed to hold these (12) 205w panels was about $300.

Coach Dad · September 2013

Re: Solar Array Mounting

Here are some pictures of the mounts I built. They are 1-axis adjustable and since it only takes me about 10 minutes to adjust them I do it 4 times per year.

jcheil- You did a beautiful job on those mounts.

Toonces- If you normally get snow in your area, make them adjustable... A top of pole mount works nicely... Make sure the panels are higher than your max expected snow depth.

Here is a picture of one of my pole mounts (home made).. the bottom of my panels are about 6 feet high when they are vertical... I adjust them 3 times per year, and it takes less then 10 minutes to do it..
Attachment not found.

peakbagger · September 2013

Re: Solar Array Mounting

Installing a pole mount in rock isn't that hard, you just need to design the baseplate heavy enough to resist the moment load from the panels. Any structural engineer can design a baseplate. A rock drill, rebar and epoxy make some good anchors, if the rock is wet there are some water reactive anchoring compounds that would well. The biggest hassle is shimming the pole up so its vertical in both planes. I suggest grouting in the plate afterwards but many don't. Many folks don't realize that most utility poles are not set in holes drilled in rock, they are usually attached to the face of the ledge with baseplate and some anchors drilled in.

A top of pole mount can be stabilized fairly easily with subsidiary braces run from the lower corners to fixed anchors, as long as they are in tension opposing each other its not that hard to rig up. I have two braces for my winter angle and use one of them in other seasons.

niel · September 2013

Re: Solar Array Mounting

no matter if you put the height higher to account for snow buildup or not one has to consider safety and the vandalism and theft aspects. ground mounts are easier to install, but make the other points more likely to be a factor too. odds are peakbagger's pvs will not be stolen, but is still reachable by hand for vandalism. somebody who is 6ft tall or taller could also walk into the bottom of the pvs and get hurt. fencing the area can help with the accidents, but if low to the ground as in low pole mounts or ground mounts the fencing could wind up shading the pvs. if willing to take some chances then i would probably say go with the average annual snowfall as the minimum height. i have seen my snowfall cover the bottom of the pvs at about a 2.5ft height and i have a 43in/yr average here in pittsburgh which is just east of eastern ohio. now manually removing snowfall can also influence your decision, but i'm going with no removals for times you aren't present.

vtmaps · September 2013

Re: Solar Array Mounting

Coach Dad wrote: »

If you normally get snow in your area, make them adjustable... A top of pole mount works nicely... Make sure the panels are higher than your max expected snow depth.

Here is a picture of one of my pole mounts (home made).. the bottom of my panels are about 6 feet high when they are vertical.

Nice! I admire all top-of-pole mounts that can go vertical. All of the ones I've seen are home-made. As far as I know there are no commercially available top-of-pole mounts that can go all the way to vertical.

--vtMaps

niel · September 2013

Re: Solar Array Mounting

vtmaps wrote: »

Nice! I admire all top-of-pole mounts that can go vertical. All of the ones I've seen are home-made. As far as I know there are no commercially available top-of-pole mounts that can go all the way to vertical.

--vtMaps

i do agree that coach dad's is nice and i wish i could get more magnification to see details. coach dad, i'm getting to be a forgetful old fart so i have to ask if you went into detail on your mount elsewhere in the forum?

jcheil,
i believe some have indicated that the copper in pressure treated lumber can be reactive to the aluminum in pvs or other metallic mounting hardware over time.

Toonces · September 2013

Re: Solar Array Mounting

Wow! Thanks for all the great replies! This really gives me something to think about. This forum is fantastic!

One more quick question while we're at it. I'm not sure if I should start another thread for this though. But what is the
easiest way to find true south for panel facing?

niel · September 2013

Re: Solar Array Mounting

some use a compass and compensate for true north, but if you know an area close by that gives the sunrise and sunset times the time directly in between them (solar noon) is the time of the sun facing south. i don't know what areas in se ohio may have that, but possibly stuebenville ohio, zanesville ohio, or wheeling wv. you can be a few degrees off and it won't matter.

NorthGuy · September 2013

Re: Solar Array Mounting

Toonces wrote: »

One more quick question while we're at it. I'm not sure if I should start another thread for this though. But what is the
easiest way to find true south for panel facing?

If you miss by 2-3 degrees, it won't make any significant difference.

waynefromnscanada · September 2013

Re: Solar Array Mounting

niel wrote: »

i believe some have indicated that the copper in pressure treated lumber can be reactive to the aluminum in pvs or other metallic mounting hardware over time.

Very much so Niel.
One time they used a mix of arsenic and copper sulphate, and you could use galvanized fasteners with that wood. New environmental and safety standards came along and out went the arsenic, so a lot more copper needed to be used to preserve the wood. All this extra copper will definitely cause sever corrosion in any aluminum in direct contact with the treated wood. (I've had personal experience) It will also rot galvanize fasteners, so special epoxy coated screws etc, or stainless steel fasteners must be used if you want it to stay together longer than 2 or 3 years. And use a plastic barrier between the wood and the aluminum to prevent direct contact. Same thing goes to prevent direct contact between the wood and anything galvanized.

jcheil · September 2013

Re: Solar Array Mounting

niel wrote: »

i believe some have indicated that the copper in pressure treated lumber can be reactive to the aluminum in pvs or other metallic mounting hardware over time.

The way I have the panels mounted to the framework, the panels themselves are not in direct contact with the wood. They are attached with galvanized connectors which lift them off the wood about 1/8"; so the only thing touching the wood is the connectors. The head of the bold fits into the drilled recess thus leaving the mounting bracket to fit flush against the wood while still eliminating contact of the panel and the wood. And if the galvanized connectors ever do have an issue, it is an easy swap to stainless steel in the future. But everything I have read shows galvanized (hot-dipped prefered) is recommended with PT wood.
Attachment not found.

Cariboocoot · September 2013

Re: Solar Array Mounting

Galvanized = zinc. PT lumber = copper. Put the two together and add a little moisture and guess what happens?

Coach Dad · September 2013

Re: Solar Array Mounting

vtmaps wrote: »

Nice! I admire all top-of-pole mounts that can go vertical. All of the ones I've seen are home-made. As far as I know there are no commercially available top-of-pole mounts that can go all the way to vertical.

--vtMaps

Thanks vtMaps....

Originally posted by niel.... do agree that coach dad's is nice and i wish i could get more magnification to see details. coach dad, i'm getting to be a forgetful old fart so i have to ask if you went into detail on your mount elsewhere in the forum?

niel... Here is a magnification of it... I hope it comes out clear enough for you to use.
Attachment not found.

It is a pretty simple concept.

niel · September 2013

Re: Solar Array Mounting

thanks for the mag coach dad as that helps, but the top of the pole is still obscured some and not well lit. i was interested in that transition detail.

Coach Dad · September 2013

Re: Solar Array Mounting

First of all.. Toonces sorry for distracting your thread.

niel wrote: »

thanks for the mag coach dad as that helps, but the top of the pole is still obscured some and not well lit. i was interested in that transition detail.

niel... Here is a magnification of the transition detail..
Attachment not found.
This is what I did... (lots of welding)
I welded a plate to the top of the pole..
I welded angle iron to the plate
I welded to short lengths of pole to the angle iron
I drilled holes in the short pipes and welded a nut over the hole which is for the lock bolt.
I slipped the cross pipe through the support pipes and I use a bolt to lock the pipe
I used unistruts for holding the panels and I used muffler clamps to attach the unistruts to the cross pipe
I bolted another unistrut across the bottom of the panels and I welded a small piece of unistut to it to hold the adjusting arm.
I welded bolts to the pole that are used to secure the adjusting arms to the pole.

Oh I also cut up some rebar and welded in into a cage. Then I welded the cage to the bottom of the pole. The cage around the pole keeps the pole from being able to turn after you pour the cement post and it reinforces the cement...

niel · September 2013

Re: Solar Array Mounting

gotcha except for,
"I slipped the cross pipe through the support pipes and I use a bolt to lock the pipe"

exactly where did the bolt get placed to lock it and how are you able to change the angle and relock it?

jcheil · September 2013

Re: Solar Array Mounting

Cariboocoot wrote: »

Galvanized = zinc. PT lumber = copper. Put the two together and add a little moisture and guess what happens?

I agree there is an issue with dissimilar metals (all metals actually), but in this case, you are way overthinking it.
PT wood has TRACE amounts of copper in it from the PT process.

The standard wood connector in the construction industry is Simpson Strong-Tie connectors, all of which are galvanized.
If it were THAT big of a deal, they would be out of business and my deck, and parts of your wood framed houses, would have fallen to the ground already.

Sure, SOMEDAY, maybe 20+ years from now, there MIGHT eventually be a corrosion issue that will affect the structural integrity of the forth-eight 75-cent connectors that are actually touching the PT lumber, but at that time, should I need to, I will simply spend the $48 (inflation adjusted dollars) to replace them for another 20 years.

Cariboocoot · September 2013

Re: Solar Array Mounting

I hope you're right.

Some experience of others have shown that it does not take nearly so long, depending on climate.

Coach Dad · October 2013

Re: Solar Array Mounting

niel wrote: »

gotcha except for,
"I slipped the cross pipe through the support pipes and I use a bolt to lock the pipe"

exactly where did the bolt get placed to lock it and how are you able to change the angle and relock it?

The attached picture shows the 2 bolts at the top of the pole and the 2 nuts at the pole that keep the panels locked in place.
I circled the 4 points on the picture...
Attachment not found.

For the upper BOLTS, I first drilled holes into the support pipe, and then welded nuts over the holes. Then I screw the bolts into the pipe (via the welded nut) and tighten them until there is enough pressure on the cross pipe to keep it from moving.. There is NOT any hole in the cross pipe. It is just a pressure lock.

For the lower section... I welded Bolts to the main pole. I slip the unistrut over the bolt using the proper hole from the unistrut and then lock it in place by screwing the nut on.

To change the angle,,,, I loosen the 2 upper bolts, I remove the 2 lower nuts, I pivot the panels and put the proper unistrut holes over the bolts, replace the nuts and lock the upper screws back in. I painted the holes on the unistruts so I don't have to measure the angle every time I change it.

waynefromnscanada · October 2013

Re: Solar Array Mounting

Cariboocoot wrote: »

Some experience of others have shown that it does not take nearly so long, depending on climate.

In just one year of having aluminum framework in direct contact with PT wood here in Nova Scotia I had a real good start on serious corrosion. I was shocked. Learned the hard way. The old PT wood had a different chemical mix and wasn't nearly as corrosive as the new stuff which is supposed to be less poisonous among other things.
If you use it with disregard to the issue and get away with it, that's awesome, fantastic. But if you run into trouble - - remember you were warned.
http://www.oaa.on.ca/professional+resources/resources+for+architects+&+practices/pressure+treated+wood+alert

Best of luck to anyone using the latest PT and conventional fasteners etc.

Vic · October 2013

Re: Solar Array Mounting

jcheil wrote: »

The way I have the panels mounted to the framework, the panels themselves are not in direct contact with the wood. They are attached with galvanized connectors which lift them off the wood about 1/8"; so the only thing touching the wood is the connectors. The head of the bold fits into the drilled recess thus leaving the mounting bracket to fit flush against the wood while still eliminating contact of the panel and the wood. And if the galvanized connectors ever do have an issue, it is an easy swap to stainless steel in the future. But everything I have read shows galvanized (hot-dipped prefered) is recommended with PT wood.
Attachment not found.

Just to nit-pick a bit;

To me, "galvanized" means Hot-Dipped Galvanized (HDG). The photo appears to be a Strut type angle bracket (as in Uni-Strut, Super Strut, B-Line Strue etc). Whatever is it, that consistent blue hue appears to be from Zinc PLATING. Plating is much thinner than is the coating resulting from dipping items in molten zinc (HDG).

Wood that is PT with Copper compounds seems quite corrosive. IN CA, believe it or not, the el-cheapo PT process uses Arsenic instead of Cu.

HDG IS a preferred connection technique for fastening to PT wood, as is Stainless.

Personal opinions, Vic

Cariboocoot · October 2013

Re: Solar Array Mounting

Shall we mention there's also like five different grades of pressure treated lumber?

peakbagger · October 2013

Re: Solar Array Mounting

When I upgraded my pole mount I did detect a slight amount of corrosion between the HDG rails and the aluminum frames (after about 7 years). On the new install, I ordered some HDPE not much thicker than milk carton (1/16') and made slotted square washers that slipped down between the aluminum panel frame and the HDG strut. I used SS fasteners to connect the panels to the racks using strut nuts on the rack. In theory there is not contact between the frames and the racks. This should work for PT and I expect making the washers out of milk cartons would work instead

waynefromnscanada · October 2013

Re: Solar Array Mounting

peakbagger wrote: »

When I upgraded my pole mount I did detect a slight amount of corrosion between the HDG rails and the aluminum frames (after about 7 years). On the new install, I ordered some HDPE not much thicker than milk carton (1/16') and made slotted square washers that slipped down between the aluminum panel frame and the HDG strut. I used SS fasteners to connect the panels to the racks using strut nuts on the rack. In theory there is not contact between the frames and the racks. This should work for PT and I expect making the washers out of milk cartons would work instead

I've done basically the same thing, and find it works great. Used plastic cut from a child's "Magic Carper" snow toy. It's tough plastic, thin and out of the sun, durable. Where any length of panel frame would be in contact with PT, I found heavy plastic construction tape, such as is used with Typar house wrap, works very well. All it needs is to prevent direct contact and the transfer of chemicals.

jcheil · October 2013

Re: Solar Array Mounting

waynefromnscanada wrote: »

I've done basically the same thing, and find it works great. Used plastic cut from a child's "Magic Carper" snow toy. It's tough plastic, thin and out of the sun, durable. Where any length of panel frame would be in contact with PT, I found heavy plastic construction tape, such as is used with Typar house wrap, works very well. All it needs is to prevent direct contact and the transfer of chemicals.

That seems like a good way to "insulate" it. Another option I just thought of would be small washers made out of rubber shower pan liner which is very durable. I will keep an eye on those few points of contact that I have between the connector and the PT lumber and see what happens over the next several years.

Perhaps also climate IS the deciding factor? I notice most of you are all from the north where snow is an element. Here in Florida we get a lot of rain, but 20 minutes later it is dry as a bone again. Yeah we have high humidity, which might also contribute, but I just gotta say in the 27 years I have been down here, all of the construction I have seen, and done, using PT and galvanized connectors (both methods) don't seem to have corrosion issues.

Part of me wouldn't mind taking the 30 minutes to make 48 washers as discussed and slide them under the connectors but the other part of me says to just wait and see and if the time comes to have to swap out those $1 connectors then I will use the washers at that time. Perhaps we'll revisit this topic in a few years and I will have more historical information then.

Vic · October 2013

Re: Solar Array Mounting

jcheil wrote: »

I agree there is an issue with dissimilar metals (all metals actually), but in this case, you are way overthinking it.
PT wood has TRACE amounts of copper in it from the PT process.

The standard wood connector in the construction industry is Simpson Strong-Tie connectors, all of which are galvanized.
If it were THAT big of a deal, they would be out of business and my deck, and parts of your wood framed houses, would have fallen to the ground already.

Sure, SOMEDAY, maybe 20+ years from now, there MIGHT eventually be a corrosion issue that will affect the structural integrity of the forth-eight 75-cent connectors that are actually touching the PT lumber, but at that time, should I need to, I will simply spend the $48 (inflation adjusted dollars) to replace them for another 20 years.

Hi jc,

1. Just to belabor the point. In the photo of post 14, that lumber is NOT, repeat NOT NOT Pressure Treated, not even close to PT. That wood appears to have been brushed on one surface only with a very, very dilute copper solution. A PT board of the same dimensions would have 1000 times or more Cu (in this case) treatment compound. All of the PT wood that I have seen is quite discolored by the treatment, and has hundreds of small slits mechanically made in the surface of the wood. PT lumber is immersed in the treatment fluid that is usually hot, and PRESSURE forces this compound into the wood usually "to the point of refusal"

See this Wiki article, close to the bottom there is some info on the PT process:
http://en.wikipedia.org/wiki/Pressure_treated_lumber

2. And again, that blue-hued metal bracket (connector) in your post #14, is not Galvanized (as in Hot Dipped Galvanized). It is Zinc Plated -- not at all the same. The requirement for real PT wood is that fasteners to be HDG (and at that, meeting a certain specific spec), or better yet us usually Stainless. Weather or not insulating washers are used to protect the Al frames of the PVs from corrosion, fasteners in real PT wood will be exposed to the corrosive effects of most of the treatment compounds used in the PT process.

Wiki article on HDG:
http://en.wikipedia.org/wiki/Hot-dip_galvanizing

Agree with you that the amount of Cu on the example shown in post 14 is close to negligible, and therefore probably not a large corrosion issue between any fastener and the PT compound on the one surface of that particular board.

Do not want to be too strident or beat on you too hard. But believe that it is not overthinking at all, in the general case of fasteners, PT wood treatments, and the exact nature of the HDG process. Opinions, Vic

jcheil · October 2013

Re: Solar Array Mounting

Vic wrote: »

Hi jc,

1. Just to belabor the point. In the photo of post 14, that lumber is NOT, repeat NOT NOT Pressure Treated, not even close to PT.

I can assure you that it *IS* PT lumber, #2 Southern Yellow Pine. Guaranteded. Thats what ALL PT lumber looks like down here. Now, I have seen the "texture" you describe in other PT lumber but I have mostly seen that in the northern states. I have never seen any other kind of PT lumber (with the slits) other than what I have in that picture, down here in Florida. And a matter of fact, I am pretty sure there are still the tags on the ends of those boards, I will take a picture of them this weekend just to confirm.

But I do agree that the small brackets are Zinc Plated, which like I said, are the only thing in contact with it and they are expendable IMO and if/when the time comes, they can easily be changed out to stainless or as the other poster suggested using a barrier.

But I honestly do appreciate your thoughts and concerns; even if we disagree as to the potential severity of the issues.

waynefromnscanada · October 2013

Re: Solar Array Mounting

The "old" PT wood we used to get was as Vic describes. The latest stuff however is quite different. It's actually not easy to tell the difference between regular wood and the new PT stuff we get now. Time will tell if it's as good as the old stuff, but I will be surprised if it is. The old stuff lasted too long

Re our climate, most of the problem is not the result of snow, that tends to be dry and inert compared to rain. At least until it melts. We usually get a LOT of rain here in Nova Scotia come Oct and Nov. When things get wet, that's when the corrosion gets going.

Solar Array Mounting

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