Building a ground mount rack for my panels. Looking for ideas

Fe-Wood

I am looking for ideas on mounting systems that don't come as a kit. I have a complete fabrication shop at my disposal.
Anyone built there own mounting/racking system and want to share what you did?
Thanks!!

niel

Re: Building a ground mount rack for my panels. Looking for ideas

i'd be open to ideas for myself as well, but i'm curious as to what type of mounting you have in mind as i need an extended wall mount that i just haven't been gun ho in pursuing? did you have roof, ground, or pole mounting in mind? adjustable or not? you need to elaborate for people to make proper comments on it.

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Thanks Niel, That is sorta a half asked question...

My situation is open ground. I want to keep the profile low. My panels are approx. 3'x5' and I am going to mount them long-ways or landscape orientation. I will do 2 racks, one behind the other. They will each be about 27' long. Space is not an issue, hight is. I'd love to have them adjustable w/o a major PIA factor. My soil is rocky so I'm thinking I will pour a footing on top of the ground rather than dig a trench. I would like to use steel because it is cheeper.

The rest is open to ideas/suggestions-

niel

Re: Building a ground mount rack for my panels. Looking for ideas

steel won't last the 20-25yrs that you'd have pvs warranted for. high grade aluminum would probably be better to use as the steel could need replaced 2x, 3x, 4x, etc. multiplying the install costs over the warranted lifetime of the pvs.

now i'm guessing you don't have a snow problem in the winter, but some higher elevations there may and you'd need a bit of height to allow for snow buildup. no snow? then how about overgrown weeds or clippings getting thrown at the pvs? low profiles are not a good idea in most cases.

inetdog

Re: Building a ground mount rack for my panels. Looking for ideas

Fe-Wood wrote: »

T My soil is rocky so I'm thinking I will pour a footing on top of the ground rather than dig a trench.

An acceptable solution to the problem as long as you take into account in your calculations that the major problem for the structure is the overturning moment caused by wind loading rather than the downward force of the weight of the system.
When you dig a deep footing, you gain the effect of the mass of earth surrounding the footing. When you pour a shallow or on-surface footing you need to consider the footprint and ballast weight of the concrete, not just its bearing area.

niel

Re: Building a ground mount rack for my panels. Looking for ideas

i guess the extra height would add to the wind loading dilemma. just add more reinforced concrete to add weight and it could stabilize it. you could do this in shorter increments too as more than the basic 4 corners of stabilization would become additive. ie, every 10ft-12ft place another concrete base.

i should also point out that having pvs behind pvs, like the rows you see on many solar farms, creates a shadow in the morning and the evening and the degree of which is determined by the amount of overlap and the distances between them.

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Thanks for the input! Wind is the issue. I see 50 to 80 MPH winds at least once a winter. Usually coming from the south but not always. I am basically going to use poured grade beams for the footings. I will use either 3 or 4 footings per section, depending on what I put together as my frame design. I don't really have an issue with the steel not lasting long enough. I'm not looking at uni-strut and I can incorporate Hot Dipped Galv. at the ground interface. I'm really interested in seeing clever and easy designs that are strong.

Ideally, I would like to see pictures of peoples home built systems that show bracing, mounting clips designs and wire management.

niel

Re: Building a ground mount rack for my panels. Looking for ideas

the making it adjustable would pose an extra problem. maybe raising from the bottom rather than the top would be easier, but it has to be extra stiff so as to not sway and would involve more than 1 point of lift. that is stumper as to what would be good to use to raise them. to prevent shadowing maybe pushing from underneath somehow? if you did the raising in smaller sections one section at a time then it may simplify things, but would mean each would need a raising mechanism.

fewood, did you have any thoughts on this initially?

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Niel,
I had thought about how to raise and lower the array. One thought was a trailer type of screw jack but disregarded it because of the uneven lifting caused by 3 or 4 different jacks. I like the thought of raising the bottom. Could be a balance type of system perhaps with stops at the right angles.

Photowhit

Re: Building a ground mount rack for my panels. Looking for ideas

I don't know if this will help, but I did my cabin system originaly with the intent to change the orientation for summer sun with the 'rack' set for winter sun. The ones on the left are setup with 2 sets of 2 panels mounted to 2 sections of pressure treated 2x4's, and 'hinged' a single bolt on each side. a simple triangle with 4 braces on the angle which the panels rest and a single diagonal across the back, which you can see some of, in the photo. The second drawing is of the whole thing from an arial veiw, showing the 4 smaller braces behind the panels. My battery box sits on the bottom, outer frame, obviously I have lots of protection from wind in the back here. Since I had not setup the panels to the right when I angled the panels on the left they shaded the panels on the right during the setting sun and I didn't bother to make the center panels angle when I remounted them similar to the ones on the left (mostly for strain relief, since they are directly mounted to the rails they were under some pressure at all times, they made it 3-4 years this way, but I figured I was rolling the dice. The panels are much stronger than you would think!) This has been through 60 mph winds into the face.

Attachment not found.
Attachment not found.

niel

Re: Building a ground mount rack for my panels. Looking for ideas

fewood,
would the screw jacks give you enough to get a good angle that is capable of adjusting far enough? if so the screw jacks may be your answer. in fact if you break it up into sections then each section can be lifted and locked into place. if the screw jack is part of the bracing then the jack would need to stay put and you'd need a jack for each section unless you can work out a way to lock the pvs into position higher up that won't interfere with the lowering (added ing casuse i caint spell sumtimes:p) of the pvs later and won't cast a shadow and that would free up the screw jack to be used for each section.

Ralph Day

Re: Building a ground mount rack for my panels. Looking for ideas

fewood,
Check the build section of my signature. Steel and concrete, one person can change the seasonal angle in a couple of minutes. Have a helper if it's windy (or wait for another day).

Ralph

Photowhit

Re: Building a ground mount rack for my panels. Looking for ideas

Hi Ralph, glad you found this post, I did a search for your earlier post here, when I saw this guy was into metal fabrication, I used balance and ground mount, just couldn't find your post, perhaps it was never here, or in the stick show us yours (which is another good spot for him to check).

Still one of the best setups, if a bit labor intensive, but he'll need the heavy base as well.

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Niel,
I haven't done the math on the angles and what the effective length of the screw jack would need to be. I'm guessing the "live" weight of the of the panels and rack for each section would be somewhere in the neighborhood of 300 to 325 pounds, panels are 45 pounds each. If I used the balance point of the actual PV array I could possibly use 1 jack in the center to move it and have bracing on either end of the rack that fit into holes or slots that are set to the desired angles. That would give me 3 points of support while using only 1 jack to change angles.... Hmmm, I think this might be something worth looking into further....

Ralph,
Thats one heck of a system!!! Mine is a puppy in comparison. I like your racking. Do you have pictures of the tilt system? Looks like you put the pivot in the center of the arrays? Did you use bearings for the pivot? How do you move it and stabilize it?

Photowhit,
One nice thing about designing my system now is that its close to the shortest days of the year. I can see were the shadows will be, real time. I assume you made just the 4 panels have tilt for summer because the added summer sun offsets the loss from the shaded panels? How is the wood holding up?

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Photowhit,
Good idea! Looking at the show us yours sticky!!!

Photowhit

Re: Building a ground mount rack for my panels. Looking for ideas

Fe-Wood wrote: »

One nice thing about designing my system now is that its close to the shortest days of the year. I can see were the shadows will be, real time. I assume you made just the 4 panels have tilt for summer because the added summer sun offsets the loss from the shaded panels? How is the wood holding up?

No, I didn't need the extra wattage, as I only had 4 golf cart batteries, when I finally switched to a forklift traction battery I found a property that was too cheap. 2.2 acres w/ a 16x60 2000 model tin can(mobile home) and moved there. The wood is holding up fine, I have one back span(too long) 2x4 that has warped a bit, I'll replace it when I get a chance.

I think people on the forum are somewhat paranoid about wood, I'm from north Florida and my mother's 2200 square foot beach home is on 23' poles, has been for 20+ years. I just put in a 4Kw array at my new place and did a fixed wood mount, and will do the same with phase 2 - 2.5 Kw array built into/above the front porch.

inetdog

Re: Building a ground mount rack for my panels. Looking for ideas

Photowhit wrote: »

I think people on the forum are somewhat paranoid about wood, I'm from north Florida and my mother's 2200 square foot beach home is on 23' poles, has been for 20+ years.

What kind of wood is it and how was it treated? Between the cost of cypress or all-heart redwood in structural sizes and the environmental limitations on what preservatives can be used, in many cases they literally don't make them like that anymore. :-)

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

The thing about internet forums and sadly so many other things, is that the information put out by responsible members caters to the lowest common denominator. Example, Choice of materials. Aluminum is thought to be the best. It is good in most all situations. Mostly true! I was surprised when Niel thought I might have to replace my steel mounting structure 1 to 3 times over the life of the panels.

All materials have their merit if looked at in relation to site location, expectation, life cycle of the material, weather conditions and construction method. For me, steel is the best choice.

I did go thru and look at the "show me yours" thread. Lots of great systems but no detail pictures of racks

niel

Re: Building a ground mount rack for my panels. Looking for ideas

fewood,
you work with steel and would probably know better in many cases than i, but steel rusts. if you are thinking until it gets to the point of punch through you would find the pvs are on the ground far before this happening due to the stresses on the weakened area. the remedy might be to make it very thick, but this only serves to delay the inevitable failure due to rusting and the framework will be quite heavier than need be. aluminum has its problems too, but in comparison aluminum wins hands down. there's a reason pv frames are aluminum and not steel and furthermore, if you do opt for a steel mount then you will need to isolate the steel from coming into contact with the aluminum pv frame or the rust-through will occur even quicker.

galvanized coatings and other coatings on the steel will help to delay rusting, but they don't stop it.

inetdog

Re: Building a ground mount rack for my panels. Looking for ideas

niel wrote: »

f
galvanized coatings and other coatings on the steel will help to delay rusting, but they don't stop it.

Unbroken coatings should totally prevent rusting. A problem with galvanized in particular is that if the coating develops a pinhole you can get significant rusting under the coating before you notice it.
But someone familiar with that problem can be on the lookout for it.
Fe-Wood stated that he will be using substantially thick members, so I will leave that to his experience. But I will also second his mention that for those who get Unistrut off the shelf it can be a much bigger problem.

Reactions between either bare steel or galvanized and some treated wood can also be a issue.

Eric L

Re: Building a ground mount rack for my panels. Looking for ideas

Here are some details I posted of mine. Superstrut on concrete piers and tilt-angle adjustable. I'm reasonably confident it will hold up to corrosion, although I did primer and paint points where I broke the galvanized coating (the cuts).

Edit: I just saw that the OP wants to mount them landscape 2 high, I had thought of doing that too, and I think could also work with this design (it would have a higher backbrace, obviously).

Photowhit

Re: Building a ground mount rack for my panels. Looking for ideas

We've discussed isolating the different materials, and have used a variety of matierials for roofing paper, and rubber roofing to just plastic, I had been careful on my original panels and when I hung a couple new panels figuring I'd change them within a year I didn't bother and was surprised at the minimal reaction between the treated wood and aluminum mounts some 3 years later when I changed them.

Others have found a lot of reaction between materials. I had put some single dipped scews into a frame over night and when I took them out the next day they looked like 'brights!'

Of course Stainless bolts between the steel and aluminum, with something between them should keep you safe.

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

eric,
Thanks for showing that thread! Lots of great ideas there.

I didn't really want this to turn into a debate about rack materials. I am looking for clever mounting ideas and rack designs, regardless of materials used.

However, I am feeling compelled to respond to Niels continued push to use Aluminum.

Aluminum is the hands down choice for more reasons than just its supposed non corroding properties. It does corrode in coastal climates. What makes Aluminum attractive is the ease of manufacture into shapes designed to hold nuts or other configurations via the extrusion process. I think the main reason for its appeal is that it is light and can be easily cut with a woodworkers chop saw on site. If we were truly looking for a racking material that would last as long as the glass part of the panels, we would use Stainless Steel.

I trust that everyone here evaluates the racking system materials available and uses what is appropriate to there needs. For me, Aluminum is harder to get, costs more and I don't need the rack to be light.

DanS26

Re: Building a ground mount rack for my panels. Looking for ideas

I used off the shelf racking materials for my fixed ground mount. Ironridge racking on 3" posts, but I thought you might be interested in how I leveled and aligned the posts. Some pics are here at this site:

http://www.civicsolar.com/installation/85kw-ground-mount-system-fronius-inverter

With this method I did all the work myself without help.

niel

Re: Building a ground mount rack for my panels. Looking for ideas

fewood,
i agree that there are problems that can arise from using aluminum too and i thought i mentioned that somewhere before. they do make coatings for aluminum too. the weight is also a major factor, but it is not me that is "pushing" it as the solar mount industry are the ones utilizing it extensively. stainless would be great, but it is heavier and more costly. i would love to have stainless mounts as it would take away allot of worry in time.

i think the reason for discussing the materials used is because it can influence what a mount may be capable of doing or handling, but if you wish steel then we need to put our thinking caps back on for what you asked for, configurations.

petertearai

Re: Building a ground mount rack for my panels. Looking for ideas

Are you off grid or grid tie? I made my mount from wood, been in for about 4 years. No sign of corrosion. If off grid don't bother with varying the tilt , just set for the best winter tilt. Mistake I made was to have too low( 18 inches) on the low side, and I have to keep a eye on the grass height in front of them. Use stainless bolts for attaching .
Regards Peter

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

There have been some great ideas and designs shared here. These designs have opened up my thinking in terms of rack design, material isolation, strength, cost and longevity. I still have about a month before I start my build. My current thinking is a hybrid rack of sorts. Painted Steel for the main structure, bolted to the concrete grade beam. The panels themselves might be mounted on Aluminum stretchers.... Or.... maybe Redwood. I do have a large pile of Redwood..... Hmmmm.....

Niel,
I appreciate your input. I just didn't want to get pigeon holed into using 1 material because that is the industry standard

Fe-Wood

Re: Building a ground mount rack for my panels. Looking for ideas

Peter,
I am off grid. Don't you loose to much potential for summer sun only having the one set point? I'm hoping mine will be able to run a small AC unit in the summer. I'm thinking I will have my rack start at 24" off the ground.

petertearai

Re: Building a ground mount rack for my panels. Looking for ideas

Good point, didn't think of air conditioning for summer.
Where I live air-con isn't really necessary so my year round demand is much the same. Possibly a little more in winter as lights go on around 5-30 instead of 8-30 in summer.

niel

Re: Building a ground mount rack for my panels. Looking for ideas

fewood,
do you go below freezing there?

reason why i'm asking is we are overlooking hydraulics to lift the pvs with.

Photowhit

Re: Building a ground mount rack for my panels. Looking for ideas

You can get a big benifit from a tracking array, but (and it's been a few years) the benifits of a tilting array over a fixed array, fixxed at, or close to the angle of your latitude, is minimal 10-15%(from my faulty memory).