Finally - My solar PV installation

[semipro]

I've been threatening for years here to get solar PV installed and its finally happening. I bought 30 Peimar 315 watt PV panels and am now building a structure to mount them on. Our house is well shaded by trees and roof mounting didn't make sense because of that and other related issues. This structure will also serve as a carport and host to a future EV. I plan to mount the EV charger in the carport and have uninstalled the conduit underground to service it. I've purchased a Sol-Ark inverter which I've yet to install. Though expensive it has some interesting features that I hope will serve us well.
The structure is mounted on 3 poured concrete curbs that should provide sufficient weight to counter wind loads and are tied into large boulders in the subgrade. I made my concrete onsite so that was an effort in itself.
Rather that going with commercially-available ground mount hardware I decided to use dimensional lumber to build a structure that would host solar panels at 40 degrees from horizontal while also providing cover for our cars. I intend to use the PV panels to create a water shedding roof.
Thus far I've done all the work by myself with the assistance of an old man (person?) lift that I bought and repaired. I'm sure I'm getting older/weaker but damn!, saturated treated lumber is a pain to move around.
I'll post follow-ups or "how I got to here" photos if there's interest. I've felt like a poser for so long WRT solar PV, and its good to be moving forward with it.

 

[Z33]

Super cool project.

Can't wait to see this one done!

 

[Where2]

If I explained how long my personal DIY solar projects tend to take, you'd wonder if the sun is going to go dark before I finish them?
Looking great!

 

[semipro]

If I explained how long my personal DIY solar projects tend to take, you'd wonder if the sun is going to go dark before I finish them?
Looking great!

So I'm not the only one with multiple languishing projects. Good to know.
I've still got a roof deck , shop/garage, basement conversion, bedroom floor, house exterior energy upgrade, etc. etc. to finish.
I'm going to have to live a long time to finish it all.

 

[byQ]

So, 30 x 315 = 9450 watts. That is a good sized system. Does the power company in your local allow customers to use a 'smart type' meter (it runs backwards) or are you doing a battery bank? Do you see this system taking care of most of your electrical needs?

 

[peakbagger]

Great Project. Now some questions.

You going with a string inverter (what brand) or microinverters? WIth that size array you could go with two 5KW Sunny Boys and get two SPS circuits.

If string inverter, are you mounting at the pole or in the house ( I am a fan of indoor located inverters, usually a better environment and lower electrical loss in the cable from the array to the house.

Are you putting a local disconnect at the array?

How are you dealing with lighting strikes?. I have a SPD at the array and a #4 running in the trench back to my house ground and a SPD at the inverter on the AC side.

How are you isolating the racking from the PT? (PT can be aggressive on aluminum and galvanized over the long run). I use plastic spacer washers and stainless)

Are you installing a fence around the array , making the wiring "inaccessible without a tool" or just not worrying about it.

A FYI is if you are doing your own racking make sure the PV panels have a 3/8" gap on all sides. Yes that means water can leak through but they do expand and contract. Some folks have gotten creative and put gutters underneath the gaps so it stays dry underneath.

The second FYI is cover the panel when you go to wire the up of do it at night with headlamp. The DC arcs produced by the array are very impressive and can melt the MC connector. MC connectors are not designed to be connected energized.

Have fun, I find designing and installing PV arrays a very fun project with long term benefits. I have built 3.

 

[maple1]

Had to reply so I could keep watch.

Very interesting. I went to an evening solar promotion seminar thing here a couple weeks ago. Have been thinking I would likely prefer ground mount to roof, and wondered to myself about constructing of wood. I saw a quick pic somewhere the past while (likely on FB) of one that someone built themselves, but it was a bad camera angle with no details. The guys doing the seminar kind of ball parked a 30% cost premium, on ground over roof mounts. (Talking contractor pricing).

The main thing I was wondering about, was coming up with a structure design that I could be sure would hold up to what it was going to be carrying, and the wind (we're on a mostly exposed hill top, and bad wind events are becoming more frequent) . Did you have any guidance there?

 

[ispinwool]

So I'm not the only one with multiple languishing projects. Good to know.
I've still got a roof deck , shop/garage, basement conversion, bedroom floor, house exterior energy upgrade, etc. etc. to finish.
I'm going to have to live a long time to finish it all.

My favorite saying: "God put me on this earth to accomplish a certain number of projects; I'm now so far behind, I'll never die!"

 

[peakbagger]

Had to reply so I could keep watch.

Very interesting. I went to an evening solar promotion seminar thing here a couple weeks ago. Have been thinking I would likely prefer ground mount to roof, and wondered to myself about constructing of wood. I saw a quick pic somewhere the past while (likely on FB) of one that someone built themselves, but it was a bad camera angle with no details. The guys doing the seminar kind of ball parked a 30% cost premium, on ground over roof mounts. (Talking contractor pricing).

The main thing I was wondering about, was coming up with a structure design that I could be sure would hold up to what it was going to be carrying, and the wind (we're on a mostly exposed hill top, and bad wind events are becoming more frequent) . Did you have any guidance there?

IMHO installers want a quick install and that is roof mount. A good crew can be in an out in a day, They keep a stock of panels, microinverters and racking and they pretty well can do any roof install. A ground mount is multiday project and requires custom parts. If also needs trenching and concrete work which usually means a subcontractor. If they are looking out for the owner they also need to do some engineering up front to size a string inverter as its lower cost.

As for structure if your local inspector requires a PE stamp that is one issue, otherwise if you copy the framing of a garage you will not be that far off (its probably overkill but easy) As for foundations if you have ledge its easy, just drill into the ledge, If you are in soil, you need to get down below the frost line and use a "big foot" footing, https://www.lowes.com/pd/Bigfoot-Sy...VC5SzCh2LOwWoEAQYAiABEgKQcfD_BwE&gclsrc=aw.ds
Now slide a sono tube down over the bigfoot and back fill the holes. Drop a couple of lengths of 1/2" rebar down to the bottom and then mix up the Sakrete and fill them to the top of the tube. Ideally if you can borrow a vibrator its good to vibrate the tubes to get rid of voids but usually smacking the protruding section of the tube helps. You need to design for snow load plus wind uplift so make sure you install a long j hook down into the concrete and make sure the anchor you use is set up for lift.

The only other trick is since you are not sheathing it like a garage you need to put some diagonal braces on the side walls. The PV panels will act as diagonal bracing once installed.

 

[semipro]

So, 30 x 315 = 9450 watts. That is a good sized system. Does the power company in your local allow customers to use a 'smart type' meter (it runs backwards) or are you doing a battery bank? Do you see this system taking care of most of your electrical needs?

Net metering is allowed where I live in VA but with enough caveats that I may not do it. We do plan to use batteries. I'm starting with a Chevy Volt battery pack that I salvaged and have broken down into 48 VDC modules.
This system should take care of all of our power needs. We've done a lot to increase our efficiency over the years and we don't use a lot of power. In fact, I think the use of the solar PV will result in a higher overall energy use at our house as we stop using pellets and use our heat pump HVAC more.

 

[semipro]

Great Project. Now some questions.

You going with a string inverter (what brand) or microinverters? WIth that size array you could go with two 5KW Sunny Boys and get two SPS circuits.

If string inverter, are you mounting at the pole or in the house ( I am a fan of indoor located inverters, usually a better environment and lower electrical loss in the cable from the array to the house.

Are you putting a local disconnect at the array?

How are you dealing with lighting strikes?. I have a SPD at the array and a #4 running in the trench back to my house ground and a SPD at the inverter on the AC side.

How are you isolating the racking from the PT? (PT can be aggressive on aluminum and galvanized over the long run). I use plastic spacer washers and stainless)

Are you installing a fence around the array , making the wiring "inaccessible without a tool" or just not worrying about it.

A FYI is if you are doing your own racking make sure the PV panels have a 3/8" gap on all sides. Yes that means water can leak through but they do expand and contract. Some folks have gotten creative and put gutters underneath the gaps so it stays dry underneath.

The second FYI is cover the panel when you go to wire the up of do it at night with headlamp. The DC arcs produced by the array are very impressive and can melt the MC connector. MC connectors are not designed to be connected energized.

Have fun, I find designing and installing PV arrays a very fun project with long term benefits. I have built 3.

I was hoping you'd chime in @peakbagger
I'm going with a Sol-Ark (https://www.sol-ark.com/) inverter that allows inputs from 4 strings on two separate MPPT inputs. The inverter will be mounted in the basement next to our breaker panels.
Good question on the lightning protection. The inverter maker does not recommend grounding the panel array which mystifies me. These guys do seem to understand spurious power though as they design EMP-proof systems. I would think I should at least ground all the panel frames to a ground rod near the array.
I'm doing permitted work but the county says a disconnect is not required. I plan to install one anyway at the array and label it for responders and for service use. The county says I do need to label the conduit housing the PV power cables that enter the house. I assume this is so responders can cut them if they need to.
I plan to isolate the IronRidge PV panel mounting rails from the treated purlins using either plastic spacers or maybe self-adhering flashing. I'm using stainless lag bolts for mounting. I'm very careful to use the right hardware with treated lumber as I've seen how quickly it eats up unprotected metal. I was planning to use IronRidge's UFO mounting bolts to clamp down the panels but I'm now planning to attach the panels to the rails using the holes already present in the backside of the frame. This will take some extra effort but should result in something that will shed water better.
The panel manufacturer recommends a 1/4" gap between panels for thermal expansion. I plan to seal this gap with backer rod and a high quality sealant. That will be tricky.
Where we live is rural so a fence shouldn't be needed. Panel wiring work will require special tools and I will route the wiring neatly under the array, maybe in a protective conduit or chase, primarily for protection from squirrels and mice. The array is fairly high off the ground, 5 ft. at the lowest and 19 ft. at the highest so casual access won't be easy.
Yeah, the high voltage DC concerns me even though I've been shocked many times. Covering the array would be real tough so I'm planning all my wiring work for the dark hours. I'm getting used to that as I'm working a few hours into dark with a headlamp trying to get this thing online this year.
Thanks again!

 

[semipro]

Had to reply so I could keep watch.

Very interesting. I went to an evening solar promotion seminar thing here a couple weeks ago. Have been thinking I would likely prefer ground mount to roof, and wondered to myself about constructing of wood. I saw a quick pic somewhere the past while (likely on FB) of one that someone built themselves, but it was a bad camera angle with no details. The guys doing the seminar kind of ball parked a 30% cost premium, on ground over roof mounts. (Talking contractor pricing).

The main thing I was wondering about, was coming up with a structure design that I could be sure would hold up to what it was going to be carrying, and the wind (we're on a mostly exposed hill top, and bad wind events are becoming more frequent) . Did you have any guidance there?

We get frequent high winds here too.
I built heavy concrete footer/curbs to secure the 6 poles using embedded bolts. I based the concrete size on wind loading calculations. In some areas, bed rock or large boulders were present so I tied into them using re-bar epoxied into the deep holes I drilled.

Edit: As you can see from the photos I posted below, running the wiring underground can be quite a job especially if you have rock present. This is one very compelling reason to go with a rooftop install. Our roof is not at a favorable pitch and is shaded by some very nice Maple trees. I also like the idea of being able to clean the array of snow or dust from the ground.

 

[semipro]

Since there seems to be interest I thought I'd share some more photos and plans.
1. Side view of what i'm building with my truck shown for scale
2. Aerial view of the site before construction, lots of big trees to harvest.
3. Aerial view of the planned route for underground conduit and wiring after trees removed.
4. Trenching excavation from above.
5. Trenches and rocks
6. Damn big rocks
7. Conduit connection to house
8. conduit to center footer/curb for PV, carport power, power to a nearby future shop, and for an EV charger in the carport.
9. Another view of conduit in the foundation
10. Finished footer/curbs
11. A hopper I built to use my tractor's FEL to load gravel and sand into my concrete mixer.

 

[peakbagger]

Consider my comments are as much for those following the thread as for you.

The whole grounding/bonding thing makes my head hurt and I swear even the licensed pros cant agree. I do have taller trees and a nearby utility power line in the street so its likely I will not get a direct strike but could get a reflected strike. My theory is I want to put as much energy from a strike into the local ground rod and keep it from getting into the house wiring. My pole and my frame is grounded to a local ground rod and then my DC lines go through a midnight solar surge suppression device (SPD) mounted at the local disconnect switch on the pole and the SPD output is connected to the local ground rod. I then tied the local ground rod to a #4 copper that runs in the same trench as the conduit. It ties into my main ground outside the house near my meter. I have an artesian well with 60 feet of casing that is also tied into the main house ground (my suspicion is the well casing probably has the lowest ground resistance)The theory is any strike will go directly down into the ground at the pole and the SPD will hopefully catch any surge from getting into the DC wiring to my inverter. Tying the local ground rod to the house ground assures that the surge doesn't decide to use my DC wiring to get to the house ground rod which has a lower potential. My understanding is if the panels need to be bonded to the house system it would require an additional wire in the conduit which would eventually tie into the main power panel where the tie to the main ground rod is made. So my guess is with your panels you do not need to bond them but you do need to ground them.

One minor issue that may not apply down in Virginia is that in our area we cannot put in rigid conduit from above ground to underground unless we put in slip couplings so that if the soil moves relative to the building that the conduit doesn't get stressed. In your case it would be at the house only as your conduit goes into the footing at the array. We also have to go with a thicker wall PVC conduit where its exposed near the ground (or put in steel).

Up north we need to get the footings down below frost line so we generally do not worry about wind uplift when sizing footings as 4' of soil on top of them provides plenty of anchorage. The frost line is at least 4' in my area (and the soil is even bonier than yours) . The normal goal is keep the footings deep and then just run sonotubes up above the frost line to reduce the amount of area that the frost can grab onto.

It looks like your footings were sized with extra concrete to deal with wind uplift as you dont have any soil on top of them. In either case, the connection to the footing has to be designed for uplift as well as compression.

I am curious how you are dealing with the lateral wind load. The posts look to be pin type connections so they dont provide a lot of side to side resistance. I see the angled box bean up high that presumably is a fixed connection that provides some lateral stiffness but since the sides of the structure are wide open I would normally end up wanting to put in some diagonal bracing to stiffen things up in the open bays. One option would be go with some galvanized cables making a big "X" on the open sides. Unless the cables are shiny, they would tend to visually blend in from a distance. The other way around for someones future project is turning the footing connections into fixed connections instead of pin connections by sinking some angle iron down into the footings sticking up a couple of feet and bolting the posts to the angle iron.

It does look like you thought it through and its going to nice looking result.

 

[semipro]

My responses embedded below.

Consider my comments are as much for those following the thread as for you.

The whole grounding/bonding thing makes my head hurt and I swear even the licensed pros cant agree. I do have taller trees and a nearby utility power line in the street so its likely I will not get a direct strike but could get a reflected strike. My theory is I want to put as much energy from a strike into the local ground rod and keep it from getting into the house wiring. My pole and my frame is grounded to a local ground rod and then my DC lines go through a midnight solar surge suppression device (SPD) mounted at the local disconnect switch on the pole and the SPD output is connected to the local ground rod. I then tied the local ground rod to a #4 copper that runs in the same trench as the conduit. It ties into my main ground outside the house near my meter. I have an artesian well with 60 feet of casing that is also tied into the main house ground (my suspicion is the well casing probably has the lowest ground resistance)The theory is any strike will go directly down into the ground at the pole and the SPD will hopefully catch any surge from getting into the DC wiring to my inverter. Tying the local ground rod to the house ground assures that the surge doesn't decide to use my DC wiring to get to the house ground rod which has a lower potential. My understanding is if the panels need to be bonded to the house system it would require an additional wire in the conduit which would eventually tie into the main power panel where the tie to the main ground rod is made. So my guess is with your panels you do not need to bond them but you do need to ground them.

Lightning has been a problem here. Its taken out our underground dog containment system several times. I've had a strike hit the top of a cedar only 20 ft. away as I was standing with my wife on a boulder. I stood, awed and by the time I turned to my wife she was nearly to the house. I've also been shocked while doing plumbing work in our house during a thunderstorm. I've installed whole-house surge protection system.

I agree on the complexity of grounding/bonding and that panels should at least be grounded locally but maybe not bonded to the house wiring. For now, I plan to follow inverter maker's recommendations. They claim that spike suppression is built into their system and adding bonding or spike protection will only cause problems. I have oversized all the conduit so extra conductors can be added as needed.

One minor issue that may not apply down in Virginia is that in our area we cannot put in rigid conduit from above ground to underground unless we put in slip couplings so that if the soil moves relative to the building that the conduit doesn't get stressed. In your case it would be at the house only as your conduit goes into the footing at the array. We also have to go with a thicker wall PVC conduit where its exposed near the ground (or put in steel).

Slip joints were considered but not installed as frost depth over the last 10 years has not been much. Our design frost depth is 18 in. here. I did install the stronger schedule 80 aboveground as required by code.

Up north we need to get the footings down below frost line so we generally do not worry about wind uplift when sizing footings as 4' of soil on top of them provides plenty of anchorage. The frost line is at least 4' in my area (and the soil is even bonier than yours) . The normal goal is keep the footings deep and then just run sonotubes up above the frost line to reduce the amount of area that the frost can grab onto.

I started by trying to bore dig deeper holes with a tractor mounted post hole digger but large boulders stopped me. I rented an mini-excavator and dug some up and bonded the footer/curbs to them where they were to big to dig up. What you don't see in the photos is that each footer/curb either has deep holes at either end that reach well below frost depth or that large boulders there were anchored to.

It looks like your footings were sized with extra concrete to deal with wind uplift as you dont have any soil on top of them. In either case, the connection to the footing has to be designed for uplift as well as compression.

I built the footer/curbs with both upward and downward forces in mind. Its hard to tell but there is a total of 5 tons of concrete in the 3 footer/curbs. Each post is anchored using an embedded bolt and a hefty metal structural base. I've built it so that these posts can be raised later as needed to deal with any settling of the foundations. This structure is built on a slope so the footer/curbs will be used to retain gravel parking installed below the array.

I am curious how you are dealing with the lateral wind load. The posts look to be pin type connections so they dont provide a lot of side to side resistance. I see the angled box bean up high that presumably is a fixed connection that provides some lateral stiffness but since the sides of the structure are wide open I would normally end up wanting to put in some diagonal bracing to stiffen things up in the open bays. One option would be go with some galvanized cables making a big "X" on the open sides. Unless the cables are shiny, they would tend to visually blend in from a distance. The other way around for someones future project is turning the footing connections into fixed connections instead of pin connections by sinking some angle iron down into the footings sticking up a couple of feet and bolting the posts to the angle iron.

I've not shown any additional bracing in the sketch yet until I decide where and how to build it. I'd like leave the sides open if I can so I'm trying other ways of providing lateral stiffness. If the box beam and rafters are of sufficient strength and well connected their geometry as built should provide adequate support. I plan to add the tension cables you describe if needed. I frequently use metal pipe, strap, or wire rope in my projects for this sort of thing. I've already added some diagonal braces on the front and rear sides. I'll provide shots of those as things progress.

It does look like you thought it through and its going to nice looking result.

Its hard to imagine how much though goes into this sort of thing but it sounds like you've been there.
I've been planning PV solar since I was about 13
Many thanks for your detailed replies!

 

[sloeffle]

Impressive work @semipro. I like the drone shots too.

 

[DBoon]

Thanks for the photos and the detailed description - it's fun to see the process. Makes me glad that I just wrote the check but a little wistful that I don't have the time, equipment and certainly some of the skills to do the work myself.

 

[peakbagger]

I do look forward to your battery work. What are you going to use for a charge controller and battery protection.

 

[semipro]

I do look forward to your battery work. What are you going to use for a charge controller and battery protection.

The charge controller is built into the SolArk inverter and is fairly configurable. I will need to come up with a BMS though. Given that batteries are lithium-based I'm considering the potential for fire and how and where the batteries are stored. I'm looking at options like paint lockers. I'm also considering outside storage in an insulated and maybe climate controlled enclosure. Fortunately the SolArk can be configured to operate with or without batteries so I may have more time to deal with battery issues.

 

[semipro]

Impressive work @semipro. I like the drone shots too.

Yeah, I keep finding uses for the drone on our property. As it turns out, getting some photos from high up is pretty useful. My adjacent neighbor just did a survey and this post reminds me that I need to fly and record the locations of survey flags.

 

[Agent]

Nice work on a build-your-own ground mount! I just went through the same thing this past spring. 26 x 305W Mission Solar panels with two strings each going to a 5kw SMA inverter. Mainly due to the cost savings of lumber, I did this for just a bit over $9k including a new meter pedestal, main panel, and sub panel.

Mine was a bit less engineered as yours, but it survived a nearby mini-tornado this summer that took out a few big trees in my yard.

It's great to see power made from the sun. Best wishes on finishing up!

 

[semipro]

I thought I'd post some photos on progress. The weather has been relentless. It rains just enough to keep the ground soggy and when it freezes then thaws its a real challenge to even walk let alone carry around panels.

The structure from the side looking East. I will likely add some diagonal cables between the two center posts and additional diagonal braces on the outer southern (short) posts.


Looking southeast. Metal roofing to be installed. A barrier will be installed between metal roofing panels and the treated rafters to prevent roof corrosion.


Half the panels mounted - looking north.


Close up of panel installation and rope used to hoist them into place (or at least to hold them while I push them up. The panels are mounted to the rails using the holes in the back of the panel frame and a tee-nut that fits within a groove in the top of the rail. There are neoprene washers between the rail L-brackets and the treated rafters. (looking north)

 

[semipro]

Oh yeah, I also bought the EV that will garage under, and be charged by, the solar panels.
I using it as a commuter and saving my truck (in the background) for more important tasks.

 

[SpaceBus]

Oh yeah, I also bought the EV that will garage under, and be charged by, the solar panels.
I using it as a commuter and saving my truck (in the background) for more important tasks.
View attachment 257957

Very nice, I look forward to the day I can do the same.

 

[semipro]

I finally finished this project.
I post a few photos here: https://www.hearth.com/talk/threads/cutting-trees-for-marginal-solar-improvement.181710/post-2444666