Ground Mount Solar Panel Array

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AllPawDrive
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Ground Mount Solar Panel Array

Post by AllPawDrive » Fri Jul 31, 2020 11:50 am

Hello all,

For a given solar panel array output power for an off grid home where real estate space is not a concern, is there any short or long term advantage of installing a smaller array with higher wattage panels over a larger array with lower wattage panels? Also assume a location with no shading.

Of course, it’s a smaller footprint and there will be some installation scale of economics savings, lower racking costs, probably a lower $/W for the panel itself.

Also, if anyone has any experience with https://www.mtsolar.us/ pole mounts, it would be great to hear from you.

Also, I’ve noticed a gap in the availability of panels. There doesn’t seem to be any available (at least where I’m looking), between 200 and 300 watts. Is there some intrinsic aspect of solar panels that creates this gap?

Thanks,

Dave

raysun
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Re: Ground Mount Solar Panel Array

Post by raysun » Fri Jul 31, 2020 12:06 pm

AllPawDrive wrote:
Fri Jul 31, 2020 11:50 am
Hello all,

For a given solar panel array output power for an off grid home where real estate space is not a concern, is there any short or long term advantage of installing a smaller array with higher wattage panels over a larger array with lower wattage panels? Also assume a location with no shading.

Of course, it’s a smaller footprint and there will be some installation scale of economics savings, lower racking costs, probably a lower $/W for the panel itself.

Also, if anyone has any experience with https://www.mtsolar.us/ pole mounts, it would be great to hear from you.

Also, I’ve noticed a gap in the availability of panels. There doesn’t seem to be any available (at least where I’m looking), between 200 and 300 watts. Is there some intrinsic aspect of solar panels that creates this gap?

Thanks,

Dave
Assuming the use of MPPT charge controllers and 60 or 72 cell panels, the larger output panels have the benefit of lower installation cost, fewer connections to maintain, smaller footprint.

The 200 - 300W gap is most likely marketing and economics. With 400W panels coming online, and the major cost of manufacturing in fabrication, why put out a 200-300W panel? Not cost competitive.

Looking at the modern panels, check into the split-cell technologies. (120 - 144 half cells in a panel.) These are giving another marginal improvement in panel performance for little, if any, additional cost.

FWIW, setting up 10 380W panels on an FM80 is probably easier and cheaper than 12 320W panels.

provo
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Re: Ground Mount Solar Panel Array

Post by provo » Fri Jul 31, 2020 12:25 pm

AllPawDrive wrote:
Fri Jul 31, 2020 11:50 am

Also, if anyone has any experience with https://www.mtsolar.us/ pole mounts, it would be great to hear from you.

Also, I’ve noticed a gap in the availability of panels. There doesn’t seem to be any available (at least where I’m looking), between 200 and 300 watts. Is there some intrinsic aspect of solar panels that creates this gap?
I don't know that brand of pole mount, but I'm a big fan of pole mounts in general (I have two 13-year old UniRac frames on 6" poles). They make it easy to experiment with different azimuths and elevations. I change the elevation four times a year, which adds around 8% to the annual kWh's.

If too high, they can be harder to wash than some ground mount methods, but WAY better than roof mount in that regard.

As far as panel wattage, I would just think the research and improvements tend to go into the larger wattage panels, so panels under 300W are not cutting edge anymore. Personally, I'd go for the highest wattage panels you can get that meet your budget and put out a Vmp you can live with.

AllPawDrive
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Re: Ground Mount Solar Panel Array

Post by AllPawDrive » Fri Jul 31, 2020 1:03 pm

raysun wrote:
Fri Jul 31, 2020 12:06 pm
Looking at the modern panels, check into the split-cell technologies. (120 - 144 half cells in a panel.) These are giving another marginal improvement in panel performance for little, if any, additional cost.
Half is the new full. Interesting.

After further careful review of my seasonal power needs and my seasonal sun-hours, I’ve decided to break on through the 4kW ceiling. Still need to decide between two FLEXmax 80s or one FLEXmax 100.
provo wrote:
Fri Jul 31, 2020 12:25 pm
I don't know that brand of pole mount, but I'm a big fan of pole mounts in general (I have two 13-year old UniRac frames on 6" poles). They make it easy to experiment with different azimuths and elevations. I change the elevation four times a year, which adds around 8% to the annual kWh's.
Thanks for the tip on UniRac. MTmount pole mounts have a manual screw drive that can be operated from the ground to adjust the vertical angle between 5 and 90 degrees. And it’s continuous, not discrete fixed angles like some other ground mount racks.

Seasonally adjusting the azimuth is not so easy but I wouldn’t be getting much from that adjustment anyway. Maybe adjust it a little west in the summer to get more afternoon watts. I ran some numbers through https://www.nrel.gov and I can pretty much set the vertical angle once and forget it for the summer. Very little difference across the summer months.

I’ll be running at 47 degrees north so frequent winter vertical adjustment is really needed. Plus I can place the panels at 85 degrees if I leave for an extended period to keep the snow sliding right off. Very little wattage lost compared to the ideal winter angle.

provo
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My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
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Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: Ground Mount Solar Panel Array

Post by provo » Fri Jul 31, 2020 1:35 pm

AllPawDrive wrote:
Fri Jul 31, 2020 1:03 pm

MTmount pole mounts have a manual screw drive that can be operated from the ground to adjust the vertical angle between 5 and 90 degrees. And it’s continuous, not discrete fixed angles like some other ground mount racks.

I ran some numbers through https://www.nrel.gov and I can pretty much set the vertical angle once and forget it for the summer. Very little difference across the summer months.

I’ll be running at 47 degrees north so frequent winter vertical adjustment is really needed. Plus I can place the panels at 85 degrees if I leave for an extended period to keep the snow sliding right off. Very little wattage lost compared to the ideal winter angle.
I'd love a screw drive to adjust the angle! I'm at 38°N, and I change the elevation 2 months before and after each solstice, and 1 month before and after each equinox. Kind of a fun ritual :grin: .

pss
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Re: Ground Mount Solar Panel Array

Post by pss » Fri Jul 31, 2020 1:52 pm

I have 3 large ground mount arrays. The first concern is will you be pulling a permit? If so, you may need an engineered plan of the ground mount showing wind loading and connections.
Now, you really don't need any fancy stuff. Standard in Southern California for a wind load of up to 110 mph is to drill a 36" deep hole, 12" in diameter and place Sono Tubes or equivalent. Depending on the size of the panels and the number of panels, you can easily find free software online that will tell you the exact distance between the placement of the Sono Tubes and tell you how many rows and columns of tubes. Then, you use Schedule 40 galvanized steel pipe cut at least a couple of feet in excess of the final height you need and wrap the bottom 4 feet of the pole in 10 ml vinyl pipe tape to protect the steel from the concrete. Drill the number of holes you need and set your Sono tube about 6 inches above grade. Locate your 4 corners of the array, pour your concrete and plumb the tubes, and ideally use string around the poles to confirm the angles of the array posts. After the 4 posts are set, use the straight line strings to set your posts in line with the corner posts. When all posts are set from the ends of the array, run string from the back post to the front post at the angle you want your array to have. Allow enough height at the front posts to work underneath a panel, at least a couple of feet. Then cut all of the posts to the heights marked by the string to achieve the angle of your array, back posts the tallest, then middle row of posts if you have one and then shortest posts in front. Next, with the height of all your posts set, connect the posts across all of the rows by using Hollaender aluminum tee connectors and sliding more of your schedule 40 galvanized pipe through the tee fittings. This pipe can be easily obtained in 20 foot lengths. For arrays wider than 20 feet, use Hollaender connectors to connect one end of pipe to another. After completion of this step, your array should have the rows of posts all connected across the array from the left side to the right side with schedule 40 pipe, but not from a front row to a middle or back row. Now, using galvanized deep channel strut, connect the struts to the rows of the schedule 40 pipe that go across the the posts. They are being laid so the front of the strut goes about 6 inches in front of the lowest crossing pipe row and the back of the strut goes about 6 inches past the top row pipe. Fasten the struts with U bolts to the pipes and make sure they are parallel in pairs. When the struts are attached, you should have 2 struts for each panel, whether you lay the panels in portrait or landscape. The separation between a pair of struts depends on the panel size and manufacturer instructions. You want to lay the struts so that when the panels are attached to the struts, there is little to no space between the panels. It is the attachment of the struts that finalizes the angle of your array to the Sun based on how you originally cut the tops of the poles off.

Cutting Schedule 40 2" pipe (which is not 2 inches) is best doen with a portable band saw at the array site, makes it easy like working with PVC.

Finally, if you cannot dig 36" or more into the ground due to geology, there is a ground mount solution for that too.

Questions please?

pss
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Re: Ground Mount Solar Panel Array

Post by pss » Fri Jul 31, 2020 1:54 pm

Two of my arrays used Prosolar rails on my ground mounted arrays (prosolar.com) and the other 36 panel array uses galvanized struts to mount the panels.

Mike Curran
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Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Ground Mount Solar Panel Array

Post by Mike Curran » Fri Jul 31, 2020 5:35 pm

That's a pretty detailed description. Can you post a photo of one of your mounting structures?
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

pss
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Re: Ground Mount Solar Panel Array

Post by pss » Fri Jul 31, 2020 5:54 pm

As a favor to Mike, I will post photos tomorrow. If you cannot penetrate ground due to rock, septic, etc, you can fabricate 24"x24"x24" concrete forms, build a rebar cage, place then just 6-12 " in the ground in the proper positions, then square up and pour the four corner posts and plumb them. Then pour the interior concrete forms using guide string around the four corners to align and plumb the interior posts. Each concrete form will weigh about 1,000 pounds. Using hollaender junctions, tie the blocks together from front to back with schedule 40 steel pipes attached low on 1 vertical to higher on the other pipe. This locks all the blocks together so the array won't go sliding anywhere. I had this design engineered to code, inspected and passed. Made the forms, rebar cages and poured myself. Fun project.

raysun
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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
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Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
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Re: Ground Mount Solar Panel Array

Post by raysun » Fri Jul 31, 2020 7:59 pm

pss wrote:
Fri Jul 31, 2020 5:54 pm
As a favor to Mike, I will post photos tomorrow. If you cannot penetrate ground due to rock, septic, etc, you can fabricate 24"x24"x24" concrete forms, build a rebar cage, place then just 6-12 " in the ground in the proper positions, then square up and pour the four corner posts and plumb them. Then pour the interior concrete forms using guide string around the four corners to align and plumb the interior posts. Each concrete form will weigh about 1,000 pounds. Using hollaender junctions, tie the blocks together from front to back with schedule 40 steel pipes attached low on 1 vertical to higher on the other pipe. This locks all the blocks together so the array won't go sliding anywhere. I had this design engineered to code, inspected and passed. Made the forms, rebar cages and poured myself. Fun project.
Gonna call you Stonehenge from now on.

Mike Curran
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Posts: 1810
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Ground Mount Solar Panel Array

Post by Mike Curran » Sat Aug 01, 2020 5:35 am

http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

pss
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My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Ground Mount Solar Panel Array

Post by pss » Mon Aug 03, 2020 8:45 am

Mike,

I took weekend off, but I did look at your link. I have never seen that product in Southern California. In fact, unless it is rainey season here, even trying to screw a 12" stake into the ground becomes a two person challenge. the problem is in most of So Cal, the bedrock can be as shallow as 20 inches below the surface. the the surface is a crumbly loamy dirt. When we plant, we dig out the hole for the planting and then use soil amendments. It then becomes up to the plant to go through granite or around it.
mount 1-1.jpg
mount 2-1.jpg
mount 3-1.jpg
These three photos show a mount you can build yourself. Set only 6-12" into the ground, they consist of 24x24x24" steel re-enforced concrete blocks with Schedule 40 2" pipes inserted. The blocks are tied together by the use of hollaender tees from the front to the back vertical posts, while they are tied in the other direction by the posts along the top of the front to back rows. Each block has a weight of 1,000 pounds and is providing wind load to 110 - 120 mph. Each block takes about 10-12 bags of concrete mix.

This array also utilizes Prosolar aluminum rails. These rails are strong, lightweight and not expensive. However, the U bolt hardware from Prosolar must be installed by aligning the rail and then marking and drilling holes through the aluminum. a little time consuming, but very easy to drill with a template. This solidly locks down the rails and creates the grounding bond too.

pss
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Re: Ground Mount Solar Panel Array

Post by pss » Mon Aug 03, 2020 8:51 am

mount 5-1.jpg
mount 4-1.jpg
The first photo illustrated the use of 12" sono tubes 36" deep and 2" Schedule 40 pipe. The pipes are connected with Hollaender tees and the rails are Prosolar aluminum.

The second photo also uses sono tubes and schedule 40 pipe, but the rails are galvanized metal struts available at your home improvement center. You can also see how the use of structs across the verticals allows for placement of the combiner box, a disconnect switch and the conduit routing away from the array.
All of this can be done quite easily. The only tool that I highly recommend is a portable band saw that can cut metal. I use the Milwaukee, but I cut a lot of stuff. It will go through steel pipes and strut like cutting soft butter. But there are also others out there cheaper and now HF has one.
Also, schedule 40 pipes can usually be had from a pipe dealer in the area for a a lot less money in 20 foot lengths. If you calculate your needs, they will usually free or for a small fee deliver and drop off. Then you cut the lengths you need.
To keep the pipe from torquing in the concrete, attach a U bolt or other piece of steel to the pipe about 6" from the bottom.

pss
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Re: Ground Mount Solar Panel Array

Post by pss » Mon Aug 03, 2020 9:28 am

mount 8-1.jpg
mount 7-1.jpg
mount 6-1.jpg
Laying out your non-pentrating 2 foot by 2 foot by 2 foot concrete forms.

pss
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Joined: Mon Jul 24, 2017 8:40 am
My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Ground Mount Solar Panel Array

Post by pss » Mon Aug 03, 2020 9:31 am

mount 12-1.jpg
mount 11-1.jpg
mount 10-1.jpg
Bottom of the Schedule 40 pipe is wrapped in 10 mil PVC tape and has u bolt attached to prevent torquing of post ion concrete. The concrete form contains a steel re-enforced cage surroudning the post. Again, a portable band saw cuts rebar like butter. And laying out the array posts, starting with the 4 corners.

pss
Forum Czar
Posts: 636
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Ground Mount Solar Panel Array

Post by pss » Mon Aug 03, 2020 9:33 am

combiner box-1.jpg
grounding rod-1.jpg
mount 13-1.jpg
Building the array supports after concrete is poured. Using a jack hammer to install grounding rod at array. And wiring in combiner box with lightening arrestor. Photo is of my electrician, not the author of this post!

Mike Curran
Forum Emperor
Posts: 1810
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Ground Mount Solar Panel Array

Post by Mike Curran » Mon Aug 03, 2020 12:11 pm

Thanks for the pics, pss. Pretty impressive install, looks like it was a lot of work. You make it sound like it was easy...
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

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