Ground Mount on Hill

[ChrisG]

Here is my cabin where solar, not grid tied, will be going. Due to wind in this location (120mph) and a one week old new roof, it has been recommended to not go roof mount. Ground is rock, like immovable boulders. The angle shot is looking looking north so I’m south from the cabin. The area directly in front gets 4 hours of sun (early blocked by trees, later blocked by cabin). Looking to do 10-400w panels. Few questions: 1)What type of ballasted ground mount could go here? 2) Are there other options than conduit in the ground to run PV wire (impossible to trench especially on this hill. 3) What are some other possibilities?

I don’t have much room on my property line behind the cabin so having west facing panels is not possible. The other acreage of my land is heavy forest with no clearings and again this ground is solid. The flatish area is a service road so I can’t put anything there.

 

[Kornbread]

That looks like a tough location for ground mount solar. Lots of shade = not much production. I'll see around 10%-15% production on cloudy days vs sunny. Maybe check in to what roof mount systems people are installing in hurricane areas. As per this pic, the roof looks like the best spot.

 

[Vigo]

I agree. I went far bigger on my panel array than my actual ‘load’ to try to and buy some tolerance for cloudy weather, and the results are STILL less than i hoped. My takeaway from that is it is impractical to ‘panel your way out of’ bad location/placement. That roof looks pretty dang good for solar to me. I think whoever you were talking to was just unfamiliar with solar racking (me too, so no judgment) and if it was coming from your roof installer he was almost certainly trying to protect his bottom line by dissuading you from taking him out of his comfort zone or using another installer who was more experienced on roof-mount solar issues.

I would just try to find a contractor who actually gives you confidence that a roof mounted array would be installed prfessionally, leak-free, and wind rated. I suspect your ground mount location will end up disappointing regardless of how good the hardware or install is. Ive only setup one (~10kw) solar array so far so take it for what it’s worth coming from..me. ?

 

[ChrisG]

The roof is absolutely the best place. Every year the south facing roof side needs shingles replaced so I just replaced the entire roof with GAF high wind certified roof on this week with 50 year non prorated wind warranty. Not willing to risk damage with panels or void of warranty. Maybe I need to take the approach of a massive backup system with panels I can deploy when needed. Or I convince my wife to let me to a 300x300ft clearing but still can’t trench conduit. My well pump that is relatively new is just buried outdoor rated romex a few inches under the soil top.

 

[Vigo]

Nice property! Sounds like you’re JUST PAST the ideal time to have figured out the roof mount and are now trying to work around the decisions of the recent past. That’s tough but relatable!

I think given the constraints of the space, my main suggestion would be to ready yourself for low daily output and make sure you are going to hook enough battery to it to fully absorb the available PV energy during your narrow window. As far as conduit, i guess that depends on whether it has to pass some kind of inspection and if so, what are the relevant codes. I personally dont know much about ground mount ‘anchoring’ for high wind, so i’ll be interested to see what i can glean from whoever else will be along shortly that actually knows something.. ?

 

[Kornbread]

The pv production gained by clearing/topping some trees might make it worthwhile. If the thought of clearing trees bothers you (it does me so I simply prune and deal with the pros n cons of shade), consider that nearly 60% of electrical generation is through fossil fuels.

The rocks present another challenge. They had to anchor your house to the ground, how did they go about that? I would definitely put the pv home run in some kind of conduit, especially if it's going to be buried shallow.

 

[Jack Rabbit Off Grid]

Think of it like this. You replaced the roof so if you cover it with panels they will take the brunt of the wind. Other then winter snow removal.

Im in the same situation but my hill gets plenty of sun. I got the Tamarack double top of pole mount system. I’m going to setup my forms and pour large counter balance blocks right on top of the ground. Then cut the poles to to the height I need them to make the panels level.

 

[ChrisG]

The rocks present another challenge. They had to anchor your house to the ground, how did they go about that?

I am the second owner. My understanding is that the area was shaped with core drilling and blasting.

 

[Kornbread]

Wow, that may be a major issue in trying to anchor a ground mount. Have any local contractor friends with knowledge of the terrain? Maybe talk with them about your plans.

 

[Shimmy]

The roof is the right place, but if you want to put it on the ground a slab for ballast is likely your best option. I'd worry more about tree limbs taking out the panels than the wind at ground elevation though.

 

[rhino]

Was the new roof asphalt shingles or metal? Why was it recommended not to install on the roof unless you are concerned about having to clear snow? As others have mentioned a competent installer should have no issue installing it up there and would solve the issues you are trying to work around. You are surrounded by large number of tall trees which would make huge difference in wind exposure compared to an open field.

 

[rhino]

Looking at the pic of that roof again you'd even be able to fit those 10 panels (plus more) on the roof area over the outside deck so wouldn't even need to break the thermal envelope of the house. They really should go on the roof.

 

[Kornbread]

Don't get me wrong, I can totally understand the op's hesitance to roof mount, and it sounds as if the installer of his new and probably expensive roof may not uphold the warranty if panels are mounted, but darn, it looks to be the only real feasible place for the panels.

If the wind blows consistently, have you thought about wind turbines?

 

[Bluedog225]

Curious where you are. Generally

 

[Shimmy]

If snow (or access in general) is the concern, I would put in a fixed ladder system on the north pitch of the roof and fixed anchors to hold a ladder at the outside staircase to give you safe access. (I would also add in some safety harness tie-off points as well, but that is just because my wife would kill me if I fell off the roof and died.)

 

[Hedges]

(I agree roof mount looks best, but ...)

for mounting on a solid granite boulder, or whatever that mountain is, why not hammer drill holes into the rock? Either set anchor bolts in the holes, or epoxy rebar into it. Bigger holes (core drill) and 2" pipe could be set in it.

 

[ChrisG]

Curious where you are. Generally

Cabin is in the NC/TN mountains.

 

[ChrisG]

Don't get me wrong, I can totally understand the op's hesitance to roof mount, and it sounds as if the installer of his new and probably expensive roof may not uphold the warranty if panels are mounted, but darn, it looks to be the only real feasible place for the panels.

If the wind blows consistently, have you thought about wind turbines?

It’s not constant but when storms roll in up here they are pretty wicked. I’ve tried a few expensive weather stations to track wind velocity but they get destroyed after a few storms. It’s not uncommon to get 120mpg gusts in the winter.

 

[MarkSolar]

If you have that much wind why not use wind generation instead of solar.

 

[ChrisG]

Looking at the pic of that roof again you'd even be able to fit those 10 panels (plus more) on the roof area over the outside deck so wouldn't even need to break the thermal envelope of the house. They really should go on the roof.

@rhino Here is a close up of the roof. The trees near the house were cut down two weeks ago before the roof went on. Worried about chimney shading (not in deck cover area). South roof takes the straight line winds and the section that always needs to be replaced. By the way, love the idea of just covering deck area, could that be done on N and S side? Both do get sun but not as direct as south. Other option could be on east/west small roof portion I guess.

I’d rather do ground but options are limited. Will not be able to get completely off grid here but mainly want critical loads on solar with battery with no sell back. Difficult to get people/contractors here to do quality work.