Ground mount ballast 11000 pounds 5.5tons!

[BlueMarblePA]

I am trying to put eighteen panels in a row landscape format using the power field plastic buckets. I have a rarely used dilapidated tennis court where I want to put them along the long 120 foot fence wall. I asked power field for a ballast design, and they first recommended 16000 pounds of ballast - 8 tons.

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I then asked for redesign as I can install a windbreak as many tennis courts have them on the chain link. The redesign still requires 11000 pounds of ballast based on PA location. Elevation 411 feet and category C. 120mph wind.

I am thinking I can lower these requirements by using duck bill anchors, but the panels are not secured together as they would be with a traditional ground mount system.

Maybe there is a way to run unistrut across all the panels and use that as a ladder brace so the duckbill anchors can support and anchor the whole structure?

Any thoughts from the group

 

[SamDeleted]

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[cs1234]

How about Renusol tubs or similar no dig ballast ground mounts ?

That's what the Powerfield tubs are. They are just claiming an absurd amount of ballast required because of all the regulations regarding wind.

Those things can hold up to 400lbs of ballast per bucket. I can't even imagine the wind required to blow one of those things over with a panel covering it protecting the rocks inside. Your whole house would be gone anyway.

 

[SamDeleted]

That's what the Powerfield tubs are. They are just claiming an absurd amount of ballast required because of all the regulations regarding wind.

Those things can hold up to 400lbs of ballast per bucket. I can't even imagine the wind required to blow one of those things over with a panel covering it protecting the rocks inside. Your whole house would be gone anyway.

Thank you lmao !

 

[BlueMarblePA]

That's what the Powerfield tubs are. They are just claiming an absurd amount of ballast required because of all the regulations regarding wind.

Those things can hold up to 400lbs of ballast per bucket. I can't even imagine the wind required to blow one of those things over with a panel covering it protecting the rocks inside. Your whole house would be gone anyway.

I guess I could get away with maybe 100 pounds per 60 cell panel?

 

[JoeHam]

8 tons is one small dump truck of gravel right ?

For 57’s thats just a couple hundred bucks around here.

That’s gotta be a small portion of your system cost.

 

[Solar Guppy]

It will be whatever the PE says it needs, and most have no idea what wind, which energy applied is cubic function can force upon a structure.

Either you meet code ( and engineering sign off ) or you wing it.

 

[cs1234]

8 tons is one small dump truck of gravel right ?

For 57’s thats just a couple hundred bucks around here.

That’s gotta be a small portion of your system cost.

I concur, it's probably not the highest cost involved.. the plastic tubs themselves cost like $60-100 plus shipping I think.

 

[OffGridForGood]

The material in the tubs can be anything heavy, if getting gravel delivered it not a great option use clay, silt, sand, loam, blast rock, broken concrete/brick rubble, un-welcome in-laws (oops strike that last one) whatever you have that makes up the weight you're after. I think the idea of some longitudenal members connected to both the tubs and the solar panels, then tie those down with duck bills is a reasonable idea too, especially at the ends where the wind may get under the panels. There has got to be something heavy laying around you can get to the tubs.
your stuff, your money, your risk, your choice!

 

[cs1234]

It will be whatever the PE says it needs, and most have no idea what wind, which energy applied is cubic function can force upon a structure.

Either you meet code ( and engineering sign off ) or you wing it.

I would like to see these wind loads that are going to knock those 400lbs of rock buckets over that are about 2 feet high. Even if such wind loads exist in that area, what kind of (flood zone like) time line are we talking about in that location, once every 100 years? Maybe homeowners insurance just needs some sort of low cost rider available to cover the likelihood of a tornado or hurricane hitting that thing directly and picking it up and throwing it somewhere.

People have unsecured trampolines in their backyards, rickety fences, yard tables, flimsy sheds, who knows what. Those things are more likely to come loose and go flying than a solar panel attached to a 400lb bucket of rocks. Most peoples roofs will probably tear off and go flying in a storm before a 400lb tub of rocks sitting directly on the ground. Not every safety code needs to be so incredibly overkill.

I could see some safety concerns with high voltage dc cabling coming loose, but that's not what the structural concerns are even directly addressing.

 

[cs1234]

I am surprised the filling of the buckets is the problem vs the cost / requirement of multiple buckets per panel. With two buckets on a single panel, we are now talking up to 800lbs per panel ! The ballast itself is pretty cheap though, if you are paying $100 per bucket, you may as well fill that empty space up.

 

[cs1234]

I guess I could get away with maybe 100 pounds per 60 cell panel?

I wouldn't, I would fill my buckets up. You pay a lot for those buckets, no point in going cheap on some rocks.

 

[OffGridForGood]

It is not a tub sitting on the ground that will blow over, it is the tub sitting on the ground with 24-sqft of sail attached at an angle to it that will blow over. - I think these things are set up one panel per tub are they?
A 41.5" x 84" PV panel is 24.2 sqft and the wind uplift (depends on wind speed, exposure etc) can easily be 15-20 lbs/ft^2 x 24 is 360-480 lbs, but the tub doesn't lift totally off the ground to fail, it tips over, only half the force is needed to tip it compared to lifting it. That (and liability) is why they set the weight so high. The duck bills are a good idea, but fill the tubs with something, you bought them afterall.

 

[Bluedog225]

It sounds like a lot. But in reality, it’s do-able. Remember the song “loaded 16 tons”?

I shoveled many tons of gravel. It’s good exercise.

 

[cs1234]

It is not a tub sitting on the ground that will blow over, it is the tub sitting on the ground with 24-sqft of sail attached at an angle to it that will blow over. - I think these things are set up one panel per tub are they?
A 41.5" x 84" PV panel is 24.2 sqft and the wind uplift (depends on wind speed, exposure etc) can easily be 15-20 lbs/ft^2 x 24 is 360-480 lbs, but the tub doesn't lift totally off the ground to fail, it tips over, only half the force is needed to tip it compared to lifting it. That (and liability) is why they set the weight so high. The duck bills are a good idea, but fill the tubs with something, you bought them afterall.

They are recommending him two tubs per panel I think in his diagram. That could be up to 800lbs of ballast.

I just don't think it's reasonable to require a solar panel mount to have to withstand 120mph direct hit winds, but nothing else somebody can buy and put in their backyard requires it. How about their barbecue grill sitting on their back porch, what kind of winds does that have to sustain before it goes airborne? The couple of 20lb propane tanks they have sitting on the grass? A picnic table? Why do we treat solar panels like they are nuclear waste? I don't want to be hit by any flying objects from my neighbors yard during what amounts to an F2 tornado coming through their yard, but some things we just risk for the sake of not being absurd nannies.

Maybe it's just because they might have high voltage DC lines left dangling or something? I somewhat understand that as an issue, but they don't base the mounting requirements on it's dc voltage configuration, only on it being a solar panel.. better secure it like it's made of gold and somebody wants to steal it.

It just reaks of people that want money and / or eliminating competition having gotten their hands in it.

 

[OffGridForGood]

Maybe it's just because they might have high voltage DC lines left dangling or something?

I expect that is part of it, and the glass, and someone signed on the line to say "this will be stable in a 120mph wind" to sign that you will want to be damn sure, especially if that same design is applied x 100,000 locations they are going to think about the accumulated liability.

How about their barbecue grill sitting on their back porch, what kind of winds does that have to sustain before it goes airborne?

MY BBQ went airborne this spring, and it wasn't no 120mph wind either! over a railing onto my driveway below, that with a full propane tank attached, and another one (spare) inside the BBQ !

I have to agree with you, there is a tendancy to go overkill on some of these things. HVDC and pieces of glass aside, if the OP lives on a good sized chunk of land -ie no nearby (litigious) neighbours - I wouldn't worry about it too much myself, but hey that is 'me', he has to do 'him'.

 

[SamDeleted]

It sounds like a lot. But in reality, it’s do-able. Remember the song “loaded 16 tons”?

I shoveled many tons of gravel. It’s good exercise.

1 ton a day, it'll be done in less than a week




Or just hire someone to do the shoveling... What's a day labourer cost in the USA ? I could get 5.5 tons moved in a day for a about £80 (probably have to stand and whip the lad to make him do it lmao)

 

[Q-Dog]

It sounds like a huge amount of work but it really isn't. You can easily move 200lbs at a time in a wheelbarrow. 10 of those is 1 ton. It will be some work but not nearly as bad as you think.

Invite a few friends and make it a contest ... 2 wheelbarrows, 2 shovels side by side like a drag race ... fastest time to load, move and dump a wheelbarrow gets a case of their favorite sudsy beverage.

 

[SeaGal]

I guess I could get away with maybe 100 pounds per 60 cell panel?

What is not clear from the images is whether the tubs are as big as the panels or not - if not, there will be greater sail area from the panels.

Our ground-mount use Renusol tubs which are almost as wide as the panels are long, so not much lift from the panels. Plus I have them back to back in an east-west configuration, so no wind can approach from behind them.

FWIW; Renusol also sell wind-deflectors, for use on flat roofs where wind may be more of an issue... maybe Powerfield have a similar concept or you could add a DIY wind-deflector yourself? They're just expensive bits of plastic!

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[SamDeleted]

It sounds like a huge amount of work but it really isn't. You can easily move 200lbs at a time in a wheelbarrow. 10 of those is 1 ton. It will be some work but not nearly as bad as you think.

Invite a few friends and make it a contest ... 2 wheelbarrows, 2 shovels side by side like a drag race ... fastest time to load, move and dump a wheelbarrow gets a case of their favorite sudsy beverage.

I've got a fence I need painting , do you want to come help? trust me it's really fun ?