Ballasted ground mount

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Ozymandias

Member
Location
Missouri
Hi all,
I could land a project of several remote rural telecommunication hubs in the midwest that need a ground mounted PV, if it goes in-house, but management decided to bring an outside quote. I sit in the meeting and we are discussing racking, because of logistics we prefer non concrete options. We talk ground screws, we have a mini-excavator we could use. Outside representative suggests 10 degree ballasted racking on the actual ground.
Is this a thing? I've only heard of this for cast or pour in place ballasts or brownfields and then I think snow since a higher panel at 30 degrees can easily slide snow off.
Any thoughts? Thank you.
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
The RULE OF THUMB for panel elevation angle, maximizing year round production, is the site latitude. Mid-Missouri would put it at maybe 35 degrees.

One thing often overlooked is that wind results in lift which is sometimes significant.
 

Carultch

Senior Member
Location
Massachusetts
Hi all,
I could land a project of several remote rural telecommunication hubs in the midwest that need a ground mounted PV, if it goes in-house, but management decided to bring an outside quote. I sit in the meeting and we are discussing racking, because of logistics we prefer non concrete options. We talk ground screws, we have a mini-excavator we could use. Outside representative suggests 10 degree ballasted racking on the actual ground.
Is this a thing? I've only heard of this for cast or pour in place ballasts or brownfields and then I think snow since a higher panel at 30 degrees can easily slide snow off.
Any thoughts? Thank you.

The term "ballasted" means that the self-weight of what you build, is enough to resist environmental loads on the structure. In other words, there is no fastening or embedment with the soil or building beneath it. In practice, "ballasted" will imply concrete in some form or another, because that's the most cost-effective way to "just add weight". It could be built with masonry units in a ballast tray (as is common on systems made for rooftops), a pre-cast block, or a pour-in-place form.
 

Ozymandias

Member
Location
Missouri
The RULE OF THUMB for panel elevation angle, maximizing year round production, is the site latitude. Mid-Missouri would put it at maybe 35 degrees.

One thing often overlooked is that wind results in lift which is sometimes significant.
Right, I don’t know wind loads of top of my head but 30 degrees is what I’m shooting for with unirac
The RULE OF THUMB for panel elevation angle, maximizing year round production, is the site latitude. Mid-Missouri would put it at maybe 35 degrees.

One thing often overlooked is that wind results in lift which is sometimes significant.
Right, I don’t recall wind load of top of my head but I’m using unirac’ ubuilder to design it. 30 degrees is what I was shooting for.
 

Ozymandias

Member
Location
Missouri
The term "ballasted" means that the self-weight of what you build, is enough to resist environmental loads on the structure. In other words, there is no fastening or embedment with the soil or building beneath it. In practice, "ballasted" will imply concrete in some form or another, because that's the most cost-effective way to "just add weight". It could be built with masonry units in a ballast tray (as is common on systems made for rooftops), a pre-cast block, or a pour-in-place form.
Noted, so it is a viable option, I just thought of snow coverage but it is the same conditions as a rooftop.
 
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