New ground array

[pudding]

3 tons of concrete! Was hoping to not get involved in digging big holes and mixing concrete.

A concrete block is 18kg or so, 3 of those under each triangular support which I can anchor bolt into, thats 9 blocks under each frame ( was planning on 2 frames, with 4 panels each), then another 2 blocks put on the 'sole plate' of each triangular frame, so another 6 blocks weighing it down, so thats 324kg of weight, not including the timber and panels themselves, call it 350kg ballast there. If thats not enough and it moves then I think I could get one or 2 of the helix screw piles to 'tie' it down further?

Out of interest, how would you attach pv panels to scaffold poles?

[Moxi]

Just be aware that wind loads will be substantial.

As an idea, I have 16 panels and they are bolted in to 3 piers of concrete which add up to 3 tons. That's on an aluminium frame.

Is that in a very exposed position Andy ? or is the ground particularly poorly consolidated ?

Moxi

[Stinsy]

3 tons of concrete! Was hoping to not get involved in digging big holes and mixing concrete.

A concrete block is 18kg or so, 3 of those under each triangular support which I can anchor bolt into, thats 9 blocks under each frame ( was planning on 2 frames, with 4 panels each), then another 2 blocks put on the 'sole plate' of each triangular frame, so another 6 blocks weighing it down, so thats 324kg of weight, not including the timber and panels themselves, call it 350kg ballast there. If thats not enough and it moves then I think I could get one or 2 of the helix screw piles to 'tie' it down further?

Out of interest, how would you attach pv panels to scaffold poles?

Wind load calculations are complicated. However I can say with confidence that laying a few concrete blocks on the ground will not be sufficient. Screw piles on the other hand will do the job.

I’ve seen PV panels attached to scaffold poles with U bolts.

[Andy]

Just be aware that wind loads will be substantial.

As an idea, I have 16 panels and they are bolted in to 3 piers of concrete which add up to 3 tons. That's on an aluminium frame.

Is that in a very exposed position Andy ? or is the ground particularly poorly consolidated ?

Moxi

North of scotland 600 feet up. Last year the whole mature woodland about 250m away got laid flat. However I do have leylandii behind the panels that I will never take down.
There are graphs somewhere that show expected max winds you need to plan on for your area.

[Stinsy]

Ah, already ordered 70m of the solar cable, so twin wall conduit it is! Anything in particular or any twin wall that google comes back with?

Here's a rough sketch of the initial timber frame plan. I thought about scaff and uni-strut, but the timber just works out way cheaper from what I could see. was hoping to keep total costs under £1000.

Plan was to use pressure treated 100x100 vertical posts and 100x50 for the horiontal 'sole plate' and diagonal brace and 'rails', glued and screwed using the gorilla PU adhesive I've already got.

50mm twin-wall duct is what it is (I buy electrical stuff from TLC but any local electrical wholesaler will have it).

It isn’t best practice to use timber bolted to the side of another timber to carry weight when exposed to elements. The strength of the joint comes from friction and is strong initially but as the wood rots it shrinks and you’re left with the 10mm bit of wood under the bolt holding all the weight (inevitably leading to premature failure.

In your design where 100x100 vertical fence posts are supporting 4x2 diagonals, it is better to cut a notch in the fence posts and have the 4x2s sitting in that. You can screw or bolt the diagonal to the post but the fixing isn’t carrying weight it is just keeping the pieces together.

Edit: just to make sure the bottom edge of the panels is far enough off the ground so that weeds/grass don’t cover the bottom edge of the panels. 1ft if you’re diligent with your strimming, 2ft if you’re not would be my suggestion.

[Andy]

As an idea, I have 16 panels and they are bolted in to 3 piers of concrete which add up to 3 tons. That's on an aluminium frame.

Is that in a very exposed position Andy ? or is the ground particularly poorly consolidated ?

Moxi

North of scotland 600 feet up. Last year the whole mature woodland about 250m away got laid flat. However I do have leylandii behind the panels that I will never take down.
There are graphs somewhere that show expected max winds you need to plan on for your area.

I did contact a company for screws in Dec. Not heard back. Are they even bothered with smaller installs?

[Moxi]

As an idea, I have 16 panels and they are bolted in to 3 piers of concrete which add up to 3 tons. That's on an aluminium frame.

Is that in a very exposed position Andy ? or is the ground particularly poorly consolidated ?

Moxi

North of scotland 600 feet up. Last year the whole mature woodland about 250m away got laid flat. However I do have leylandii behind the panels that I will never take down.
There are graphs somewhere that show expected max winds you need to plan on for your area.

Anyone know where to find said graphs ? I’m 300 ft higher than Andy and very exposed to Westerlies so I would be interested to find this information out ready for when I expand to ground mounts across the road. Emailed another contractor today to see if they will quote me for a duct under the road.

Moxi

[Joeboy]

I have done quite a number of fence posts over the years. My fave method is start with a slim spade, go down to compacted soil (usually about 600mm). Once there take the time with a handtrowel to bell out the bottom of the hole. This provides a strong anchor and cuts down on concrete needed. I also like the screw pile idea but not seen it in action. Great to see a project develop!

[AlBargey]

I did contact a company for screws in Dec. Not heard back. Are they even bothered with smaller installs?

I've used the DIY type ground screws to anchor a community garden pagoda type thing, It could work well for solar arrays, you can also hire petrol/ corded screwing machines for longer/larger screws. For us though it was above an old car park with the odd bit of rubble which stops the screwing dead, but it was softish ground so with a long bar and some sweat two people can screw them in for a solid foundation, if avoiding rubble/rocks. I forget where we got them from but there are quite a few places online for diy ground screws.

Screws:


Temporary Screwing Handle:


Pagoda

[Comper]

Assortment of ground screw lengths at F H Brundle.
Have used them quite a few times good service.

https://www.fhbrundle.co.uk/decking-and ... und-screws