DIY ground mount for solar PV - what size key clamp pipe and fittings

[Bramco]

Hi,

 

Been putting off making decisions about how to build a ground mount system for our solar PV system.
 

There's a system 'Tm Type' which uses key clamp fittings and galvanized pipe - looks pretty simple to implement as a DIY project.  One set of documentation says that the clamps and pipe are size 2 which is only 34mm OD which seems a bit small. It's not that much more expensive to use size 4 (48mm OD) which would be more sturdy.

 

Here's a side view of the structure 

 

 

Has anyone built a ground mount with key clamp fittings and pipe?  And if so, what size did you use?  Also, if you've done a similar system, how did you drive the poles into the ground to support the structure?

 

Thanks for any advice or thoughts on this.

 

Simon

[SteamyTea]

I take it you don't get many winds over 4 m.s^-1

 

 

[Bramco]

The structure in the kit is rated at 55km/hr - so not sure where the arbitrary 4m/s comes from?

 

Simon

[SteamyTea]

27 minutes ago, Bramco said:

arbitrary 4m/s comes from?

Close to 10 MPH (8.8)

Is there bracing across the back of the modules?

[Dillsue]

With no bracing shown on the sides Im guessing the vertical tubes get knocked well into the ground?? 

[Bramco]

33 minutes ago, Dillsue said:

Im guessing the vertical tubes get knocked well into the ground

890mm according to the diagram.......   So very little, if any, movement front to back or side to side.....

 

Simon

[Dillsue]

27 minutes ago, Bramco said:

890mm according to the diagram.......   So very little, if any, movement front to back or side to side.....

Rock solid then. If youre not used to swinging a sledge hammer, get someone who is to do it!!!

[SteamyTea]

16 minutes ago, Dillsue said:

If youre not used to swinging a sledge hammer, get someone who is to do it

I was at work university with a guy who worked for the Moscow State Circus as a rigger.

He was also the GB under 85kg Arm Wrestling Champion at one stage.

My partner called him The Neanderthal.

[Nick Thomas]

I had to get some new posts into soft ground to fix the allotment fence today. Picked up a https://www.toolstation.com/post-driver/p96574 to get it done, although I wasn't going down that far.

 

It's a bit specialised, but helps a great deal if you're doing this kind of thing by yourself.

[Nickfromwales]

Why not in pods / tubs? You don't need a frame system, other options are out there.

[Bramco]

5 minutes ago, Nickfromwales said:

Why not in pods / tubs?

Pods are a pretty low angle, so don't give the output.  We're looking at 45deg which will give us about the same as the optimum for our location (35deg) but increases the winter output by about 20%. You can play around with the angles etc. on the EEC PVGIS website. 

 

Simon

[Nickfromwales]

Just now, Bramco said:

Pods are a pretty low angle, so don't give the output.  We're looking at 45deg which will give us about the same as the optimum for our location (35deg) but increases the winter output by about 20%. You can play around with the angles etc. on the EEC PVGIS website. 

 

Simon

Got one such install, ground graduated slightly with the mini-digger to help with angle, and that's chucking out a megawatt a month through summer  

[Bramco]

2 hours ago, Dillsue said:

If youre not used to swinging a sledge hammer, get someone who is to do it!!!

Petrol post driver could be fun...

[Dillsue]

10 minutes ago, Bramco said:

We're looking at 45deg which will give us about the same as the optimum for our location (35deg) but increases the winter output by about 20%.

Youre frames look easily adjustable so no plans to change inclination seasonally?? 

[Miek]

Driving the 48mm pipe down almost a meter will be challenging in hard ground if done by hand. Make sure you have a good pilot hole made with a bar first. Get hold of a big bolt (M36 or so) and drop this into the top of the tube to protect the tube from deformation and drive it home with a sledge.  

 

You could hire a tool to do this but success almost entirely depends on your soil type. 

 

 

[jamieled]

Postcrete? We have a timber frame I built, so a bit different but it worked ok.

[Bramco]

10 hours ago, Dillsue said:

Youre frames look easily adjustable so no plans to change inclination seasonally?? 

They are but using PVGIS it looks as though there's a window between about 30deg and 45deg where the annual total doesn't change much but the winter output is a lot more, the higher the angle.  At the moment, there's no battery, so we'll be exporting a lot of our summer output, so I think we'll aim for the higher winter output and not worry about changing the angle in the summer.

 

9 hours ago, Miek said:

You could hire a tool to do this but success almost entirely depends on your soil type

The soil survey shows made ground down to about a meter and then turning to clay - we had to go down a meter for the house foundations.

 

9 hours ago, jamieled said:

Postcrete? We have a timber frame I built, so a bit different but it worked ok.

Probably just more faff, and definitely expense, although on one iteration of the plan I had thought of using postcrete.