DIY Ground-Mounted Solar Array on Scaffold Tubes

At the end of 2022 I built a ground-mounted solar array in my garden: Jinko 460 Wp panels on a frame made of galvanized scaffold tubes, with two SMA Sunny Boy 3.6 inverters in a small metal shed.

No welding is needed. The posts go 1 m deep into the ground, the frame is assembled with tube clamps, and the panels are fixed with exhaust-pipe clamps from a car parts website.

The build took about two months, from the inverter shelter in November to the connection of the inverters at the end of December.

Solar

1. 36 Jinko 460 Wp half-cut solar panels, black frame (one pallet). Check the pallet when it is delivered: two of mine were broken.
2. 2 SMA Sunny Boy 3.6 inverters (SB3.6-1AV-41)
3. Solar cable, MC4 connectors and an MC4 crimping tool
4. A DC box with DC breakers and surge protectors
5. AC breakers in a small box
6. Yellow/green earth cable

Structure

1. Galvanized steel tubes, Ø 42.4 mm
2. Tube clamps for Ø 42.4 mm tubes:
3. 48 adjustable tees, 30° to 60° (JM129-C42)
4. 40 offset crosses (JM161-C42)
5. 16 internal joiners (JM150-C42)
6. 28 grey end caps (JM133-C42)
7. About 170 exhaust-pipe U-bolt clamps for 42 to 45 mm pipes, to fix the panels (Walker 84285 and FA1 911-943, from car parts websites)

Shelter

1. A small metal garden shed kit for the inverters
2. A wooden board for the back wall

Tools

1. Angle grinder with a metal cutting disc
2. Tape measure and marker
3. Earth auger
4. Laser level, string line and wooden boards for the layout
5. Hex keys and wrenches

I first drew the whole installation in SketchUp: the frame, the panels and the shelter for the inverters. It helps to count the tubes and clamps before ordering.

Check the datasheet of your panels for the mounting holes. The panels must be held at the positions given by the manufacturer (circled on the drawing).

A ground-mounted installation may need a building permit. Mine did, and the municipality asked for a surveyor's layout report before the work could start. Check the rules where you live before buying anything.

The inverters stay outside, so they need protection from rain and direct sun.

I bought a small metal garden shed kit, assembled it, and placed it at the end of the array.

Inside, I fixed a wooden board on the back wall to mount the inverters and the protection boxes (see Step 10).

Clear the area and level it roughly.

Mark the outline of the frame with wooden boards and a string line. Check the right angle with the 3-4-5 rule.

The string line also keeps all the posts in line.

Measure and mark each tube, then cut it with an angle grinder. Mounting the grinder on a cutting stand makes it much easier to get square cuts.

Remove the burrs and sort the cut tubes by length. The lengths depend on your design (see Step 1).

The vertical posts go 1 m deep into the ground.

I drilled the holes with an earth auger and checked the height of every post with a laser level.

Start with the corner posts, then set the posts in between along the string line.

Assemble the frame with the tube clamps. No welding is needed: just tighten the set screws with a hex key.

1. The adjustable tees (30° to 60°) set the tilt of the panel rails.
2. The offset crosses join two tubes that cross each other.
3. The internal joiners extend tubes that are too short.
4. The end caps close the open tube ends.

Add diagonal braces so that the frame cannot move in the wind.

I fixed the panels on the horizontal tubes with exhaust-pipe clamps (colliers de pot d'échappement) bought on car parts websites. They are made for 42 to 45 mm pipes, so they fit the scaffold tubes perfectly, and they only cost about 1.50 to 2 euros each.

Place the clamps at the mounting holes recommended on the panel datasheet.

Start at one end of the frame and keep the rows straight.

Each Sunny Boy 3.6 has two MPPT inputs, so the array is split into 4 strings (two per inverter).

Crimp MC4 connectors on the solar cables and mark each string with a coloured tape. That way you always know which cable belongs to which string.

All strings go through a DC box with DC breakers and surge protectors before they reach the inverters.

Never connect or disconnect MC4 connectors under load.

Connect the metal frame to the earth of the house with a yellow/green earth cable, bolted directly onto the tubes.

Check what your local electrical rules require for the earthing of the frame and the panels.

Mount the two inverters on the back wall of the shelter, with the DC and AC protection boxes next to them.

Connect the 4 strings to the DC inputs, then the AC outputs through the AC breakers to the house.

Register the inverters on the SMA portal to follow the production.

Depending on your country, the installation must be inspected and declared to the grid operator before you use it.

The array has been running since the end of December 2022.

Here it is in January, after the first snow.

If you have any questions, leave a comment!