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Lots of documentation
The sheer amount of documentation that surrounds a commercial solar project is immense. In addition to the standard electrical paperwork required there is also specific project management and site documentation and of course all the customer paperwork.
This presentation will attempt to systematically look at what is required from a site documentation perspective.
On site and ready to go but . . . .
The team has been assembled ready to start the first process of getting the feet onto the roof. The solar component is over 200 kW. The roof is vast, actually a cold storage facility, and as part of the team jump onto the EWP ( Elevated Work Platform) and start ascending questions are asked:
- Where are we depositing these feet initially?
- Where are they finally going?
- Where is the A3 laminated site folder showing the actual feet layout?
This does happen!
Creating and having available when needed the right documentation is important for so many reasons.
At the beginning of any site work the project manager, site supervisor must organize a folder containing all the relevant information concerning the construction, the procedure and processes involved in putting the system together physically.
Step 1: determine where the feet, fixings etc will be deposited. Remember double handling is inefficient and should be minimized at all costs.
Now what about that feet layout drawing?
Feet layout drawings
The designer must provide onsite documentation showing the actual position of the feet, the number of rows, the variations between rows if applicable and any other pertinent information.
If well organised the assembled feet are brought to the roof and directly dropped in their approximate positions ready to be fixed down.
Now the rail. . . .
In this particular project we’re installing rail FTR ( Flat to the roof).
Now all aluminium rail has a coefficient of expansion and the manufacturer of the particular rail being used will advise what is the maximum unbroken length of rail ( joined segments of course) that is allowed.
For example Clenergy’s PV-ezRack® SolarRoof™ “total rail length is recommended not to be over 30 meters considering rails thermal expansion problem”
In this example, due to roof configuration and other design limitations the unbroken rows will accommodate 20 panels. This has resulted in the following design:
- 20 x panels per row
- Total of 32 rows
- Each rail row length is 20,660 mm
- Individual rail sections are 4,200
Step 2: put together a rail cutting schedule. In this case it is fairly easy to follow as all rows are equal and the “ waste” left from the top rail is not used with the bottom rail. Lucky eh 😀
Now how does the rail go onto those feet again?
We now have all the rail cut, we know the total rail length, how many panels per row, the feet spacing.
Are we missing anything? Yes, the rail cantilever.
What are we talking about here? This is the amount of rail that hangs over the first and last foot in the row.
Thankfully as part of the rail design etc this has been calculated as being 300 mm but has this been communicated to the install crew? Is there a drawing?
Gotta splice rails and attach to feet but before . . . .
Hang on. We have to attach the feet to the roof and in this case we are not penetrating the roof sheet but clamping onto a rib.
Ok we clamp onto the rib. That sounds easy. We use a wrench or drill and go for it!
No we don’t!
Step 3: Clamp roof fixing torque schedule
Clamp roof fixing torque schedule
In our case we are using a clamp that has three sections that require 2 x different torque settings:
Bottom section: 16 - 20 Nm
Middle section: 16 - 20 and 10 - 12 Nm
Top section : 16 - 20 Nm
Hang on. Do we even have a torque wrench? The torque settings have come straight from the manufacturer and if not followed . . . .
Ok, so NOW we can start with affixing the rail. . . .
So the rail has to be spliced together and then connected to the roof fixing system used.
The install crew now has access to the site documentation showing rail feet interface, cantilever measurements and torque settings.
What’s next on the agenda?
Depending on your modus operandi the next step is laying the cable tray.
So what cable tray is being used? How long are the runs? How do we transition from one sized cable tray to another?
Where’s the cable tray schedule? Step 4: cable tray site plan
We have a cable tray plan and the tray has been laid down, affixed to the roof, transitions have been worked out and all is good in the world.
The guys have been working hard. There have been no hold ups so far. So the next step is getting the cable to the roof and slapping it down.
You guessed it, another step. Step 5: Cable schedule
Solar cables, not difficult . . . . .
In this example we are just using 4mm2 solar twin DC cable but in some bigger jobs where the DC runs are longer etc, 6 mm2 cable is used.
Now without a DC cable schedule confusion may occur and 6mm2 may go where 4 mm2 should go and vice versa.
And what about the strings? Are we paralleling strings or not?
And hopefully all the DC volt drop calculations have been made as well! 😶
DC cable schedule
Now the inverters . . . . .
Now we need to put together the inverter schedule. In this case we are using three inverters. Two of three are 100 kW capacity and the third is 50 kW.
They are all installed at a roof inverter station in conjunction with the GridSafe *secondary protection board.
Maximum distance between the inverters and the SPB is 7 metres. Connection is to the MSB which is 30 metres away in the plant room.
Step 6: inverter schedule
Inverter location cable schedule
Large commercial solar projects contain a myriad of tasks that need to be organised, implemented and completed. The task of onsite documentation is not to make things laborious but to help streamline all the processes on site. If you have a plan it can be executed and developing onsite documentation helps with this.
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