My solar Setup

[Fnm]

Hi there, my first post on the forum.

My workshop is from home with a few CNC machine's, to run them I need 380v 3 phase power.

My consumption per month is +- 2500kwh,sometimes up to 3500. This is my shop and house together.

I started of by measuring the house only which is +- 21kwh per day (+-630kwh per month)

After investigating inverters to manage the amount of power I use, I realized that I need some special 3 phase setup to manage the 40 amp per phase with spikes of up to 100amps for a

millisecond or so.(ups required)

First of all I calculated the amount of panels needed, not enough roof space for them to start of with, so going off grid not possible and the battery bank and inverters will cost a arm and a leg.

So in November I installed 18 x 250w panels with renesola micro inverters, 6 panels per phase. 9 panels facing east and 9 facing west. This system generated on average 180kwh per month per phase (+- 540 kwh per month total)

This month I added 9 x 310w panels + 5kva mecer inverter and 8 x 200ah battery bank which I wired into the red phase of the house only.

On this phase is all the lights, some plugs and the fridge's. Geysers (solar already), stove, washing machine ens is still on the other 2 phases.

The last 2 days with a lot of washing and tumble drying my consumption dropped already to 8 Kw per day. I will see what the rest of the week happens.

I wonder now if there is something available that I can connect the micro inverters to that can manage the amount of power needed per phase and move one phase that need little to the one that needs more. What happened to day was that the red and yellow phase needed no power from the grid but the blue phase needed a lot, I know the red phase(battery backed up) will be available to help the blue but how can I shift the set of inverters from the red phase to supply extra to the blue phase?

 

Thanks

Francois

[SilverNodashi]

That's quite a setup there. Some pointers: 

• I wouldn't have mixed the panels like you did. If they're all connected to the same MPPT charge controller, you'll loose a bit of energy on the 310W panels. But if they're on two separate MPPT's it's fine. 
• The Axpert inverters can run in 3phase very nicely and you can have unbalanced phases, i.e. 1 per phase to get 3 phase and then another one on say the red phase if the house appliances are on that phase. This allows you to "grow" your existing system nicely.
• If you already have a large UPS that can cater for the momentarily spike, don't worry about getting a large inverter - it would cost quite a bit! If not, investigate some of the bigger brands and see what you can afford. Victron's can also run in 3 phase but for the price of say 3x that of an Axpert. 
• Try and reduce your load as far as possible. Use LED lights, solar water heating and gas where possible. it makes a big difference.

[Fnm]

Thanks SilverNodashi,

The 250W panels have a micro inverter each, 18 panels with 18 inverters. Each inverter supply 230v, the beauty is that if a panel is in the shade

only that panel is effected and not the hole string.

6 Panels is connected to a phase, each inverter only supply 1amp ac thus I only get 6 amps ac per phase if fully operational. I need around 40amp per phase (5 x more)

The 310w panels is connected 3 in series and those 3 strings in parallel and they are connected to the axpert inverter. 

The axpert supply the house, work perfect.

I just would like to be able to switch the micro inverters to a different phase when the shop is off, but this must be a auto something.

 

[SilverNodashi]

37 minutes ago, Fnm said:

Thanks SilverNodashi,

The 250W panels have a micro inverter each, 18 panels with 18 inverters. Each inverter supply 230v, the beauty is that if a panel is in the shade

only that panel is effected and not the hole string.

6 Panels is connected to a phase, each inverter only supply 1amp ac thus I only get 6 amps ac per phase if fully operational. I need around 40amp per phase (5 x more)

The 310w panels is connected 3 in series and those 3 strings in parallel and they are connected to the axpert inverter. 

The axpert supply the house, work perfect.

I just would like to be able to switch the micro inverters to a different phase when the shop is off, but this must be a auto something.

 

Aah, ok. I'm not sure what you can use in this scenario. 40amp per phase is a quite a lot, I'm not sure what will support your setup like that, other than just running 3 sets of panels, each with their micro inverters, but you'll need plenty roof space and at minumum 120 solar panels! I take it you're using the Renesola micro inverters? I haven't used them yet so I don't know how efficient they really are but some quick calculations suggest that you need 35 x 250W solar panels, per phase if you want 40A - when using a normal inverter. 

That's 5 panels more, per phase than using micro inverters. I'm not sure what they cost and how more complex it would be to wire that many into your micro grid, as apposed to using a 32Kw (?) inverter instead.

[Louw]

My knowledge on 3phase is limited but I am wondering what is stopping you from adding all the inverters to the one phase permanently? Eskom power should balance it out.

[Fnm]

Well to install micro inverters is plug and play, they connect one in each other and then you feed it directly into the grid.

No dc isolators or any fuses needed,I only have a normal ac isolator between pv and db.

Installation by far easier than string inverters with batteries.

They do not have a grid limiter so don't use them with prepaid meters!

@Louw, that is no problem to do but what I want to do is to move a phase over a week end to the phase that the washing machine is on.

On the moment I am wasting all the possible produced power when the shop is not working.

Eventually I will anyway over produce as I am planning at least another 12 panels with micro inverters, roof space big problem.