Good Day All,

Firstly, huge thank you to all the folks on this forum.  I have been lurking for quite some time and have learnt a huge amount from the comments and advice offered here...

We are based in Outer West Durban, planning to take the Solar plunge and would appreciate any comments/advice in this regard.  Our phase 1 will still have Grid available with change-over for Genny.  Phase 2 will be off-grid, Genny as backup - Proposed setup:

- Victron 5kVa MultiPlus II

- 16 x 285W ARTsolar - 4S4P - 4.5Kw

- SmartSolar MPPT 250/100

- 2 x PylonTech US3000 3.5Kwh

Stove is full gas and in the process of converting Geyser to Solar

Busy gathering quotes for the above - was wondering where/who might be a reputable supplier for PylonTech.?

Thanks in advance

Graham

Welcome smurfdbn, as a start I suggest you read the following thread, most of the homework has been done here. https://powerforum.co.za/topic/2946-victron-grid-tied-setup-from-scratch/

 

Hi @dvdwalt

Thank you, very informative

Apart from doing a lot of great reading, have a question re: Panel config and MPPT 

Using the Victron spreadsheet, starting with 15 x 285w panels, 3 strings of 5 - this is within the specs (V, A and W) for the 250/100 MPPT

If I decide down the line to add a 4th string, the result shows ACCEPTED and Amps "limited" as per attached snap...

Is there cause for concern/risk running MPPT at max Amp limit? 

Thanks

Graham

I'd say you are OK.

The MPPT will function to clip and limit the current if you exceed it.

However, you will not often be clipping the current:

1. Because your charging voltage is actually higher than 48V, so the current is lower.

2. Because your panels will only very rarely function at there capacity limits. In practical terms, the few times I have measured I think 75% is a fair rule of thumb, (this of course can vary).

3. Due to differing and tilt and direction of the strings they may actually never peak at their maximum output at the same time.

 

Edited January 16, 20205 yr by phil.g00

In fact after you're done, you might come back to us with real world measurements and let us know if in reality you could manage a 5th string.

Edited January 16, 20205 yr by phil.g00

Ok, makes sense, thanks @phil.g00

Other than having to save for the extra string/s, the spreadsheet seems to be happy with 5th 🙂

 

I am certainly an advocate for maxing out on panels.

You don't want drive it so hard, that it is clipping often, so you are losing out on a lot of available power, but you don't want to under-size the array, so that you not making full use of that MPPT you paid so much for. Try to aim for a sweet spot.

I would also suggest you consider combining E and W strings if you can, ( as you can have more panels without clipping), that you can with a North facing array.

That might seem like a strange thing to say, but it is much more useful to spread your power production over the day,  the the W array picking up as the E array is dropping off.

A N facing array may possibly provide an unusable excess of power at noon.

Mmmm, makes perfect sense...  - this is why this forum is so great - Thank you!

Sooo, with this in mind, I have re-jigged the layout and propose to have 1 additional string facing E with the original 3 strings on the roof.

Without an E string, by my very rough calcs, we would only have panel power from about 7:30 onward in Summer, probably around 9:00 in Winter.

However, with the E string, we should start pumping possibly as early as 5:00 in Summer,  Winter around 8:00, possibly earlier

Late morning onward, E string will drop off so MPPT shud be happy 

As for a W string, an absolute winner in Summer, Winter not so much due to available mounting space/angle etc.  gonna have to come up with a plan down the road..

Thanks again, have a great day

I am running. Very similar setup, with the 250/100 MPPT, using 6000wp artsolar panels. 20 x 300w pure black panels. 4 x 5s. This was my solar power for yesterday:

the MPPt just limits the output current to 100 amp by drawing less current from the panels. No problem.