choosing a solar pv system

[madwoman]

hi all, new to this so please excuse our ignorance, we are considering a system not for any "Green" reason, this is purely financial. So, therefore, we want to make the best of this, so here goes. The basics are covered, ie, sound roof, south facing. We have have shade issues, also, the system may have to go on two parts of the roof, ie, the main south facing ridge roof and a flat roof at the back of the property with the same sunshine amount to achieve near as dammit a 4Kw system. After some research on the internet and one visit by a company, we would like to consider buying a bespoke system consisting of one of three panels, either Sharp, Sanyo and possibly Schuco. Also, with the shading issues, we have learnt that this can have quite a detrimental effect on electricity production, ie the system not running at the capacity it could do. So, with the inverter issue, instead of using the usual Sunny Boy SMA which would only average the voltage and not allow us to split the system into two parts, thus making two inverters necessary. Would a solar edge inverter take into account the system being in two parts and the shading on the panels and enable the system to run at maximum with that amount of light, or slow it down to the amount that the shaded panels are producing? Phew!!! Thanks for reading this far!! All comments and suggestions would be very welcome!!

 

[Worcester]

The leading makes of inverter are SMA and Fronius, others are good, however these are the ones that set the standards, and others should all be judged by.

The SMA SB 4000TL's have two MPP trackers allowing you to connect up multiple strings of different sizes, giving you the equivalent of two inverters, and the excellent Optitrak Global Peak , Fronius have a similar system and also offer multiple MPP's

However is putting you off SMA is doing a sales job on you!

For more information on Shading visit the Solar PV section of our webiste.

 

[MorganPVI]

What Fronius has DMPPT Worcs?

 

[Worcester]

My apologies, must be getting late , you are correct Morgan123, the Fronius does indeed only have a single MPP tracker.

That leaves us with:
SMA SB4000TL-20
and
Power-One 3.6 / 4.2

And .... not a lot else,

Maybe a Kostal or a Nedap

as far as I'm aware that's about it for < 4kW twin MPP systems,

I don't believe that the Solar Edge inverter can cope with the two configurations (I may be wrong ) - that needs twin MPP trackers, or multiple inverters.

So, with the inverter issue, instead of using the usual Sunny Boy SMA which would only average the voltage and not allow us to split the system into two parts, thus making two inverters necessary

That just isn't true.

The SMA SB4000TL will do exactly what you are looking for, that what the 2 MPP trackers are for.

 

[BruceB]

Power-One PVI-3.0-OUTD
SMA SB 3000TL-21
are both twin mppt.
And a nice man from SMA promised me the latter was not a figment of someone's imagination and was available here now.
Regards
Bruce

 

[MorganPVI]

Really, a 3000-21. Has anyone seem one in the "wild" yet?

 

[Worcester]

@BruceB

Thanks, I was looking for 4kW as that was what the OP's system was sized at.

The SB3000TL-21 will make a big difference we just need the 3600TL now and SMA will have a full house!!

 

[ingflying]

more info

 

[SolarCity]

Agreed. The 3600TL will plug a huge hole in the SMA range.

 

[madwoman]

thanks for that, cleared up a lot

 

[madwoman]

Thanks everyone! I understand now that the Sunny Boy can handle two strings, but can they control individual panels? We will have shade creeping accross part of the roof and understand that shade on one panel can shut down the rest of the string or is each panel controlled separately? Do Solar Edge panels work separately, and if so, which would be best in our situation? Many thanks again!!

 

[VMan]

Have you thought about stecagrid 2000+ master and slave unit, each will handle 2kW (2Kw master + 2Kw Slave) and each has 2 trackers, so in effect 4 trackers for 4kWp system and if i remember correctly start voltage is just 80V!
ideal for shading issues..just a thought

 

[series530]

I'm going to jump on my hobby horse now (sorry for all of those who have heard this before from me) :

If shading is an issue and if the shadows creep across the array (or arrays) you will always struggle with performance being as poor as the lowest denominator. You can add something like a Tigo maximiser which tries to squeeze that bit more out of each panel or you can take a completely different approach and use micro inversion. This approach uses a small inverter per panel and each inverter tunes itself to that panel. Your output will diminish on the shaded panel or panels but, unlike a string inverter, the whole of the string (be it half or all of the panels) will not be dragged down to the worst performing link in the chain

Micro inversion costs more up front and has more to go wrong. The units accredited for UK usage come with a 20 year warranty so you do get peace of mind. Overall, the initial outlay will be higher but you could end up getting an overall higher yield over the life of the FIT. How much better is very dependent upon shading circumstances. Certainly with very little shade it is probably over kill. However, with moderate shade it is seriously worthy of consideration.

Needless to say, that is how our system is being set up... as my signature shows below.