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Thank you edexlab. I can't see how to edit post so will just advise here please ignore erroneous info on post 10 ref 4000TL / Sanyo Hybrid compatibility.
 
Gordon, can you maybe run a 4000TL through pvsol. I realise it will show oversized but I'd expect still to see a higher output with the advantages of twin mppt and the TL higher efficiency.

PV*SOL throughs a wobbler as it oustside the permissible sizing range - see attached (click on it to enlarge), so it won't run the economic simulations!
East - West Split - How many invertors??? 4000TLnverters - EletriciansForums.net
 
Gordon, did you adjust the sizing parameters on your version of PV Sol? My version only likes 90% - 120% before it starts to panic.
 
Thank you edexlab. I can't see how to edit post so will just advise here please ignore erroneous info on post 10 ref 4000TL / Sanyo Hybrid compatibility.

No problem we're all here to learn I can't tell you how much this forum has helped or even just caused a bit of doubt which is no bad thing as most people will then go and check for themselves and the correct info is brought to light
I have been on other forums and there is always someone on there spouting rubbish and no one questions it .
but this is the best one I think with some really good participants
 
@BiggSolar,

I always let my system choose by spec and location, here it is tweaked to allow 80% sizing, output is very similar to the SB3000TL-20, even with the twin MPP.

East - West Split - How many invertors??? 4000TLnverters_2 - EletriciansForums.netEast - West Split - How many invertors??? 4000TLnverters_2_output - EletriciansForums.net


My guess is that with two equally sized strings, where the primary generator is being slowly switched through the day from east to west with a balance at or around miday when both will be getting similar irradiance, is that the system is just coping.

We need someone to set this up with all three invert configurations and then measure the voltages across the strings and the current through them over a 12 hour cycle and then plot it out along with the actual Wh (not kWh) generated by the inverter at the same time..... (of course in the single tracker set up, I would expect both string voltages to be the same, though with different current flows)
 
Fascinating and I fear I've made a schoolboy error in assuming that an E/W must benefit from 2 inverters or at least 2 MPPT's. If you look at a typical panel power/voltage curve the peak power voltage point is very similar across the full range of irradiation. If you then also consider that the diffrence in irradiation between E and W at any given time will never be huge (because line of sight sun is only 1 part of the overall irradiation) their max volt points will be even closer. And provided we have 2 strings in parallel the different currents will be aggregated. I think the only problem would be with 1 long series string where the sunny side roof output would be pulled down to the same level as the shady side - or am I making another schoolboy error.
I would suggest the 3000TL outperforms 2x1700 perhaps because the start voltage is slightly lower and mainly because of overall efficiency difference, (Max 97.0 v 93.5, and Euro 96.3 v 91.8), bearing in mind that from Gordon's pvsol calcs I think there is less than 3% difference.
 
I've just been designing a system with an East/West split and thought I'd let you know my results so far.

Using 16no. 250w Sanyo panels, all on the east side of the roof, using an SB3800 inverter and using the climate data from Plymouth, a yield of 3,258.1 kWh is predicted.

Using 16no. 250w Sanyo panels, 8 on the east side and 8 on the west side, using two SB2000HF inverters and using the climate data from Plymouth, a yield of 3,123.6 kWh is predicted.

I've tried a few different inverer combinations but still get similar results. PVSol Expert consistently returns a better yield on an East or West facing roof rather than using a West/East split.

For comparison, if the same roof was adjusted to face due south, the same array would return 4,042.7 kWh. This means that the east facing array works at around 80% of the efficiency of the south facing array (consistent with SAP figures) and the West/East split configuration performs at around 77% of the optimum. Roof angle with all calculations was 37 degrees.

My conclusion so far is that an East/West split is useful when space is an issue, but not a good option if the goal is purely to maximise yield - not least because an East/West option is more expensive (dual MPP trackers/two inverters, extra scaffold).
 
@BiggsSolar, Ireckon you're right, in a simple installation, one big East facing array would be best, if not then spilt with either dual MPP's or two inverters.

So here's the big one,

And it goes back to @Claypole's initial discussion of overpowing inverters.

How can I maximise the power I generate from my roof (for the sake of discussion assume cost irrelevant) when it faces East / West and staying within the G83 16A limit for as long as possible during the day?

The two arrays/strings have mirror image power generation profiles (morning / night), with peaks probably being very close to each other around late morning and early afternoon.

So what would be the optimum/maximimum size I should put on each side?
And which inverter(s) perform best when overpowered to clip at the combined output of 16A. I would suggest it would be a single inverter (that way 16A can't be exceeded) with two MPP's, however wether it clips or 'cuts out' is probably the most important issue, and just how big can those arrays be?
 
I'd imagine that the big problem with these kind of set ups is the midday period, where both arrays would be getting lots of sunlight. I can't run this through PV Sol but I'd imagine that using a 16a limited inverter with a combined east and west array of much more than 4kWp would experience losses during this peak period as the inverter 'clips'.

In reality, this isn't really an issue because the 4kWp threshold on the FITs prevents us from installing in this way anyway.
 
http://download.sma.de/smaprosa/dateien/7418/TempDerating-UEN103910.pdf
The above download finally crystalised this for me, with some excellent charting to demonstrate the logic. Until reading this I was very firmly decided that there was no good reason to size the inverter smaller than array except initial cost. I'm now wholly committed to the opposite view. For my system using SB4000TL and 245 Sharps the sweet spot, in terms of kwh/kwp was something like 4.9kwp, bearing in mind the inverter max dc is 4.2 kw. I found this almost impossible to believe until I read the above download and understood the logic.
The 4kw FIt band doesn't prevent you exceeding 4kwp. It may well be that doing the sums shows that the larger array on a lower FIT rate band will still have the best rate of return, although in practice this is perhaps then governed by the DNO connection. However, from Ted's excellent DNO/G83 thread it seems most of the DNO's are swinging round to using inverter output figures, so provided they'll accept 4kw and G83 at the particular installation site that problem is removed. I also live in hope that Ofgem may at some point issue guidance that TIC may be based on inverter max dc input (albeit that's 4.2kw on the 4000TL). Personally, I've gone down the route of 3.92 array now, to extend to 4.9 after 12 months, all through 4000TL. Based purely on the maths for max rate of return.
 
I have to say that although pvsol is a useful bit of software I don't really trust it as we've put designs through it and then checked them against manufacturers programs and vice,versa and found that pv sol sometimes reccommends a match which the manufacturer would say was not a good design or the opposite actually rejected a good match, a classic example of this is choosing a 3000tl one mpp tracker for a e/w split the whole concept of a multiple Mpp inverter was to overcome the necessity of having to use two inverters which is usually a more expensive option
 
I still wonder if E/W problem is overplayed. I WAS firm believer in 2 inverters or at least twin trackers but I'm now not certain. As stated earlier, the sun is still directly accessing both sides. Take a roof pitch of 35deg. Sun's arc is 180deg. That leaves 110 deg of the best generating part of the day when the sun is directly hitting both arrays. Given that at the lower part of those arcs will not be generating much due to adjacent buildings/terrain/diffuse light on horizon, you could be talking about 70% of the best generating time of the day when both arrays are in sun. Looking at a typical bell shaped daily production curve that's a significant amount of kwh, maybe 80/90%? And when the sun is "behind the ridge" how much difference is there in the insolation on each side? Anybody got actual figures on this from a meter? Non sun side insolation v sun side insolation at the same time. The global peak single tracker on the 3000TL will no doubt set the voltage to match peak power on the sunny side. But looking at the power/voltage curves on the panel spec sheets, this will probably only drop the power slightly below peak on the shady side, unless there is a massive insolation difference. Plus the shady cells will now also be running cooler. Given that the shady side even on 2 inverters would now be producing the least power anyway, the % drop would be an even smaller % drop measured against the total output from both arrays. If the inverter itself is more efficient than the alternative 2 inverters, then I think it's entirely feasible that the 2 factors could equal themselves out, or even that the single inverter(1 tracker) could win out. Would love to see real world figures on this. Anyone got the time and the money for a control test bed? Failing which some insolation figures would be good.
 
I should add that my next thought was well what's the point of a twin tracker? Well it would still overcome problems with physically different strings, eg number of panels or even different panels. Also I guess adds more versatility in design with regard to suitable string current and voltage matching. And then still offers you the benefit of cheaper and neater install over 2 inverters.
 
And just looking out the window now, for all the "grey" hours here in uk E/W faces will be identical to S face anyway, so again a significant portion of time where there is no difference, although to be fair these will not be high generation times.
 
I've been talking today to a potential customer who's brother has an e/w split this was installed May last year in Chester, this blokes neighbour also has a system, same installer except for the inverter , on same e/w orientation
one has a 4000 tl and the other has a different make which he was'nt sure of the name but it apparently has one Mpp tracker the customer with the TL is an electrical engineer and researched Pv and told installer that was what he wanted, both have same type/ number of yingli modules
(I've asked him to get all the specifics )
He says there's no shading so it sounds like a good comparison
customer with the TL has out performed the other system by around 260 kwh to date and they were installed one after the other so there is a small difference in total run time
this has upset his neighbour and he has asked the installer to change the inverter, to the same as his mates, to which the installer has said he will do
and he also is after compensation for poor design induced losses
now without knowing which inverter he's got its not conclusive so i'll post when i know
 
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It'll be really good to get those answers.

He'll have great difficulty getting the compensation loss unless he can prove negligence. To do that he'll also need to get the supplier to produce the original calcs (which as he's MCS registered, will of course be on the customers file :) )
Also - did they pay the same price?
What was quoted according to SAP? How has it performed compared to that?
 
That's great, love to see those figures. I guess we could be looking at something like 5-10% depending on install dates. Even looking at it from a consumer angle I think a claim for comp is a bit harsh, hardly negligent given the early stage of the industry, and if the installer is switching inverter without cost I think that's more than fair. Unless of course there are other elements to this. Meanwhile, in selfish mode, delighted to be firing up for the first time my chosen 4000TL this am!
 
sorry for the delayed reply, thanks for everyones advice and help, i finally managed to convince them to get me the SB4000TL dual MPPT and everything is working fine!!!!
 
Bumped as this might be of interest to Stubo and also to ask if edexlab has any further info on the Chester neighbouring installs (one with twin tracker and one with single).
 

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