Suntech vs. Sharp

[marshman]

Anyone have any ideas on how to easily verify panel output? I ask because I have just had another system installed. 15 x 245W Suntech panels and a SMA 4000TL inverter (3.67kWpk).  My first system - now nearly 18 months old consists of 15 x Sharp ND210W (3.15kWpk) and a SMA SB3000 inverter.

Over the last couple of days of near perfect sunshine the new system has given about 8% more output in terms of units generated over the course of a day, (today it was 13.7kWh vs 12.7kWh). The difference in system size is nearer 16% so I would have expected in excess of 10% more from the new system - especially as they are new clean panels and a more efficient inverter.  The Suntech panels are spec'd at -0% +5% of rated power so should be at least 3.67kWpk. The Sharp panels are 18 months old and spec'd at -5% to +10%.

I suspect the Suntech's are right on the 0% quoted limit and the Sharp are at the top end of theirs - i.e. +10%. This would explain the excellent performance of the original system since its installation.

I am still a little disappointed in the new systems performance especially as cable runs are shorter and the inverter is supposed to be more efficient. I still need to do some more accurate measurements of the pitch and also panel temperature - but I'm certain they are the same. The new system faces 5 degrees further east but according to PVGIS this makes less than 1% difference to system output in Sept/Oct.

Any thoughts or suggestions on ways of verifying the Suntech output other than waiting until next June 21st?

They are wired correctly as the voltages and currents on the 2 strings into the inverter seem correct.

Thanks in advance

Roger

[AlanIOW]

Hi Roger

I don't think you have anything to worry about, I think your original system is the most efficient of all the systems on here, it is nearly always top or near the top each month taking into account the size of the system, so the chances of being lucky twice are small. I expect the new system also cost considerably less, but I can see why you may be a bit dissappoited. We are not far from each other [Isle of Wight] and you can compare your systems to mine on PVOutput.org here;
http://pvoutput.org/intraday.jsp?id=2476&sid=1872 bear in mind although I have a similar very low pitch of 18 degrees my system is split SSE and SSW, which lowers the peak output, but gives a longer flatter output curve.

Tony's system is even nearer you here; http://pvoutput.org/list.jsp?id=4601&sid=3641 same inverter as both of us but a much higher pitch.

Alan

[JohnS]

You are comparing daily totals.  You should first of all be comparing actual output in good conditions.

Can you look at the spec sheets for the two panels and compare the temperature coefficient and also the output for less than STC of irradiance?  

It maybe that Sharp's output curve has broader shoulders whereas the headline figure is just the height.

[marshman]

You are comparing daily totals.  You should first of all be comparing actual output in good conditions.

Can you look at the spec sheets for the two panels and compare the temperature coefficient and also the output for less than STC of irradiance?  

It maybe that Sharp's output curve has broader shoulders whereas the headline figure is just the height.

Hi John,

I used the daily figure as it was from a day with perfect sunshine, remember these two systems are within 150 feet of each other and so are as near identical in terms of location, direction and angle. If you look at the instantaneous figures you see a similar difference. I'm trying to get data logging running so I can compare the output on a minute by minute basis.

The temp coefficient is worse (slightly on the Sharp panels) On paper the spec. of the sharp panels is worse!   The only major difference is that the Suntech are Monocrystalline and the Sharp are Polycrystalline.

Alan - you are correct my original system has performed way over expectations and I am probably (ok definately ) being a bit greedy expecting the same over performance from the second system - however with two systems in such close proximity in the same conditions it is an interesting exercise to compare claimed and actual outputs -  my gut feeling at the moment if asked Sharp or Suntech would be to say Sharp!

Roger

[furrypants]

Hi

Just out of interest have you had the systems but through PVsol to seem how they compare?  Really interested in you postings as i'm linking of getting Suntech.

[marshman]

No not used PVSol, don't see

Have put both through Sunny Design:

15 x Sharp + SB3000   =  2717.4 kWh/year, inverter efficiency 92.6%     (actual 3400kWh/year)

15 Suntech 245 + 4000TL = 3343 kWh/year, inverter efficiency  94.4%  (I'm predicting 3600kWh/year)


Thats a predicted 23% more for system in same location!!!  Yet I appear to be achieving only 7% more. As I said in my first post I need to check more things like panel temperatures etc - can't think why they would be that much different -and let it run for a lot longer to check but at the moment I would say they are disappointing compared to the Sharp panels.

Roger

[SolarCity]

Give it time.  Suntech panels perform better than Sharp panels in poor light conditions.  Compare them over a month and see how it looks.

[marshman]

Give it time.  Suntech panels perform better than Sharp panels in poor light conditions.  Compare them over a month and see how it looks.

You are absolutely correct!!  Today the Suntechs delivered 4.9kWh while the Sharp panels only managed 4.3kWh so the Suntechs delivered a whopping 13% more - nearer the expected difference.

The thing is more output/efficiency at low levels of light is, to be quite blunt, not worth a lot!.    An extra 6% in December  last year would have equated to an extra 3.36kWh of generation!  The same as an extra 1% in September when the light levels are much better. So claiming better efficiency at low light levels - which they do if you look at their specs -  is the same as saying less efficiencyat higher light levels which I think is actually the case. I still remain to be convinced that the situation will improve. In fact I am on the point of doing some serious investigation to see if they really are 245W panels!

Roger

[spluger]

That raises a good argument
is it better for non south facing to aim for better low light performance or just go for the big peak power figure's

i suppose if the high power at low light pannels got realy cheap i'm sure we could find a north roof to put them on 

David

[marshman]

i suppose if the high power at low light pannels got realy cheap i'm sure we could find a north roof to put them on 

David

Or if they are really efficient at very low light levels may be they will work at night.

However, Whilst they are more efficient at lower light levels than higher light levels. The ones I have are not impressing me even at low light levels. Todays figures 8.1 vs 8.8 so the new suntech's produced  8.6% more than the older sharp panels when in theory they should be producing around  16.5% (more if you believe the more efficient at lower light levels bit & take into account a supposedly more efficient inverter and shorter cable runs)

Roger

[GavinA]

the suntech system is towards the bottom of the acceptable input range in both voltage and total power terms of the 4000TL, and the 4000TL operates best at high voltage and high wattage, and will be worse later in the year when the peak output will be lower still.

The SB3000's efficiency peaks nearer the middle of the output curve, so will be operating at peak efficiency at this time of year.


I'd think the difference will be greater in peak summer, but it's likely the sharps were above their rated output to start with.