Solar PV Panels

Brian99_2

Just had a nasty thought.... that some nasty companies with no time to spare MIGHT put up a dead panel or two and not connect them up... and damn difficult to check the cabling under the panels... even when scaffolding is up

bill_on_line

What model of sunny boy/sma inverter to you have?
does it have bluetooth?
Does it have two strings?
If it has two strings you could use "sunny boy explorer" to login to the inverter and get spot value on the strings eg voltage current etc, as you would be really unfortunate if both strings were faulty.
Also could look up the panel spec look at the voltage for normal opperation and work out if your strings are opperating at this voltage voltage*number panels in string eg 8*45v=360V DC

I appear to be generating about 1kwh near to London with a 3.48kw stystem on a cloudy day at the moment

Iain
Any shading issues

bill_on_line

Sould have said 3.84kw system

Iain

zeupater

ProfGreen wrote: »

Many thanks zeupater, that's a good help and confirmed what I thought.

Since install we have had some very bright and clear days, with the system in full sun (about 32 degree angle, 20 azimut (i.e. SSW)). Yet the system will only peak at 700W (ave 400 W for a little while on a sunny day) and I might get 1.5 kWh in a full December day...the best has been 2.3 kWh. On a cloudy day I'm getting Zero. This is obviously pitiful and I have compared to others who are getting up to 3kW peak and about 10.9 kWh in end November.. My peak is less than 20% of capacity on a bright sunny day, so something is not right at all.
The system is 17x Schott poly 235 with a SB inverter. Inverter sits in the loft with some 15m of DC good quality cabling.. So I am trying to figure out what to expect in order to get the installer to ID the problems.. Compare to your useful link estimator, which suggest I should get 4.14 kWh on average and 128 kWh in December.. (4.14kWh on average would suggest at least 7-8 kWh on a bright day, since weather will drag the average down of course).

Any more real experience to compare with would be most welcome.

Thanks.
LPG

Hi

Take care where you're reading the peak output. If you're looking at the graph display on the inverter the peak will show the average over one hour whilst looking at the SunnyExplorer graph will show 5 minute interval averages and SunnyBeam 10 minutes (? without looking). To see a true peak you'll need to watch one of the three displays mentioned above when in full sunlight and note the actual generation reading ....

Follow Iain's (bill on line) suggestion regarding checking the panels ... with 17 panels I'd guess that you'll probably have a SB4000TL inverter to cope with the odd number and have 8 panels on one MPPT and 9 on the other (could be 10 & 7 to optimise one string), in which case look at the outputs and divide by the number of panels in the string to see the output per panel, they should be roughly the same for both strings(/MPPTs).

HTH
Z

ProfGreen

Many thanks for your replies. Had the installers over today with the electrician. They could not find a fault but agree there is a big problem with lacking production.
I have a SMA SB5000TL inverter with two strings and bluetooth. Linked up to a SunnyBeam bluetooth display. The 17 panels are laid out according to SMA recommended (which happened to fit the physical set-up on the roof), in 6 + 11 panels. The 6 are "always" in full sun, whereas there are occasional partial shading from a tree on a few panels in the string of 11. Whilst we are getting a reasonable 300-ish Volts on one string, we re only getting less than 1 Amp from either string (should be in the 100s ??). The SunnyBeam indicated a 1kW short-term peak today, and the SMA inverter gave 700W as the peak output (longer term average as you pointed out). I think the installer ran the Sunny Boy explorer and chatted to SMA Germany without getting much wiser.
They do seem to suspect a little shading of damaging the output on the string of 11, but it does not explain the poor output from the 6 in full sunlight. Latest idea is to try to move things around a bit and to isolate the few panels at risk of some shading into one string (which will unbalance things if it leaves 12 full-sun panels in the other string?)..
Interestingly the installers never had a concern with the tree shading issue, they called it little or no shading and "no problem"..

Iain if you are getting 1kWh on a cloudy day (which isn't great either) , how does that compare to your longer term average and clear-weather production in summer (assuming you've had your system for a while)?

Best regards

ctdctd

For ProfGreen - FYI,

2.5kWh 10 x 250w Hyundai, SMA2500HF, single string, SE facing, Bedfordshire.

December - sunny days about 5 - 6kWh production, peak output 1.4kWh
Full cloud day, about 400Wh
Total for month so far 51kWh (15 days)

So sounds like you have real problems!

HTH

bill_on_line

Only had my 3.84kw system from 22nd of November 2011,
I have sma 4000tl

8 panels on both strings (2 rows of 8 panels on the same South east facing roof) and usually see about 360v dc on the strings, the current varies with the light intensity.

Seen some strange voltages on the lower string 250v dc up to 400v dc at 10am to 11am in good light which i think at this time of year is due to the low sun and next doors chimmney shading the lower string. My roof has a very shallow angle 27degrees and i cannot see the shading from the ground to confirm.

From sunny explorer
total output so far 87.66kwh to the 16/12/11
Best day 09/12/11 6.06kwh
worst day29/11/11 0.707kwh
peak 27/11/11 1.836kw

Are you sure you have a sma 5000tl as this is an inverter with a maximum capacity of 5kw and more exspensive than a 4000tl.

bill_on_line

Ran the system you describe through "sunny design" with 5000tl
Typical voltage on the 7 module string is 163v dc
11 module string 299v dc

See what voltages you are getting

I have no experience as an installer but
The 163v dc is close to the default start up voltage parameter of 150v, this can be reduced to a minimum of 125v, might help the shorter string?

The supply Voltage during the day were i live is normally 248V to 250V AC. I believe high supply voltages can reduce performance, but once again not sure if this would have a great effect. Believe 253V is the maximum allowable and then you can ask the DNO to adjust the local supply voltage down.

Iain

ProfGreen

bill_on_line wrote: »

Only had my 3.84kw system from 22nd of November 2011,
I have sma 4000tl

8 panels on both strings (2 rows of 8 panels on the same South east facing roof) and usually see about 360v dc on the strings, the current varies with the light intensity.

Seen some strange voltages on the lower string 250v dc up to 400v dc at 10am to 11am in good light which i think at this time of year is due to the low sun and next doors chimmney shading the lower string. My roof has a very shallow angle 27degrees and i cannot see the shading from the ground to confirm.

From sunny explorer
total output so far 87.66kwh to the 16/12/11
Best day 09/12/11 6.06kwh
worst day29/11/11 0.707kwh
peak 27/11/11 1.836kw

Are you sure you have a sma 5000tl as this is an inverter with a maximum capacity of 5kw and more exspensive than a 4000tl.

Thanks Iain that is helpful feedback. Yes I am sure about the 5000TL, it was felt the better option as the panels were supposedly able to peak at 4kW+. Your production seem reasonable given the shading issue and immensely better than what I'm getting 9my best day has been 2.4 kWh, so the system may see a 50 year payback!:(

ProfGreen

bill_on_line wrote: »

Ran the system you describe through "sunny design" with 5000tl
Typical voltage on the 7 module string is 163v dc
11 module string 299v dc

See what voltages you are getting

I have no experience as an installer but
The 163v dc is close to the default start up voltage parameter of 150v, this can be reduced to a minimum of 125v, might help the shorter string?

The supply Voltage during the day were i live is normally 248V to 250V AC. I believe high supply voltages can reduce performance, but once again not sure if this would have a great effect. Believe 253V is the maximum allowable and then you can ask the DNO to adjust the local supply voltage down.

Iain

Thanks again, will do this on Sunday as am freezing on the golf course tomorrow (don't know why I agreed to do it..) and will ask the installer to check over the voltages too.
Cheers.