Hi members

Please I need a sanity check

I have 12 x 330 w canadian solar panels connecte 3S4P. Total theoretical watts = 3960. They are installed 30 degrees east of North and angle 23 degrees. No partial shading, nice full sun. Connected to 2 Infini V’s in parallel (4kwx2). So after a bit of research I calculated the following expected generation. 

Theoretical 3960 watts

Losses due to dirty panels, inverter inefficiency, temperature, cable losses max 20%. (Minus +-800 watts)

losses due to angle and direction. 8.6% (minus +- 360 watts)

So lets say 2800 watts. Im currently getting 1400 watts between 11 and 1 (per hour). Where am I loosing the other 30%? They almost exactly 700 per inverter so unlikely due to faulty panels.

I also did some measurements directly from solar cables. Refer to attached pic. Note voltage difference before it is connected in parallel. 131v vs  105V. Refer to my measurement points. Left to master and right to slave.

Thanks guys

p

Dear admin, please move to solar section...newbie error

Did you pull all the fuses out when checking the voltage? 

2 hours ago, 31shkom said:

Please I need a sanity check

At the time of expecting +-2800 watts, where their loads of the same wattage or more?

Because, for clarity, even if the panels can produce a potential of +-2800 watts, if the loads are say just +-100w, that is all the panels will deliver, the +-100watts.

In winter the sun is around 45 degrees above the horizon at midday. One of my panel arrays is at about 15 degrees, true north and the max power now is about 40% below nameplate. 

There are lots of queries now about power output as we approach winter solstice. Coincidence? 

4 hours ago, The Terrible Triplett said:

At the time of expecting +-2800 watts, where their loads of the same wattage or more?

Yes it was.

24 minutes ago, DeepBass9 said:

There are lots of queries now about power output as we approach winter solstice. Coincidence

I agree that there is obviously losses due to lower solar irradiation. If I do the calc based on solar radiation I still get 30% losses. 

Expected solar irradiation my area taking in concideration 45 degree North (Im only on 30) offset and the panel level = 5.42 kwh/m2 per day. Refer attached pic.

lets say I use 23 m2 of panels. That leave me with solar irridation of 124 kwh/m2 in June for my area based on my setup. The panels have a 15% efficiency. So max potential is 18kwh per day. Now lets remove all other factors as described in my OP (30%). So I should get arround 13kwh. I currently get 9kwh max for the day. The system is fully loaded for the day. 4kwh lost on 13 kwh again around 30%.

 

It has also been hazy for the last few days, not good production weather.

What does the system produce in summer, or was there no problem then?

14 minutes ago, DeepBass9 said:

What does the system produce in summer, or was there no problem then?

Its only 4 days old 😊😊

Another calc.... 

What area are you in? I can switch on a big load and take a max reading off of my panels at local noon here, should be the same as gauteng, except the air is cleaner.. I'll even take a hose and wash the dust off the panels. I have 900W at 15 degrees and 1800W at 35 degrees. I am getting nowhere near that number though. Probably an equivalent reading to 30 degrees of north will be my reading at 10:30 or 11am.

5 minutes ago, DeepBass9 said:

What area are you in?

Im in Centurion. I think Im going to climb in the roof and take volt readings of each 3S connected panels and start tracing them to the  fuse box to the inverter and check

 

8 minutes ago, DeepBass9 said:

I can switch on a big load and take a max reading off of my panels at local noon here, should be the same as gauteng, except the air is cleaner.. I'll even take a hose and wash the dust off the panel

Highly appreciated🙏

How are your panels mounted? 

2 hours ago, 31shkom said:

Im in Centurion

Just maybe for interest, I am also in Centurion, and yes It has been a little hazy this week.

Time now 11:30 and I am on 70% production of panel specs.

PV Curve pretty stable, so you should be close to that.

R

Just now, Riaanh said:

Just maybe for interest, I am also in Centurion, and yes It has been a little hazy this week.

Time now 11:30 and I am on 70% production of panel specs.

PV Curve pretty stable, so you should be close to that.

R

Yes I am currently on 1400 w. So 30%

54 minutes ago, RichieRich said:

How are your panels mounted? 

Physically?

Flat on roof with 23 degree angle. Direction 30 degree East of North. Estimated 8.6 % loss due to Azimuth and slope angle. 3S4P setup. 10cm from roof tiles to allow for ventilation 

14 minutes ago, 31shkom said:

Yes I am currently on 1400 w. So 30%

OUCH, If you at 30, and Load are still good, then there is definitively an issue somewhere. Good luck

3 hours ago, 31shkom said:

Im in Centurion. I think Im going to climb in the roof and take volt readings of each 3S connected panels and start tracing them to the  fuse box to the inverter and check

 

Highly appreciated🙏

Sorry, just became cloudy! 11:50 now, local noon is 12:10. 

OK, so the sun came out again, shining quite brightly. Time : 12:55 : The 1800W array at 35 degrees is producing 1315W : 73%  The 900W array at 15 degrees is producing 427W or 47%. 

There is definitely something wrong with your panels or wiring to the combiner-box if there is such a large difference in "no-load" voltage between the strings. I have a 3S3P configuration of 330W panels (i.e total 2970W) and their open-circuit voltage of each string is within 2 or 3 volts of each other. 

I am in Cape Town, so solar angles and levels will be different to your setup, but I am now seeing about 2200W max (i.e. 74% of rated power) in the early afternoon.  Your North-East facing array will obviously give you peak power before midday - say around 11:30am.

My guess is that two of your strings - the ones giving 105V output - are the ones at fault. This could be due to the Denguard Over-voltage protector malfunctioning/shunting the current or possible the MC4 connectors have not been terminated correctly. 

 

2 hours ago, 31shkom said:

Yes I am currently on 1400 w. So 30%

Another diagnostic approach is to remove the 2 fuses for the 105V strings and see how that affects the overall power.  This should quickly show how much power is being generated by each string.

32 minutes ago, NigelL said:

My guess is that two of your strings - the ones giving 105V output - are the ones at fault

Thanks, so what I'll do is to peak time go into roof and measure amps and volts at the solar panels. Then again just before it goes into the fuse box. Then after the voltage protector to se what goes into the inverters. You think this will work.

Can I unplug panels while inverter is stil on/working to perform fault finding?? And plug in again or should I shut all down?

2 hours ago, Riaanh said:

OUCH, If you at 30, and Load are still good, then there is definitively an issue somewhere. Good luck

Thanks will provide feedback. Sure it's something to do with wiring...

24 minutes ago, 31shkom said:

Can I unplug panels while inverter is stil on/working to perform fault finding??

NO! Do not disconnect panels under load. Edit: except with breakers that are designed to do that. Not MC4 connectors.

Edited May 29, 20197 yr by Coulomb

27 minutes ago, 31shkom said:

Thanks, so what I'll do is to peak time go into roof and measure amps and volts at the solar panels. Then again just before it goes into the fuse box. Then after the voltage protector to se what goes into the inverters. You think this will work.

Can I unplug panels while inverter is stil on/working to perform fault finding?? And plug in again or should I shut all down?

Unfortunately I don't know how your system is setup, so cannot advise on whether there are any safety issues in doing this.

I have a separate MPPT charger that charges a battery, so has no impact on the Inverter.  I have DC Circuit breakers instead of fuses for the solar strings, so can safely break the DC current. You may want to check that your fuse-holders can do this without creating a nasty DC Arc.

EDIT: Coulomb just beat me to it ;-). I agree that one should isolate the panels from the MPPT input before working on them.  You can always pull the fuses at night time if you do not have any other method of safely opening them.

Edited May 29, 20197 yr by NigelL