Low Generation

[Stuart Houghton]

I have been out to look at a system that is generating less than expected.

It has 21 x 190 watt Suntech modules. 9 on one string and 12 on the other.

The irradiance at the time of the test was 800 watts

Open circuit voltage was String 1 304 Volts and 4.47 Amps String 2 419 Volts and 4.49 Amps

The inverter is a Aurora Power On 3600 outd the display showed string 1 778 watts and string 2 1165 watts

I feel this was low for a 4 kW system.

Any thoughts? I feel the modules are ok ?

Thanks

Stuart

 

[dmxtothemax]

check to see if the panels need cleaning ?
check connections for corrosion or looseness,
check diodes for leaks or faults

 

[Wilko]

Hi, I'm not expert with solar, but I checked out that panel's spec for 800W/m2, which do seem to show reduced output at that irradiance.

Also, your Voc was about 34V, specs say about 41V at 800W/m2 (?). How old are the panels?

http://enviro-friendly.com/wp-content/uploads/2015/12/suntech-190W-solar-panel-specs2.pdf

 

[soms]

That seems OK to me.
Nameplate 190W rating of modules is most likely at standard test conditions, e.g. AM 1.5, 20oC ambient temperature, and 1000W/m2 irradiance.

At the time of your visit the measured irradiance was 20% lower and the ambient temperature was probably greater than 20oC.

I suggest finding a data sheet for the modules, it may show the difference in performance under lower irradiance and values for temperature coefficient.

 

[Worcester]

Orientation, elevation, shading, degradation, when you measured the irradiance was that perpendicular to the panels or direct at the sun?

Sounds like a 2011 system so 6 years degradation (say 5%) , panels were also probably +0% -5% at that time, so panel output possibly down by 10% anyway.