Panel Specs, STC vs NOTC

[MetricAmerica]

I noticed that the panel specs include standard power rating (STC) and normal power ratings (NOTC), now... How long have they shown the normal ratings? I don't remember seeing them when I first started looking at panels years ago... Do you find the normal ratings closer to what your panels are putting out?

Ex. https://www.lg.com/us/commercial/sol...lg-LG300N1C-G4

[J.P.M.]

I noticed that the panel specs include standard power rating (STC) and normal power ratings (NOTC), now... How long have they shown the normal ratings? I don't remember seeing them when I first started looking at panels years ago... Do you find the normal ratings closer to what your panels are putting out?

Ex. https://www.lg.com/us/commercial/sol...lg-LG300N1C-G4

What you call normal ratings - NOCT - is actually the output at "Normal Operating Circuit Temperature". The method has been around for some years now.

But it's not "normal" in the conventional sense. It's supposed to be the cell temp. achieved under open circuit conditions with a plane of array irradiance of 800 W/^2, 20 deg. C air temp., 1m/sec wind velocity , and open back. A tilt is not specified nor is an angle of attack for the wind vector. I believe the irradiance spectrum is that of a 1.5 air mass.

Since it's open circuit conditions, no electricity is leaving the cell/panel, the NOCT seems of limited usefulness. It's the temp. necessary to satisfy a heat balance on the cell, or loosely a panel. As such, it can be used to estimate heat loss coefficients for cells and loosely for panels. That's necessary information to estimate panel or array efficiency or as a backup confirming estimate to using measured cell temps at other conditions. However, since better and more accurate methods to estimate those heat transfer rates are available, IMO, the NOCT value often leads to confusion of the type seen here.

[MetricAmerica]

Why need to quote? You posted right below, do you think people will have no idea of your response to mine? Second, did you not see the example? It shows max power out put at 800 lux and amps and voltage not just open circuit. It may have been out for a long time, but why manufacturer never posted it, hense my question from the beginning...Do you find the normal ratings closer to what your panels are putting out? Between battery charging and grid-tie inverter conversions....

So why haven't they posted it before, because it is useful!