[RE-wrenches] 1.56 Rule

[Zeke Yewdall]

I've definitely seen this.  I regularly measured over 1200 watts/sq meter
in clear day skies on my sites, and if you throw in some edge of cloud
too... could get even more.  I've heard ski resorts dealing with 1400
watts/sq meter on vertical windows of lodges facing a big snowy bowl.
 I'll try to dig up a graph from one of my sites with monitoring on it.  I
was often getting near STC voltage at the same time.  These were high
elevation (8,000 feet and up) sites in Colorado, no humid haze,
thinner atmosphere, and often a bunch of snow reflection too.  I would
measure around 3.6kW peak AC output from a 3.3kW STC rated array at my
house at 9,300 feet there (had it on a 3.8kW inverter -- I greatly disagree
with certain inverter manufacturers recommendations for overpaneling, but
that's a different topic).

If you're closer to sea level or back east where the humidity blurs out the
sun more, probably a lot less chance of it, except during good edge of
cloud conditions --  which generally don't last longer than 5 or 10 minutes
max -- not three hours like altitude/snow enhanced irradiance.  I will say,
the sun breaking through the clouds on a 95% humidity 70 degree day in DC
felt hotter than any 95F day in the sun out west -- did not put an
irradiance meter on it though.

I have some rear facing irradiance monitors on some sites now, to get a
better idea of how much gain we can really expect from bifacial modules.
Be interested in seeing what they say over time.  I've been doing another
1.2 or 1.25 factor when using bifacial modules in snow country, but not
sure how realistic that is.

Zeke


> Are there  circumstances where the amperage of a PV module can go up by
> 25%?
>
>
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