[RE-wrenches] Clipping of microinverter output

[Jason Szumlanski]

Amen to that. It doesn't make sense to spend inordinate time agonizing over
the right ratio, and consumers are skeptical anyway. Unless it's way under
or over 1.0 it isn't going to make a huge difference. I did a sensitivity
analysis on this when PV cost twice as much, and I found it still wasn't
worth spending too much time on each site analysis. I just shoot for a
ratio of 1.1 south and 1.2 east or west here where it's hot. In cooler
climates 0.9 - 1.0 might make better sense, but I haven't done any cold
weather work.

​Jason​



On Tue, Oct 4, 2016 at 12:17 PM, cpickard aladdinsolar.com <
cpickard at aladdinsolar.com> wrote:

> We find it can be very difficult (time consuming) to explain this to some
> customers. So we try to keep possibility of clipping to a minimum, maybe
> with obvious clipping occurring a few days a year. If module tilt or
> orientation is less than ideal,  clipping is more rare and we might be more
> aggressive on the DC/AC ratio. This approach is not driven so much by the
> science but by the desire to avoid never-ending discussions with certain
> customer types.
>
> --Charlie Pickard
>
> TruNorth Solar
>
>
> On October 4, 2016 at 7:30 AM Will White <will at solarenergy.org> wrote:
>
> Mike,
>
> Have you read the Enphase white paper on module to inverter size?  It goes
> into good detail on why they do it.
>
> http://www2.enphase.com/global/files/Enphase_White_
> Paper_Module_Rightsizing.pdf
>
> Thanks,
> Will
>
>
> --
> *Will White*
> Curriculum Developer
>
> e: will at solarenergy.org
> w: www.solarenergy.org
> p: 802-272-3092
>
> PV Installation Professional
> # 093006-34
>
> On Mon, Oct 3, 2016 at 10:20 PM, Mike Kocsmiersky <mikek at spiritsolar.net>
> wrote:
>
> Recently I’ve been concerned about power clipping of micro inverters and
> the design ratio of PV STC array size to inverter.  If I have a 300W module
> going into a 250W micro inverter, there will be times when the potential
> power output is clipped because the micro inverter can’t handle all the
> power.  I’m thinking cold day with 1000W/m2 irradiance.  It is typical
> nowadays to have an STC array size to inverter ratio of 1.2.  Have you seen
> any analysis on how much energy is clipped, vs how much energy output is
> increased by operating at a better efficiency spot on the micro inverter?
> This assumes that the micro inverter performs better when more fully loaded.
>
> Additionally over time the crystalline silicon module will degrade
> slightly as well, reducing the amount of power clipping.
>
>
>
> I welcome your thoughts.
>
>
>
>
>
> Mike Kocsmiersky
>
> Principal
>
> Phone: 413 883-3144
>
> *Spirit Solar*
>
> www.SpiritSolar.net
>
>
>
>
>
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> --
> *Will White*
> Curriculum Developer
>
> e: will at solarenergy.org
> w: www.solarenergy.org
> p: 802-272-3092
>
> PV Installation Professional
> # 093006-34
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