[RE-wrenches] 300W 72 cell micro inverters

Tue Feb 10 19:12:07 PST 2015

Regarding the clipping, which the power electronics guys would rather I 
call "power limiting"...

To be clear, "Longer 100% production around noon" (implied in that image 
that this is somehow beneficial) means "this system could have produced 
more energy but didn't because the inverter was too small." Assuming 
similar efficiencies, a 300W micro-inverter clearly would have produced 
more energy on that day than the 250W inverter. I imagine that what you 
mean was that if you're locked into a certain ac limit here (either you 
can only use a 250W micro, or maybe your service conductors limit your 
ac rating) then yes, a higher dc/ac ratio may have more power limiting 
but will produce more energy at the expense of your kWh / kWdc yield (a 
consideration for some projects).

Given that the ABB inverters have their highest efficiencies at the 
higher end of their power outputs, which is not where PV modules 
typically operate (unless you stick a 400W module on it), I'm curious 
whether a typical 280W module would actually produce more energy over a 
year with an Enphase 240W vs the ABB 300W in most locations. Over the 
full Enphase power range it's more efficient than the ABB:

At ~100W dc input, Enphase is at about 96.4% efficient and the ABB 300W 
is at 95.8%.
At ~250W input: Enphase 96.4%, ABB 96.1%.
And yes, at 315W input: Enphase 76.2% steady-state, ABB 96.4%.

It could go without saying (but I have momentum) that you should not 
spend $2000 on a larger inverter(s) that will help your array produce 
$200 more energy over its 25-year life. It's up to you to figure that 
out given your site conditions and as noted in the last thread that 
addressed this topic, weather data probably underestimates the benefit 
due to its averaging out most short-term edge-of-cloud effects.

Anyway, maybe C250s would meet the OP's needs and they're actually the 
slightest bit more efficient than the standard 240W unit. That is, until 
you add the transformer since the output is 220-248V L-N. That 
presumably makes the ABB the efficiency winner, but hopefully the above 
is still useful. Sorry, no personal experience with any of the 
ABB/APS/C250 units. I probably should have opened with that to save you 
some time.

DKC

On 2015/2/10 13:05, Jarmo.Venalainen at schneider-electric.com wrote:
> Hi:
>
> One thing to keep in mind with clipping, (module over sizing), is that 
> if a system has 10%-15% off clipping, that will not affect total 
> annual energy harvest and depending on dust and temperature conditions 
> will likely even improve it.
>
> Heres' a graph which shows the energy harvest graphically for a 250W 
> module with a 250W inverter and a and 300W module with a 250W inverter.
>
>
> Please note the graph does not include any dust effects.  To 
> compensate for dust, the modules should always be of the order of 4% 
> more powerful than the inverter, unless you plan on washing modules 
> every month.
>
> Related to this, large commercial systems we have been supplying 
> inverters to are 30-70% oversized as the sinking cost of modules makes 
> the return on investment come out as maximized in that range of 
> oversizing,
>
> JARMO
> _____________________________________________________________________________________
> *
> Jarmo Venalainen*  | *Schneider Electric **|  Xantrex Brand*  | 
> *CANADA*  | *Sales Application Engineer* *
> Phone:* +604-422-2528  | *Tech Support:* 800-670-0707  | *Mobile:* 
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> Email:* _jarmo.venalainen at schneider-electric.com_ 
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>
> From: 	Drake <drake.chamberlin at redwoodalliance.org>
> To: 	RE-wrenches <re-wrenches at lists.re-wrenches.org>,
> Date: 	02/10/2015 06:51 AM
> Subject: 	Re: [RE-wrenches] 300W 72 cell micro inverters
> Sent by: 	"RE-wrenches" <re-wrenches-bounces at lists.re-wrenches.org>
>
>
> ------------------------------------------------------------------------
>
>
>
> That  would be at the 120% rating, so by rule of
> thumb, OK. I have a ground mount that has a
> ration of 1.15% with M-190s (figuring 199 W /
> inverter). It has quite a bit of clipping in the
> spring. It has optimized tilt for the location. A
> ballasted roof mount with a 10 or 15 degree tilt
> likely wouldn't have that issue.
>
> This system went in the spring of 2010, and has
> only  had one M-190 failure out of 24, amazingly enough.
>
> At 10:22 AM 2/9/2015, you wrote:
> >What do you typically get out of a 300 watt panel for production when you
> >are grid tied? I know in theory (STC) it is a 300 watt module but we
> >rarely if ever (except in very cold weather)see near that for an 
> output. I
> >use (as a general, 77 degrees F) design parameter, 77% for overall power
> >production output output. I'm sure you would get a little clipping, but I
> >guess a significant amount would depend on a number of variables on the
> >site, time of the year, weather conditions, etc.
> >
> >Daryl
> >
> >
> > > Yeah....if you're OK with a not insignificant amount of clipping 
> going on.
> > >
> > > -----Original Message-----
> > > From: RE-wrenches 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
> > > Behalf Of penobscotsolar at midmaine.com
> > > Sent: Sunday, February 08, 2015 2:33 PM
> > > To: RE-wrenches
> > > Subject: Re: [RE-wrenches] 300W 72 cell micro inverters
> > >
> > > Hey Jason,
> > >    The M-250's work well with LG 300 watt (60 cell) modules.
> > >
> > > Daryl
> > >
> > >
> > >> Hi Jason,
> > >>
> > >> The Enphase C250 Microinverters for three-phase commercial
> > >> applications does work with 72 cell modules.
> > >>
> > >> On Sun, Feb 8, 2015 at 12:58 PM, Jason Szumlanski <
> > >> jason at floridasolardesigngroup.com> wrote:
> > >>
> > >>> The ABB micros seem to be solid and easy to install. We have two
> > >>> sites with them with no issues. Unfortunately, the monitoring system
> > >>> sucks compared to Enphase and was far more difficult to set up. I
> > >>> really wish Enphase would come up with a good 72 cell option because
> > >>> we find ourselves competing with 300W modules occasionally, and
> > >>> consumers (irrationally) jump to the conclusion that bigger is
> > >>> better.
> > >>>
> > >>>
> > >>> [image: Logo-Sq-80.png]
> > >>>
> > >>> Jason Szumlanski
> > >>>
> > >>> Principal Solar Designer
> > >>>
> > >>> Florida Solar Design Group
> > >>>
> > >>> (239) 491-8010 office
> > >>>
> > >>> (239) 410-4985 mobile
> > >>>
> > >>> Authorized Sales Agent for Fafco Solar
> > >>>
> > >>> [image: Fafco-Solar-Enphase-Logo.png]
> > >>>
> > >>> License CVC56701
> > >>>
> > >>>
> > >>> On Sun, Feb 8, 2015 at 3:15 PM, Bill Hennessy <bill at berkssolar.com>
> > >>> wrote:
> > >>>
> > >>>> Hi folks--
> > >>>>
> > >>>> We're planning a micro inverter install using 300W 72 cell modules
> > >>>> for an area with a fair amount of shading. The choices we've found
> > >>>> are ABB micro
> > >>>> 0.3 or APS YC500A.
> > >>>> Any stories to tell about either of these or another suggestion?
> > >>>>
> > >>>> Thanks for your time.
> > >>>>
> > >>>> Bill Hennessy
> > >>>> Berks Solar, LLC
> > >>>> 371 Centennial Rd
> > >>>> Mertztown, PA 19539
> > >>>>
> > >>>> o 610 682 4300
> > >>>> c 484 560 4666
> > >>>> NABCEP certified installer
> > >>>> PA contractor #44411
> > >>>> www.berkssolar.com
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
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> > >> --
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> > >> Cordially,
> > >>
> > >> Nick Soleil
> > >> *Enphase Energy* | Field Applications Engineer
> > >>
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> > >>
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