[RE-wrenches] high insolation value and inverter undersizing

[Marco Mangelsdorf]

For that particular site, no.  As far as I know a database is not being
maintained.  That is, what you see at any given moment is what you get.  But
I will check.  Once we get into Spring and Summer with higher sun angles, I
will be able to see what kind of clipping would have taken place since I
have 245-watt modules on 300-watt micros.  (It's the one and only beta test
site in the state for these micros.)  Any time I see recorded outputs of 226
watts or higher, I will know that clipping would have taken place if I had
used M215s instead.

For me this boils down to several fairly simple points:
1) Clipping is not good since that represents harvestable solar energy that
does not make it to the end user.
2) So when the choice of clipping v. no clipping is presented, no clipping
is always, in principle, going to be the best choice.
3) Larger inverters--whether micro or string--are going to typically cost
more than smaller ones.
4) Does it make sense to pay more upfront for more inverter capacity and
reap the benefits of more delivered kWhs over time?

One can perform detailed equations until the ripe mangoes fall from the
trees (at least out here).  But from an intuitive perspective, spending
marginally more money upfront to minimize if not eliminate clipping,
especially in areas like the tropics which can have frequent and lingering
edge-of-cloud effects, makes the most sense to me.

And, really, pairing up a micro with a nameplate rating of 215 watts and max
output of 225 watts with a 255, 260, 265 watt or higher rated mod?  Does
that really pass the sniff test when there are not higher output micros out
there?  Put the choice to the consumer, educate them just a wee bit and how
do you think they will decide?

marco

@ Marco: does your weather data source have a database of insolation and
temperature over the year ?

Best Regards,

John Berdner
General Manager, North America



SolarEdge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new
address.)
T: 510.498.3200, X 747
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-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of William
Miller
Sent: Sunday, January 27, 2013 8:05 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] high insolation value and inverter undersizing

Jesse:

Do you have any way to compare the total harvest for the day for a given
module in a "clipping" scenario versus an unclipping?  The question I want
to answer is: Do we improve production enough on the shoulders of the clip
to justify the loss on the peak?


Thanks,

William Miller


At 06:25 PM 1/27/2013, you wrote:
>A while back (3 years)I installed a system (bid spec) for a school that 
>used 215W RECs and D380s on a dual axis tracker.  With the ability to 
>monitor the array, I see constant clipping.  The modules will usually 
>produce 199Ws regularly.  A few days ago we had temps of -34F and clear 
>skies.  My array at home had one of its best days this winter.  I have 
>Tigos on so I can monitor watts, current, temp and voltage. I was 
>seeing anywhere from 215W to 223W from my modules between 11:30am and 
>1pm.  The modules on the tracker were still producing 199W.  I didn't 
>get an irradiance reading that day but my Tigos showed above IMP 
>readings and way above VMP reading that day.
>
>I've only been doing this for 6 years, so I don't have the experience 
>that some people on this list have, but it seems foolish to me to waste 
>that production.  It's kinda site specific, but where I live the cold 
>temps and snow reflection seem like something we should be utilizing.

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