Re: [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 <
cpick...@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  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: w...@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 
> 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
>
>
>
>
>
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.or
> g/maillist.html
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>
>
>
>
> --
> *Will White*
> Curriculum Developer
>
> e: w...@solarenergy.org
> w: www.solarenergy.org
> p: 802-272-3092
>
> PV Installation Professional
> # 093006-34
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.
> org/maillist.html
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.
> org/maillist.html
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>
>
___
List sponsored by Redwood Alliance

List Address: RE-wrenches@lists.re-wrenches.org

Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out or update participant bios:
www.members.re-wrenches.org

Re: [RE-wrenches] Clipping of microinverter output

[cpickard aladdinsolar.com]

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  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: w...@solarenergy.org mailto:w...@solarenergy.org  
> w: http://www.solarenergy.org/  
> p: 802-272-3092
> 
> PV Installation Professional
> # 093006-34
> 
> On Mon, Oct 3, 2016 at 10:20 PM, Mike Kocsmiersky  mailto:mi...@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 Solarhttp://www.SpiritSolar.net
> > 
> >  
> > 
> >  
> > 
> > 
> > ___
> > List sponsored by Redwood Alliance
> > 
> > List Address: RE-wrenches@lists.re-wrenches.org 
> > mailto:RE-wrenches@lists.re-wrenches.org
> > 
> > Change listserver email address & settings:
> > 
> > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org 
> > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
> > 
> > List-Archive: 
> > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html 
> > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
> > 
> > List rules & etiquette:
> > www.re-wrenches.org/etiquette.htm 
> > http://www.re-wrenches.org/etiquette.htm
> > 
> > Check out or update participant bios:
> > http://www.members.re-wrenches.org
> > 
> > 
> > 
> > 
> > > 
> 
> 
> --
> Will White
> Curriculum Developer
> 
> e: w...@solarenergy.org mailto:w...@solarenergy.org  
> w: http://www.solarenergy.org/  
> p: 802-272-3092
> 
> PV Installation Professional
> # 093006-34
> ___
> List sponsored by Redwood Alliance
> 
> List Address: RE-wrenches@lists.re-wrenches.org
> 
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
> 
> List-Archive: 
> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
> 
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
> 
> Check out or update participant bios:
> www.members.re-wrenches.org
> 
> 
___
List sponsored by Redwood Alliance

List Address: RE-wrenches@lists.re-wrenches.org

Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out or update participant bios:
www.members.re-wrenches.org

Re: [RE-wrenches] Clipping of microinverter output

[Will White]

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: w...@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 
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
>
>
>
>
>
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.
> org/maillist.html
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>
>


-- 
*Will White*
Curriculum Developer

e: w...@solarenergy.org
w: www.solarenergy.org
p: 802-272-3092

PV Installation Professional
# 093006-34
___
List sponsored by Redwood Alliance

List Address: RE-wrenches@lists.re-wrenches.org

Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out or update participant bios:
www.members.re-wrenches.org

Re: [RE-wrenches] Clipping of microinverter output

[Jason Szumlanski]

This has been addressed several times on the list (check the archives). But
the best source on this still in my opinion is Enphase's Module
Right-Sizing white paper. There are regional variations that make a big
difference.

It's not so much about the inverter efficiency. It's about how much extra
energy is produced at lower irradiance levels compared to lost energy from
clipping. Look at the efficiency curve for the M250. It's flat. Efficiency
really doesn't matter.
http://www.gosolarcalifornia.ca.gov/equipment/inverter_tests/summaries/Enphase%20Energy%20M250-72_2LL-S2X_240Vac.pdf

And with PV prices creeping down to seemingly impossible low prices, it's
really becoming less of a factor. 20% more module price may only result in
5% more system price, reducing any disincentive to oversize.

Jason


On Mon, Oct 3, 2016 at 10:20 PM, Mike Kocsmiersky 
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
>
>
>
>
>
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.
> org/maillist.html
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>
>
___
List sponsored by Redwood Alliance

List Address: RE-wrenches@lists.re-wrenches.org

Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out or update participant bios:
www.members.re-wrenches.org

[RE-wrenches] Clipping of microinverter output

[Mike Kocsmiersky]

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

 

 

___
List sponsored by Redwood Alliance

List Address: RE-wrenches@lists.re-wrenches.org

Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out or update participant bios:
www.members.re-wrenches.org