Greg,
Great question.
All power generators and energy storage devices (batteries, capacitors, etc.)
have what's termed "internal resistance", also termed "internal impedance" when
frequency greater than DC is involved. This resistance/impedance is what
limits the output current of these devices.
When you short-circuit PV, you'll measure amperage flowing through the leads
commensurate with whatever that internal resistance happens to be at that
moment (dependent on irradiance, temperature, and other variables). With a
theoretically perfect zero-ohm load, 100% of the voltage being generated by the
PV at that moment will be drpped across its internal resistance. The load
(being "perfect") will have zero volts across it (E = I * R). If R = 0, so
does E.
In real life, there will always be a voltage greater than zero across your
load, no matter how infinitesimal, because no matter how large a conductor you
use, it will have some value of R greater than zero. The voltage across the
"short" may be on the order of a few millivolts (thousandths of a volt) .. down
to a few hundred microvolts (millionths of a volt) for very large conductors.
However, the value of this voltage is so low compared to normal PV operating
voltages as to be considered zero for all intents and purposes.
Dan
--- On Sat, 2/5/11, Greg Egan <g...@remotepowerinc.com> wrote:
From: Greg Egan <g...@remotepowerinc.com>
Subject: [RE-wrenches] PV voltage at Isc
To: re-wrenches@lists.re-wrenches.org
Date: Saturday, February 5, 2011, 1:30 PM
Fellow Scientists,
I got in a discussion with a wrench the other day. He is under the
impression that when a PV module is at short circuit current there is
no voltage. My understanding of electricity is that if there's no
voltage there's no current because current needs voltage in order to
flow. I'm seeing it as a difference in potential, voltage that is. If
there's no difference in potential I don't understand why current would
flow.
I googled it and the few links I checked out were on his side - zero
voltage at Isc. All this is of course irrelevant to the business of
installing PV so if you don't care I don't blame you.
So I still think that if you a precise enough meter that if you stuck
the test leads into the cables sticking out of the back of a shorted PV
module that you'd read some small voltage that was approaching zero.
Any explanation of why I am right or wrong in plain English (I'm not
really a scientist) would be welcome.
All the best,
Greg Egan
Remote Power Inc.
Fairbanks, AK
re-wrenches-requ...@lists.re-wrenches.org wrote:
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Today's Topics:
1. Re: PV Encapsulant Quality (Eric Thomas)
2. I Need a Sharp SunVista Manual (Brian Sipp)
3. Re: I Need a Sharp SunVista Manual (Jeff Irish)
4. Re: I Need a Sharp SunVista Manual (Brian Sipp)
5. Re: PV Encapsulant Quality (Jesse Dahl)
6. Re: Matching modules into Xantrex GT (Allan Sindelar)
----------------------------------------------------------------------
Message: 1
Date: Fri, 4 Feb 2011 10:33:27 -0800
From: Eric Thomas <solarepiph...@gmail.com>
To: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] PV Encapsulant Quality
Message-ID:
<AANLkTi=faxbtrhlxor9wqalejn8e7v_gygpdyepus...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Here is a great report that goes over advanced life cycle
testing of modules and their reasons for failure.
http://www.nrel.gov/docs/fy11osti/47755.pdf . It is a recent study and there
is some good info regarding encapsulents. I can tell you that the high
ranker on the results chart is the Silicon Energy Cascade module. With its
glass on glass encapsulent and integrated wireway, its the most robust
module I've ever seen. We installed the largest WA residential system
utilizing these modules in Dec of last year. They are nice to work
with...not without their challenges of course, but as far as warranty..I
think they will last the test of time.
Eric Thomas
Solar Epiphany
(206)919-3014
www.solarepiphany.com
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Message: 2
Date: Fri, 4 Feb 2011 13:21:09 -0800
From: "Brian Sipp" <brian.s...@firstsourcesolar.com>
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org>
Subject: [RE-wrenches] I Need a Sharp SunVista Manual
Message-ID: <8B7DB7ABA13B4A05A1E69FCEA166F07B@FirstSource>
Content-Type: text/plain; charset="us-ascii"
I just got off the phone with the worlds worst customer (dis)service rep. at
Sharp. It really calls into question whether I want to sell any more of
Sharp modules, if this is how they treat their past customers.
Does anyone have a PDF of the Sharp SunVista manual? The only thing I find
online, or Sharp would provide, is a 2 page cut sheet.
Brian M. Sipp
First Source Solar Systems
<http://www.firstsourcesolar.com/> www.FirstSourceSolar.com
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Message: 3
Date: Fri, 4 Feb 2011 16:31:41 -0500
From: "Jeff Irish" <j...@hvce.com>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] I Need a Sharp SunVista Manual
Message-ID:
<86FA2C8AA80F3C49AE21B7EC7BD559B8798995@HVCE-SERVER.hvcegroup.local>
Content-Type: text/plain; charset="us-ascii"
Brian,
I have one but it's a big file and I don't want to overload everyone's
mailboxes. Email me off-line at j...@hvce.com
Jeff Irish
Hudson Valley Clean Energy
and Adirondack Solar
________________________________
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Brian
Sipp
Sent: Friday, February 04, 2011 4:21 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] I Need a Sharp SunVista Manual
I just got off the phone with the worlds worst customer (dis)service
rep. at Sharp. It really calls into question whether I want to sell any
more of Sharp modules, if this is how they treat their past customers.
Does anyone have a PDF of the Sharp SunVista manual? The only thing I
find online, or Sharp would provide, is a 2 page cut sheet.
Brian M. Sipp
First Source Solar Systems
www.FirstSourceSolar.com <http://www.firstsourcesolar.com/>
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Message: 4
Date: Fri, 4 Feb 2011 14:05:03 -0800
From: "Brian Sipp" <brian.s...@firstsourcesolar.com>
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] I Need a Sharp SunVista Manual
Message-ID: <F23DB5CB2F37496092CD7CCC9A263EC8@FirstSource>
Content-Type: text/plain; charset="us-ascii"
Wow, that was fast! Thank you to everyone who replied on and off line. As
always the wealth of knowledge on the forum, and folks openness to share
always impresses me!
This made my day!
PS: Sharp - Start taking notes...
Brian M. Sipp
First Source Solar Systems
<http://www.firstsourcesolar.com/> www.FirstSourceSolar.com
Office: 530-554-1925
Mobile: 916-342-2630
_____
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jeff Irish
Sent: Friday, February 04, 2011 1:32 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] I Need a Sharp SunVista Manual
Brian,
I have one but it's a big file and I don't want to overload everyone's
mailboxes. Email me off-line at j...@hvce.com
Jeff Irish
Hudson Valley Clean Energy
and Adirondack Solar
_____
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Brian Sipp
Sent: Friday, February 04, 2011 4:21 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] I Need a Sharp SunVista Manual
I just got off the phone with the worlds worst customer (dis)service rep. at
Sharp. It really calls into question whether I want to sell any more of
Sharp modules, if this is how they treat their past customers.
Does anyone have a PDF of the Sharp SunVista manual? The only thing I find
online, or Sharp would provide, is a 2 page cut sheet.
Brian M. Sipp
First Source Solar Systems
www.FirstSourceSolar.com <http://www.firstsourcesolar.com/>
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Message: 5
Date: Fri, 4 Feb 2011 16:05:45 -0600
From: Jesse Dahl <dahlso...@gmail.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] PV Encapsulant Quality
Message-ID: <69420d91-5072-41e1-af12-4a9fe7d1b...@gmail.com>
Content-Type: text/plain; charset="us-ascii"
Wrenches,
I live in northern MN where Silicon Energy is building a new manufacturing
plant. I also teach at the local community college. I have met with silicon
energy and have seen the tests. Great module. Looks nice installed too.
Mounting options are limited but the glass on glass is a really good idea.
Jesse
Sent from my iPhone
On Feb 4, 2011, at 12:33 PM, Eric Thomas <solarepiph...@gmail.com> wrote:
Here is a great report that goes over advanced life cycle
testing of modules and their reasons for failure.
http://www.nrel.gov/docs/fy11osti/47755.pdf . It is a recent study and there is
some good info regarding encapsulents. I can tell you that the high ranker on
the results chart is the Silicon Energy Cascade module. With its glass on glass
encapsulent and integrated wireway, its the most robust module I've ever seen.
We installed the largest WA residential system utilizing these modules in Dec
of last year. They are nice to work with...not without their challenges of
course, but as far as warranty..I think they will last the test of time.
Eric Thomas
Solar Epiphany
(206)919-3014
www.solarepiphany.com
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Message: 6
Date: Fri, 04 Feb 2011 23:22:56 -0700
From: Allan Sindelar <al...@positiveenergysolar.com>
To: Kent Osterberg <k...@coveoregon.com>
Cc: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Matching modules into Xantrex GT
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