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On 1/17/2012 6:32 PM, Bill Hoffer wrote:
<blockquote
cite="mid:CAL4SeazXrKRqEziCWJx0ddZAgeJw=pojKCT5bhzHSArxgqFd2g@mail.gmail.com"
type="cite">Bob<br>
<br>
Wonder how Module manufacturer warranties will handle applying
reverse current to the module , especially if it is more than the
power rating of the module??? I would want that one in writing
before risking having to write off an array in order to melt a
little snow!<br>
<br>
Bill<br>
<br>
</blockquote>
<br>
Hey Bill !!<br>
<br>
Don't worry, I wouldn't dream of doing something that is outside the
module's specifications.<br>
<br>
Most PV module manufacturers don't quite understand how this works
either but one particular <br>
manufacturer liked the idea when I brought it up to them a couple
years ago at SPI.<br>
<br>
<br>
This mode of operation is also done in part of the UL testing.
There are certain rules<br>
that have to be followed for this and luckily, most properly
installed systems are already protected.<br>
<br>
It's actually much easier on the modules than you might think.<br>
<br>
boB<br>
<br>
<br>
<br>
<br>
<br>
<blockquote
cite="mid:CAL4SeazXrKRqEziCWJx0ddZAgeJw=pojKCT5bhzHSArxgqFd2g@mail.gmail.com"
type="cite">
<div class="gmail_quote">On Tue, Jan 17, 2012 at 4:37 PM, <a
moz-do-not-send="true" href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a>
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div class="im"> On 1/17/2012 4:18 PM, benn kilburn wrote:
<blockquote type="cite">
<div dir="ltr"> boB,
<div>If this concept were to become a working option
for the Classic, would the modules have to be
modified in any way? Why are the diodes not
blocking the reverse current?</div>
<div>benn<br>
<br>
<span style="color:rgb(0,32,96)"><font
face="'Franklin Gothic Medium'">DayStar
Renewable Energy Inc. </font></span>
<div>
<div><font face="'Franklin Gothic Medium'"><a
moz-do-not-send="true"
href="mailto:benn@daystarsolar.ca"
target="_blank">benn@daystarsolar.ca</a></font></div>
<div><font face="'Franklin Gothic Medium'"><a
moz-do-not-send="true"
href="tel:780-906-7807" value="+17809067807"
target="_blank">780-906-7807</a> </font></div>
<div><font face="'Franklin Gothic Medium'">HAVE A
SUNNY DAY </font></div>
</div>
</div>
</div>
</blockquote>
<br>
<br>
<br>
</div>
No mods. However, as you can see, if the controller is
maxed out as far as<br>
array size, that could limit the snow melting effect. I
don't have any hard<br>
data as for the minimum power needed to apply to the array
for snow melting,<br>
but it could be around twice the power to melt snow as the
power rating of<br>
the array. Yesterday's experiment was less than 2wice the
power rating<br>
and it may have been fine with with even less, so that's a
very good sign.<br>
<br>
How much power does it take to melt snow off of a car's rear
window from<br>
the electric defroster ? It's a similar kind thing.<br>
<br>
Diodes ?? You mean the bypass diodes ?? No problem.
Those don't<br>
conduct in this case.<span class="HOEnZb"><font
color="#888888"><br>
<br>
boB</font></span>
<div>
<div class="h5"><br>
<br>
<br>
<br>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>
<div><br>
</div>
</div>
<br>
<br>
<div>
<hr>Date: Mon, 16 Jan 2012 13:14:36 -0800<br>
From: <a moz-do-not-send="true"
href="mailto:boB@midnitesolar.com"
target="_blank">boB@midnitesolar.com</a><br>
To: <a moz-do-not-send="true"
href="mailto:re-wrenches@lists.re-wrenches.org"
target="_blank">re-wrenches@lists.re-wrenches.org</a><br>
Subject: Re: [RE-wrenches] Shedding ice<br>
<br>
On 1/16/2012 11:39 AM, David Katz wrote:
<blockquote> <font
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Mark,<br>
I believe the Midnite Classic has this
feature built in. Check with them.<br>
David Katz</font><br>
<br>
</blockquote>
<br>
<br>
It just snowed up here in Arlington, Washington
A.C. and we were just starting to melt some
snow<br>
on a couple of modules on our roof just now with
one of our charge controllers here in the lab.<br>
<br>
This feature is not yet in the Classic, BUT,
check out this experiment that I did about 3
years ago<br>
in my front yard with an animated gif time
lapse.<br>
<br>
One module is being powered and the other is not
powered, just sitting there for comparison.<br>
These are KC125s.<br>
<br>
The time involved here was about 3 hours and
took about 1 kW-hour of energy but gives you<br>
an idea of what may be done with this idea. One
thing not in our favor here is that the module<br>
that is being powered is resting on the ground,
in the snow, which would significantly<br>
hinder snow melting I would think rather than
being properly mounted.<br>
<br>
Oh what fun it is to melt some PV snow tonight !<br>
<br>
<a moz-do-not-send="true"
href="http://fusion.midnitesolar.com/PVsnowMelt3.gif"
target="_blank">http://fusion.midnitesolar.com/PVsnowMelt3.gif</a><br>
<br>
boB<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<blockquote>
<div> <font
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><b>From</b>:
Mark Dickson [<a moz-do-not-send="true"
href="mailto:Mark@OasisMontana.com"
target="_blank">mailto:Mark@OasisMontana.com</a>]
<br>
<b>Sent</b>: Monday, January 16, 2012
10:00 AM<br>
<b>To</b>: 'RE-wrenches' <a
moz-do-not-send="true"
href="mailto:re-wrenches@lists.re-wrenches.org"
target="_blank"><re-wrenches@lists.re-wrenches.org></a>
<br>
<b>Subject</b>: [RE-wrenches] Shedding ice
<br>
</font> <br>
</div>
<div>
<p><font color="navy" face="Arial"><span
style="font-size:10.0pt;font-family:Arial;color:navy">I
recall a conversation a while back
about the possibility of “reversing”
the current in a solar module to
increase the cell temp enough to shed
ice/rime. To follow-up, has anybody
been successful at this? I am
guessing, if so, it would entail,
removal of diodes, increasing PV and
battery capacity and some way to sense
the ice at the very least. . . It
sounds good in theory, but I am
skeptical as to whether it will work
in reality. . .</span></font></p>
<p><font color="navy" face="Arial"><span
style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font></p>
<div>
<p><font color="navy" face="Comic Sans MS"><span
style="">Best regards,</span></font></p>
<p><font color="navy" face="Comic Sans MS"><span
style=""> </span></font></p>
<p><font color="navy" face="Comic Sans MS"><span
style="">Mark Dickson,</span></font><font
color="navy"><span style="color:navy"></span></font></p>
<p><font color="navy" face="ArialMT"><span
style="font-size:10.0pt;font-family:ArialMT;color:navy">NABCEP Certified
Solar PV Installer ™</span></font></p>
<p><font color="navy" face="Comic Sans MS"><span
style="">Oasis Montana Inc.</span></font></p>
</div>
<p><font color="navy" face="Arial"><span
style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><br>
</p>
</div>
</blockquote>
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<br>
-- <br>
Bill Hoffer PE<br>
NABCEP Certified Solar PV Installer™<br>
Sunergy Engineering Services PLLC<br>
2504 Columbia Ave NW<br>
East Wenatchee WA 98802-3941<br>
<a moz-do-not-send="true" href="mailto:SunEngSer@gmail.com">SunEngSer@gmail.com</a>
Cell:(509)679-6165<br>
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