[RE-wrenches] Shedding ice

[boB at midnitesolar.com]

On 1/17/2012 4:18 PM, benn kilburn wrote:
> boB,
> 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?
> benn
>
> DayStar Renewable Energy Inc.
> benn at daystarsolar.ca
> 780-906-7807
> HAVE A SUNNY DAY



No mods.  However, as you can see, if the controller is maxed out as far as
array size, that could limit the snow melting effect.   I don't have any 
hard
data as for the minimum power needed to apply to the array for snow melting,
but it could be around twice the power to melt snow as the power rating of
the array.   Yesterday's experiment was less than 2wice the power rating
and it may have been fine with with even less, so that's a very good sign.

How much power does it take to melt snow off of a car's rear window from
the electric defroster ?  It's a similar kind thing.

Diodes ??  You mean the bypass diodes ??   No problem.  Those don't
conduct in this case.

boB



>
>
>
> ------------------------------------------------------------------------
> Date: Mon, 16 Jan 2012 13:14:36 -0800
> From: boB at midnitesolar.com
> To: re-wrenches at lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Shedding ice
>
> On 1/16/2012 11:39 AM, David Katz wrote:
>
>     Mark,
>     I believe the Midnite Classic has this feature built in. Check
>     with them.
>     David Katz
>
>
>
> It just snowed up here in Arlington, Washington A.C.  and we were just 
> starting to melt some snow
> on a couple of modules on our roof just now with one of our charge 
> controllers here in the lab.
>
> This feature is not yet in the Classic, BUT, check out this experiment 
> that I did about 3 years ago
> in my front yard with an animated gif time lapse.
>
> One module is being powered and the other is not powered, just sitting 
> there for comparison.
> These are KC125s.
>
> The time involved here was about 3 hours and took about 1 kW-hour of 
> energy but gives you
> an idea of what may be done with this idea.  One thing not in our 
> favor here is that the module
> that is being powered is resting on the ground, in the snow, which 
> would significantly
> hinder snow melting I would think rather than being properly mounted.
>
> Oh what fun it is to melt some PV snow tonight !
>
> http://fusion.midnitesolar.com/PVsnowMelt3.gif
>
> boB
>
>
>
>
>
>
>
>
>     *From*: Mark Dickson [mailto:Mark at OasisMontana.com]
>     *Sent*: Monday, January 16, 2012 10:00 AM
>     *To*: 'RE-wrenches' <re-wrenches at lists.re-wrenches.org>
>     <mailto:re-wrenches at lists.re-wrenches.org>
>     *Subject*: [RE-wrenches] Shedding ice
>
>     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. . .
>
>     Best regards,
>
>     Mark Dickson,
>
>     NABCEP Certified Solar PV Installer ^(TM)
>
>     Oasis Montana Inc.
>
>
>
>
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