[RE-wrenches] [Fwd: Re: ice accumulation]

[Darryl Thayer]

Hi BoB and others, One caution,  if the modules are wired in parallel you may have thermal runaway.  Thermal runaway is when one module takes more current or gets warmer, which makes it take more current, until it takes  all the current.  If the max current is more than one module can handle, it would fail.  

I am in Minnesota, and icing is common.
As for the deicing, I have noticed when they start to melt, the ice slides down and covers the bottom of the module even thicker.  for these situations an unframed module would be nice. 
Also I have noticed a portrait mode module is better than a landscape mode.  (again I believe this is due to the melting and refreezing on the frames.  I have not compared the Black frame and the clear frame.  

In Icing conditions, perhaps all strings should be combined in the controlled space so that BoB's deicing can be string individualized. 
Darryl
 


--- On Sat, 8/16/08, boB <bob at midnitesolar.com> wrote:

> From: boB <bob at midnitesolar.com>
> Subject: [RE-wrenches] [Fwd: Re:  ice accumulation]
> To: re-wrenches at lists.re-wrenches.org
> Date: Saturday, August 16, 2008, 1:12 AM
> Well, I just applied 10 Amps into a  KC-125G, at 24.5 Volts,
> for
> one hour...  The current ~started~ to rise at around 21
> Volts.
> The KC125G serial fuse rating is 12 Amps.
> 
>  This actually seems to make a great  245 Watt heater!
> 
> Ambient room temperature was 21 degrees C.  The panel was a
> nice and 
> evenly toasty 33 degrees C.  That's a 12 degree C 
> (21.6 degrees F)
> temperature rise.
> 
> The front area of the Sanyo HIT-195 is only about 1.25
> times more than the KC125G.
> (1826.88 square inches for the HIT-195 and about 1456 sq.
> inches for the KC125G)
> 
> This means that 700 Watts into a HIT195 should be quite an
> improvement 
> over the 245 W into the KC125G and it might just melt some
> snow or
> ice  ~IF~  there  happens to be enough energy stored
> (hopefully a generator)
> at the site and if it's not TOO  cold.  The pictures of
> Ron's mountain
> top site look like it could get REAL cold there.
> 
> I haven't tried driving a Sanyo HIT module like this
> before, but 
> assuming the I-V curves (when driving them this way) are
> similar
> to a typical poly/mono crystalline module, that should work
> out
> to be ~around~ a 27 degree C (48 F) rise.  This ~might~ (I
> don't know
> what the snow and/or ice does to this figure now), melt
> snow down to 
> less than a zero degree F. environment (-10 C ?). Getting
> even closer to
> the 15 Amps series fuse limit  would of course be better
> but run
> the risk tripping the breaker.
> 
> I guess I'll just have to try this during the winter, 
> if global warming 
> can hold off just a wee bit longer here in the NW.
> 
> boB
> K7IQ
> 
> >>
> >>
> >> On Thu, 14 Aug 2008, Ron Young wrote:
> >>
> >>> Hi Wrenches,
> >>>
> >>> I know this is a nice cool subject for these
> (hopefully) sun filled
> >>> days. I am working on a telecom system that
> has some issues with ice
> >>> accumulation on the panels that essentially
> shut the system down mid
> >>> winter. Wondering if anyone has suggestions to
> remedy the ice
> >>> buildup. It's an extreme mountaintop
> environment with very high winds
> >>> at times and the ice cakes up to 2" -
> 3" on surfaces. There are some
> >>> pics here: www.solareagle/temp/ice.html
> >>>
> >>> Access to the site in winter is totally out of
> the question so we are
> >>> hoping to find some ideas that might prevent
> or reduce the ice
> >>> accumulation. When the ice shuts the panels
> down the communications
> >>> go down.
> >>>
> >>> Someone suggested a slippery spray like RainX
> might help to prevent
> >>> accumulation but I think it would quickly be
> washed off/worn out and
> >>> I don't know the uv issues that might
> reduce power output.
> >>>
> >>>
> >>> Ron
> >>> earthRight Solar
> >>
> >
> >
> 
> 
> _______________________________________________
> List sponsored by Home Power magazine
> 
> RE-wrenches at lists.re-wrenches.org
> 
> http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org
> 
> List rules & etiquette:
> http://www.re-wrenches.org/etiquette.htm
> 
> Check out participant bios:
> www.members.re-wrenches.org