Just thinking out loud here, but wondering if it would pay to attach an insulated back to the panel for the winter months to decrease the convection. I may need to set up a lab here and find out. . .
Best regards, Mark Dickson, NABCEP Certified Solar PV Installer T Oasis Montana Inc. 877-627-4768 toll-free 406-777-4309 (0830 fax) Mark Dickson, Certified Solar PV Installer <http://www.oasismontana.com/> http://www.oasismontana.com/ <http://www.grid-tie.com/> http://www.grid-tie.com/ <http://www.pvsolarpumps.com/> http://www.pvsolarpumps.com/ _____ From: b...@midnitesolar.com [mailto:b...@midnitesolar.com] Sent: Monday, January 16, 2012 3:43 PM To: RE-wrenches Cc: penobscotso...@midmaine.com; Mark Dickson Subject: Re: [RE-wrenches] Shedding ice On 1/16/2012 1:34 PM, penobscotso...@midmaine.com wrote: Impressive, Bob, but if one 125 watt panel took 1000 watts of power, what is it going to take to melt my two 1600 watt arrays, pole mounted, (theoretically, of course, and at a 65 degree tilt)....? Just wondering as it seems a lot of power to use in the winter for an off grid or solar reliant system. Thanks, Daryl Yes, it can take a lot of energy. How much and how long depends on what the outside ambient temperature is. I think it will have a problem in extreme cold because it depends on temperature rise of the module to get it above freezing. If the sun comes out, that helps a lot so would help to reduce the energy in melting. The melting we just now tried here, melted 2 X 200W modules (series) in 45 minutes with 700 Watts of power into them (0.7 kW-hour) which is much better than my older experiment and I believe being off the ground makes a big difference. The outside temperature right now is only 31 degrees F so kind of warm. The array is sitting at about 25 degree tilt just above the metal roof on our building. It is still snowing here so no sun. Colder temperatures like the one in my animated gif will take longer but I am sure that keeping them off the ground helps a lot. My 3 year old test was sticking in the snow on the ground. There may be times though where it might be better to run some power into an array that has a chance of melting while the generator has to run anyway. If it didn't quite work then nothing much lost. Unless it has a chance of working fairly quickly without too much energy from the batteries, you'd want to have a generator running. Todays melting experiment was done off the batteries only. To have any gains, you would have to have some sun coming soon after it was melted off the array before it snowed again. This isn't a complete fix but something that may be put into the bag of tricks when it does work to an advantage. Here it is still snowing so it wouldn't make any difference but is sure fun to watch ! PS for Mark Dickson, I don't know what it would take for your 50 watt module but much less power than for the 400 watts of PV we just melted snow on in the same conditions. boB 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:m...@oasismontana.com] *Sent*: Monday, January 16, 2012 10:00 AM *To*: 'RE-wrenches' <mailto:re-wrenches@lists.re-wrenches.org> <re-wrenches@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. _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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