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gbwillson

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Reply with quote  #31 
I was thinking of ways to clear off the glazing yesterday. I hadn't thought of sticking black wires down the slots. That wouldn't be practical at this point. It would have had to have been thought of during construction. I thought of several ways to clear the glazing quickly, including throwing an old electric blanket over the top or pouring water on the glazing. I can only imagine what my neighbors would think of my "solar" heaters!! Right now the air temp is -10 degrees and with the wind it feels like -30 degrees on your face. Clear skies or not, that's gonna be hard to overcome. I'd cry, but my tears would freeze to my face before they had a chance to roll off my cheek. Actually, at these temps, boiling water thrown in the air will vaporize before it hits the ground. [eek] http://www.theblaze.com/stories/2012/12/20/this-is-what-it-looks-like-when-boiling-water-is-thrown-into-41-degree-air-hint-its-pretty-cool/
Much of your heat is going to be pulled right out of the glazing. The greater the tempature difference between two objects, the faster the transfer of heat to cold. I was seeing temps drops of 10 degrees just in the few feet from the upper sensor to the house. 

Only 2 more weeks until the winter solstice. Then the sun begins to rise in the sky. Yeah!

Greg in Arctic MN

solardan1959

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Reply with quote  #32 
Only problem is January, even with longer hours of sun, is even colder [smile].  Beautiful cold clear night, let's hope it stays that way when the sun comes up!
Dan
netttech

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Reply with quote  #33 
Scott may be right about the wind pulling the heat away, especially if the zero pass design keeps the heat away from glazing effectively.

Seatec, I also have single layer 1/8 lexan. Yea, it does defrost quicker than twinwall. That being said, extreme cold air, does affect the panel performance on single layer glazing. I experienced that with my 1st panel. I added a 2nd layer & the overall temps went up significantly. I was using the heat shrink plastic at the time, but the 2nd layer does keep extreme cold away from the collector. Like I said, I think maybe the twinwall could be a double-edge sword, good & bad.

I will test my theory (somewhat) on the wire idea. The current winter storm missed me & went south of my location. So, I don't have the blowing snow & extreme cold as mentioned in other posts.

I'm trying 2 different sizes of wire in a small section of my twinwall glazing. I have thin (17 gage) electric fence wire & a coat hanger.

I inserted the wires in the section of twinwall where my snap-switch is located. The clouds are suppose to clear tonight, but be single digits. The hot water panel 'should' be frosty tomorrow morning, but sunny. I will take a series of pictures to see how the inserted black wire performs for defrosting that section.

Jeff
Central IL.

PC061302.JPG PC061304.JPG PC061306.JPG 


gbwillson

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Reply with quote  #34 

Neat little experiment Jeff- 

I will be eager to see the results. It was -12 degrees outside this morning. With the wind it felt like -32 degrees. Thankfully, the skies were clear and the winds died down to around 6 MPH.  The sun begins to hit the collectors a little after 8am, but it's far too cold and the sun is too low to notice any heat in the collectors. Around 9am the collectors are both getting sun, but still it's raising the temps inside very little. I opened up the ducts in the basement to allow a little thermo siphoning of the basement ceiling air(65 degrees). Around 10:30 the screen collector output thermometer has topped out. It's time to turn on the fans. The fans were blowing through both collectors at 107CFM. The temps were coming up slowly, but they still have to overcome the little bit of frozen mass in the collectors. Both collectors are putting out pretty good heat now, with the screen doing a slightly better,(about 3 degrees) although it does get full sun sooner and as you can see in the photos below, the glazing on the ZP still has quite a bit of ice, frost and quite a bit of condensation inside the channels. I'm going to have to look into that, as it sure does block a bit of the sun from the collector. The top end is sealed tight and the bottom…It think is too, except for little holes for breathing. Perhaps open channels top and bottom?(at least until they go into storage). The tape kit designed for the ends is pretty expensive. I'm sure not worried about bugs making a home in the channels this time of year, but I will have to figure something out before they go into storage in the spring. 
So later today when the sun is still up but the collectors are no longer producing good heat I'm going to take the cover off the ZP. I want to check the glazing ends and also check for any leaks. Now I'm REALLY thankful for having designed my ZP to open up so easily. I don't want to be outside in the cold any longer than I have too. Once I have the condensation/frost issue fixed. I'll run a final test of output between the two. Then I will be able to start tweaking the ZP to hopefully have even better output numbers. Time to bundle up and head outside…

Greg in the frozen tundra of MN[wave]



The pics below were taken at noon today. The winds are light and the air temp is 0 degrees and sunny. 

Attached Images
jpeg IMG_0353.JPG (3.04 MB, 282 views)
jpeg IMG_0354.JPG (2.09 MB, 286 views)

netttech

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Reply with quote  #35 
Hmm, definately icing occurring...even at noon.

I don't know about anyone else, but my twinwall isn't sealed on either top-or-bottom. Probably because I never thought about sealing them.

Being open (unsealed) I can't imagine much air going thru the corrugated sections. If there is any it would be a natural thermo-siphon affect. I'm using drywall steel corner bead to hold my glazing in place & the corners aren't sealed either.

Normally I have foam weather-stripping on the panel that the glazing sits on, but noticed I had forgotten to install it this year. [smile] Oh well, too late now.

If the wires prove effective on frost I may insert some more wires across the entire twinwall glazing. It looks small enough to NOT be blocking much sun.

Jeff
Central IL
netttech

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Reply with quote  #36 
It was 6 degrees outside this morning, but the panel wasn't as frosty as I expected.

Below are the pictures I took though. I should have taken a close-up of the wires at each time-frame.
My first reaction is, the wires may work at melting the frost. I don't think the wire has enough mass to radiate to adjoining areas of the glazing. I say that because it's obvious the black wooden blocks that support the glazing from sagging melted the frost right away.

Tomorrow forecast is for light snow, so maybe monday morning (on vacation) I can get better pictures.

Jeff
Central IL
750am.JPG 810am.JPG 824am.JPG 835am.JPG 850am.JPG 905am.JPG 905am wire.JPG 925am.JPG 

gbwillson

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Reply with quote  #37 
Jeff-

Thank you for testing. If you put a wire every inch then, the spread should help clear the glazing. Can you think of a way to have the wire up against the outside surface of the glazing? Right now it lays at the bottom or back away from where it is needed. Perhaps bending a "wiggle" would keep enough against the glazing. Or, if nothing else, you would see if having the wire tight against the outside glazing helps or hurts performance. If you try this experiment again, zoom in if you can to show the "spread" the wire makes. I went out this morning to a balmy -14 degrees. The high temp today is -1. I went out this morning to pull the glazing off the ZeroPass, but I needed my hands without gloves. I'll try again later once the sun is not producing any usable heat and it "warms up" later in the day. [wink] Thank goodness the winds are light. 

Greg in not so balmy MN[wave]



netttech

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Reply with quote  #38 
I haven't removed the wire & likely won't thru the winter. I'd like to snap some pictures when the glazing is 'very frosty' or ice-snow covered. This coming week is supposed to be sunny-clear, but cold (midteens, 20's). I'm on vacation monday & tuesday so I may be able to get decent pictures.

I'm not sure placing the wire on the outside would really do much. I'm guessing the outside temp, wind would siphon away the heat it absorbs from the sun. Although having a method to completely clear the glazing would be great, having the wire close together may block the sun too much.

Hmmmm, maybe a single layer of screen framed that could be placed on the glazing directly (outside), may work. It could be easily lifted off once the frost/ice cleared.

Shortly after I posted the pictures & made the test results post, I proceeded recording panel temps.

As I stepped into the garage I heard the hot water panel pump running. The return tank temp was 70, checked the panel thermometer, 100??? No way....the panel couldn't be producing that much raise. The pump was still running as I went to check the panel. Normally the pump cycles on/off for a while. After watching a few minutes, the temp continued to raise.

I rushed back to the return tank & nothing was actually flowing. A line had froze up! Outside, under the porch, a 1' section of insulation had gotten pulled away from the pipes (critters??). I rushed in, grabbed a drop cord, hair blower & placed it on the pipe section. I went the pump reversed the water flow, nothing, scampered to my panel where I have a valve between the upper/lower pipe layers & steam blows out.

I checked the thermometer on the hot water exit & it's now up to 160. I keep large pieces of cardboard for various reasons & yesterday it was used as a cover. The temp raised to 180 by the time I got it covered.

Ten minutes later the pipes finally cleared of ice. Once the panel cooled off I checked my Anti-Freeze rating....+10.  The AF must have gotten diluted when I flushed the system in the spring. I had forgotten to check the AF rating before this winter. [frown] Geeessh, what a scamper, but no damage to the pipes or panel though.

Jeff
Central IL

PC071320.JPG PC071321.JPG 


solardan1959

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Reply with quote  #39 
Jeff,
   I don't think the cardboard makes good glazing, But I guess you do like to reuse available materials. [smile]
gbwillson

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Reply with quote  #40 
Well…

The cardboard IS corrugated! Makes for better insulation. And very Sanford and Sons. Do you happen to have a washing machine out back, or is it on the front porch behind the cardboard?[biggrin]
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