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PostPosted: Jul 3rd, '18, 17:30 
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Gunagulla wrote:
>> panel is covered in condensation drips whenever it's running, showing that it's pulling heat out of the air as well as from direct sunlight

Actually, it just means that the panel temperature is below the dew point of the air, so moisture condenses on it ;)


And it has to dump a bit of energy into the panel to condense I know it's not a lot let me cling to my illusions. :-P

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PostPosted: Jul 3rd, '18, 17:36 
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:) ok

However, what you really want to see is condensation around where the water enters the panel, and no condensation where it leaves, showing that the water temperature has risen above the DP :)

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PostPosted: Jul 3rd, '18, 20:14 
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Gunagulla wrote:
:) ok

However, what you really want to see is condensation around where the water enters the panel, and no condensation where it leaves, showing that the water temperature has risen above the DP :)


...Huh. Well, I know the condensation isn't even across the panel; I must have a look at it tomorrow while it's running to see if there's less/none over on the exit side. (I want to say there is less there, but I could be doing some wishful misremembering. :lol: )

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PostPosted: Jul 10th, '18, 00:00 
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Nope, there is no real difference in the amount of condensation across the panel, unless you look at it right after a bunch has dripped off. :funny1: To be fair, it's humid enough in there that it'd have to get really hot before it got above the dewpoint.

We had a lovely sunny day on Sunday (appropriately enough!) so even though it was bloody cold and didn't get above 12 C outside (I don't believe it, it was never above 10 anywhere I was!) the water temperature hit 17.5 C and the fishies were hungry!



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PostPosted: Jul 10th, '18, 06:53 
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The dew point is always less than the air temp (or equal in fog=100%RH), so if your water is above air temp then it is certainly above dew point, and there shouldn't be any condensation!

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PostPosted: Jul 10th, '18, 16:19 
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Gunagulla wrote:
The dew point is always less than the air temp (or equal in fog=100%RH), so if your water is above air temp then it is certainly above dew point, and there shouldn't be any condensation!


My water is well above outside air temp, and often above the air temp inside my hoop house as measured at the level of the growbeds. The daytime air temp inside my hoop house at the top of the arch where the solar panel hangs, on the other hand, gets a lot warmer! Like, warm enough that if my water was warmer than it I would have fish soup. :shock: My glasses steam up when I first go in on sunny days, and if I stay in there for more than a few minutes my hair starts going frizzy from the humidity. :laughing3:

The plants love it, the nasturtium is still working on its world takeover and we've moved my husband's bonsai in there. The horseradish is really the only plant that's getting unhappy; it's on the outside of an end growbed and probably gets the coldest nighttime temperatures. It's dying back for the winter and I plan to harvest it soon.

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PostPosted: Jul 12th, '18, 15:33 
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I was curious about actual numbers, so I checked today. :think: It was pretty darn cold out (about 8 C at the time) and not sunny; the temperature down at growbed level inside the hoop house was 15.6 C, and the same probe read 23.2 C up next to the heater panel (in the shade).

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PostPosted: Jul 16th, '18, 07:08 
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Mel,,excuse me using your thread but its all relative.

I now have approx .5 kilometer of 10 strand solar pool piping and about .3 of 6 strand, have the manifolds arriving from Ebay this week so building should start soon, not expecting big improvement as I still only have bird netting and shade cloth covering my house....

but with yours what pump are you using?.... please

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PostPosted: Jul 16th, '18, 20:01 
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No worries Tonzz, it's all good! :thumbleft:

I'm using a Pond One Shark 7500; it's overpowered for the job and I'm using a t-junction and a tap to divert a lot of the flow, but two sizes smaller than it was definitely too weak. You need a slow steady flow and it takes a lot of oomph to get it because the panels add some serious drag.

My panel is 0.7m deep and 3.8m long, so 2.66m2 surface area. The guys who sold it to me said that a flow of around 7-10 L/minute would be best, but so long as it was coming out faster than a trickle and had a perceptible difference in temperature from the input water it should do OK. If you've got more total surface area you'll need faster flow; when we were discussing using three panels they were talking about 21 L/minute.

Even though you'll be losing a lot of the added heat at night, hopefully it'll be noticeably better than without it!

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PostPosted: Jul 17th, '18, 06:58 
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Thanks Mel, gawd more $$$$s required for 'development'. :laughing3:

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PostPosted: Jul 22nd, '18, 08:09 
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Mel, sounds like the pump is run the at night, that would cool the water again. A timer or thermostat would fix that issue.
Do you filter the water before it gets into the solar panel to reduce muck collecting in the tubes?

I think if you had placed the SP on a rack so it could be lying more flat and closer to the roof you'd get more heat captured in the same time. Are you planning on covering it with something in the Summer time?

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PostPosted: Jul 22nd, '18, 20:13 
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Petesake wrote:
Mel, sounds like the pump is run the at night, that would cool the water again. A timer or thermostat would fix that issue.
Do you filter the water before it gets into the solar panel to reduce muck collecting in the tubes?

I think if you had placed the SP on a rack so it could be lying more flat and closer to the roof you'd get more heat captured in the same time. Are you planning on covering it with something in the Summer time?


No, it's not run at night; with the temperatures we're getting now (-7C predicted for tonight, brrrr!) that would definitely be a bad idea! I've got it on a timer that's set to turn it on after the sun hits the top of the hoop house, and off again after it's no longer in direct light. There's no filter as such, but the pump to it is in the sump tank and only very fine particulates make it through the RFF into there... and thank you for the reminder, part of my plan for keeping muck from collecting in the tubes involves turning the bypass off for a minute every few days to up the flow and blast them clear, and I didn't do it last week.

It technically is on a rack! I built it a frame. I have it pulled slightly forwards on an angle with wires to better match up with the angle the sun comes in, but given that it's hanging from the top of a homemade hoop house, there's a limit to how much sideways stress I can put on it before I start worrying about structural integrity. We already added a timber brace below the ridgepole to stop it bowing inwards with the weight. :shifty: Besides, this time of year the sun's low enough that it's near enough to horizontal.

I'm planning to leave it as is in Summer, and set the timer to run it for fifteen minutes (the shortest interval I can set) in the middle of the night just to make sure nothing icky grows in there. If my water temperatures get higher than I'm happy with but we're having cool nights I might be able to run it at night as a cooler, too.

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PostPosted: Jul 23rd, '18, 03:57 
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Cool, or you could drape some white plastic over it to reduce the solar effect.

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PostPosted: Jul 23rd, '18, 08:32 
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https://www.canberratimes.com.au/national/act/yet-again-canberra-breaks-record-for-lowest-2018-temperature-20180723-p4zt06.html

Uuuuuuuuuugh. :upset:

Yeah, it was cold. Thick ice on the fishponds this morning, and the hoop house temperature dropped closer to zero than it has so far this year, but the aquaponics water stayed just over 13 C because we've had a couple of nice sunny days pushing it up. It's supposed to be sunny again today and tomorrow, so it should bump up again nicely.

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PostPosted: Jul 23rd, '18, 17:00 
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Well... records are there to be broken but gotta say Id rather be in 43 degC all day than neg nine all night.
Good thing you've got that SP installed in time :thumbleft: There's only one thing worse than having the gear but not installed in time that is dreaming about having the gear.

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