Author Topic: Looking for input?  (Read 5595 times)

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cheapskate

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Looking for input?
« on: September 12, 2014, 06:19:20 PM »
I've wanted to get into alternative energy for quite a while and now I get my chance. I was hoping some of you experts could make comments on my plan?

I have a 12x20' extension to an existing unheated garage. No doorway between the two, just a shared wall that I will insulate as part of the addition. R20 walls, R28 roof, continuous vapour barrier. I have three 3'x5' double-glazed window panes that I would like to build into flat plate collectors to heat PEX tubing in the garage slab (8" spacing between loops, within 2" of the slab surface) and could source a fourth pane. I would like to fill the system with glycol and run an electric pump off a solar panel so the system will stop pumping when the sun goes down and stops generating heat from the sun - seems to me that I wouldn't want to cool the system off at night any faster than it's going to cool on it's own. Plus it makes it a totally independent system. I plan on covering the collectors in the summer.

I'd be pretty happy if this system kept the extension near 0 degrees C all winter. I live at 52 degrees north latitude, average winter temperature is -17C in the winter, mostly sunny. Am I out to lunch? I'm not looking for exact calculations, just a rough idea as to whether I'm on the right track or if the system is too small.

Thanks in advance!

SparWeb

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Re: Looking for input?
« Reply #1 on: September 12, 2014, 09:36:55 PM »
Hi Cheapskate,
Welcome to the forum.

If you haven't already checked it out, make sure to research Gary Reysa's website www.builditsolar.com.  Since he lives in the NW states, he knows what snow is.
Speaking of which, you don't happen to live in that particular city at 52 degrees N where it was snowing last Tuesday, do you?

Before deciding to pour a complicated concrete slab, have you considered heating the extension purely by air heating in those collectors?  The 3-4 window panes that you have sound like they can do the job, but I'm basing my guess on Gary's air-heater collectors projects.  The concrete slab in your extension is a heat sink that will help moderate the temps inside, even if it's heated only by the air above.

If you do decide to heat the slab with a glycol loop, then for efficiency's sake you'll be looking at insulation underneath it, and around the exterior wall surfaces, to keep that heat from conducting away. 

It sounds simple, but I suspect that running the pump directly from a solar panel could have problems.  For instance, the pump may shut off as a cloud passes, but the air cells are still warm.  When the sun comes back out, the collectors start cold.  While the glycol isn't circulating, the heat they've collected is just radiated away from the collector.  In partial sun, the collector may continue to warm up while the pump can't start.  If the pump's solar panel is shaded by a tree or someone parks their van in the wrong spot, the collectors could be hot for a long time.

But with careful design, it does sound practical.  There's a building heat loss calculator on Gary's site.  If you look into the glycol heating collector a little more, perhaps from a scientific perspective, you may find some research or analysis that will help you guess the sizes of all the components.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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keithturtle

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Re: Looking for input?
« Reply #2 on: September 13, 2014, 12:38:52 AM »

If you do decide to heat the slab with a glycol loop, then for efficiency's sake you'll be looking at insulation underneath it, and around the exterior wall surfaces, to keep that heat from conducting away. 


Even if you don't circulate hot water in the slab, it is a good idea to insulate it as a heat sink, as SW says.  I poured cement over 2" blueboard for a 24x30' service shop floor.   Even in the coldest weather, it only took minimum heat to keep it warm, once the bay was brought up to temp.  Worked like a champ.

I ruled out the hot water piping after a consulting a neighbor that had a similar arrangement.   Once it warmed up, if the weather got much warmer, the room was unbearably hot and you couldn't cool it down.

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Mary B

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Re: Looking for input?
« Reply #3 on: September 13, 2014, 07:39:13 PM »
I would add a battery to the system and a rudimentary temp switch to turn the pump on and off.

thirteen

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Re: Looking for input?
« Reply #4 on: September 14, 2014, 12:15:04 AM »
How about a warning signal  things are not running with sensor using MayAlana battery backup for power. Idea. It could call your cell or send a signal to the house. Just an idea. 13
MntMnROY 13

cheapskate

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Re: Looking for input?
« Reply #5 on: September 14, 2014, 08:07:39 PM »
Thanks for the input! I had planned to insulate under and around the slab and keithturtle brings up a good point. I'd never considered insulating under an unheated slab but it sure makes sense.

I was leaning toward the floor heat since I plan to use this as my sled repair shed - I'm tired of fixing my kid's machines in a snowbank! I thought the heat from the floor might help also help keep it dry. Is this normally the case? I've read that melting snow and evaporating the water will eat up a lot of energy but if it had all week to recuperate, it might be OK? I will look into the air heaters, sounds very interesting.

Sparweb - no, we didn't have snow last week and boy am I glad for that! :) Glad I don't live there!

cheapskate

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Re: Looking for input?
« Reply #6 on: September 14, 2014, 09:12:59 PM »
I forgot to mention - this project will be at the lake and I would only be there on weekends. I have access to power and gas on the site, but I would like to be more creative.

SparWeb

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Re: Looking for input?
« Reply #7 on: September 16, 2014, 11:52:33 PM »
Hi again,
Check out the "Canada Plan Service" and look up plans 9732 and 9731.
http://www.cps.gov.on.ca/english/frameindex.htm
They were tested in Winnipeg, though that's waaay south of you at 50 degrees N.

Thawing out snowy toys:  give the water a place to go, with channels in the concrete, to someplace they can collect.  That brings up the question of drains...   Kind of don't want to bring up the subject, it adds so much complication, but there are those big pools of water on the floor one afternoon, which become solid ice overnight.  If heated enough there will be significant amounts of evaporation.  If the air in the building isn't cycled, however, then that moisture will collect as frost on every surface inside once it cools down overnight.  I've had that happen in my own garage, and in my case the source of snow is just cars, and it's not heated and far from air-tight.  Usually winter driving doesn't bring in enough snow for that to happen, though, and maybe a wet ski-doo isn't either.  Maybe your own judgement says otherwise, or you can ask someone with a heated detached garage.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
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cheapskate

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Re: Looking for input?
« Reply #8 on: September 18, 2014, 12:17:16 PM »
Great points, thanks! The thermosyphon seems like a better and simpler plan than the radiant in-floor heat. I'm sure glad I stopped by for some advice!

I'm pouring my footing next week and hope to start building after that.

MattM

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Re: Looking for input?
« Reply #9 on: September 19, 2014, 06:24:43 AM »
For all the cost of a fancy system you could add insulation in the ceiling to reach R38.

You have a continuous vapor barrier, so it's a moisture trap.  The good thing is that if you have a higher elevation you probably don't mind the moister air.  If that is not the case than you need a way to dry the air.  Using a wood burning stove, too, perhaps?  Is there indoor plumbing where a frozen drain isn't an issue?

If you don't add the pex into the floor now you'll only wonder later coulda shoulda woulda.  You can always utilize it at a later date.  But if it's not added when you pour the floor it's too late.

Frank S

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Re: Looking for input?
« Reply #10 on: September 20, 2014, 02:00:49 AM »
When considering using a fluid radiant floor heating system, remember that for most applications it is recommended that the tubing be covered with no more than 2 inches of concrete.
 Also you should find out what the winter ground temperature is in your area to be able to calculate the amount of insulation under the slab and around the foundation
  There is another option that is the use of electric heat mats or even a combination of both
  Not Germane to your application but While in Kuwait I was part of an engineering committee that designed a 3 Million cubic foot cold storage facility to replace a much smaller facility that had heaved about 3 ft or more above original grade in some areas.   With the water table being only about 6 ft. below surface, the ground had been cold soaked and frozen to a depth of over 20 feet deep for over 10 years 
  The old building was only capable of -20°f the new one could flash freeze to -40°f in any of the large rooms
  We kept the floors from icing by using heat mats just 2 inches under the surface
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cheapskate

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Re: Looking for input?
« Reply #11 on: November 16, 2014, 07:52:44 PM »
Thanks for all the input. Just finished installing today!

SparWeb

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Re: Looking for input?
« Reply #12 on: November 19, 2014, 02:25:54 PM »
Give you a nice, warm feeling, doesn't it?

:)

(couldn't resist the pun, sorry)
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca