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gregkn73

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Reply with quote  #1 
In my backyard I have already a greenhouse and a LTM sunspace (own a presentation), and I want to built another hydronic project, most probably of Aretha type, but I am not having a lot of free space without shades. So is it a good idea to place the new collector inside the greenhouse or sunspace? What will be the negatives if I do so?

Thanks in advance ,

Greg

stmbtwle

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Reply with quote  #2 
You're not going to get any heat that isn't already in the space, but you will concentrate and save it. Could be a good thing.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
gregkn73

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Reply with quote  #3 
Quote:
Originally Posted by stmbtwle
You're not going to get any heat that isn't already in the space, but you will concentrate and save it. Could be a good thing.


Willie i didn't understand. If my greenhouse top T is this season 35°C, the T in Aretha type collector placed inside the greenhouse, won't get any higher?
stmbtwle

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Reply with quote  #4 
It will get hotter, possibly quite a bit hotter, but the temperature in the greenhouse won't get quite as warm.  The TOTAL heat gain entering the greenhouse will be the same, but the collector has captured some of it, concentrated it, and pumped it off to storage. Were the collector not there, the sunlight would be absorbed by the floor, structure and plants instead.  With the collector shading them, those items won't get as much sun.  If your greenhouse tends to be too hot, it would be a good thing.

The only way you're going to capture MORE total heat would be to put the collector outside where it does not shade the greenhouse.



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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
gregkn73

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Reply with quote  #5 
I actually was thinking to place the collector vertically at the north side of the greenhouse, not shading anything, just insulate more the greenhouse....it will replace a plastic film :-)
stmbtwle

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Reply with quote  #6 
That might work pretty well, as it would catch sun that might otherwise escape the greenhouse.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Gordy

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Reply with quote  #7 
gregkn73,

Just wondering what are your plans for the heat you capture? If it is to store heat for the over night period in the greenhouse, there are many examples of an insulated north wall that is lined with black barrels or buckets full of water to catch and hold the heat. Other plans force hot air from the top of the greenhouse down through PVC pipe buried in the floor of the greenhouse, to use the ground as a heat sink.

If you have not found it http://www.builditsolar.com has many interesting ideas.

Gordy

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Gordy,
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Rick H Parker

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Reply with quote  #8 
Willie i didn't understand. If my greenhouse top T is this season 35°C, the T in Aretha type collector placed inside the greenhouse, won't get any higher?

Heat is a quantity of energy. Temperature is a measurement of energy density. If you take X amount heat and compress it into a smaller area the Temperature (energy density) will increase but the quantity of heat is still X. It is like compressing air into a air tank, the pressure (energy density) of the air goes up but the mass of the air stays the same.

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Rick H Parker
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gregkn73

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Reply with quote  #9 
My plan is to heat water for space heating
stmbtwle

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Reply with quote  #10 
If possible put your water storage in the space you are trying to heat. Any heat 'lost' will go into that space. Outside, you'll need LOTS of insulation. Inside you may not need any.

An ARETHA can heat water to 70C, maybe more. That said it takes a while. In any single "pass" through the collector you'll only get a temperature rise of maybe 2C above input temp. You can get a greater rise by reducing the flow, but the actual heat gain remains the same. This is true of ALL solar collectors.

Once your (slightly) warmer water enters the storage, it's diluted. You may not be able to measure the change right away, but trust me, it DOES add up. As the storage graduall heats up, the input to the collector rises, and thus the output. How hot it actually gets depends on the amount of storage and heat input.

Putting the collector inside the greenhouse may actually benefit. The collector is protected from the wind and is operating in a warmer environment.

If I had the space, I'd put several drums along a wall and build a nice cabinet over them. Vents in the cabinet and maybe a fan will release the heat into the room.

In your case I'd put them in that sun room, so the heat from the drums is picked up by the blower you already have installed.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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