Author Topic: Solar Greenhouse Heat Sink  (Read 3119 times)

kiwi

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Solar Greenhouse Heat Sink
« on: June 23, 2011, 01:35:05 AM »
Found this article and instructions on how to make a solar greenhouse heat sink from a UK website, the whole website has some interesting stuff for those interested in Renewable energy.

http://www.reuk.co.uk/Solar-Greenhouse-Heat-Sink.htm


I wonder if it is something Jock could do with his access to computer parts and the new greenhouse he built.

This is the new area I am interested in, growing food in the winter (lean) months if anyone has any neat tricks especially if it involves recycling I would be interested to read them,  Thanks in advance.

Also looking for tasty Offal recipes, anyone have a good black pudding, haggis or faggot recipe that would be cool.
« Last Edit: June 23, 2011, 01:37:03 AM by kiwi »

kathyprepper

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Re: Solar Greenhouse Heat Sink
« Reply #1 on: June 23, 2011, 01:46:48 AM »
We had a solar pool cover that was heading to the landfill. My DH cut it to fit the north and west wall of the greenhouse. He actually put up two layers and it seems to be working well. We have a stone walkway that soaks up a lot of heat. On a cold night you can add a metal bucket of hot ash from the stove. With banking the exterior with bales of hay the soil inside never freezes here ine zone 4.

Jock

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Re: Solar Greenhouse Heat Sink
« Reply #2 on: June 23, 2011, 08:31:54 AM »
That looks like a seriously interesting project. I already have pretty much all the parts lying around including the small solar panel and the way the greenhouse base is constructed would lend itself to excavating the heat sink without risk of structural collapse.
50 gallon water butt sunk into the ground might make a good heat sink.
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TravelsHopefully

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Re: Solar Greenhouse Heat Sink
« Reply #3 on: June 23, 2011, 10:07:07 AM »
Looks interesting, although I'm skeptical that a fan that small can pump enough air to make that much of a difference.
When the Sun is out, on my greenhouse, the 4 roof vents are wide open (4 vents with an open aperture of about 2x1 foot each) + a side louvre aperture (1 square foot) - say 9 square feet to allow hot air to escape
Even with all this, it still gets pretty warm in there.
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hillwalker

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Re: Solar Greenhouse Heat Sink
« Reply #4 on: June 23, 2011, 12:31:15 PM »
it's pretty cute, and at first blush i thought it even made sense.

I'm sure it is effective.

That said, something is ass-backwards, , lemme see,

The physics of this is quite involved, and I'll readily admit I don't fully understand it.
Insofar as I do understand it, explaining it would be tedious and overly wordy,
suffice to say, a green house results in 'excess' heat that does warm the air.

Moving that warmed air via counter-convection using additional mechanical power
even though the energy for that power is derived from solar, is super inefficient.
Air has very low thermal mass. Very low.

What would be better, would be to use a solar hot water collector, run some tubing
from the collector through the thermal mass storage and circulate the water with
a small pump and pv panel. You'd gather a whole lot more heat that way.
keeping the small hot water collector in the greenhouse would neatly side step
all the normal headaches involved with a closed loop solar hot water system,
as it wouldn't likely be subjected to freezing temps. It could be a simple drainback
system. Further, there would be no need to run the pump 24x7, only when the sun
shines, so there is no need for a battery. The energy storage would be the thermal
mass storage (pebble bed) and maybe a small drainback water tank.

Further, to retain heat in ANY greenhouse, it's best to cover the green house at night.
Seriously. I've done this experiment, and have been able to make ice in a small solar
oven by placing a black uncovered pot with water in it and pointing it at the black sky
(outside the 'milky way') at night, when the ambient temp didn't drop much below
50 degrees F.

On a clear night, the heat radiating to deep space from the green house will give up
a LOT of energy. Covering the greenhouse at night prevents this heat loss.

--edit---

the solar hot water collector wouldn't have to be anything fancy, nor 'store bought',
you could build it yourself.

here's some ideas:

http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm#Collectors
  
« Last Edit: June 23, 2011, 12:33:47 PM by hillwalker »

haniel

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Re: Solar Greenhouse Heat Sink
« Reply #5 on: June 23, 2011, 04:39:05 PM »
What hillwalker said, not efficient. 

If you could figure out how to do it without electrical power, even better.

A wind pump pushing warm water up though heat absorbing black tubes on the back of the into an insulated storage container.  Then at night, let the water flow back at a set rate and the heat radiates back into the greenhouse.  My solar pool heater raised 1,000 gallons of water by 4f every hour.

If wind is not an option, use solar power to pump the water.  When the sun goes down, the water flows back.  No loss of energy on the battery.
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hillwalker

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Re: Solar Greenhouse Heat Sink
« Reply #6 on: June 23, 2011, 07:21:24 PM »
What hillwalker said, not efficient. 

If you could figure out how to do it without electrical power, even better.

A wind pump pushing warm water up though heat absorbing black tubes on the back of the into an insulated storage container.  Then at night, let the water flow back at a set rate and the heat radiates back into the greenhouse.  My solar pool heater raised 1,000 gallons of water by 4f every hour.

If wind is not an option, use solar power to pump the water.  When the sun goes down, the water flows back.  No loss of energy on the battery.


Could likely do it with thermosiphon. Would be worth trying anyway. No pump.

haniel

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Re: Solar Greenhouse Heat Sink
« Reply #7 on: June 23, 2011, 07:29:01 PM »
What hillwalker said, not efficient. 

If you could figure out how to do it without electrical power, even better.

A wind pump pushing warm water up though heat absorbing black tubes on the back of the into an insulated storage container.  Then at night, let the water flow back at a set rate and the heat radiates back into the greenhouse.  My solar pool heater raised 1,000 gallons of water by 4f every hour.

If wind is not an option, use solar power to pump the water.  When the sun goes down, the water flows back.  No loss of energy on the battery.


Could likely do it with thermosiphon. Would be worth trying anyway. No pump.

Not sure if you'd get the volume you need to be a good heat sink that way but would be worth a try.  A pump might only be needed to supplement siphoning
http://peaksearch.blogspot.com

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Jock

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Re: Solar Greenhouse Heat Sink
« Reply #8 on: June 23, 2011, 09:39:56 PM »
Let's start with the heatsink. Excavating a 1 meter sq hole is no problem.

I have access to all stuff available at a commercial recycling centre, eg metal skips, wood skips, glass skips, white goods etc etc etc.

Come up with some ideas and I'll have a crack at implementing them.

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kiwi

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Re: Solar Greenhouse Heat Sink
« Reply #9 on: June 24, 2011, 02:47:54 AM »
I think it is a great project, got hubby gathering bits and pieces now, I like the idea of the water butt.

I don't think it would be a great project for a very large greenhouse, and I don't think it will "heat" the greenhouse to summer levels, but if it gives a jump start on spring and it doesn't cost a lot to do with recycling then great.

hillwalker

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Re: Solar Greenhouse Heat Sink
« Reply #10 on: June 24, 2011, 11:25:37 AM »
I think it is a great project, got hubby gathering bits and pieces now, I like the idea of the water butt.

I don't think it would be a great project for a very large greenhouse, and I don't think it will "heat" the greenhouse to summer levels, but if it gives a jump start on spring and it doesn't cost a lot to do with recycling then great.

Just as a point of reference,



Not greenhouses exactly, but high tunnels.

There is no thermal mass at work here, the heat exchanger tubing runs through the soil beds, keeping the soil warm, promoting growth.
This array provides a lot of heat for the two high tunnels, one of which you can see in the picture.

haniel

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Re: Solar Greenhouse Heat Sink
« Reply #11 on: June 25, 2011, 04:18:30 AM »
What's your growing zone, hw?
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hillwalker

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Re: Solar Greenhouse Heat Sink
« Reply #12 on: June 25, 2011, 05:11:25 AM »
What's your growing zone, hw?

Boundary area zone 5-6 (more 5 than 6)


kiwi

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Re: Solar Greenhouse Heat Sink
« Reply #13 on: June 25, 2011, 06:24:50 AM »
Well Hillwalker we aren't comparing apples to apples, if you can imagine my greenhouse is a little bigger than Jocks then maybe you would understand why I and Jock are interested in it.  You would easily get ten of my green houses in your tunnel house probably twice that many, I only need a little heat as I am zone 8 I think,  Jock would probably only get a jump start on spring where as I would get a giant leap into Summer with mine.

kathyprepper

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Re: Solar Greenhouse Heat Sink
« Reply #14 on: June 25, 2011, 11:39:09 AM »
We are comparing apple to oranges. I'm zone 4 and my goal is provide some green stuff a few times a week in the dark days of winter. I then get to use it to jump start my seeds and it gives me enough heat to grow a few luxuries like cantelope or eggplant. My two greenhouses are small. One is 8x10 and the other nly 6x8. I don't want to use more resources than I get in return so scavenged pool covers and left over stove coals are fine. Yours is a serious greenhouse and you clearly use it for way more growing than I do. It's very cool btw. I am a bit green with envy.