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insulating with bubbles

 
steward
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Wow.  That's some innovation.  I wonder how well it works.

http://video.google.com/videoplay?docid=9141143967660224381&hl=en-CA#
 
gardener
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So he used soap?  If so those bubbles will break in no time.

It is a shame he doesn't speak or add any information, like where he got the idea and what he is hoping it will achieve or how well it works.
 
pollinator
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This technique is quite well known here in Canada.  it is basically soap bubbles.  The bubblemaker puts out a very small bubble which lasts a couple of hours.  The bubblemaker is on a timer to replenish the bubbles during the night and be off during the day to allow light in.  The bubble generators are fairly expensive but can save a lot in heating costs.  a home made version might use lots of aquarium aerators.
 
                            
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that's quite amazing,  I noticed it was 3 yrs old and wondered about now.
So they are used mainly for green houses in Canada also?  I was thinking maybe since it was soap it would still let enough light in, but you say they are turned off in the day, I wonder how much the temperature drops?
 
gardener
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Its a great idea. Not to be a downer but the cost for the bubble maker is up in the thousands. One source said it was about 18 grand for an 18×24 greenhouse. You'd need to be growing some 'high' priced crops to make that a viable option IMO.

There's gotta be some way to do a cheap DIY bubble maker...
 
pollinator
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Travis Philp wrote:There's gotta be some way to do a cheap DIY bubble maker...



It might be fun to collaborate with some of the online techies at a site like Hack a Day. They might be happy to hear about a hacking opportunity that's both useful, and moderately challenging.

It also might be the kind of tinkering that the Open Source Ecology project would be interested in pursuing once they're on their feet. Mikey over at Holy Scrap Hot Springs might be able to take on the challenge sooner, but he seems less of a mechanical guy from what I've read, and is in a climate that doesn't need foam-filled greenhouses.
 
Max Kennedy
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Travis Philp wrote:
There's gotta be some way to do a cheap DIY bubble maker...



The people would probably share the bubble solution formula then my 1st try would be an air compressor and industrial sized aquarium aeration stone.  For controls a LED light on the outside and a light detector on the inside near the top, bubbles will slide down to fill space as they burst so the top will thin first, Light reaches a certain level and turns the system on.  A timer to allow dissipation during the day.

During the day the sun heats the greenhouse to growing temperatures so the loss of heat then isn't a huge concern unless you are trying to harvest the heat for the home.  Even then the gain due to transparency is greater than the loss as the bubble reflect much of the light away.  Keeping the bubbles all day would sort of be like the scheme for automated ships to vaporize ocean water creating clouds that reflect sunlight back out to space.  As noted in the article they could be used in the summer for a cooling effect.

http://www.eta.co.uk/cloud_making_ship_fights_global_warming/node/11030
 
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I have seen this basic idea before.  At that time, it was done with styrofoam pellets that were blown between glass windows at night.  They sealed in the heat of the day.  It was not very effective.  Movable insulative panels are effective, but they require placing and taking down, and storage space, too.

There is a professor who has kept a soap bubble alive and well for over twenty years in a glass jar.  What some people will do for fun!
 
Joel Hollingsworth
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Here are two sets of plans for a DIY foam machine. (Via Hack A Day, which I linked to above).

The guy who authored the plans (and sold a few units on eBay) has this to say:

Costs about $400 to make. Will take a few weekends and some experimenting to get it working.



Downloads

It looks like a very simple device: spray diluted bubble bath onto a screen, and force air through that screen. The $400 was all brand-new equipment and materials.
 
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Amazing, bleeding edge, but truly practical?

I wonder about the eventual scum buildup, and maintenance of a very complicated setup.
If you were going  to invest in a system like this (say $400 for the machine alone, plus the additional structure and layer to the greenhouse), wouldn't using an insulating sheet in/over the greenhouse serve a similar purpose for far less money and materials?
 
Max Kennedy
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For small greenhouses yes but the larger they get the larger and more expensive the sheet is and it quickly becomes more expensive.
 
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You know what would be awesome.  Two mobile high tunnels of different size.  In extreme conditions like the Canadian winter, you could use the bubble insulation.  At warmer times you could separate the tunnels and rinse them off. 

I bet you could improvise a bubble maker out of any air blowing device.  If the bubbles last well under plastic it wouldn't be too expensive in terms of energy consumption.
 
Max Kennedy
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Mangudai wrote:
You know what would be awesome.  Two mobile high tunnels of different size.  In extreme conditions like the Canadian winter, you could use the bubble insulation.  At warmer times you could separate the tunnels and rinse them off. 

I bet you could improvise a bubble maker out of any air blowing device.  If the bubbles last well under plastic it wouldn't be too expensive in terms of energy consumption.



Interesting idea.  put one on rails/wheels so it pulls out in summer and nests in winter.
 
                        
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No idea of the exact date but this has been around for several years  and may be the original one. http://www.tdc.ca/bubblegreenhouse.htm
 
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decades ago I saw the use of blowing shredded styro foam into spaces between two windows for night time insulation. the same blower could blow the poly styrene beads into the space went needed or vacuum them out of the space when the sun was out to heat the interior. The biggest problem was that the static electricity make the Styrofoam want to stick to the windows. always thought it was great way to use recycled packing foam.
kent
 
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I got pretty far along in designing a farm scale production greenhouse using a bubble insulation layer and decided it wasn't worth the effort in its current state.
Its a pretty specific bubble that you need.  Its not a foam its a dryer larger bubble that is needed.  There are a couple of examples that actually have been able to generate bubbles but by in large most peoples projects putter out.  For someone who is worried about production aka a farmer the technology is not nearly bullet proof enough to justify building one of these guys.  There is rumbling about a greenhouse manufacturing company building a kit that you could order.  The bubble generator is not to tough to build but the bubble formula is tricky.  The guy from canada use to sell some stuff that a phd. had figured out for him but he has stopped. 
Its also tricky to get the timing right for bubble regeneration cycle.  The uk greenhouse that is most often shown didnt actually work the thermal mass of the water inside the greenhouse plus some other factors kept the greenhouse warm for the short time it was running.  The other one in canada does seem to work, but his generates cost more that a couple thousand i believe. 
Growing things in high tunnels with row covers with appropriate vegetables seems to be a much simpler and more practical use of space but thats just the conclusion i have come to.
 
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That this thread is 8 years old astonishes me.  I only recently ran across this idea about bubbles being insulating.

My background is that of Materials Science and Engineering.  The strength of polycrystalline materials (such as steel) is a function of the "grain size" (the size of individual crystals).  The model that worked with, was the linear bubble model (Hyundari and Ryum I believe; this was mid 1980s).  This model has isolated bubbles connected by pipes, and is allowed to "evolve".  The reason it evolves is that the pressure in a bubble is a function of its radius of curvature; small bubbles are under high pressure, and hence the gas inside the bubble diffuses to the neighboring bubbles and eventually the small bubble disappears.

If we can make a foam (bubbles touching each other) where all the bubbles are about the same size, we expect most of the bubble to be tetrakaidecahedrons (a regullar solid with 14 sdes).  Two bubbles in contact with each  have a "face" in common.  If the pressure in the two bubbles is the same, the face will be planar.  If the pressure in the two bubbles is not the same, the "face" will be curved, with the centre of curvature directed towards the bubble of the higher pressure.

I am going to ignore the possibility of convection within a bubble.

If we consider a lake, a ray of light is refracted when it moves from the air above the lake to the water beneath the surface.  Every bubble "face" in the foam, is a place where refraction happens (as the refractive index of the walls of the bubble is not the same as the gas inside the bubbles).  After traversing some number of randomly distributed "faces", the "incoming" energy (heat photons for this discussion) becomes homogenous.  It does not matter what the initial direction was, after this number of bubble faces have been traversed, any given photon has equal probability of being in any direction in 4 Pi steradians.

What this "bubble depth" is, depends on the size of the bubbles, the composition of the bubbles and the interior gas (refractive indexes of both).

Unless you can figure out how to make a foam consisting of almost equal sized "bubbles", the foams will "evolve" due to the differences in gas pressure.  So the size distribution of the bubbles will change from where they are generated, to where they enter the "sink".  But for the most part, the faces of the bubbles are either planar, or not too far different from planar.  So you could just assume some random distribution (in terms of orientation) of tetrakaidecahedrons for how the bubbles scatter light.  It's only as a "small" bubble is in the final stages of disappearing, that any of its faces has significant curvature.  And that is just for a small interval of time.

A foam is nominally 100% bubbles.  I suppose a person could have a larger space, and try to suspend bubbles in the gas.  Now each bubble is (ideally) a sphere, and scatters light differently depending on where the incoming light ray strikes the bubble.  There is probably some number of bubbles that the light ray has to traverse before the light distribution becomes homogeneous.  My guess is that it is different from a foam, but it could be close to a foam?  I spent a little time looking to see if these two problems are compared, and my Google-foo wasn't showing anything.

To continuously make a foam, requires energy.  Maybe what you need to do is just circulate "ping-pong balls"?  Probably much smaller, possibly with different optical properties of ping-pong balls.  But this would be at about the phase boundary between isolated bubbles in a gas, and a foam.  So it is possible some new physics comes to light?



 
Gordon Haverland
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Going back to foams (mostly).

You need your foam to be deep enough, that the scattering has become homogeneous.  Deeper than that, doesn't help.

How much heat transfers through a sphere (isolated bubbles) or a tetrakaidecahedron (foam) by convections depends on the size of the "bubble".  Typically, I see that heat transfer decreases as bubble size decreases.  I have seen no data about really small bubbles, so I don't know if this extends to the nano-world.

 
gardener
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I remember reading about greenhouses with double glass walls, or double plastic walls, with a blower and vacuum system that would fill the gap with blown styrofoam bits for insulation.

When searching for that,  I found this article about the soap bubble insulating greenhouse thing:  From Farm Show Magazine
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