Solar Evacuated Tube Vacuum Tubes DIY Test in the Sun
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- Опубліковано 21 лис 2008
- Solar Evacuated DIY solar tubes. This is part 2 of the Solar Tubes with a control bottle and sun exposure. My website link for the results and videos are www.greenpowerscience.com/SOLA...
- Наука та технологія
@lerch25 Hi,
Heat conducts through air molecules. A vacuum has almost none so it keeps heat inside. This is just like a regular vacuum thermos but clear outside and dark inside so sunlight can build heat faster.
Dan I love your videos. I like that you build high performance things on the cheap as well that has science, it helps me think.
Thats pretty neat. Those things have all kinds of possibilities.
You Sir, you are bless. Thank you, it's not the first video i watch from you, I share the same driving that you show from your creations, thank for sharing your discoveries.
this system basically converts radiant energy (photons) into kinetic energy (heat) and the vacuum acts sort of like a diode, it lets the photons through but doesn't allow the heat to go out
I actually will be doing one in a few, waiting for the panels to go on sale.
we have proper solar hot water systems using evacuated tube technology as standard here in australia. they have recently stopped using the old style "black pipes in a glass box" technology and gone for evacuated tube technology with gycol in them and then heat exchangers (with water) in the top of them.
I was wondering, as to what time of year was this project tested? I know it was uploaded in November, but I just wanted a clarification.Thanks.
Hi,
I think you would need at least a 30x40 Spot lens and heat the rocks outside in a safe area then bring them in? Actually a mirror array might do you more good. 5 30x40 mirrors are about 3-4 KW. You could expose the heater without burning down the house:-)
The square footage of sunlight is what matters for larger things like a box of rocks. You do not get the super high heat, but it would not transfer to all the rocks unless you have a very big Fresnel lens.
Also the solar cooker idea.
i think there will also be a temperature increase if you use air instead of vacuum. the ideea is to enclose the air, to not let it move around and up the bottle as it heats up and thus taking valuable heat from the bottle. kind of double layer window principle
Hey Dan I love your channel I've watched for a long time. I just noticed I wasn't subscribed. So I hit the button. I'm curious of the effects of a three chamber cup. Inner atmosphere pressure middle pressurized and outside vacuum. I'm thinking the middle layer of excited squished particles would increase the transfer. Any thoughts on that?
Dan , will you be doing anymore updates anytime soon? i am working on pool heater with this concept and would love to see more experimentations.
Nice job.
Is this essentially what is at work in solar/steam generated electricity plants?
(I'm thinking of the kind built in the 70s -- and returning now -- where water or oil travels in a transparent tube along a curved/parabolic mirror, over a long distance, then introduced to water to turn a steam turbine.)
Do those systems vacuum-seal their tubes?
I feel that all hot water tanks for new residential & commercial builds, should have passive heat exchangers installed in them. This should become mandatory.
One way of supplying the heat exchanger would be to design a ridge vent system that works in two ways. During sunlight, the ridge could be designed to become marginally hotter than the temperature of the ambient attic air. This would naturally draw this air to the vent. It would cool the attic and at the same time heat the hot water.
looking to make a vacuum pump by enclosing a car tyre 12v pump in a small enclosure sealing the around the "pump out" hose and installing a nossle on the container for a suction port. How strong a psi rating should the pump be??
Regards Dan
Thanks for all your vids :)
Hi. Extra question..
Yesterday I left a question in your last video about materials proven inflammable after wide-angle fresnel lens exposure.
I asked b/c I was curious about the use of a fresnel for heating sauna rocks - what do you think? (Foreseeable issues: getting rocks hot enough/too small fresnel exposure area/rocks not transferring heat to one another timely enough; and of course burning your sauna down by being inattentive &/or no having inflmmable protective material where need be.)
Good work :D
This video is so cool
You would probably get just as high of a temperature with the same setup but no vacuum. In order for the conductivity of the space between the inside bottle and outside clear tube to be significantly lower you need to get the pressure down to the point where the mean free path of the air molecules (O2 and N2) is longer than the distance between the bottle and inside wall of the outer tube. I am going to estimate that distance at about 1vm which works out to roughly 1 micron. Some laboratory oil filled rotary vane pumps can reach this value, if the device you are trying to evacuate has very low outgassing and very low permeability (and of course not even the slightest leak), and the pumped air has a very short distance to the pump. A plastic tube and glue does not begin to meet these requirements.
I would be surprised if the setup in the video could reach 100 microns, which is not going to provide any insulation performance advantage over simply leaving the air.
Interesting point. It would have been a much better comparison if he had put the "naked" bottle in a similar container, unevacuated. As shown here, the sun is heating paint on the outside of the glass bottle (poor conductor) so much (most?) of the heat delivered to the paint will be lost to the enviroment. Perhaps he does that in a later video, I'll have a look around. Another thing that interests me is that the evacuated container can pretty much eliminate losses from convection and conduction, but the black surface inside will re-radiate some of the infra-red. Do they use a special glass?
Bill Juhasz
Dan,very interesting show us what the heat difference would be without the vacuum, but still in the same contraption. I think your vacuum isn't strong enough to make a very big difference regarding convection cooling. You're mainly seeing air as an insulator I hypothesize.
Gotcha, thanks.
I'm not building, but curious about a off-grid solution. Electric sauna rock heaters I've seen listed are usually 3KW models - I suppose an array of mirrors could match that. B/c the rocks need to maintain a constant temp, it doesn't sound like a lens would provide an easy solution. I was hoping it'd be as simple as placing the lens in the sauna besides a large angled window.
Maybe this would just work to keep the general temp up.
The temp diff you have is because the heat can leave non vacuum bottle through convection of the air on the contact surface, while the bottle in the vacuum valve cannot rid heat that way. The vacuum valve preserves the energy better than the other one because of this. Still heat can dissipate through radiation.
For a control, you could use no vacuum in the housing.
You would find that a bottle just in a green house would perform very well.
For even better comparison I would also like to see a bottle inside the bottle but with no vacuum. Basically a double glazing and obviously much easier to make and maybe the difference in temperatures wouldn't be huge?...
What a poor test please do some reserch before testing
Can a wood burning heater be fed from within the sauna, or only outside?
I'm wondering if you could direct the hot sauna air into a colder part of the house when finished, without introducing carbon monoxide from the heater.
(Not too familiar w/ saunas, just toying with how you'd get the most out of it in an off-grid home.)
Can you get natural/passive circulation by giving the sauna a vertical circular shape and placing the heat source strategically?
Have you thought of sealing a dome over your mirrors outside of the focal point a installing a coil to be heated at the focal point. The sealed chamber could then be evacuated.
Thanks for triggering the ideas. Good work you do.
liquid inside tube absorbs photons, liquid increases in temp because of this and the atoms start to move around faster, this "mechanical" heat is retained because of the vacuum, without it the atoms would bounce against the bottle and transfer some energy to the surrounding air thus loosing kinetic energy ie temperature
I was going to try to use a copper tube inside another copper tube, put a vacum on the inner copper tubing and paint the outer one flat black. would I still gain the heat difference with the vacum in the inner tube?
Hmn. cool. Well, thank you for your responses.
I suppose a less fussy option would be to just dump the air directly into a greenhouse.
Heat does travel through a vacuum. heat is low frequency (infrared) radiation. Does quite well through a vacuum. Heat works better by conduction and convection though. I'm sure wikipedia would validate this.
are there any vids you might suggest to demo this ? I am trying to understand it :)
12 years and still being linked to
I believe that another test is missing here. It is the greenhouse effect. Without the evacuation effect.
I cook a large chicken in 4 hours. just putting a pyrex vessel inside a transparent baking bag and then inside a small fish tank and a car windshield reflector.
The trick is to store the sun's heat and protect it from heat loss by the wind factor. If there is an internal black object storing the heat and a reflector outside multiplying the heat. everything is gain for cooking
Would a parabolic mirror in a vacuum be more efficient or am I missing something?
5 stars I think you need a another control like a darkened beer bottle the glass encasement w. no vacuum, that way you know weather there was an insulated and magnifying effect due to the glass surrounding the bottle .
@GREENPOWERSCIENCE hey what would happen if you use argon instead of a vacuumed atmosphere
can you fill one of these with co2 to see any difference.
Isn't the point of having the vacuum to remove molecules that would otherwise contribute to heat loss through conduction?
Argon gas is easier. Seal does not experience excessive force like a vacuum.
What type of paint do you use? many thank
Ok, ok so we can make cheap tea,
let's get to work on important stuff, like chilling beer!
;-)
5 stars.
@johnnythefridge maybe through infrared rays
why dont we have more uses for vacuum seals?
double glazed windows, ovens lined with vacuum walls, houses with vacuum walls rather than pinks batts
we could benefit alot more from this technology
the bottle you made on this video would be excellent for heating up my lunch time soup, maybe even make a cup of tea, saving me money boiling the jug
How do u make it ?
Thanks, great brain food.
or u could buy professional off the shelf evacuated tube solar hot water systems we have here in australia.
The difference in temp. is mostly due to the extra layer of clear material and not due to vacuum.
so you're saying there's no point in manufacturing vacuum thermos flasks?
could you explain the physics of why this happens? I am baffled by this
interesting...
Ok sure. But thats not what I meant. No vacuum or argon. Just still air between the walls. How would the temperatures differ then... Thanks
yes 2000 years ago and now we have got nuclear plants instead of solar storage using vacuum. so my friend we need to share those informations because we did not evolve in the right way
@advthinker If heat wont travel through a vacuum. How does the sun warm planet earth ?
if you are "still" in business, try, not vacuum, not paint surface, but an insulating layer without vacuum
Stirling Engines are great .
If you want to get the Plans To Build your own Stirling Engine
And Combine it with Solar Power - Go to Google and search for
"Solar Stirling Info" Pick the first Result .
@GREENPOWERSCIENCE There is a problem. This is not true. You have created a kinda greenhouse. If you want real results put the other one bottle from the right in the same condidtion, add a greenhousem or put two bottles in a transparent cube. Think ag
I found the beeping very irritating
magic black paint is not as good as baileys bottles
I tought it's a diy vacuum tube....the one for amps.