[Chris Clean Republic]

Buy them here: http://www.electric-bike-kit.com/solar-tubes.aspx

What are the Solar Vacuum tubes?

Heat water with the power of the sun.

They are a glass Borosilicate vacuum tube, with a high heat absorbing coating on the external inner tube. This allows you to place the tube in direct sunlight which heats the inside up to hundreds of degrees. Each tube can hold up to 1 liter of liquid, and can boil water in approximately 2 hours. The tubes can be constructed in an array to provide your home with hot water without paying a dime to your utility company!

These tubes soak up the energy in sunlight, absorbing it into the super-insulated inner tube of their incredible double-wall heating system. Once inside, the heat of the sunlight is trapped inside the inner wall of the inner glass tube. Highly-reflective layers of steel, aluminum, and copper trap the infra-red energy of the sunlight, and the nearly perfect vacuum between the inner wall and the outer transparent wall protect the inner tube from heat loss due to convection, just like a high-grade drink thermos. This thermos effect can quickly heat water to boiling temperatures in direct sunlight, and keep the water well over 100 degrees even over night!

How do I use them?
We just supply the tubes, it's up to you to build a system that works for your needs. We have developed several working prototypes (videos below). We have sourced all of the non tube parts from local hardware stores. Mostly PVC piping rated to withstand 200F and a water proof epoxy were needed to construct our prototypes. We rely on our smart DIY minded customers to build their own system. Feel free to share your ideas in this forum.

Tube Specs:
-20 1/2" long (about 500mm)
-2 1/4" outside diameter (about 58mm)
-1 3/4" inside diameter (about 43mm)
-Double wall structure with vacuum between walls
-Super-absorbent inner tube coating quickly soaks up solar energy
-Steel, aluminum, and copper coatings for infrared reflective insulation
-Incredible thermos-like properties can keep water hot even over night

Here is another potential application of these tubes http://www.honeycombvalley.com.au/product/solar-cooking-ovens/solar-rocket-solar-kettle-thermos

Buy them here: http://www.electric-bike-kit.com/solar-tubes.aspx

Below is our video series, showing our working prototypes:












Pictures:








Buy them here: http://www.electric-bike-kit.com/solar-tubes.aspx

[Conor5]

We installed two 30 tube panels on our roof in 2006. They made 100% of our domestic hot water and contributed a tad to our in-floor heating. We recently ordered 3 more panels to add to the existing 2 because we wish to heat our house even more using solar.
In order to add on, we had to remove the existing tubes so we could drain the system. While we were removing the tubes we found 23 of the 60 tubes had gone bad. Upon inspection, we found the slim copper tube inside the glass had expanded and split at the bottom. The copper looks like a bloated puffer fish! This released the water inside the copper and made the tubes useless in conducting heat. We live in northern Wisconsin and it's not uncommon to have -20 degrees for weeks on end. We believe the copper inside the evacuated tube froze and burst. We don't know if the vacuum had been lost, and thus lead to freezing? Each tube seems to be completely in tact, no glass is cracked or broken. Even the seal between the glass and the metal looks fine. Can the liquid inside the copper freeze even with a vacuum? And why did 23 of them go bad and not the full 60?

My husband believes the vacuum still exists in those bad tubes, but the copper still got cold enough to burst. He believes this because there is a stretch of coiled metal going from the glass to the big copper head at the top of each tube. It's the skinny neck part. This neck part isn't insulated. This neck is exposed to that cold air on frigid January nights. Could that cold be entering the neck and traveling down the copper tube and freezing it? He believes this is what happened. He believes the 23 unfortunate tubes were the ones that slipped a bit past the manifold and really got exposed to the cold air. They slipped a bit when we cleaned the snow off them. When I slipped a bit, I mean like 1/4 inch. There's nothing but a strip of plastic on the bottom of the manifold protecting that neck, and the tubes could easily slip a bit beyond that plastic strip. The new Kingspan tubes have a clip to hold them into the manifold so they can't slip. But the necks still aren't insulated. Don't they think cold can penetrate that uninsulated strip of plastic?

To add insult to injury, Thermomax was bought by Kingspan Solar in 2007, and all tubes sold before that aren't covered under warranty. So we lost our warranty. But since we already have 37 good tubes, racks, and a system in place we will be purchasing 23 more tubes from Kingspan. But we are going to insulate those wire necks ourselves to make sure they don't freeze.

Also, we never would have known these tubes were bad if we hadn't ordered more panels. We don't annually go up on our roof to check tubes after winter has passed. We never thought it was something we had to do. Kingspan says they've not have any complaints on solar sold to northern climates. But do those panels get checked annually? Maybe they have bad panels and don't know it.

Looking at our solar data, it seems the tubes went bad after the first year because our production really dropped. We thought it was just a really sunny first year and never thought about it more than that. If we would have done an annual check up, we could have maybe caught it soon enough to be under warranty before Thermomax went belly up. If you wish to install evacuated tubes in a cold climate, be prepared to annually check your tubes.

[Chris Clean Republic]

Conor5,

Thanks for all the info. I'm going to do some research on the freezing problem and get back to you. As this was a different company, I'm not sure our tubes will have the same problem, but I'm going to check into it. I do know that the copper insert that we use has a water/glycol (anti freeze) solution to help prevent this very problem. Whether the glycol can handle -20F is a good question.

Anyone else have similar issues with other companies brand of copper tubes?

[buckhall]

How does the water circulate through the tubes? The appears to be only one opening. Buck Hall

[mtmtntop]

i have a 75 tube array that has been operating about 2 years, and i had no trouble with seals. (although i did go back to check my data based on earlier post). i am looking for someone that has used evacuated tubes with a parabolic trough. I am trying to build a manifold to harvest the heat from an array of evacuated tubes in a parabolic trough. The array would be based on this design,
http://www.ffwdm.com/solar/solar-index.htm
only with evacuated tubes, generating alot higher temps., i still want hot water, not steam, and would use it to heat the house in the winter. in the summer, it would probably be covered.
has anyone done this? i'd sure like to hear from you.

[Chris Clean Republic]

Hey mtmntop,

Thanks for sharing that link. That is some really cool stuff! If anyone has constructed a system with our solar tubes like this we would love to see it. Include photos.

[FirstwaveAquaponics]

It would be very helpful if you could post the exact measurements of the tubes (mm/inches) so we can spec out potential applications; especially the outside and interior diameters. I'd like to use them to heat the water in my aquaponics system. I need to maintain a temperature of 80-85 degrees and would love to use the sun for this. You can track our efforts on Facebook.com/firstwaveaquaponics. The advantage of the solar tubes is that we can minimize the use of PVC plastics.

Bill

[pshebanow]

I would like to second the motion for accurate dimensions.
I have never seen short 2 footers of these before and think these would be great for experimentation.

I would like to know more about the heat pipes. This is a technical question and I'm not sure it can be answered without cutting one open.

There is a distinction between a 'thermosiphon' and a 'heat pipe' in that a heat pipe has a vapor phase and that the thermal siphon is liquid-only convection that drives it. The heat pipe would have a porous ceramic-enamel or fibrous lining of the tube which acts as a wick for the coolant and there is usually a very small amount the coolant in a heat pipe where a thermal siphon would be 'filled'.
http://en.wikipedia.org/wiki/Heat_pipe
http://en.wikipedia.org/wiki/Thermosiphon

There was also a YouTube video of yours which I got to through somewhere that showed one of these units broken up. I would be interested to know the thickness of the various layers of glass and the coatings. Also the dimensions of the centering clip and a closeup photo of one of these would be handy.

As I mentioned, I am a CAD user and have already produced a SolidWorks model based on the displayed measurements and photos. The detailed measurements would naturally make the model more accurate and when done, I'll give you a copy and/or put them on http://www.3dcontentcentral.com.

[justn1185]

Hello all, I'm exited to find this forum!
I'm about to purchase some tubes for a pet project of mine and wanted to bounce ideas off some heads. I have a medical condition that requires I only drink distilled water. And, in fact, most medications (as we are slowly finding out) only work properly when coupled in this manner.
Instead of using this process to provide warmth, could we safely gather the steam in order to drink its distilled product?
I own a rain barrel: why not use this as a source? Distillation is a well understood process but to keep this fairly aseptic sounds like an interesting challenge.
Also, I have thought about using a linear fresnel lens to heat up these tubes and encourage the process, would that damage them? What about if I only pass the beam over them for a few passes to speed it up?
Thanks!

**(if this works of course) why not find a way to set up systems generating clean water for people in countries that only have access to dirty water? Would make one heck of a humanitarian project!

[justn1185]

Dan Rojas of Green Power Science believes the fresnel could do some serious damage if used as point but backing up (out of focus) a bit would help. If it was used to distill he also states the pressure required might be a bit dangerous in these vacuum tubes. I still want to try the experiment (with all the necessary safety precautions) for a working model that could be reliably reproducible and relatively simple.