Broken evacuated tubes - Solar Thermal & Power Diverters

RE: Broken evacuated tubes

David999 — Fri, 20 Sep 2024 11:40:39 +0000

When I installed my thermal solar years ago I thought that I should increase the capacity to compensate for winter. Navitron at that time advised that more capacity would simply mean reaching the 30c during winter faster but unable to produce the 60c or more during summer and be an issue during summer producing too much heat. Does that still apply?

RE: Broken evacuated tubes

David999 — Wed, 18 Sep 2024 15:57:05 +0000

@transparent nothing to beat working from home. 😂

RE: Broken evacuated tubes

Mars — Wed, 18 Sep 2024 15:43:15 +0000

@transparent you're working way too hard. You need to take a break 🤣

RE: Broken evacuated tubes

Transparent — Wed, 18 Sep 2024 15:34:05 +0000

Erm... I'm not quite sure of the temperature,
but the water's pretty warm today.

It's been a 'busy day at the office'

8371

RE: Broken evacuated tubes

David999 — Wed, 18 Sep 2024 13:59:58 +0000

What’s yours putting out today, it’s a clear sunny day and my 20 tube putting out 50c. I thought a bit more but my angle is a bit shallow. I felt the tubes and there is a bit of warmth at the base but nothing like before.

RE: Broken evacuated tubes

David999 — Tue, 17 Sep 2024 18:27:00 +0000

@transparent got me thinking, but no greenhouse. Got a garage though but heating it is not a great idea, the heat in fire stations rots the appliances, I never thought that but there you go. Car is best under a canopy with air circulation.

RE: Broken evacuated tubes

Transparent — Tue, 17 Sep 2024 18:11:42 +0000

If you've recovered 15 tubes which still seem to work, then you could consider using them in a greenhouse environment.

Even if they are now only half as efficient as they used to be, that would be ample to raise the temperature of a cultivation bed with water-pipe snaked below it.

Have a look on ebay or AliExpress to find a short manifold for the required diameter evacuated tube - 47mm?

A PV panel on the greenhouse would provide sufficient power to drive a 24v motor as a pump.
Of course, that would run faster on days with lots of sunshine... which is what you'd want anyway.

RE: Broken evacuated tubes

David999 — Tue, 17 Sep 2024 16:06:34 +0000

@transparent I just stuck them all flat, probably not ideal as you say but holding onto them for the meantime. I have a thought of sticking them in a smaller unit for winter use and cover it during summer, or something but I hate waste so figure out something.

no casualties fitting them although the wife managed to get covered in thermal grease. She usually gets fingers jammed somewhere and I get the blame

RE: Broken evacuated tubes

Transparent — Tue, 17 Sep 2024 15:46:25 +0000

I put them all outside for a bit and monitored the heat build up in the copper tips with my infrared thermometer.

....Quite surprised how quickly they heated up at the tips....

At what angle?

I'm unsure what fluid is within the copper tube, but my understanding is that it changes density, thus rising up to the top when hot.
If you change the angle of the tube (wrt the direction of gravity) then the speed of heat transfer alters accordingly.

If you hold the tip of the copper inner-tube tightly in your hand, and allow the glass vacuum vessel to hang vertically, then it breaks...

... because you've just burnt your hand and dropped it! 😯

RE: Broken evacuated tubes

David999 — Tue, 17 Sep 2024 15:28:33 +0000

@transparent fitted the foil to the roof with spray contact glue, a bit sceptical whether I was wasting my time but half way through it I had to go and get my sunglasses, and that caught me off guard if I’m honest. Will see how it goes and if a success look for a quality material.

in relation to the tubes they all look fine, other than the damaged ones of course. But out of interest I put them all outside for a bit and monitored the heat build up in the copper tips with my infrared thermometer. The ones with hot tubes are slow to build up temp and cooler at the tips than the ones with cool glass. Quite surprised how quickly they heated up at the tips but my take is, if the tubes are warm then the vacuum is either gone or deteriorated to allow thermal transfer to the outer tube. No condensation in any and look identical to the ones where the tubes are cold on the outside. Perhaps I’m wrong though and holding onto the 15 tube just now.