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OnOff

Mad Inventor™
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In between NOT fixing laptops was explaining to the six year old why black things heat up quicker. We are fairly big on recycling and one thing led to another......................based on the fact that I have a stack of left over greenhouse glass left by the previous owner. Was going to skip it. Then I found the bag of scrap 50mm Rockwoll batts, copper off-cuts, old floorboards. Work in progress:





Link to all the piccies:

http://s1185.photobucket.com/user/clicon357/media/Solar/SAM_5932_zpsb814f905.jpg.html

............this is primarily on the basis of avoiding doing the gardening, "But I'm teaching the kits about being green!"

 
solar thermal Im taking a guess at.......
Yep, got it in one!

More a proof of concept that anything else for the kids. Carcass now has a back in it and all painted black. Need a few more cans to complete.......takes a while as I don't really drink any of it so scrounging them here and there. NOT yet resorted to picking them up in the street yet though I suppose that would tick the "green" box a bit more. Trouble is round my way that though they CAN'T repair pot holes they seem to find money for street cleaners! If I see a can run over now I'm in tears! 

So, 50mm of Rockwool offcuts go in the bottom then an aluminium sheet atop that. The "collector" will be 4x7 cans, etch primed and sprayed black. Horizontal feed & exit in 22mm top/bottom with 15mm verticals running up through the cans. Hoping the semi-sealed air gap between can and pipe will get nice and warm. Sort of evacuated tubes on the cheap! Rockwool then to all 4 sides of the collector.

Plan is it costs nowt, as in must be done with stuff I already have or can get for nothing. Going to work on the "fitting-less" (keeping the cost down) copper tube "matrix" next. Should be fun Starrett cutting 16mm holes into the 22mm then fluxing and soldering the 15mm pipes in (wonder if a 14mm will cut a tad oversize?).

MIGHT just about heat a paddling pool.....................

 
Ah you see I had got it all wrong.

I thought it was going to be a solar thermal panel but in two halves.

The left hand half made of silver coke cans, and the right hand half made of black coke cans and piped separately.

Then see which gets the hottest, thus proving the silver / black argument.

 
This reminds me of the air con repair I did many years ago.

Full install plus brazing of the pipework, purge and vac out

plus charge.  The brazing rods were beautiful.  Never seen

them since.

 
That joint will work but won't be very strong.

Reminds me of the hot water tank in my caravan. Stainless steel tank with a pipe soldered into a hole in the top.

I've had to re solder it 3 times now with SS solder. It cracks after a while, probably the vibration of it being in a touring  caravan.

 
Ah you see I had got it all wrong.

I thought it was going to be a solar thermal panel but in two halves.

The left hand half made of silver coke cans, and the right hand half made of black coke cans and piped separately.

Then see which gets the hottest, thus proving the silver / black argument.
thats what I thought too Dave.

do you need any green cans?  ;)

 
Getting jiggy with it! More scrap floorboard to make a jig to drill the 22mm.....holes are a bit ragged compared to the sample piece tbh but should do:



 
A bag of Rockwool offcuts destined for the tip. 2" in the bottom:



Whoever doubted the direct soldering instead of using fittings was a wise man! It was a biatch but all done now. Had to almost get the solder like a weld fillet. Had one leak on 14 joints:



"Pressure" testing:



Didn't quite finish today, the only thing that collected the Sun's rays was the top of my head! But getting there. Needs a bit more insulation then to spray the cans matt black tomorrow. Glass in, bit' of silicon here and there, paddling pool or similar. Then to see if we can get it thermal syphoning!

Etch primed the can "collectors":



Will video it IF it works!

The white sheet with angled sides is a sheet of aluminium with a sticky back covering YET to be peeled off. The cans will be sprayed black all sides. NOT SURE whether to spray the sheet black or LEAVE shiny "mirror" silver to reflect light/heat back at the underside of the cans???

 
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are you gonna have it as a direct system, or indirect?

can I suggest, if you do indirect to put some antifreeze in the cans, better heat transfer that way,

if you want to run it as direct, you could use some water wetter , it is also a lot better than just water, but no nasty stuff in it.  :)

OK, so Ive looked again,

Im a bit puzzled to the actual purpose of the cans,,,,,

have you slotted them? I thought you were using them as collectors.......

what is the actual point of having them?

 
are you gonna have it as a direct system, or indirect?

Im a bit puzzled to the actual purpose of the cans,,,,,

have you slotted them? I thought you were using them as collectors.......

what is the actual point of having them?
First thing this is more a "proof of concept" thing. Probably NOT going to use THIS one for anything but move on to a bigger version for plumbing into the house. I'll play with this one measuring water temp in/out and just get a feel for it. As for direct/indirect...............from limited research (I'm a total numpty with this) I'm guessing an indirect tank with two coils - one fed from the solar thermal  side and one from the oil boiler.

How it works.................well, I'd been looking at the evacuated tube design. I obviously haven't got a vacuum set up. As I understand it, because of the vacuum the copper pipe inside remains relatively unaffected by temperature changes?

With my effort the 15mm copper runs up the centre of each can "stack". The cans have their ends removed. The can stack is fairly well sealed along it's length - by close fit/paint between the cans and silicon round the pipe at the ends (maybe expansion at the joints as it heats up?). So I'm hoping that this "space" will get nicely warmed up and transfer to the 15mm tube. That's the theory..................

So no water in the actual can / space between 15mm tube and inside of can. I AM though worried as to whether this space will fill with condensation?

Anyway, looking to be a sunny day, the wife/kids are still akip so I'd best get on. Then hopefully when they out at a party later Ican nick the washing up bowl and some food dye and see if it works!!!

 
Have you thought of controls?

As I understand it, every solar thermal system leaves the water in the tubes static, monitoring the temperature. Then when it reaches a certain temp, it turns the pump on and moves the "slug" of hot water around to heat the tank.

Once the heat has been transferred to the tank, the pump stops again and waits for it to heat up again.

That's how they achieve a relatively high temperature.

It sounds like you are just going to let it thermo syphon, which will probably result in a continuous flow of only slightly warm water. Not much good for heating your domestic hot water, but I agree might work well to keep a kids paddling pool warmed up.

 
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Have you thought of controls?

As I understand it, every solar thermal system leaves the water in the tubes static, monitoring the temperature. Then when it reaches a certain temp, it turns the pump on and moves the "slug" of hot water around to heat the tank.

Once the heat has been transferred to the tank, the pump stops again and waits for it to heat up again.

That's how they achieve a relatively high temperature.

It sounds like you are just going to let it thermo syphon, which will probably result in a continuous flow of only slightly warm water. Not much good for heating your domestic hot water, but I agree might work well to keep a kids paddling pool warmed up.
Yep, I got a book years back from CAT (Centre For Alternative Technology) in Wales on something similar - two options they gave for making the panels; old radiator painted black or copper tube matrix like mine mated to CLOSE fitting flat aluminium plates "pressed" with a half round former to fit the pipes.

In that book was a circuit for a controller, make your own PCB etc, diodes from memory epoxied onto the cylinder / panel exit as sensors etc to give a differential control and stop back syphoning. Of course I LENT the book out so must get that back. Time to dig out the old UV box and ferric chloride! I'll CAD the PCB design up for later use etc.

Only came in from the garden from painting the cans black and the off chance she might have made a brew! Back for the second coat now via the kettle as I'm neglected.

TBH I'll be made up if I get semi hot water coming out of the top!

 
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Most Solar Thermal systems need a heat dump but not them all, my solar thermal system is a drain back system so if the water temperature is below 5deg C the system circulation pump ( a small solar pv powered pump) stops and the water drains back to a flask to stop frost damage.  If the water temp gets above 80 deg C (I think) the pump switches off again allowing drain back to stop the system overheating.

Top tinkering by the way Onoff.

 
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