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Onoff

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Posts: 34
Reply with quote  #1 
Good evening, Just joined the site tonight. Living in southern England in an old, cold and draughty house. I've taken baby steps into the word of DIY solar thermal with a small panel built entirely from scrap materials. It was more done to teach the youngest about the subject. Planning shortly to upscale the design and plumb into a pre heat tank to supplement our fuel oil fired hot water and central heating. Based on pop cans:

Everything was scrap btw and destined for the tip!

So taking some 18mm chipboard flooring offcuts I made a simple box, lining with 2" Rockwool offcuts:

32608573381_6151b1a09f_z.jpg 
I'd had a load of 15 & 22mm copper tube in a long cardboard box that the elderly, incontinent cat had decided to pee against. I didn't want to use the copper as it was quite pitted and corroded. A quick bleach and sanding and I made a fitting-less matrix:

32352099950_903025cd63_z.jpg   
330ml pop cans were drilled top and bottom and positioned in tight fitting stacks. When drilling the tops I found it far easier to do so filled with water as less chance of collapse:

32691587976_5b6d1c64ac_z.jpg 
At either end of the can stacks they fit into recesses in boards:

31888698824_c0618aac30_z.jpg 
I folded an aluminium reflector to go atop the Rockwool / under the cans. Ideally I'd have this mirror finish but that wasn't achievable. The idea is that any light and thus heat gets reflected back to the underside of the cans. It's in now way an evacuated tube but I figure as the cans expand where they abut that must seal pretty well.

32352093110_cee90f9138_z.jpg   
A sheet of green house glass finished the front off. It was the abundance of this that drove the overall size - about 4' square. I used a can of satin black Bedec Barn Paint over some etch primer on the cans:

32691574616_54e62d66b3_z.jpg 
Anyway I got it thermo-syphoning without a pump and was getting just over 80degC at the output which was in excess of 50degC above ambient measured via a Binder point on the outflow.

32608551201_de5d2c5464_z.jpg 

A little old brewing barrel was pressed into service as an uninsulated tank. Losses were pretty massive but I was getting in the 40's in the tank which was basically acting as a radiator!

31918113803_ae40c545f7_z.jpg 

Managed a few al fresco (a tad too hot) showers much to my kids amusement and a number of hot car washes!

32731927115_8395146e26_z.jpg 

The whole picture thread, warts and all is here:

https://flic.kr/s/aHskQHCTRu

Plan is to upscale and use as a closed loop for pre-heating. Pretty sure I'll use tees and elbows rather than my fitting-less design next time as I've concerns over it's longevity. This was more proof of concept!

Anyway, hoping to learn and save a few pounds in the process. Thanks for looking.

stmbtwle

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Reply with quote  #2 
Welcome to the forum! I hope you find the site useful and we'll follow your progress with interest.


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Willie, Tampa Bay
Onoff

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Posts: 34
Reply with quote  #3 
As an aside, from looking here and elsewhere on the net would I be correct that the "American" method of choice seems pretty labour saving by basing everything on an 8'x4' panel size. Thinking big of course! 

- sheet of 8'x4' backing board (no cutting).

- batten and screw on say 6"x1" sides

- drop in a full sheet of foil faced PIR or "polyiso" as you call it. Again no cutting.

Et voila, one box ready for adding your pipes, soda cans or grid of choice & glazing. Guessing out there you might get 8'x4' (twin?) wall glazing sheets? Again, just drop into the box supported by battens.

I can't quite get my head around how/if poly iso is good at the high generated temperatures.

gbwillson

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Reply with quote  #4 
Welcome Onoff!

The reason we build using materials with a 4x8 sizing is simply because that's how plywood, polyiso insulation and glazing sheets are sold on this side of the pond. But nothing says you can't or shouldn't go with a different size. And if you are building from recycled materials, you use what's available. A 4x8 collector will nicely heat up a room or two. But it won't warm an entire house. Anything smaller, and it limit its effectiveness to a small bedroom room, bathroom or foyer. And a large collector is not much more work to build than a small collector unless...

you are building a can collector.

I admire your use of cans. Not many built that way around here anymore. It's quite labor intensive, as you know. A large can collector could have over 200 cans! But for a first collector, or to get others interested in solar heating, such as your little one, can collectors are ideal. Can collectors attract interest and spark conversation. But there are far easier collectors to build, that are every bit as effective as one built out of cans. Most of the collectors built around here that used to use cans, now use aluminum gutter downspouts. They are cheap(but not free), and you don't have the cleaning, cutting, and stacking labor can collectors do.


Greg in MN



Rick H Parker

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Reply with quote  #5 
"I can't quite get my head around how/if polyiso is good at the high generated temperatures."

Good in what terms?

PIR is fire resistance and it is one of the insulations that have a higher R value at higher temperatures.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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Reply with quote  #6 
I don't get on here too often but like to keep upto date where I can, but being UK based (Nottingham) hopefully I can help?
Quote:
Originally Posted by Onoff

As an aside, from looking here and elsewhere on the net would I be correct that the "American" method of choice seems pretty labour saving by basing everything on an 8'x4' panel size. Thinking big of course! 

- sheet of 8'x4' backing board (no cutting).

- batten and screw on say 6"x1" sides

- drop in a full sheet of foil faced PIR or "polyiso" as you call it. Again no cutting.

Et voila, one box ready for adding your pipes, soda cans or grid of choice & glazing. Guessing out there you might get 8'x4' (twin?) wall glazing sheets? Again, just drop into the box supported by battens.

I can't quite get my head around how/if poly iso is good at the high generated temperatures.


Twinwall is usually sold upto 1050mm wide, as they don't like diy'ers trying to span more than that unsupported so the 8'x4' goes a little awry. It's difficult to see what size the box is, but from a backyard diy enthusiast go for as big an inlet into the property you can. When I first messed about I tried plumbing supplies of 40mm. Complete and utter waste of time and effort. I've got a 5" bore into the house now and this is really a minimum I'd advise. Our homes tend to be constructed quite differently compared to our American brethren so a little ingenuity is often required

It took a while to get my head around, but you want lots of air flow and temperatures of not too a high a gain. You may quickly find it's just your first step. I'd built 3 before settling on my fourth revision. The first box I could get 80*C out of but the air flow was poor due to my limited understanding. Now I get around 40*C but with a good airflow from a 150mm inline twin speed extractor fan.

Good luck with it, if I can help with any of our British eccentricities please ask!
Onoff

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Posts: 34
Reply with quote  #7 
I must get to a proper pc and try and tidy my first posts, apologies for the layout!

In the UK we don't always have the space for big panel builds in terms of roof space or land (luckily I do). Most passive house builders go for PV panels here and often use the excess electricity to heat water if not exporting back to the grid. Sunamps are pretty popular too. There's been major changes over the FiT rate paid by the government to householders with PV here. Whereas it was very good and led to a thriving solar industry it's now next to nothing.

As an aside I think yesterday was the first time in history in the UK that no coal was burnt to produce power for the grid.

I'm aiming to fit a large TS so I can use oil boiler and any solar thermal I come up with.

I'll tidy my posts when over this man flu!
Onoff

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Reply with quote  #8 
Opening thread tidied up!
stmbtwle

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Reply with quote  #9 
I thought it was fine...

I have a question though, why the cans in what is obviously a water collector? Is there any connection between the cans and the copper grid, or does the hot air in the cans heat the copper tubes? If so I think you've invented a new type of ARETHA (AiR Exchange Thermal Assembly).

Would love to see more on how it works!

Congratulations on the UK burning no coal! Big as we are, we in the US are falling farther and farther behind the civilized world. [frown]

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Willie, Tampa Bay
Onoff

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Posts: 34
Reply with quote  #10 
How it works? We'd had a hard sell guy come to the house pushing evacuated tubes. We showed him the door but I could see the attraction. I looked on the net on the plethora of soda can types and figured to try and combine elements of the two systems. You are correct in that there is no physical connection between the copper tube and aluminium cans. The aim was for the air temperature in the space between tube outer and can inner surfaces to be significantly hotter than outside the can anld as long as the sun's shining just keep transferring to the water via the copper with low losses. It can't "lose" from the base of the can stack as hot air is rising. Any loss at the top of the stack will just heat that portion of the copper. Saying that losses are minimised I think at the ends of the stack by silicon around the pipes where they pass through the wood and between cans due to simple expansion. It's not in any way an evacuated tube but I reckon it's pretty unpleasant in there temperature wise! One thing I did worry about was possible condensation in there?

The idea of the reflector was to try and get 360deg heating of the pop can outer surface.

Really it needs some sensors built in but I wouldn't know where to start!

The nice thing for me was seemingly decent performance from a very small panel but that was more of a gut feel having nothing to judge against.

I guess it's time for the 8'x4' version!
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