can I build a solar water heating collector without using copper pipe?

[strider3700]

I've been thinking/planning on building my own solar water heating system and at the moment I'm thinking about building the collector.  My first idea was an insulated box with some copper sheeting I have inside and then a copper pipe system finally covered with more copper sheeting.  bind it all together and paint it black.  This is basically your typical homebuilt collector.  My concerns where the copper sheeting is 3 oz so really really thin,  and the pipe is going to cost a pretty penny these days. So I was trying to come up with ideas to do this cheaper and I got the idea of running smaller pipe but more of them and that didn't work out any better.  Anyways last night my mind came up with the idea of doing away with the majority of the pipes and instead basically use the two flat sheets as the "pipe" roll and seal the edges and then but a pipe on each end to get the fluid into it.   use some appropriately sized wire to act as spacers to keep the sheets from compacting down and pinching off...  

Anyways I have lots and lots of this 3 oz sheeting.  It's a 4' wide roll and I bet I have 20 feet of it.   It's also free which is always a good thing.   Can anyone tell me if they think this will work?  If not why not.   My concerns are about the pressure holding capabilities of the sheeting and if it will be even close to efficient enough.  I'm sure it will get hot in the sun so I figure that should transfer to the fluid as it passes through...

Thanks for any insight

[fcfcfc]

Hi: 3 0z is pretty thin and any wear do to corrosion and your dead. It would have to be an open loop drain back so the only pressure it sees is due to head resistance and just the weight of the fluid. There have been many attempts over the years to get away from the expense of Cu. Most of the ones that work half decently are in the hot air category rather than a liquid based unit. If money is a real problem then a black fiberglass matt style air collector might be the way to go and use a liquid to air exchanger to get the heat into your DHW. You could keep the blower small to raise the output temp a bit and use twin wall poly carb for the glazing, AL sheet metal sides and back, etc.. That's probably the cheapest solution you can get that will work half at all worth talking about. If it is for a typical res DHW sit, I would go about 100 SQFT of collector and 80 gallons on the preheat tank.

[Marco Polo]

The flat plate solar collector has been around for over 100 years in the US.  Try to see if you can get a copy of Bruce Anderson's, "Solar Energy: Fundamentals in Building Design", 1977 McGraw Hill Book Company.  Perhaps the local library has a copy.  Chapter V-B," Flat Plate Solar Collectors, has every possible flat plate configuration ever thought of by man.  Page 152 shows a collector made out of corrugated aluminum roofing that is painted black.  The supply header on the top has holes drilled in it corresponding to the low points in the corrugation.  The water trickels over the plate and is collected in a trough that gravity drains back to the system.  The chapter even gives you recipes for creating sellective black surfaces if you don't want to paint and want to play with your chemistry set, .

[davidmlantz]

I saw a homebuilt parabolic concentrator that focused on aluminum pipe painted black at one point.  It used mylar film for the mirror, held in a frame made from Masonite or OSB (I can't remember)  That was used a pool heater.  Used focusing equipment from RedRok in a peanut butter jar.  I would expect that to be cheaper.  I'm personally interested in the fresnel linear focusing technology. I would like to build a small field of these by bending a piece of pipe into a circle to ride on rollers, put two of these circles at each end of each linear mirror and drive one of the rollers with a small gear motor... it could work and would probably be the cheapest way to do it.  The focusing area could be galvanized ductwork painted black or even an open trough painted black... just a few thoughts

[BigBreaker]

Linear freznel is getting some press lately and for good reason.  It is really good technology.  It's worth investigating both orientations to see what works best for you.

[34PatentAcres]

I saw where someone had taken twinwall polycarbonate attached a header pipe (split the long way) to the top and bottom painted the back side black and got a pretty effecient trickle water system.  If your set on using copper why not simply sheet flow the water down it on an incline and gutter collect it on the lower side. (saw this done with dark green metal ridged roofing with clear fiberglass glazing over it.  Otherwise use a plastic poolheater on a bubble foil insulated backer board, box it and glaze it.  (caution overheating the plastic may be possible keep your water circulating at maximum flow rates in sun)

[paborralho]

When you play with these things on your house´s roof, you don´t want to see any drop of water anywhere. I tried more than 3 times with policarbonate circulating the water inside the cells, it worked great for some time and some days after it would loose water from some part. At last I decided to  use hot air to heat up the water, and now the water circuit is closed, no pumps, just thermo sifon, with more than 3m2 hot air panel, and an old propane water heater as the absorver. Works great (dont know efficiency yet). have some photos if you'd like.

Have fun

Paulo Borralho

[libra]

I am looking to play with a solar wall this summer. Was looking at 200 sq ft metal solar wall (stand alone away from the house) with polycarb glazing and have the water trickle down the face and gravity flow back to the storage tank, a small pump would return the water.

I can see possible water loss to evaporation and some inefficiency due to condensation on the glazing.

What have I overlooked?

Ps I would appreciate any photos of similar systems

Libra