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ChrisJ

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Reply with quote  #31 
"Your aware of the risk, its your project, your wallet."

Rick, would you have spent more money on copper fins or gone the CPVC route?

Maybe do something different all together, care to enlighten us all?

Rick H Parker

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Reply with quote  #32 

I would never do dissimilar metals for the reasons I have already stated.

 

Copper does have better thermal conductivity than aluminum, almost most twice as much .. but aluminum's thermal conductivity is enough to to keep up with the collector's production and it cost less.

 

Would I have done something something different all together? .. most likely. However that is the nature of DIY. Each of of us has a different skill set, knowledge, different set of tools and a   different junk pile stock pile.

 

What you did with the copper pipes and aluminum flashing is the same technology as automotive radiator technology. One big difference between the two is that the automotive radiator is engineered for optimum performance. A small radiator could transfer the heat harvest of a much larger series of screen absorbers.

 

You guys have already work out the performance and cost cutting advantages of screen absorbers.

 

Around here I can go to the local pick and pull and get any automotive radiator for $45.00, the fan that go with it are $37.00 per motor. How does this compare to what you spent on your collector’s copper- aluminum assembly?

 

I’m visualizing a new solar hydronic collector design, where a automotive fan circulates air through a series of screen absorbers behind double glaze, the automotive radiator then returns to the front. I am thinking this design will cut the cost of materials, simplify construction and boost performance.

 

Thoughts, input?

 

Rick H Parker

 


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Rick H Parker
Kansas, USA
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Reply with quote  #33 
You can get brand new automotive radiators and fans on Ebay, for any vehicle you want, for probably less than you would pay for them at an auto salvage (not to mention the aggravation and driving around).  All-aluminum "racing" radiators are generally less than OEM replacements. You can get them with matching fans. Here's both for $60. Fans alone about $20, 30 for two.
http://www.ebay.com/itm/FULL-ALUMINUM-2-ROW-CORE-RADIATOR-12-BLACK-COOLING-FAN-CIVIC-DEL-SOL-INTEGRA-DC-/191123275179?hash=item2c7fd5bdab:g:II8AAOSw3v5Yt6tW&vxp=mtr

I would have used a radiator but as my collector is quite small I can't find a radiator that will fit in it.  I have an auto fan but it is too powerful and draws too much current (4 amps) for my 20 watt panel.  I've had really good luck with computer fans, they're all plastic, can take the heat (so far) and being brushless will run for a LONG time.  I also use brushless pumps for the same reason.

Here's my HVAC heat exchanger: 
http://www.ebay.com/itm/8X8-Water-to-Air-Heat-Exchanger-1-Copper-ports-/302173170811?hash=item465aecac7b:g:kdkAAOSw2xRYXEH~
One problem with HVAC heat exchangers is the thickness.  I think a radiator would be better as they're quite thin and could be stacked for a two-stage setup. In a cross-flow type like the jeep cherokee, the air could be routed through the cold end first then reversed back through the hot end, to pick up more heat.  

My first ARETHAs used automotive oil coolers, while they work well they are serpentine in nature and you can't push a lot of water through them. I used this one: 
http://www.ebay.com/itm/HAYDEN-TRANSAVER-OIL-COOLER-1405-Transmission-Cooler-OC-1405-/190772518479?hash=item2c6aed9e4f

I'd love to see someone else working with the ARETHA concept.  I think it shows a lot of promise.

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Willie, Tampa Bay
Rick H Parker

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Reply with quote  #34 
Need a small heat exchanger that is constructed like a radiator ...  heater core.

An alternative to cross flow: Most automotive radiators today have plastic tanks, top and bottom. Remove one top tank, one bottom tank, stack them, then braze them together.

Rick H Parker


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Rick H Parker
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Reply with quote  #35 
I thought so too but I couldn't get it to work.
https://simplysolar.supporttopics.com/post/willies-zp-aretha-8407113?&trail=10

Braze aluminum? I didn't know that could be done, certainly I can't.

It would be easier to just connect them in series which is what I did with the oil coolers. It worked very well. The only reason I considered the crossflow was that I thought it might be less work and cheaper. That's the whole concept behind the ARETHA.

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Rick H Parker

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Reply with quote  #36 

45 pages of stuff, that should keep me busy today. If I come up with anything I'll move this conservation to that topic.

Aluminum can be brazed with a propane torch, brazed not wielded.

Cross flow would be better, serpentine is for getting large changes in temperature (force)  in a single pass. Keep in mind the equation for Work is Work = Force * displacement. A smaller force with a much larger displacement can be more work.

Rick H Parker


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Rick H Parker
Kansas, USA
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ChrisJ

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Reply with quote  #37 
I have pipe insulation left to install on this copper mess. Solar shed 30.jpg

I have connected the heat pumps desuperheater and the DHW heat exchanger to the un-powered electric water heater.

Solar shed 31.jpg 
Hopefully I can get a few years out of the collector before I have a heap of corrosion under my sliding glass doors.
 

Rick H Parker

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Reply with quote  #38 
"Hopefully I can get a few years out of the collector before I have a heap of corrosion under my sliding glass doors."


There is an argument that has been around for five years, saying solar thermal water heating is dead.
The argument is: Photovoltaic driven, electric air to water heat pumps are more economical then solar thermal heated hot water.
For professionally installed systems the argument is pretty good, for DIY not so good (the labor cost) . However if the cost of Photovoltaic keeps falling it might come true for DIY also.

Maybe next time around A photovoltaic driven electric air to water heat pump will be the way for you to go. A lot less to go wrong and lower maintenance.

Rick H Parker



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Rick H Parker
Kansas, USA
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Reply with quote  #39 
That's been discussed somewhere on here and I think it would depend on the region.  A heat pump takes it's heat from it's surroundings, making them colder.  Here in the south that benefits the AC, but in the cold country you have to make up that heat somehow.  So depending on where you are, resistance water heating may make more sense.  Yes you need more PV, but the water heater is a whole lot less expensive, and considering the price of PV it may more than make up the difference.

I have a professionally installed solar water heater, and it wasn't cheap.  Since then I've had to replace the absorber (freeze damage in FLORIDA?) for another $1500.  That alone would buy a LOT of PV at today's prices, and PV panels won't freeze.  If it fails again, I'll replace it with PV, maybe a heat pump, maybe resistance.

Then there's the efficiency argument.  Any water heater eventually hits it's upper limit and the thermostat shuts it off. Now the collector is not running (0% efficiency).  A PV system can still be generating power to run other appliances, charge the batteries, or feed the grid. 


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Rick H Parker

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Reply with quote  #40 
A heat pump, moves heat from one area to another, that is why it is call a heat pump. The area it takes from gets colder but the area the heat is move to gets hotter. That is why a heat pump can heat or cool your house. There are heat pump hot water tanks on the market, for every joule of electrical energy use, they move two joules of heat. You get twice the water heating for the same amount of electrical energy. That make twice the sense of resistance heating.  Cuts the number of required PV panels in half.

Freeze damage on the absorber? That should not of happen at all any where. How in the beep did that happen?

Good point, PV is more multifunctional than a thermal panel.

Rick H Parker



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Rick H Parker
Kansas, USA
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