I Built a Solar Collector (DHW)...

[WES999]

Here are some pics of my solar DHW heater. My solar collector is based on the design by Gary Reysa

http://builditsolar.com/

I made some things a little differently. I used 20G steel studs for the sides, I used .030 aluminum for the absorber plate, and I installed the absorber plate with the copper tubing facing out.

I used special solar selective coating collector paint form Dampny Co http://www.dampney.com/Products/Products.asp?ProductID=28

Instead of silicone for bonding the absorber to the copper tubing I used Permatex® Copper Spray-A-Gasket® Hi-Temp Adhesive Sealant.

http://www.permatex.com/products/Au...r_Spray-A-Gasket_Hi-Temp_Adhesive_Sealant.htm

I chose the Permatex because my absorber plates fit the copper tubing very tightly, I figured the copper sealer would give a bit better heat transfer; I did not think I needed the gap filling ability of silicone.

The absorber plates were formed on a bending break; I designed and built the dies myself.

I used a sheet of 1” poly iso insulation and strips of ½” polyiso under the absorber and tubing.

A few weeks ago I did some testing of the panel, I used an insulated cooler holding 12 gl, the pump is a computer cooling pump running about 1.50gl/min. I started at 9:30AM with 60* water and by 3:30PM the water in the cooler was up to 165*, it was a sunny day with a temps in the 70’s. I was quite happy with the initial results. Not bad for a $200 collector.

There is still a lot more work to be done, I plan to build another collector, get a differential controller, mount the collectors on the roof and tie them into the heat exchanger tank I am using for the wood stove water heater.

 

[bsearcey]

Very cool. I've wanted to attempt to build one of the, but just haven't really put in the effort. I've been watching a craigslist ad here in the Richmond area with a guy selling vaccum tubes for $25 a pop. Anyway good work and keep us posted.

 

[begreen]

That's a pretty fancy brake you have to work with. The results look very good. Is the copper pipe completely isolated from the steel stud frame to avoid galvanic reaction??

 

[Wallyworld]

Very nice, I've got one in the works also. Mine is going to hopefully heat my shop floor. 22 yards of concrete, a little over 1000 feet of pex and a 9 by 15 collector. 3/4 headers and 1/2 risers, covered by aluminum flashing. Thanks for link on the coating, have to look into that.

 

[WES999]

That's a pretty fancy brake you have to work with. The results look very good. Is the copper pipe completely isolated from the steel stud frame to avoid galvanic reaction??

Having a machine shop at work comes in handy. The copper pipe does not touch the metal frame, there is a rubber grommet where the pipe passes through.

I have more pics, for some reason, the forum would not let me post them. I will try again tonight.

 

[midwestcoast]

Nice. This would be a one day project for me. As in maybe I'll get around to it one day ;-P In the grand plan I take out a big part-dead Silver Maple giving a spot for solar thermal collectors to pre-heat DHW and supply some radiant for a small porch I'm getting starting to fix-up.
Keep us posted on your progress.

 

[WES999]

Very nice, I've got one in the works also. Mine is going to hopefully heat my shop floor. 22 yards of concrete, a little over 1000 feet of pex and a 9 by 15 collector. 3/4 headers and 1/2 risers, covered by aluminum flashing. Thanks for link on the coating, have to look into that.

Wow 9' X 15" collector, that's going to one heavy collector. Mine is 4' X 8' not exactly a lightweight.

Here are some more pics

 

[Wallyworld]

Very nice, I've got one in the works also. Mine is going to hopefully heat my shop floor. 22 yards of concrete, a little over 1000 feet of pex and a 9 by 15 collector. 3/4 headers and 1/2 risers, covered by aluminum flashing. Thanks for link on the coating, have to look into that.

Wow 9' X 15" collector, that's going to one heavy collector. Mine is 4' X 8' not exactly a lightweight.

Here are some more pics

Mine is being built on the wall on my shop( no picking it up), where I don't want it for DHW, I'm going vertical so when its winter and the sun is low I get heat(also no snow on the collector). In the summer when sun is high, I'll probably still get heat so I'll have to cover it.MY hope is it keeps the shop from freezing. I'm pretty sure it will but we'll see . I have 2 -3 by 8s on my house for DHW, work great

 

[peakbagger]

I realize that there is a level of "fun" and pride associated with building a collector from scratch, but do want to point out that unless materials are free, generally you can buy a collector made of equivalent materials for less than you can build one. The other plus with buying a SRCC rated panel is that the federal government will give you a 30% rebate which you cant get with a home built. Most homebuilt units usually dont perform as well as commercial units as the commerical units use Low E glass (not usually available to a homeowner) and the selective black coating on the absorbers is usually a custom process.

The good part about homebuilt units is that they still usually work pretty well (compared to homebuilt solar panels).

 

[midwestcoast]

"unless materials are free, generally you can buy a collector made of equivalent materials for less than you can build one. The other plus with buying a SRCC rated panel is that the federal government will give you a 30% rebate which you cant get with a home built. Most homebuilt units usually dont perform as well as commercial units as the commerical units use Low E glass (not usually available to a homeowner) and the selective black coating on the absorbers is usually a custom process."

Gary @ Build-It-Solar claims that his panel using AL absorbed fins & PEX tubing costs about 1/5'th of commercial units, that using copper tubing adds only a "modest amount" to the cost, and that a unit like WES999 built can get ~95% of the performance of commercial units. So where can we find SRCC rated panels for less than the cost of this one?
I don't get how Low E glass would help that much on a solar hot water panel since it would decrease energy xfer in both directions, but maybe I'm wrong. Also I thought there were more restrictions on the Fed 30% credit, like that it has to apply to a whole system that must supply at least X% of the hot water demand. That makes it tougher to take advantage of 'cause you have to shell-out for the whole system up-front instead of expanding over time with DIY components.
I'm not trying to flame, I have used several tax credits & would love to use this one, but my read is a good DIY is much cheaper in this instance.

 

[Wallyworld]

Any more news on your collector? I almost finished my piping system yesterday, got the pump and expansion tank in, all hooked to floor heat manifold and to the collector. Filled the system with air, find out if it held the air overnight in a little while hopefully it did. Now I have to finish wrapping the copper with flashing. Still don't have a differential controller, not sure what to buy?

 

[James Gautsch]

Wallyworld, you may want to check out this site for controllers. http://www.jc-solarhomes.com/

 

[WES999]

Take a look at this guys site: http://sites.google.com/site/mydtcstore/
I e-mailed him a few weeks ago, he said he did not have any ready for sale but he was working on it.
I am very interested in this unit, reasonably priced and has data logging feature.

I am waiting for some more heater hose to come in from Ebay, then I will try hooking up the panel to the storage tank.

 

[smokinj]

That looks as good as any I have seen......Great skill set you have there, Tie 3-4 of them in with a boiler would be very sweeet!

 

[Wallyworld]

Here is a pic of my collector in the beginning stages
added a pic of the interior piping

 

[WES999]

Here are a few more pics of the colletor and the heat exchanger. I am just starting to build the second collector.
The plan is to mount 2 on the roof.

 

[Wallyworld]

Take a look at this guys site: http://sites.google.com/site/mydtcstore/
I e-mailed him a few weeks ago, he said he did not have any ready for sale but he was working on it.
I am very interested in this unit, reasonably priced and has data logging feature.

I am waiting for some more heater hose to come in from Ebay, then I will try hooking up the panel to the storage tank.

That looks pretty cool, thinking I could build that pretty easily from his kit. I'm using 120v pump though so I'd have to get a cube relay or something to run the pump with.

 

[WES999]

Take a look at this guys site: http://sites.google.com/site/mydtcstore/
I e-mailed him a few weeks ago, he said he did not have any ready for sale but he was working on it.
I am very interested in this unit, reasonably priced and has data logging feature.

I am waiting for some more heater hose to come in from Ebay, then I will try hooking up the panel to the storage tank.

That looks pretty cool, thinking I could build that pretty easily from his kit. I'm using 120v pump though so I'd have to get a cube relay or something to run the pump with.

I don't think you would need additional a relay, look at the specs, he has 2, 10 A relays for the pumps, I will probably use a 120 vac pump too.

 

[WES999]

Update, the system is operational :coolsmile:
Last weekend I tied the solar panel into the DHW heat exchanger/tank.
The system is far from optimum, there is only one collector (I plan to build another), it is not mounted on the roof where it will receive more sun,
the hoses are not insulated, no differential controller, and the tank is only partially insulated.

Even with these shortcomings the temp in the tanks (50 gl ea) at the end of the day (6:00 PM when I get home) has been between 95 °F - 99 °F. Right now I am using a basic temp controller that has a thermocouple attached to the collector to to turn on the pump at 105 °F , this seems to work OK but a differential control would probably work better.

So far the results are encouraging.

 

[begreen]

Nice going. This is really starting to come together. Congratulation! Is the whole system plumbed with PEX?

 

[WES999]

If you look closely at the pics you can see the brite red is PEX, which is for the heat exchanger, the pink hose is 1/2" ID automotive radiator hole which is the supply/return for the collector.

 

[WES999]

Another update, last week I installed the collector up on the roof.
I spent some time thinking how to get the collector hauled up on the roof, I didn't have much luck with alien levitation technology, so I settled on the inclined plane and ropes and pulley. I used a rope with a pulley tied to the bumper of my truck on the other side of the roof, I tied a rope to the collector and pushed the collector/pulled the rope to get it up on the roof.

My roof faces about 140* SE and has a 30* pitch, affording to http://www.roofray.com/calculators
about 80% solar potential, not too bad. The collector gets a lot more sun up on the roof than sitting on the ground
leaning against the wood shed.

Over the last week the tank has been running 105 °F - 110 °F . Today the pump came on at about 8:30 am,
the tank temp is 105 °F and the collector temp is now 135 °F .

I still need to insulate the lines and finish insulating the tanks.
I am going to build a simple differential controller like this one http://www.jc-solarhomes.com/differential_thermostat_kit.htm
I have most of the parts already.

 

[Bad Wolf]

I found this on CL. http://hartford.craigslist.org/zip/1849258369.html
If I didn't already have 9 uninstalled panels I'd be all over it.
Over the years I've seen several similar postings for free or cheap panels from homeowners that have no interest or can't make them work.
My first 6 were free (3'x7') and the next 3 were $10 each (3'x6')
If you are getting that kind of performance from one panel I might actually do pretty good with 6. (the smaller 3 are for the pool)

 

[Wallyworld]

So I bought the DTC controller. Not sure how its going to work but I used hyper terminal and a serial cable and talked to it from my laptop. Set the parameters and it turned the relay on at the setpoint. Got the data logging setup, all I have to do is get the glazing on my collector. I used flat black barbeque paint for the coating on my collector. made a 15 degree difference from the shiny aluminum flashing to the painted blk flashing. Need to order the glazing and get the controller set up. Think I'll still use a cube relay, must have one kicking around somewhere, that way I keep low and line voltage separate as much as possible. Still have a few months to put it off though

 

[WES999]

What do you think of the controller so far? I am thinking of getting one my self.
Seems like a great value, more features and less money than other controller out there.

BTW if anyone is interested Gary at builditsolar.com put up a nice write up on my system,
read about it here:
http://builditsolar.com/Projects/WaterHeating/Metal1K/Metal1K.htm