A Homemade Solar Water Heater

For one Florida family, it made more sense to build a homemade solar water heater before they actually had a home.
By William J. Weber
September/October 1979
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The homemade solar water heater enables Bill and his family to clean up at the construction site, because he built the heater before he built the house!
PHOTO: WILLIAM J. WEBER
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Last summer my family and I started digging out the foundation for our new home. However, after only two sweaty days of laboring under the Florida sun, I realized that we might be going about the whole project in the wrong order. Maybe, I thought, we should erect the solar water heater and shower — which we'd already planned as part of our new homestead — before constructing the house! Well, the more I considered this notion, and the more layers of grime built up on my tribe's bodies, the more that bit of backward logic began to make frontward sense.

As you can probably imagine, the whole family clapped and cheered when I proposed my topsy-turvy suggestion to them. So I sat down to research the current literature on solar water heaters. I studied every book and article I could find, but ended up more confused than educated! All the plans called for elaborate pumps, sensors, control switches and other complicated paraphernalia.

(Oh, I did learn one thing: we sure weren't going to buy a heater. Some of those commercial solar units cost over $2,000!)

It took a lot of time and sifting, but I finally devised a simple and inexpensive homemade solar water heater that I knew "us regular folks" would be able to build. In fact, my design involves only three steps:

First, build a glass-covered wood "hot box" to catch the sun's heat.

Second, install a manifold of copper water pipes inside this collector box so the gathered warmth will heat water.

Third, hook the outlets from the manifold to a storage tank (this container should be set above the heat collector) so the thermosiphon principle will move water from the collector to the tank. (That fancy-sounding phrase, "thermosiphon principle," simply means that, since hot water rises and cold water sinks, liquid heated in the closed loop system will move up toward our elevated storage container, while cooler water will circulate downhill toward the collector to soak up more sun.)

Glass, Wood, and Copper

We initially planned to construct a 48-by-96-inch collector box, but quickly scuttled those dimensions when I learned that a sheet of glass large enough to cover such a container would cost over $60! That price tag forced me to do some rethinking and to come up with an economical solution: I decided to make panels out of old aluminum awning-type windows! Several of the discarded 15-by-34-inch glass rectangles were lying around our homesite, and I was able to scrounge up a few secondhand panes for $1.50 each. Then all we had to do was adjust our collector size (we made it 34-by-90-inch) and line up six windows in a row to get $60 worth of glass cover for less than $9.00. (Besides, the lightweight aluminum units are a cinch to install and would be easy to replace from standard sources of supply if broken.)

A plumber friend gave me an old water heater to use for our storage tank, and I was able to "scavenge" all the black plastic pipe and odd fittings I'd need to connect all my units, and plenty of nails as well. Still, try as I might, I couldn't get around shelling out hard cash for my wood and copper materials.

The lumber costs weren't too severe. In fact, I bought all the wood I needed for the box's sides and support pieces, plus two sheets of styrofoam insulation and one of pegboard Masonite, for a very reasonable $25.59.

Our project did require one "killer expense," though: copper. I didn't want to spend any money I didn't have to, but I also figured that the outlay for our conducting medium was no place to cut corners. Copper is incredibly efficient at absorbing and releasing heat. And any less expensive collector material would have given us a "temporary gain but a permanent drain."

So, to build the manifold, I bought three 20-foot lengths of three-quarter-inch copper pipe, two rolls of 50-50 solder, one can of flux, and numerous fittings. That added up to an admittedly not inexpensive $75.72. (Of course, half-inch pipe and parts would have cost less, but such smaller diameter lines are too restrictive for good thermosiphon flow.)

I also paid $45 for a large 12-gauge copper sheet, which became the main "heat catcher" inside the box. This material is commonly sold in a 36-inch width, so, rather than cut off two inches of copper to meet my 34-by-90-inch requirement, my local sheet metal salesman kindly bent a one-inch border along each side, which made the piece both more rigid and easier to fasten.

To Work, To Work

At last we were ready to build. We made the 34-by-90-inch (measured on the inside) frame from two 12-feet long 2-by-6's. This rectangle had 2-by-2's spiked along its sides and 2-by-4's at its ends to support the collector plate. An extra 2-by-4 was nailed across the middle of the box as a brace. Then we covered the frame's "bed" with a piece of one-eighth-inch pegboard Masonite and two sheets of heat-holding Styrofoam insulation.

Next we started on the main task: welding our copper pieces together. The first stage of this "penny metal" work involved constructing the pipe manifold, a "jail-door" structure that had four "bars" inside a frame-fitting rectangle. (Since each interior pipe section had to be fastened to the top and bottom pipe lines by three-quarter-inch T's, we did a lot of cutting and soldering at the manifold's ends.)

After that job was done, we laid the $45 copper collector sheet on a level concrete surface (so the heated material wouldn't warp) and brazed the manifold to this backing. Then we put the pipe-to-sheet assembly in its wood and Styrofoam frame bed, soldered the supply, discharge and relief valve lines in place, and topped the finished structure with the six awning windows.

A Trying Moment

To test the airtightness of our manifold, we plugged the collector's intake line, attached a garden hose to the top outflow opening, and trickled water into the pipeworks until air quit coming through the relief valve outlet. Then we tightened up the release mechanism, opened up the hose spigot and let 'er have it!

Sixty pounds of water pressure rushed into our lines. The pipes held for about ten minutes, then a small trickle started running down the collector, so we drained the conduit and resoldered the leaky seal. We left the equipment under pressure all night for its second test, and — thank goodness — when we examined our "sun catcher" the next morning, not one drop of H20 had escaped.

Hot Times

The last construction steps were to paint the collector sheet and manifold flat black, coat the exposed wood with a protective oil-based covering, set the water heater in place (at a 45 degree angle), attach the storage tank and rig up our outdoor shower.

That was that. For about $160 in materials, we'd built a solar heater that now gives my whole family an abundant supply of free hot water. (In fact, we actually had to add a cold water line to our shower stall to keep from getting scalded on especially sunny Florida days!)

Now I'll admit that our fresh air facility does look kind of silly perched by itself on the side of a hill, but we're all as blissful as bluebirds over our outdoor showers. After all, it may take us more than two summers to finish our house, but we're enjoying the pleasures of sun-heated bathing right now!


Bill of Materials

Lumber

(2) 2" x 6" x 12'              $6.30
(2) 2" x 2" x 8'                1.50
(1) 2" x 4" x 10'               2.31
(1) 1/8" x 4' x 8' pegboard     6.98
(2) 1" x 4' x 8' styrofoam      8.50

Copper

(1 ) 36" x 90" 12-gauge sheet  45.00
(3) 3/4" x 20' pipe~ type M    52.20
(11) 3/4" T's                   6.50
(5) 3/4" L's                    1.50
(3) 3/4" male adapters          1.32
(2) rolls 50-50 solder         13.02
(1) can solder flux             1.15

Miscellaneous

(6) l5" x 34" awning windows    9.00
(1) relief valve                4.50
(2) metal insert adapters       1.50
Total Cost                   $161.31

EDITOR'S NOTE: While we congratulate Bill for his clever design, and acknowledge that Mr. Weber's homemade water heater is perfectly suited to his family's needs, we should also add that his device won't be appropriate for everyone because there's no feature in Bill's collector to keep the water in his pipes from freezing! Since such a mishap would obviously damage the unit, any folks who want to copy William's ideas, yet live in colder climates than the Floridian enjoys, should include some method of preserving their pipes. 

One solution to this dilemma would be to use Bill's solar collector in the summer and a wood-burning stovepipe system in the winter. This approach is explained in "Use Your Wood Stove as a Water Heater."  

The most common "collector-protector" technique, though, is to install a heat exchanger in the storage tank so that fluid coming from the collector warms water in the tank but remains, itself,  within a closed heating circuit. The sun-grabbing liquid in this sort of rig can be mixed with antifreeze to protect it from bitter weather. Two examples of the method are discussed in [1] "Doyle Akers' $30 Homestead Solar Water Heater" (Doyle used salvaged air conditioner coils to build his exchanger), and [2] "More Ways to Recycle Old Refrigerators Into Low-Cost Solar Water Heaters" (MOTHER EARTH NEWS' researchers recycle a gas-fired hot water tank into an efficient heat exchanger. The article also displays a passive no-heat-exchange unit that our inventors designed. This particular model is protected from frostbite because it can be closed up at night!) 

Several examples of direct heaters that, like Bill Weber's model, are inexpensive do-it-yourself solar devices but don't have any freeze protection appear in "The Khanh Solar Water Heater,"  "Build a Simple Solar-Heated Shower," and "Recycle a Refrigerator Into a Solar Water Heater. 

Lastly, a good explanation of the solar thermosiphon principle can be found in our interview with David Wright. 


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Post a comment below.

 

jake_13
1/19/2010 7:50:01 AM
I recently made a solar water heater. It cost $300 and has no moving parts. I also came up with a $30 electric backup system for cloudy days. It heats water to 135F (55C) on sunny days in a 80 gallon (310 liter) tank. Blog post: http://www.teaters.com/modules.php?name=News&file=article&sid=217 Video: http://www.youtube.com/watch?v=KOY49bH7Ocg

aadhar_1
10/23/2009 9:52:23 PM
I was wondering if this solar water heater can be adapted to heat water in a 800 gallon water tank?http://besthomemadeenergy.com

Peter_2
2/17/2009 1:10:44 PM
My own collector invention is a similar framework but using a network of CPVC tubing attached to it and imbedded in just enough cement to cover the tubes. The cement is black of course. Very inexpensive and plenty hot. Glass is optional but will probably keep things hotter, your choice. The answer to our energy needs is there every day in the sky.

Charlie_3
10/26/2008 11:32:42 PM
I live in the Caribbean, so I don't have to worry about freezing pipes! We more worry about water rationing. I was wondering if this solar water heater can be adapted to heat water in a 800 gallon water tank?

Eddie Herrington
10/10/2008 7:30:09 PM
My calculations showed that I saved $182 this month on utilities compared to the same month last year. What I did: 1. tinted all of my windows in my manufactored home. 2. Two of my skylights were sprayed with water and I put bubble pak on them (four layers acting as insulation)The water spray sort of glues the bubble pak to the glass. This allows the light in but keeps the heat out. 3. Since I only use my A/C unit in this hot desert of AZ I used styrofoam as insulation in all of my cieling H2O cooler vents, and plastic store bags to seal any drafts in the vents. I removed the swamp cooler, insulating and covering up the hole with a sheet metal cover. 4. changed all lite bulbs to CFL's. I only use one light at a time, makes no sense to lite up the whole house. 5. set my thermostat two degrees higher than last year (to 81 degrees) 6. Turned my gas hot water heater down to vacation mode (still hot enough for me). I wash all of my cloths in cold water. All of this came out to about $150 investment. Not too bad of an investment, better than anything else I could invest in. During this winter I hope to have built a solar H2O heater. I'm open for suggestions and do subscribe to Mother Earth News. Eddie

Chief_1
8/11/2008 9:27:57 AM
I am considering using this type of system to heat a hot tub. We don't worry about freezing as much as over heating. A good summer day here is 100++. Like the idea of using an old patio door-safety glass)Could I use a small pump to move the water?

miguel z. montes
7/19/2008 7:32:31 PM
Se me hace muy interesante los conocimientos que ponen a disposición para elaborar un calentador solar : y en base esta información voy a eleborar uno usando los siguientes materiales 1.-madera para formar el cuerpo como aislante 2.-tuberia de pvc color negro diametro de una pulgada para formar el colecctor. 3.-placa de vidrio frontal de 3 mm 4.-El boyler de 40 galones lo voy a usar como tanque de almacenamiento de agua caliente 5.-el solar collector lo voy a poner en la azotea conectado directamente al tanque de almacenamiento de agua fria. Si alguien tiene experiencia en hacer celdas solares fotovoltaicas agradecería mucho me orientara a mi correo electronico mmmmontes16@gmail.com

charlie beaubien
7/18/2008 2:14:29 PM
In 1931 when the last Doble steam car was built it was refined to the point where it was a very good and dependible car. Why is it that today there over 70 years later there is no intrest in this field with multifuel applications such as wood coal, and anything that burns could be used as fuel. If there is someone out there who is intrested in a venture of this nature bearing in mind a knowledge of steam principles is necessary just let me know because I would like to participate in a venture of this nature. C Beaubien ( cctb990@yahoo.com)

Arne
7/9/2008 5:22:17 AM
I am interested in the cheap water-heater - but are there anybody who have any idea of how to put the heat collector on a tripod with a unit so I can track the sun?? Arne

RH
7/5/2008 9:46:03 AM
I am curious why the water heating tubes are not set up as a serpentine, or one long back and forth tube? It would seem to bring a higher end temperature to improve the thermosyphen which would also allow a second "water heater" storage container for high use periods and cloudy days. If one of the "hot water" storeage tanks were an old gas water heater a wood fire box could be built under it for winter water heating and the resultant smoke from the gas water heater simply pipped away to the outside.

Tina Knight "Wurtinger"
7/4/2008 12:03:53 AM
My father used a similar method back in the 1980's to help my grandparents with heating costs. He used aluminum cans. He said they were narrowed at one end in the 80's. He just fit them together like tubing. He said he isn't sure if they still are or not, he hasn't taken the time to notice.

Dan_1
6/29/2008 2:24:51 PM
The author says he used 50\50 solder, which implies 50% tin and 50% lead. Lead is no longer allowed to be used in soldering plumbing connections because of the health hazard, at least that is what the experts say. You have to use a lead-free solder on the connections, available in any plumbing section of a hardware store.

Penny_1
6/25/2008 10:11:30 AM
I wonder if your researchers could rate each system of water heating, solar panels for houses, etc., not only for 'best design', 'ease of making', etc., but also according to geographic/weather areas. Up here 30 miles equidistant from the North Dakota and Mannitoba, Canada, border in Minnesota, we've 120 degree fluctuation every year. It is difficult to determine which methods and products would be not only the cheapest (DIY) but also the most hardy.

Dan Ankrom
6/23/2008 11:17:28 AM
You can improve ease of assembly and durability for your collecter box by using a discarded Patio Door pane (It's REALLY hard to break these, and when you do they crumble into glass 'gravel' instead of dagger like shards). I actually ended up with more than one of these when i scavenged glass from the debris lot of a small window replacement business. They WANT to get rid of this stuff, too -otherwise they have to pay for it to be hauled away in a dumpster! (you can also gat decent used 2x4's and such). You end up with a large, durable, one piece collector box lid. Also, the toughness of these pices of glass made me think "glass bottomed boat", bu that's another project....

tipster
11/23/2007 10:10:18 PM
Kudos to you for making this. One tip that will improve the performance will be if you position the connections on the inlet and outlet headers on opposite corners. If they are as you have it (middle of each header) or positioned on the same side then the tubes nearer the connections will have slightly higher flow while the others will have lower which will affect the performance. If they are positioned on opposite corners then the distance along any tube between the inlet and outlet will be equal and therefore provide a balanced flow and therefore more even heat and better performance. For this reason a commercial hotwater panel has the connections in opposite corners of the panel.

Heidi Hunt_2
7/10/2007 11:09:28 AM
The illustrations are in the Image Gallery at the top right of the article, under "Related."

mama_1
7/10/2007 10:30:55 AM
the article was good only if u could include photos coz there might be some of us who want to build a solar panel ourselves..so ud be giving us god ideas

Max_7
3/21/2007 9:57:16 PM
One problem with solar water heating is that the system is either underdesigned in winter, or over designed in summer. Why not accomplish not just water heating, but also space heat and air conditioning with the same system? Find out how in my blog. Max www.energy-guru.blogspot.com








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