Instructables
The goal: Build a passive solar water heater to make the frigid water in the public bathroom less shocking to the human body. It needs to be a closed loop system because it freezes where we are a few times a year. Having water run through the collector will freeze the sitting water in the winter month nights and apparently scald hands in the summer months. 

The background: We know a solar water heater can be made, but making it work everyday without requiring constant adjustment and fiddling is the tricky part. I'm lucky, my mother owns a hardware store (awesome place to grow up) and she decided to fund the project. She let me build it at the store and agreed to deal with the ridiculous time line I often fall into on pet projects like this. This will be installed to provide warmer than ice cold water to the hardware store bathroom and will only really be used for washing hands and cleaning etc...

I've broken the project into three phases:

1- The Collector: A heat exchanger that will collect the sun heat energy and efficiently transfer it to whatever fluid media we end up using to carry the heat to our desired location.

2- The Emitter: Yet another heat exchanger that will deliver the heat from my carry fluid to the water the end user will come into contact with.

3- The Install: making it all work as maintenance free as possible... probably the hardest part.

This 'ible covers Phase 1. I will not be as long winded in the steps as I was here.
 
Remove these adsRemove these ads by Signing Up
Kraplax2 months ago

I know the cllector box is sealed, but if it's still possible to open it - i would suggest adding a light reflective film to the back of the box itself. I am not sure, but i guess heating the box itself doesn't make much sense, but reflecting the light to heat the backside of the black painted pipe seems quite reasonable. I have no experience and have not yet built any sun collectors, but you did and you can experiment with it :)

Excellent project, I must say! I feel inspired to try something similar.
Although I am curious about a couple of things:
1.In what season did you test this and where is your geographical location?
2.What diameter copper pipe did you use?
3.Since this solar collector does not have an absorber plate, how do the pipes heat up primarily? Is it through the absorption of thermal radiation or conduction of heat from the warmed air trapped behind the glass?
Thanks!
Mak5 (author)  Chicken of Steel1 year ago
Thanks for the feedback.

1. Early August in El Paso, Texas right on the US/Mexico border.
2. 1/2"
3. Good question, both are at work; but I'm not sure which method of heat transfer is carrying the load. I'm thinking it's convection from the air...
Great job, really surprised it came out so hot. I know you said your mother funded it but is there a solid bill of materials and any way to know about how much this all cost?
Mak5 (author)  Disasterpeace1 year ago
Thanks for the compliment.

Unfortunately, in my haste to build I did a poor job of recording what I was doing as I went. I would think I can probably build a pretty accurate BOM from the photos.

Good call, I'll do that and update the thread.
wing1 year ago
Mak, great writeup and workmanship!

One quick question tho: wouldn't it be more effective to connect inlet of the collector with an outlet at the bottom of bucket and outlet of collector in the top of bucket? this way, when rising the bucket a little higher than the collector, natural circulation should do the work. And also, due to the fact that you would take the cold(er) water from the bottom of the bucket to be heated, it should prevent the problem with the vapor lock (well, at least til the whole bucketfull is boiling :) ?
Mak5 (author)  wing1 year ago
Wow its been awhile since I've been on here... Really appreciate the feedback. Apologies for the late reply.

You might be correct, I think there are likely a number of things that could be improved during testing. Your idea is probably the first place to start.

I still have the the collector sitting in my garage, maybe some day ill pull it out and do some more testing.

Again, thanks for the feedback!
What are the dimensions on your box and how long did you cut the length of your pipes?

Have you done further testing to on this hot water heater? Does it work?
Horsehockey2 years ago
I would like to comment about using the glass to cover the collector.
If you look at the edge of a piece of glass and it is a light green color, the glass contains some iron. The iron cuts down on the suns heat transmission. Clear glass lets the infared thru. Also when you seal the glass to the wood box , eventually you will get moisture trapped in the box.
While studying the coverings for collectors several years ago I found that Visqueen (trade name) plastic sheeting allowed more of the desireable infared rays into the collector. I used 6 mil thick sheeting. An added benefit was that the collector needed to be cleaned of dust periodically. The plastic sheeting was cheap and replaced when the dust was cleaned out..

Now that you have constructed a collector capable of producing steam, carry your experiments a little farther. Absorbtion refrigeration systems work on heat. An example is refrigerators in campers operating on propane.
At one time Absorbion refrigeration was popular in the south for airconditioning homes. Industrial plants use large absorbtion systems operating on steam to cool their office spaces. Carrier makes 100, 200, and 300 ton units. Several companies made units for homes. Bryant, Arkala, Servel, and two others were popular brands. Their airconditioning units worked fine. Their problem was in the servicing. The units were sold thru Natural Gas and Propane suppliers and their heating techs didn't know how to service the absorbtion systems. I attended a very large Solar Expo in Phoenix several years ago and the Japanese had absorbtion units on display that operated on solar collectors. Google Absorbtion Refrigeration to find out more.
You are to be commended for your achievements. The Instructable is well written and your pictures are clear and informative.
Mak5 (author)  Horsehockey2 years ago
Thanks for the feedback and the history lesson.

As for the covering: there are definitely better light transmitters out there. I was limited to what was on the shelf (built and tested in less than two days) I chose glass over plexi for light transmission and for it's durability to the sun. Plastics will often break down very quickly under UV exposure. Not sure how the Visqueen is UV rated.

Sealing the box: hindsight is 20/20 on that one. As you can see in the test photos the moisture trapped inside the box condensed on the glass covering. It was interesting to watch- the second I turned on the water hose and allowed cold water to flow through the coil the heat was immediately sucked out of the air in the box and the condensation was completely gone. It was a physics/thermo experiment all it's own.
EmcySquare2 years ago
HINT:

Why not save all that effort and money and simply repurpoue a discarted fridge radiator?
Already designed for that purpouse, already black, adds extra blades that allow better heat exchange...
;-)

AFAIK they don't work very well for this, fridges don't need so much heat flow, whereas with solar you need a kilowatt or so.
Awesome build! I look forward to seeing the other parts. :D