Thermosyphon Solar Water Heater

[Jay64]

I have been doing a bit of searching for ways to help my mom cut her $500/month (she has multiple houses on her property) utility bill. It looks like one of the easiest things to do is to build a few Thermosyphon Solar Water Heaters for her houses. She lives in Hawaii, so she gets really good sun most of the year. I've seen quite a few DIY sites, this one seems to give quite a lot of info.
http://homepower.com/view/?file=HP58_pg30_Bocci

basic_layout.JPG (132.43 KiB) Viewed 772 times

I am planning on doing a few yard mounts, basically a little lean-to with the slanted side being the solar thermal collector and the box housing the tank. Since she a collection of small 200 sq/ft buildings next to each other as her "house" with the bathroom already being a separate building, I was also thinking of making a shower house for her. Something less than 200 sq/ft, that has the roof slope to the ground on one side at about 30 degrees. That side will have the solar collector, under it will be the tank, and the rest of the room will be a big shower room. In Maui, structures under 200 sq/ft don't need building permits.

So, I've been mulling this over in my head and searching a lot. Thinking that one day when I have enough for the materials, I will put one together to test some things out. Then, today on the way home from the post office, I pass a house that has 2 huge glass panels leaning on the tree out by the curb. I check with the home owner and get his blessings to haul them away. They look like they are probably from a sliding glass door or something. I have read that there are other types of glass that are better for efficiency, but you can't get much more efficient than free. I had figured that the glass and the copper pipe would be the most expensive parts of the build, so this is going to be a huge aid in getting them built on the cheap. So now I'm inspired to get the rest of it built to start doing some DIY testing.

[spinningmagnets]

That glass will work just fine. Also, polycarbonate will work too, and its a common mistake to buy cheap plastic glazing that ends up warping.

The best site for info on this is builditsolar.com
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

[Jay64]

I have gone through that build it solar site, I believe that is how I found the link I listed above. Definitely lots of good info. I didn't go through it again right now when you posted it, I just browsed it to see what it was. But in that quick scan, I think I saw some other plans for something similar to this, so I will go and check that out too.

[Jay64]

Unfortunately I didn't have my gloves in my van when I passed by and grabbed them. but the edges didn't seem sharp, so I just grabbed them and loaded up. But by the time I was finished my hand was covered in blood.

I guess the weight of the sheets pushed the slight edge into my finger. Didn't hurt at all, in fact I didn't even notice until I saw a puddle of blood on the cardboard under the sheets. I always have a roll of paper towels right by the back door of the van where I was standing, but I didn't have that either. I didn't want to get blood everywhere on the drive home, so luckily I had a box of latex gloves sitting right there and was able to put one of those on for the ride home till I could clean it.

[Jay64]

I tried to put pics up earlier and it kept failing, so I only put the one up. I'll try more again.

This is the break down of the layers.

assembly.jpg (204.85 KiB) Viewed 760 times

[Jay64]

Here is an idea of what I want the "lean-to" for the yard mount to look like.

yardmount.JPG (226.24 KiB) Viewed 760 times

[Jay64]

This is a very quick/rough photoshop to get the idea of what I would want to do with the "shower house."

shower_house.jpg (211.16 KiB) Viewed 760 times

[CrazyJerry]

Jay64,
As you probably guessed, the magic is really in the collector. I completed a solar hot water shower last year. The collector is an old fireman's field day beer cooler. Inside the cooler is about a 65 foot hose coil. This thermosiphons up to a 22 gallon tank in a box with glass top. This things gets all 22 gallons steaming hot - I can't imagine the heat you'll get with a collector like you've shown. Good luck!
http://diesel-bike.com/Solar_Shower/Solar_Shower.htm
~CrazyJerry

[Jay64]

Sorry, for the misunderstanding. Like I said it was just a very quick photoshop job to sort of give an idea of what the building idea would be like. I just took a pic of a shed from some plans I had and modified it so that the roof came all the way to the ground. That is the roofing material being shown, not the collector size I had in mind. I didn't put a collector on the pic. I was going to wait to see what size water tank I could get, probably a 40 gal, and I will build the collector according to the final tank size.

[Alan B]

We had a commercial thermosiphon system some years ago. Two things different from your sketch:

1) There was a tempering valve that would mix cold water with the water coming out of the tank if it exceeded a set temperature (such as 160 degrees). Otherwise it could generate hot water that exceeded user expectations, creating a hazardous situation.

2) there was a thermostatic valve at the bottom of the panel inlet that would bleed water on the roof below 40 degrees. This way water would keep the panel from freezing. Perhaps not necessary in Hawaii, but the temperature looking into the clear night sky can be quite cold.

One problem with a system like this is when something goes wrong it may not be obvious how to operate the valves and safely shut it down. We had one failure of the low temperature valves and I drained the system and bypassed it until I could get new valves. When procuring them the solar place told me that a school district with many systems had a similar problem but failed to drain them and they ruined all their systems at once due to improper understanding of taking them offline.

So I would recommend a written procedure that could be followed to take the system offline and drain it safely to protect it. The panels may need to be covered as well to prevent overheating without water.

The system worked quite well, though it was not worth what it cost to buy and have installed. Of course if you build it yourself it might be worthwhile.

We had two panels and each panel had a storage tank. They were in series and then fed into the regular water heater. So the water heater rarely needed to run anymore. All it could save is what it costs to run a waterheater.

[Jay64]

I'm sure I could build them for less than $500 with buying a water heater. I'm going to size it with a calculation of 2 gallons of water heated with each square foot of collector.

[Alan B]

How long will $500 worth of gas run a good water heater there?

[Jay64]

Well, it wouldn't be $500 of gas if some of that money had to be used for buying the water heater. I'm pretty sure I can build it for lot less if I find good deals, like scratch and dent heaters, used glass panels like I found today. And I guess I would like to use something I build even if it was the same amount of money that I would have spent to the utility company. And they also have a hot tub that uses a lot of electricity. I could build a thermosyphon collector that goes right into the hot tub and the tub would be the storage tank.
Oh, and it doesn't get anywhere near cold enough to worry freezing temps at her house, even in the dead of winter, up in the air, in the middle of the night.

[nechaus]

http://www.youtube.com/watch?v=00vIoTPJNtQ

redneck pool heater