Thermosiphon...

As we enter into the age of Aquarius... things begin to flow as they never did before.

thermosiphon...

I am going to be fleshing this thread out over the next several weeks/months. I will be sharing with you my learning experiences on the subject of thermosiphon. I have built several thermosiphon systems from scratch; with all of the associated mistakes, cost over runs, and mishaps of R&D.

Topics I intend to cover:

the hot water chimney effect
check valves
speciality diverter t's
tempering devices
passive hot water
passive absorption refrigeration
positioning the system
woodstove water heating
solar water heating

I encourage you to post your personal learning experiences and links on the subject.

For those of you new to the term... thermosiphon is the tendency of warm liquid to circulate to the surface of a body and for cold liquid to go down in its place.

Using the power of the sun, I am becoming quite proficient at heating the conventional 40 gallon domestic pressurised hot water tank; and you can too!

Please visit my signature for a few starter links.... I have to get back to the torch... there is tinkering to be done on the system.

also:
The Ecotope solar water heater manual
caution 10megs pdf

www.aidg.net...


and...

absorption refrigeration
www.limsi.fr...

Hot is on the left.
Cold is on the right.

Poop may flow downhill,
but hot will always flow uphill.

Plumbing in the new paradigm...

I am,

Sri Oracle

[edit on 24-3-2008 by Sri Oracle]

The Hot Water Chimney Effect

This thread is not to be a passive solar 101 but rather a passive solar 201... I kind of expect you to come to the table with some understanding; and questions.

So you have a tank in your house and a solar panel outside. The tank is situated above the panel and you have lines running to the appropriate locations...

but no thermoflow.

hrmm...


Think of your solar collector like a wood stove...and the water flowing inside like the smoke flowing out of the stove.

One thing I have realized that has made the world of thermosiphon clear is that the "pump" of the system comes from a well designed solar collector exhaust; that is, the hot return to tank.

Simply plumbing your panel exhaust to your tank hot connection using the "easiest" route possible will NOT produce thermal flow.

My systems all heat 20-40 gallon tanks and I usually use 1/2" copper lines to connect everything together... except for the exhaust riser, for which, I use 3/4" copper.

The exhaust riser, aka solar panel out, is your "hot water chimney" and you want it to be a strong flowing pump. The idea is to get the natural thermal heat rise to propel your water upward.

Immediately upon leaving the solar collector the exhaust riser must pitch upwards and continue pitching upwards until it is above the top of the hot water tank. Doing so allows the system to capture the flow of heat and create a flow of water. At its peak it can then extend towards the tank horizontally... a distance no greater than twice the total rise for straight shot horizontal runs. All vertical piping on the exhaust end I keep in 3/4... when it reaches the top of the "hot water chimney" I convert to 1/2 to increase flow rate during the horizontal run; thereby decreasing heat loss.

Again, out of your panel: VERTICAL FIRST... horizontal second.

I find it best to just run straight up with my exhaust riser... although I have found that a pitch of 1 inch rise for every 10 inches run will work effectively. This is much steeper than one would pitch conventional sewer drain lines, where 1 inch of rise over ten FEET would be sufficient. Bottom line, the steeper the better. You are fighting the tendency for heat to rise right through the wall of your pipe; which is why an immediate vertical run makes the best pump. All of your piping should of course be insulated.

You'll find that at the top of your water heater you have more connections and valves than a "conventional setup" all this additional metal will act as a heat wick and draw energy out of your tank. I usually insulate this cluster of valves and pipes with a laundry basket worth of old rags, towels, and sheets... much more effective than lots of little pieces of "conventional" foam pipe insulation; EVERY HOT WATER TANK...conventionally heated or not... IMHO should have a blanket over top of it to conserve energy. Does yours have a blanket? Is your meter spinning? Go give it a blanket; its chilly for a 125 degree warm blooded body.

The cold return from the bottom of the tank to the bottom of the solar collector can be 1/2... this return is like the air intake on a woodstove and needn't be as wide a diameter as the exhaust.

In future designs I will be experimenting with a 1" riser and 3/8 soft copper horizontal and return lines. I expect the 1" riser would capture more of the thermal flow. The 3/8 return lines should speed the water along faster on the horizontal runs so less heat is lost in transit. Using soft copper return lines will also eliminate many of the 90 degree elbows which should increase flow. On my most recent system I have opted for double 45's in place of elbows for this same reason.

Those are my thoughts for today... I'll be back with more.

I am,

Sri Oracle

[edit on 25-3-2008 by Sri Oracle]

Sri, just when I'm thinking I'm going to take a dislike to you, you got do something practical ! .

Seriously, I think the 'end of the world' types have got it wrong. We're heading into rough economic patch that's will shake modern human civilization to it's foundations.

That said, every joule of energy that a person can harvest from the sun will keep a lot of hard earned coin in their pocket. I amazed how many folks don't see this. It's damned amazing what a few billion dollars worth of investment in energy saving devices like your water heater could to cut back on overall US energy demand. The average US home doesn't need marble tile entranceway or designer kitchen as much as it needs a solar powered lighting and water heater.

Do you read Homepower?

Originally posted by crgintx
Sri, just when I'm thinking I'm going to take a dislike to you, you go do something practical ! .

Do you read Homepower?

You'd be surprised how much practical stuff I do on the daily... I've got acres that I keep green; 5000 sqft of pre-1920's structure to tend... turbines, solar panels, gasifiers, and absorption fridges in the works.

I do read homepower from time to time... and motherearthnews... mostly back issues.

Much of my research I do online... this internet is a great thing while it lasts... Other than that... I fiddle... meditate.... fiddle.... meditate.... fiddle... meditate.... fiddle... until something starts working like its supposed to.

I do think there will be an "end of the world" but I agree with you that most have it wrong.

The end of the world to me will come as society is divided into 2 groups:

Those that can effectively make use of what is flowing down the river, dug up from the earth, or shining down from the sun...

...and those dependant upon what they can buy with currency.

This seer foresees a dismal future for the corner store junky.

If you are interested in the subject of non electrical use of solar, do a google search on:

larry hall icy ball
isaac refrigerator

there is a thread I started on "carbon methanol absorption" here on ATS... I'll have to find it.

I'd rather dance in the rain than fret over whether we will survive the storm.

I am trying to get my rental properties off grid... the biggest challenge is obtaining financing and insurance for an "off grid" structure... you'd be surprised how difficult it is to insure an old house with wood heat and solar hot water. That all seeing eye just doesn't seem to like the movement; couldn't imagine why....

Sri Oracle

Hey great to see people are still talking about the hot water system from the wood stoves.
Got a question for you maybe you can help. We have had a thermo-siphon system for about 20 years works great! Last year we bought a new stove, same brand etc, but opted not to drill the holes in the stove and try them on the outside first. We looped it on the side and around to the front then back again and up the wall to the tank. At the tank in the attic we changed the pipe configuration slightly, because we actually added a second floor, the pipe runs up the wall makes a 90 degree right turn then runs about 12" then another 90 degree left turn then into the tank. The problem is it does not seem to be siphoning and circulating properly into the tank. It is definitely getting hot and no pipes are running downhill or anything but this is absolutely driving us crazy trying to figure this out. Do you think you know what is happening or know someone who can help? Thanks for your help look forward to hearing from you. D & B