Instructables

Cheap and Easy Passive Solar Water Heater for your Home. ($300)

video Cheap and Easy Passive Solar Water Heater for your Home. ($300)
Heat your water for free with a solar water heater.  This $300 DIY solar water heater system even includes an electric backup water heater for cloudy days.  It heats water to 135F (55C) on sunny days in a 80 gallon (310 liter) tank - and there are no moving parts - it relies in a thermosyphon to circulate the water.  

http://www.myfixlog.com/fix.php?fid=1
This heater uses PVC instead of copper.  PVC has a much lower thermal conductivity than PVC does, however there are a few ways to over come this weakness.  

One way to I increased the efficiency was to use old florescent light bulbs as sleeves over the PVC pipe to act as a double glazing.  This helps insulate the PVC and increases the efficiency of the heater.  I also insulated the PVC connections to help shield them from the intense heat of sunlight. 

The other way I increased efficient was increasing the surface area.  Since PVC is cheap it did not cost much to run more pipes that would be exposed to the sun.

 I also installed an automatic electric backup heater for $30.  It is a bucket heater that turns on at 80 degrees and off at 110.  Click on the link above to see more about that.
colmmcg2 months ago

Hi
I have wanted to build one of these for a few years now, but I have been stuck
on one step which this tutorial seems to skip over, and it relates to dealing with the
mercury vapor that is present in florescent tubes. Its only realy visible as a shadow under uv light and behaves a little heavier than air. While "How stuff Works" refers to the mercury contained within "as a little bit of mercury" and the instant of a bulb breaking there is a slow release of mercury the mercury vapor, over the life of the tube mercury will have leached into the interior surface of the tube, the glass and the electrodes so placing a number of them in a contained
space over or adjacent to a living space a demonstrated in this tutorial it probable not to be recommended.

Please search Google images for the exact phrase "mercury free fluresent tube" before proceeding with this tutorial.

Washing the interior of a glass tube with sand is a good general cleaning method
, but with respect to dealing with mercury vapor it may be more like using a mouth wash after smoking a cigarette to avoid lung cancer.

I had really wanted to have found a solution to the step of dealing with the mercury vapour in the tubes. If you find one please post it. Other than this step that I am stuck on, everything else about the tutorial is great which made it all the more important that this issue be mentioned.

Regards

Colm

resago4 years ago
PVC has a low tolerance to UV, unfortunately.
I would cover the tubes with a black tarp and let the UV destroy that, instead of the pipes. then all is good.

Could I cover the pvc with Aluminum Foil and spray paint the foil black with high-heat flat black spraypaint? Would that protect it from UV while increasing the heat absorbed?
yeah, that should work fine.
nmvb resago2 years ago
Aluminum roofing painted black and placed on the top and bottom of the tubes would also probably work.
nandosv2 years ago
Is the water tank pressurized or does it have a float valve to let new cool water in?
PVC has a much lower thermal conductivity than PVC does??????????? I believe that needs to be changed. Otherwise a great instructable!!!!!
greenspider3 years ago
Jake, you're on the right track so far, this is good re-purposing and should work nicely.
I am concerned with what you did with the "dust" you removed from those fluorescent bulbs.
That dust contains Mercury.
You do not want to breath it when you clean out the bulbs, AND you want to dispose of it PROPERLY.
This may make it more difficult, but you, the water you drink, and the air you breathe will thank you for it.
13blue3 years ago
This is the best explanation of a passive solar water heater I've ever seen. Thanks for taking the time to do the project and the video.
sparks3 years ago
Great instructable, thanks for posting it. Especially like the repurposing of the Fluorescent tubes.
nfarrow4 years ago
thanks for the CC on the video. really helps out with people like myself at working tiring to be sneaky and check out instructables
erik_mccray4 years ago
Wow, now thats making the most of whats at hand. You may like to check out a guy name William Kamkwamba if you haven't heard of him all ready. You two seam to think alike.
freak13th4 years ago
good instructable and a good way to go green
the "dust" in the glass tubes is toxic as it has mercury in it. you and the readers should know that if they don't already.
Great video explained everthing very well