Solar Hot Water Heater For Domestic Potable
After a lot of thinking about how much power I wasted by
heating our water with Electricity or Propane, I came to
the conclusion that its almost silly to not use the
sun in the months where its readily available &
staying above the freezing mark, which for us in North Idaho
is generally a minimum of 7 months.
I initially spent a lot of time researching the issue
and found that the solar hot water heaters available on
the market were both expensive ($1,000 plus...http://www.siliconsolar.com/solar-hot-water-heaters.html)
& complex, from the perspective that you had to (A)
use an electric pump & controller & (B) use a heat
exchanger that was separated from the water you are heating.
I didnt want this, as a thousand bucks is too much
PLUS I want it simple
So, I bought a couple of the How To Do It Yourself
instructional programs on building a hot water heater, and
tried to learn from them. Heres what I learned, and
what really works.
First off, in the manuals they generally all came up with
this idea that you use a reflective surface inside of the
heat exchanger box to reflect sunlight & (heat?) back
towards the actual heat exchangers. This is wrong, and doesnt
work. You want to ABSORB the heat inside of the box, but
never reflect it. So, the idea is to paint the inside of
the box black.
My primary concern was with the idea of if I would be able
to heat ENOUGH water to supply my family or if I was just
going to heat a small amount of water. I wanted to make
the heat exchanger as large as possible, but still make
it moveable, as it had to come apart & be moved in springtime.
The other thing was that I wanted it to work through thermo
siphon, (NO PUMPS, Ma!) so another consideration was the
elevation relative to my hot water tank (more on this later).
The premise of Solar Hot Water Heating is simple; heat
water and send it to a storage tank. I wanted to one
better the plan, so I built mine using Thermosiphon
to move the water for FREE!!!!
Below, Ill show you how I built it, and how it works,
plumbing, and thermosiphon:
Heres a good link on how Thermosiphon works:
Heres how I built mine:
I bought some Slant Fin Baseboard heat radiators, the simple
kind you buy in your house to radiate hot water heat ( http://www.pexsupply.com/Slant-Fin-101002060-E75-3-4-Steel-Baseboard-Element-6-Length
). I bought these used, they were inexpensive, I think I
paid $15.00 or so for all I needed. Then, bought some 3/8
inch glass, and (2) 12 foot 2x6s, and another 6 foot
2x6, all treated. Together, for the heat exchanger, I think
I have about $200 or so in it.
First, I built (2) small manifolds for the Slant Fins.
These are simple, paralleled manifolds, one for the bottom
(where water comes in) and one for the top (where water
leaves & flows back to the hot water (Storage) tank).
I installed these in Parallel so that when water
comes into the bottom of the exchanger, it spreads out evenly
across all 6 Slant Fins. The manifold at the bottom has
a 45 degree angle on it for easier hookup.
to Solar Hot Water Heater
After I made the manifolds, I soldered together the Slant
Fins (they are ¾ inch copper), and connected them
to the manifolds.
I made a box out of the treated lumber that measures 11
feet long & about 30 inches across, and installed the
Slant Fins & Manifolds inside. Painted them black, and
then installed the glass over the front.
I installed a thermometer inside (mistake
). You dont
want to do this; it will get hot enough inside later to
destroy the thermometer.
Thermosiphon has been used by mankind for millennia, it
is an OLD way of moving water without pumping it.
Hot is lighter than cold, and the same applies to water.
You hook up the BOTTOM of your hot water TANK to the bottom
of the solar hot water heater, ensuring that there is a
drop of at least a couple of feet between your storage (hot
water tank) and the Solar Hot Water Heater.
Then, install the Solar Hot Water Heater at an angle (doesnt
have to be anywhere near perfect) that is looking at the
sun. 45 degrees maybe?
Last, install a return line FROM the Solar Hot Water Heater
TO the hot water tank, arriving at the hot water tank at
the TOP, and having an upwards climb of at least a foot
between the two devices. Make SURE that there are no droops
in the pipe. Install a one way flapper valve
at the input side of the hot water tank, where your return
line connects to the hot water tank, and install bleeder
valves so that you can bleed the air out of the lines when
you install turn on the system. Also, ensure that the flapper
is positioned so that the flapper is hanging
down inside of the valve. (It matters
) Get THIS
valve, as its Brass, can withstand the heat, and
Return from Solar Hot Water Heater
Now, heres how it works:
Like I said before, cold water is HEAVIER than warm water.
The cold water leaves the hot water storage tank, and goes
into the Solar Hot Water Heater at the bottom. As soon as
the sun hits the Solar Hot Water Heater, it heats the inside,
and FAST!!! The water inside of the Slant Fins starts heating
up, and in (literally) minutes, will rise in the Slant Fins
to the top, and start circulating back into the top of the
hot water tank.
The cold (HEAVY water will push the lighter hot water
back into the top of the tank.
Water leaving the Hot Water Tank for the Solar Hot Water
Heater leaves at about 55-60 degrees & returns at 120-130
degrees. It makes more than enough water to supply hot water
for a family as long as the sun is out. When it gets colder
outside, as long as it isnt freezing weather, the
Solar Hot Water heater will assist in warming up the water
The best part is
..NO moving parts, no failures.
Output to Solar Hot Water Heater
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