Earthwalker has been living in his Class C RV for thirteen years now. Because he lives in
sunny Nevada, he wanted to take advantage of the abundant sunshine and live as green
as possible. This is the story of how he created his own solar hot water system and
installed a 480 watt solar system. It may look complicated but both systems are easily
doable by anyone with basic handyman skills. Lets get started!
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Solar Hot Water
picture is an overview of the simple.
he spray-painted black. He choose PVC
because it is light, cheap, and very
unlike some plastic pipe, solar hot
water system. It is very water stored
20 foot sections and 20 foot sections
and cut them down to 7 foot sections
(his to 7 foot sections (his RV is 7 1/2
foot wide, you would cut foot wide,
you would cut them to fit your
vehicle). He your vehicle). He
estimates that the 8 sections he used
hold about 4 gallons of water. While
that is not an abundance, it is enough
for one person with frugal use. If you
used 2 inch PVC, you would have 8
gallons which should be plenty for a
couple, or extra for one person.
used basic off-the shelf PVC parts
available at Home Depot or any used
basic off-the shelf PVC parts cut the
PVC and then you just apply available
at Home Depot or any the cement and
press the parts hardware store. A
hand saw will easily together. Print out
these pictures and take them to Home
Depot, and a clerk can help you get
everything you need.
workbench and then carried them up
to the roof. In these pictures
you can see the cargo rack that came
with his RV. To avoid drilling more
holes in his roof, the tubes are
attached to the rack and not to the
roof. At 8 lbs to a gallon, his 4 gallon
water system weighs 32 lbs. While
that's light, it is enough to hold the
system in place without need for
elaborate hold-downs.
Because he used a regular RV 12 volt
water pump, this is a pressurized
system, meaning as water is used, the
pump automatically replaces it. At the
end I will tell you how to make a
without water tanks or RV water pump.
In these pictures you can see the
three tubes feeding into and out if
the system. The yellow hose on the
left is cold water coming in from the
pump. The white hose in the middle is
hot water going out to the RV to be
used. So the water comes in from the
left and is pumped back and forth
through the tubes to the outlet hose
on the right. Because the tubes are
painted black, they get very hot in the
Nevada sun, heating the water in them.
The reddish hose was a first attempt
at a drain that didn't work. The drain
is important in winter if you run into
freezing weather.
In the picture to the left
you can see the drain
that did work. He cut a
splice into the tube at
far left. In the picture
to the right you can see
the drain tube running
down the back of the RV
so it is easily opened and
closed to drain the
system.
The system works extremely well. Under the summer sun it will warm the of
the water, it will be hot again about an hour later. However, in the winter it
does not work as well. The water does not heat up much above the outside
temperature, which in December through February is in the 50s and 60s. That
doesn't get the water hot enough to use, so he just drains the system in those
months.
As I am writing this he is designing a new system to solve this problem. He will
take the old system down and install a whole new one, but this time it will be
enclosed in a box to capture and hold the weak winter sun. The bottom of the
box will be 3/8th inch plywood cut large enough to hold the tubes. The side
walls will be either 1x3s or 1x4s, depending on whether he uses 1 inch or 2 inch
pipe. On top will be a sheet of acrylic or Lexan to let the light and heat in and
to retain it. The tubes will be painted black as before. He isn't sure what to do
with the inside of the box. He's certain he will paint the bottom and sides with
Elastometric, a thick white paint used on trailer roofs to seal and keep heat
out (in this case it will seal the joints and keep heat in). One option is to cover
the bottom and sides with aluminum foil to reflect the light and heat onto the
black tubes. Another, and probably best, option is to line the inside of the box
with a product called Reflectix. It has two very heavy layers of aluminum foil
on the outside and has a type of bubble-wrap in-between for insulation. This
would reflect the light/heat onto the tubes and also retain the heat in the box.
What is unknown is if the Reflectix can hold up in the high temperatures the
box will generate in the summer. When the new system is in place, I will update
this article.
A Gravity Fed System:
Earthwalker lives in an RV so it was easy to adopt it to a solar hot water
system. He already had fresh water tanks and a 12 volt pump. But most of us in
vans or campers don't have those, so how can we copy his idea? Actually, it
isn't hard at all. Where he is using a pump to force water through the tubes, we
will use gravity. His tubes are lined up in a level row, but we will line ours up at
an angle so that when we pour water in from the top water inlet, gravity will
pull it down to the outlet at the bottom. Here is an exaggerated side view of
the tubes to explain what I mean:
O <--System filled with water from the top.
O
O Gravity pulls it down, going back and forth through the tubes,
O where the sun heats it up.
O
O <--Water drains from system from bottom.
draw a line from the top right corner to the bottom left corner. Next dry wide
apart the holes in the 1x4 need to be. Then draw 2 inch circles centered on our
diagonal line, spaced the right distance apart. The longer the 1X4 is, the more
tubes you can get in it. I would run the tubes across the back of the van, so
they will be about 5 1/2 feet wide. I would start with a 1X4 about 4 foot long
to see how many tubes it will hold. You may find you need a 1x6 instead. Getting
the design figured out will take some trial and error. You can practice on
cardboard first so you don't waste wood. When you are sure of the lengths,
get a hole saw and cut out the circles on the wood, and that is the framework
to hold the tubes in their right spots.
For a van you will probably want to use 2 inch PVC tubes to offset the
narrower width of a van. More water in the system will weigh more, pushing
down with greater force and pressure. If you use it for a shower, you want all
the pressure you can get when rinsing your hair.
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