Homemade Solar Water Heater

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ILLUSTRATION: MOTHER EARTH NEWS STAFF
Here is a diagram of Khanh's homemade solar water heater, made from a 66-gallon water tank enclosed in an insulated pyramidal framework.

Don’t try to tell Dinh Khanh that solar water heaters have
to be complicated or expensive. Khanh — a resident of
Gainesville, Florida designed and built the compact (26-by-42-by-52 inches), low-cost ($180), sun-powered water-warmer … and it’s about as un complicated a
device as you could hope to find.

Basically, Khanh’s heater is nothing more than a
flat-black-painted 66-gallon water tank enclosed in an
insulated pyramidal framework consisting of 1inch plywood,
Plexiglas outer glazing, and a Tedlar inner glazing.
(Behind the tank is a 42-by-52 inches reflector surface made from
recycled aluminum printing plates.)

What Khanh has done is lean this odd-shaped solar
collector against the south side of his house at a 45 degree
angle (to take maximum advantage of the low winter sun), run cold water into the bottom of the
66-gallon tank, and route CPVC pipe from the top of the
solar unit to a conventional water heater inside the Khanh
dwelling. This way, incoming water is pre-warmed
by the solar collector to a temperature of about 100 degrees Fahrenheit
before entering the house’s conventional electric heater … and the Khanh family enjoys a 50 percent savings on their
monthly hot water bills.

Dinh sees no reason why others can’t build their own
semi-triangular solar water heaters (and enjoy similar
savings), as long as certain rules are followed during
construction. For instance: “It’s important,” says Khanh,
“that all angles and proportions be kept the same as in the
original design, and that the tank is mounted at least four
inches away from the underlying reflector. Also — to
maintain the best balance between high energy absorbance
during the day and low heat loss at night — the builder
should only use a 16- to 18-inch-diameter water tank of 42
to 66 gallons’ capacity.” (The Vietnamese born inventor
emphasizes, too, that the tank should be leak-free, able to
withstand 75-psi pressure, and either galvanized or
glass-lined.)

At 400-plus pounds all-up weight, the Khanh heater isn’t
exactly feather-light. (“Be sure to take this into
account,” the inventor warns, “if you plan to install the
device on your roof!”) The dandy little solar hot box,
however, is one heck of an inexpensive, compact,
easy-to-build “answer” to high water heating bills. In
fact, if there’s a better way to turn 66 gallons of cold
water into 66 gallons of hot water … we haven’t seen
it!