An Experimental Solar Water Heater Design

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PHOTO/ILLUSTRATION: MOTHER EARN NEWS STAFF
Left: Ken Whetzel poses with  his completed unit. Right: An illustration of the heater's parts and fittings.

Ever wonder whether you could put the sun’s energy to work
for you where you live? Well, a former neighbor of MOTHER EARTH NEW
asked himself that question, and to find the answer
he built a solar water heater right here in northern Ohio.

Though Kenneth Whetzel describes his little machine as
“experimental”, there’s nothing tentative about the hot
water it produces. Ken likes his shower about 105°, and
there wasn’t one day in all the time the test system was
running that he couldn’t have washed comfortably in the
device’s output (had he been equipped to do so). That’s not
bad for 60° weather. It should be noted, however, that
since Ken didn’t intend actually to use his heater’s
product, the contents of the tank are routed back through
the collector — an arrangement that makes the model
operate more efficiently than a working system in which the
warmed liquid is frequently drained off.

The collector that produced these results is a 2′ X 4′
piece of sheet metal with about 24 feet of half-inch copper
tubing soldered to it in a zigzag pattern. This whole
heat-absorbing area is contained inside a wooden frame
sealed over with clear plastic sheeting. The tubing that
carries hot water away from the enclosure is insulated with
a layer of half-inch foam rubber and leads to a raised
11 1/2 gallon reservoir protected by a styrofoam jacket
one inch thick. (Whetzel built the contraption entirely of
scraps scavenged from his construction job, so it’s hard to
say just how much it would cost you to fabricate a similar
unit.)

One feature of Ken’s design that really cuts the device’s
cost, and which should be pointed out, is the fact that it
needs no mechanism to force water through the collector and
into its storage tank. Why? Because of a basic fact of
thermodynamics: Water, like air, expands and becomes
lighter per cubic measure as its temperature increases.
Rather than use electricity to run a pump, Ken took
advantage of this principle and set up his creation so that
the warmer and lighter H20 rises through the
cooler layers and on up the pipe into the top of the tank,
where the liquid sinks down into
the collector again for reheating as it cools.

A very simple, streamlined experiment, isn’t it? And best
of all, it works. The first day Ken set up his invention
(pointed 10° west of south and tilted 30° downward
from the horizontal) the water temperature at 7 a.m. was
60°. By the time the experimenter got home from work at
5 p.m., the contents of the tank had been heated to
128° … too hot to put your hand into.
And—because of some nearby trees—the sun’s rays
hadn’t even hit the collector until about 10 in the
morning.

Overnight, Ken’s hypothetical bath cooled only to 96°,
and when the second day turned out warmer and sunnier than
the first (with a high near 70°), Whetzel knew he could
look forward to some really impressive readings. Sure
enough, by evening his system’s water temperature had
climbed to 138°, nearly twice as hot as the
surrounding air! Thereafter the tank’s 5 p.m. temperatures
ranged from a low of 108° (a cloudy day) to a high of
148° — and on top of that record, the inventor
thinks he might be able to pick up 30% in efficiency by the
use of reflectors.

Ken was convinced. The last we heard—when he and his
wife left for their five-acre homestead in Florida—he
intended to employ the results of his experiment to set up
two practical solar heating systems: one to warm the house
in winter and another for domestic hot water. He figured
that three 2′ X 8′ collectors mounted on the garage roof
would supply at least 72 gallons of bath or wash water
(1 1/2 gallons to the square foot) per day, and
probably a lot more, considering Florida’s fabled weather.

Our ingenious neighbor also thought his winter heating
system might be used to cool the house in summer by
circulating cold water from a well, but when we last talked
to him he hadn’t worked out all the details of that
modification. Let us know when you do, Ken!