Save with Solar Hot Water
(Page 2 of 6)
HOT HOUSEHOLD WATER
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I n most homes, domestic hot water (water for washing
dishes and clothes, for bathing or cooking) usually is
provided by an electric or gas-fired water heater, or
boiler or furnace that also heats the home. Heating water
with electricity is expensive and will become even more
costly as the price of fossil fuels used to generate it
continues to climb. And, although heating water with gas is
less expensive than heating with electricity, burning gas
still contributes to pollution and global warming.
In concert with an electric or gas-fired backup unit, solar
domestic hot water can reduce the requirement for
conventional water heating by two-thirds or more. The total
amount the solar hot water system can contribute depends on
your household's hot water consumption, and the amount of
sunshine the collectors receive daily and throughout the
year. In general, most solar systems are designed to meet
one-half to three-quarters of a family's domestic hot water
need. During the summertime, the system may usually meet
all of their hot water needs. On average, an efficient
collector in good weather will heat between 1 and 2 gallons
of water per square foot per day. (A solar contractor can
help you correctly size the collectors, storage tank and
backup system.)
SMART SOLAR SHOPPING
If you're haunted by horror stories of the 70s and '80s,
when fly-by-night installers, more interested in selling
tax credits than reliable systems, left unwitting
homeowners with poorly designed, difficult-to-maintain
systems—it's time to shed those fears. Today,
performance standards govern most active solar components,
making comparisons between products possible (see Sources,
Page 80), so when you shop, you can shop smart. Most
manufacturers warrant their systems for at least 10 years;
in many cases, the collectors and insulated piping may last
as long as your house. Since it tends to degrade over time,
the circulating fluid should be inspected every few years
by a qualified technician.
SYSTEM COMPONENTS
Solar hot water systems consist of collectors connected to
one or more storage tanks by piping. For active systems,
pumps, sensors and controllers may be added.
Flat-plate, evacuated-tube and batch collectors are all
common collectors; each is suited to different needs.
Flat-plate collectors (see illustration at right), with a
"black chrome" or a similar selective-surface coating,
which absorbs the maximum amount of solar heat while
minimizing radiant cooling, are the most common. Small
tubes inside an insulated aluminum box with a tempered
glass face contain either potable water or a heat-transfer
fluid; the collector absorbs and transfers heat energy to
the fluid in the tubes, which is then carried to the heat
storage tank by insulated piping.
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