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SOLAR HOT WATER SYSTEMS
Summary by Solar Assist
Download printable summary here
Download printable schematic here
Solar Hot Water systems
can be used for a variety of purposes. The most predominant
system is the solar domestic water heater. Since every
home and many businesses use hot water year 'round
this is a consistent load that can be significantly offset
by simply preheating the cold city water that feeds the
electric or gas water heater with solar heated water.
The intensity of the sun varies with the seasons and so
does the temperature of the solar water produced.
Summertime months typically result in nearly 100% solar heated
water for a well sized system. The winter months average around
25-50%. This results in an annual average of about 60-70% of
your hot water load being provided by the sun.
Simple proven technologies result in durable, efficient systems
that insure your full value invested will be returned to you
through lower utility bills. There are many usable and
efficient solar water heating designs but the two predominant
systems are the “Drain-back” and the “Closed loop glycol”.
They both utilize rooftop collectors, a pump and control, and
a “Solar Storage Tank” dedicated to maximizing energy gains
from the sun. The primary difference is how they protect
themselves from freezing. One “drains-back” and uses
normal water in the solar loop. The other stays full and uses
a non-toxic antifreeze to prevent the collectors from freezing.
Solar Hot Water applications span a
wide array of temperatures from lower temperature pool
heating, thru mid temperature domestic hot water to high
temperature commercial and process heat. There are
a variety of collector technologies optimized for different
application temperatures. These range from bare plastic
absorbers for swimming pools, to the most commonly seen
boxed and glazed "flat plate" collectors
used for domestic water heating and some space heating. Evacuated
tube systems, more effective at higher temperatures are
becoming more common for domestic water heating and space
heating also due to reduced costs.