Scanning for ideas: Solar help for home water heaters
This closed-loop antifreeze-filled system from Butler Sun Solutions, Solana Beach, Calif. (butlersunsolutions.com), should supply half the hot-water needs of a family of four living in southwestern states or about 1,700 kW-hr annually.
It includes
40 sq ft of collectors
and a solar-wand heat
exchanger for about
$2,500.
The solar wand is a
double-walled copper-in-brass in-tank heat
exchanger with about
2 sq ft of heat-transfer
area. Inside of it, copper
tubing runs side by side
the brass outer tube,
but plastic standoffs
limit tube-to-tube
contact. Tubes are also
insulated with closed cell
foam insulation
from a collector-to-hot-water-tank umbilical,
which also includes
all electrical and fluid
connections.
The system can
be controlled with
a conventional
115-Vac differential
temperature controller
or a photovoltaic-powered
12-Vdc pump.
The working fluid is
propylene glycol, a
common antifreeze
liquid.