Design New England - March/April 2012

green
design decision

Dual Power
Plastic tubing under
roof slates carries glycol
At the Zarrella house, tiles and tubing are used to collect the
sun’s rays — two technologies that can work independently,
but are used together for a bigger solar bang. The system,
designed and installed by Dawn Solar of Brentwood, New
Hampshire, supplies about one-third to one-half of the hot
water, electricity, heat, and air conditioning for the 5,000-square-
foot house. SunSlates, photovoltaic tiles made by Atlantis Energy
Systems, were installed on an enlarged south-facing roof.
They convert solar energy into direct current electricity, which is
then converted to alternating current for domestic use.
Beneath the tiles are tubes filled with a nontoxic glycol
solution that collects the sun’s heat, then flows to the
basement, where it releases that energy into a hot water
storage tank. A traditional water heater is fed the preheated
water, while the heating system uses a heat exchanger so the
stored water can augment the forced hot air heating system. An
oil furnace serves as a backup heat source. A glycol tube also
runs to another tank in the pool house to heat the water for the
year-round pool. To conserve energy, foam insulation was
added to the entire house to bring it to an R- 50 level, further
reducing the use of fossil fuels.
Photovoltaic roof slates
Direct current
Hot
glycol
Inverter
AC electricity
Hot Water
heater
Cold
glycol
Oil
backup
Heat
exchange
water tank
Pump
Heated water
tank for pool
Forced hot air
heating unit