Paul Bias, a green builder in Arcata, Calif.,
frequently works on sites where it’s
difficult to get temporary power. Rather than use a
generator — which is loud and dirty and easy
to steal — he powers his tools with energy
from the sun (1).
He first tried this approach when the technology
center at a nearby university hired him to do some
work and loaned him a trailer-mounted photovoltaic
(PV) power system. By the time the job ended
he’d decided to build a similar system for
On an old cargo trailer, he installed an adjustable
aluminum rack supporting four 170-watt solar
panels; they’re wired to a charge controller
and a bank of deep-cycle batteries inside the
trailer. The batteries put out 24 volts of DC
power, which an inverter converts to 110-volt AC
that powers two 20-amp circuits.
Cloudy weather is not a problem. When fully
charged, the batteries contain enough juice for
three carpenters to work for two or three days. In
a pinch, Bias can recharge them by plugging the
inverter into an electrical receptacle.
Building the system cost $11,500 — $4,000 for
the batteries and $7,500 for the panels, inverter,
and control mechanisms. Although he admits that
getting power from a generator or the grid is a lot
cheaper, Bias says his portable PV system offers
numerous advantages: It’s clean and quiet and
doesn’t emit greenhouse gases; its power is
available the moment he arrives on site; and the
trailer can be used for storage.
Best of all, he says, is the free publicity. The
trailer has been written up in the local paper, and
people now seem to recognize it and associate it
with his company. Perhaps someday, Bias muses, one
of them will decide to build a green home, and the
first company they’ll think to call will be
the one with the solar trailer.