The next decision Carey made
was to install Photovoltaic Panels on her roof for producing solar electric
energy for her car and home.
This process started with a
visit from Jonathan Cohen with Imagine Energy.
Jonathan got up on the roof with a solar gauge that
could tell how much sunlight would hit Carey's roof throughout the day and over
the year to see if the project would be viable. Her neighbor to the west
have a large tree that shades the south part of the roof in the afternoon.
After determining there would be enough sunlight hitting the peak of
the west facing roof slope, the project was a go.
A south-facing slope is the
ideal location for photovoltaic cells. When given the choice between east
or west facing slopes, west facing are generally more favorable due to
Portland’s morning clouds and fog that often burns off by afternoon.
Since Carey's roof was
older, it needed to be replaced before the panels could be installed.
There were also two small chimneys that were no longer used to vent
anything. These had to be removed to avoid any shadows on the PV
panels. The term ‘flagpole effect’ comes
from the concept that even a narrow shadow cuts out more power than indicated
by its area due to connections between multiple circuits being disrupted.
The electrical contractor
also had to do extensive work in the garage. The existing 100-amp circuit
breaker box was replaced with a 200 amp one. This was partly due to a
simultaneous switch from a gas furnace to an electric heat pump furnace.
Since the panels bring in
solar energy via DC, direct current, it has to be transformed into AC,
alternating current. An inverter box was installed to the left of the
circuit breaker box. Carey keeps a hand written log to determine
the energy produced from the panels at different times of the year.
The third piece of
electrical equipment installed in the garage is a meter required by the Energy
Trust. This assures them that the system is hooked up and working fine,
since they paid for part of the unit.
Portland General Electric
(PGE) has a net metering agreement with homeowners who generate energy. They
buy excess energy produced by Carey's solar panels and send it back to the