Chapter 24 Energy Conservation
401
would take up a space of 10 square meters.
This unit would be expected to generate
roughly 1000 kWh in a year. The size of the
unit selected for a particular task is based
on the power needed. Some PV modules
are large enough to cover the entire roof of
a building, Figure 24-14. Others are large
enough to produce over one million watts
of electricity.
Photovoltaic systems
PV systems produce dc. Small PV systems
can be used to charge batteries or run a small
piece of electrical equipment. Larger systems
use an inverter to change their output to ac
and connect them to the grid. The grid is a
wiring network that is spread across most of
the United States. In the event of an electrical
outage in one area, electrical power can be
provided from a substation from another loca-
tion. The grid provides ac electrical power,
while the PV system produces dc. Therefore,
an inverter is needed to convert dc power to
ac. The inverter also performs the following
tasks:
• Synchronizes the grid to the PV system.
• Turns on and connects to the grid after
sunrise.
• Matches the frequency of the PV system
and the grid.
• Monitors the voltage and current
generated.
• Turns off and disconnects from the grid
around sunset.
• Collects and saves energy data.
• Provides a safety disconnect during
outage from storms.
Figure 24-13. Photovoltaic modules.
PV module
Figure 24-14. This roof is being installed with
photovoltaic roofi ng shingles. (Southface)