Photovoltaic
cells are connected electrically in series and/or parallel
circuits to produce higher voltages, currents and power levels.
Photovoltaic modules consist of PV cell circuits sealed in an
environmentally protective laminate, and are the fundamental
building block of PV systems. Photovoltaic panels include one or
more PV modules assembled as a pre-wired, field-installable unit.
A photovoltaic array is the complete power-generating unit,
consisting of any number of PV modules and panels.
The
performance of PV modules and arrays are generally rated according
to their maximum DC power output (watts) under Standard Test
Conditions (STC). Standard Test Conditions are defined by a module
(cell) operating temperature of 25o C (77 F), and incident solar
irradiance level of 1000 W/m2 and under Air Mass 1.5 spectral
distribution. Since these conditions are not always typical of how
PV modules and arrays operate in the field, actual performance is
usually 85 to 90 percent of the STC rating.
Today’s
photovoltaic modules are extremely safe and reliable products,
with minimal failure rates and projected service lifetimes of 20
to 30 years. Most major manufacturers offer warranties of twenty
or more years for maintaining a high percentage of initial rated
power output. When selecting PV modules, look for the product
listing (UL), qualification testing and warranty information in
the module manufacturer’s specifications.
