Cell Type & Efficiency.
If you have limited mounting space, PV module efficiency
is a key consideration. Modules with crystalline silicon PV cells—as opposed to
thin-film—will likely be required, since thin-film modules produce about half
of the wattage per square foot.
Within the crystalline module category, there are
variances in power density (watts per square foot). Average power density is
about 12.7 W per square foot, but some modules have higher power densities:
Using a module with higher power density means getting
more power out of your usable mounting area. For example, let’s say our
shade-free mounting area measures 20 feet by 10 feet, for an area of 200 square
feet. Without considering module dimensions, choosing a module with a 12 W per
square foot power density will yield a 2,400 W array; selecting a module that
yields 18 W per square foot results in a 3,600 W array—a 50% improvement.
The downside is that modules with higher power densities
typically are more expensive per watt (about 7% to 12% more). Decreased
installation and racking costs for higher-efficiency modules may—or may
not—amount to much. In most cases, if you have plenty of installation space,
you won’t likely want the more expensive modules.
Bifacial modules that produce power from both the front
and back of the module report two values
for module efficiency. These modules have clear backing, allowing some light to
pass through, and can generate some energy from the reflective light that hits
the back of the module. These modules can be good choices for awning and
carport installations that can take advantage of reflected light.
Module Size & Dimensions.
This will determine array layout—how many modules can fit
in the available space. Differing roof planes, such as trapezoids (created by
hip roofs) require carefully choosing modules with appropriate dimensions, so
that roof space is maximized without hanging modules off the roof’s edges.
Required setbacks for local fire department guidelines, accessibility for
maintenance, module mounting infrastructure, and module interconnections and
string layout will also influence what size modules will work in an array at
your site.
CONTACT ELECTRICAL SYSTEMS AND SERVICES, INC.
TO SCHEDULE A FREE SITE SURVEY FOR YOUR SOLAR
PROJECT.
