Introduction to Photovoltaic Energy Systems
Photovoltaic (PV) Energy Systems
Solar Energy
Photovoltaic Energy
PV System Types
PV System Integration Options
Why PV?
PV System Economics
PV System Incentives
PV System Types
Institutional and commercial building PV systems are typically connected
to the utility's electric grid. Wisconsin's
net metering law allows small PV systems (under 20 kWp) to turn the electric
meter backwards whenever the premise requires less energy than is being
produced by the PV system. This means that you can use the utility as a battery at no cost to you. If
you produce more energy than you consume your utility may even pay you.
At some sites PV systems are combined with a batteries to operate independently from the grid. For example a school in Massachusetts is using a PV supported by batteries for the school's parking lot lights.
A growing number of residential PV systems are located on homes that are not connected to the utility's distribution network. These homes are known as "off the grid." Off-grid homes typically use PV with battery systems simply because it costs less than running a power line to the home. It also allows them to be energy self-sufficient.
PV System Integration Options
Building-integrated PV (BIPV)
PV systems can easily be located on building rooftops or installed as
part of the building's shell. True building integrated PV (BIPV) systems
are incorporated into a building at its design stage. Such BIPV systems
have the lowest first cost because they replace other, sometimes costly
building materials (roofing materials, shade screens, atriums, facades)
they require no additional support structures, and additional construction
expenses are limited. Also, the cost of these systems can be financed as
part of the entire building.
Building-integrated PV modules can be quite attractive, adding to the building's aesthetics. Some integration options have additional benefits. For example PV shade screens will reduce the summer sun's heating of a building, thereby reducing cooling loads. A PV atrium that uses cool daylighting principles reduces lighting costs and thus cooling loads.
Photo 2. A building-integrated PV system
Retrofitted PV Systems
For existing buildings it is easiest to locate the PV modules
on support structures on the building's roof or attached
as an awning. These systems typically cost more than a BIPV system
due to the cost of the support structure, building wiring improvements,
and rooftop improvements.
Photos 3 and 4. PV systems
can also be installed on support structures independent of the building.
Photo Credits
Photo 2. Bear Architects, the Netherlands, Nature Center's PV roof
Photo 3. Solar Design Associates
Photo 4. Umweltplus, an initiative of RWE Energie AG, Germany, 56 kW PV power plant in Ibbenburen, German
copyright © 2000 WisconSUN
