Multi functional equipment and integrated systems offer the opportunity for a significant
increase in efficiency through heating water with waste heat. For example, an integrated system
that uses heat pumping to meet space heating, air conditioning, and water heating needs could
be 70 percent more efficient than the combined efficiencies of systems in use today. A demon
stration supported by DOE, the Tennessee Valley Authority, and industrial partners, is analyzing
the operation of such integrated systems.
Solar Photovoltaic Systems
Solar photovoltaic (PV) arrays are made from semiconducting devices that convert sunlight into
electricity without producing air pollution or GHG emissions. A variety of PV system configurations are
being used by electric utilities to provide green power to customers. Three types of systems are particu
larly relevant to buildings:
Stand alone systems produce power independently from the utility grid. In some off the grid
locations, stand alone PV systems can be more cost effective than extending power lines. Most
systems rely on battery storage that allows energy produced during the day to be used at night.
Hybrid systems combine solar power with additional power sources such as wind or diesel. For
most of the PV industry's history, stand alone systems have dominated, but today grid connected
systems are moving to the forefront.
Grid connected systems supply surplus power back through the grid to the utility and take from
the utility grid when the building system's power supply is low. These systems remove the need
for storage, although arranging for the grid interconnection can be difficult.
Building integrated photovoltaic (BIPV) systems produce electricity and serve as construction
materials at the same time. They can replace traditional building components, including curtain
walls (for warming ventilation air), skylights, atrium roofs, awnings, roof tiles and shingles, and
windows. They may be stand alone or grid connected systems.
Almost all locations in the United States have enough sunlight for PV systems, and these
arrays can be easily sited on roofs, integrated into building components, or placed above parking lots.
While integrating large quantities of solar photovoltaics into the electricity grid is not simple due to its
Towards a Climate Friendly