Environmental Engineering Reference
In-Depth Information
pitfalls (glare, variability, difficulty of control, requisite architectural modifica-
tions, and excessive illumination) [2].
As the interest in daylighting for interior spaces has continued, many con-
ceptual and technical improvements have made its applications easier and more
reliable. The development of architectural daylighting designs that minimize
glare and over-illumination have matured as a result of continued interest. The
combination of energy-efficient dimmable lighting ballasts and reliable ''day-
light harvesting sensors'' has enabled daylighting to be combined with artificial
lighting in a harmonious manner that achieves consistent illumination.
Architecturally effective daylighting strategies add to the aesthetic and
environmental value of modern buildings, and yet the size of our buildings
often makes daylighting options very limited. Skylights provide light in spaces
that are far from exterior walls, but traditional skylight designs have often been
associated with poor thermal characteristics and excessive maintenance issues
(leakage). Skylight designs have traditionally been large optical openings that
contribute substantially to a building's heating and air-conditioning loads,
create non-uniform lighting conditions, and are difficult to integrate into exist-
ing structures. Modern skylight designs are much more aesthetically diverse and
include a variety of passive optical features to improve the lighting performance
and versatility of the designs.
5.2 Environmental Problems Addressed by Hybrid Solar Lighting
The use of electricity for lighting is, like many other things, a blessing when
applied judiciously and a curse when expended recklessly. Within the United
States, lighting accounts for more than one-third of all the electricity consumed
for non-residential use. Conservation with respect to how we use electric light-
ing can significantly reduce that usage. Daylighting is one means for achieving
that conservation without abandoning the convenience of lighted interior
space.
To balance the demands of growing electricity needs with limited production
and distribution capability, conservation must play an immediate and sustained
role. There is neither sufficient generating capacity nor grid distribution infra-
structure to sustain our present rate of growth. Adding power plants or grid
capacity is a lengthy and complicated process. Moreover, if the power plants are
fossil-fueled, the problems of environmental pollution and greenhouse gas
emissions are only exacerbated by the new facilities.
There are incentives in the United States for private individuals and busi-
nesses to add renewable resources to their energy supply. An even more promis-
ing indicator is the Energy Policy Act of 2005, which mandates that federal
facilities ''Reduce facility energy use per square foot by 2 percent per year
through the end of 2015 or by 20 percent by the end of FY 2015, relative to
2003 baseline.''
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