Environmental Engineering Reference
In-Depth Information
SDSU 6/21/06
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Fig. 5.20 Typical plot showing electrical energy displacement by HSL
5.8 Discussion and Conclusion
HSL is providing a novel means for introducing daylighting into existing non-
residential buildings in a way that seamlessly integrates with the existing
infrastructure. By its nature, HSL is a technically complex product that has
all of the maintenance concerns of any system with moving parts and, like
other solar technologies, must be cleaned occasionally to ensure optimum
performance. Because of the precision pointing requirements the system must
be monitored from time to time and will never have the simplicity offered by a
passive skylight. In addition, HSL requires direct, unobstructed sunlight and
cannot effectively use diffuse light in overcast conditions, whereas skylights
can. Unlike other daylighting alternatives, however, HSL provides the ability
to integrate sunlight into existing buildings in a way that blends seamlessly
with other lighting systems and can be routed through complex paths if
needed. Despite its limitations, early adopters are embracing the HSL tech-
nology for its lighting quality, its ease of integration, and its novelty. The
concept of making the technology compatible with existing lighting and
architectural environments has played a major role in its early acceptance.
The HSL technology has decreased significantly in cost as the product has
evolved, but the cost is still keeping the technology limited to the early adopter
market. Cost reductions due to design changes and economy of scale are
expected to further decrease the installed cost of the systems by as much as
50% by 2010.
Acknowledgments Research at Oak Ridge National Laboratory was sponsored by the US
Department of Energy's Office of Energy Efficiency and Renewable Energy and the Tennes-
see Valley Authority.
