Distributed Renewable Energy Operating Impacts and Valuation Study

Solar Characterization
2.4 Daylighting
2.4.1 Technology Description
Overview
Daylighting is the practice of using natural light to illuminate building spaces. Rather than
relying solely on electric lighting during the day, daylighting brings indirect natural light into the
building, reducing the need for electric lighting.
In the U.S. market, dimmable fluorescent ballasts make up about 4 percent of commercial
lighting. Daylighting control solutions are installed in less than 2 percent of new commercial
buildings and in a negligible portion of retrofit applications. This is due to the costs and
restrictions associated with re-wiring components. At least three lighting manufacturers in the
United States currently market “packaged” integrated daylighting control systems. Each is
relatively new, having entered the market within the six years and brings a different set of
advantages and drawbacks. None of them claim more than a few thousand systems installed. 9
There are two basic types of daylighting systems: passive and active. Both types use electronic
controls to dim the electric lighting when there is sufficient daylight. 10
Passive daylighting systems use a prismatic dome, reflective light shaft and diffusing lens to
light the building interior. They have no moving parts. Figure 2-13 represents a schematic
diagram of a passive daylighting installation.
Figure 2-13: Passive Daylighting System
Active daylighting systems, as shown in Figure 2-14, use sun-tracking mirrors to redirect
sunlight into a reflective light well and onto a diffusing lens. They provide a building’s interior
with high levels of well-diffused light, up to an average of 10 hours per day on sunny and bright
cloudy days.
9 ACEEE, Emerging Technologies Report: Integrated Daylighting Systems (Dimming Ballasts), June 2006.
10 Data taken from www.daylighting.com
Distributed Renewable Energy Operating Impacts & Valuation Study R. W. Beck, Inc. 2-23