Environmental Engineering Reference
In-Depth Information
Fig. 5.2 One implementation of the Himawari daylighting system
had been born. One of the first attempts to commercialize fiber-coupled day-
lighting was the Himawari system, shown in Fig. 5.2.
In addition to the obvious advantages of concentration and flexibility, the
use of optical fibers and concentrating optics provided the option of filtering the
light to remove ultraviolet (UV) and IR wavelengths. The removal of the IR
wavelengths could eliminate virtually all heating from the daylight that entered
the room, and the removal of the UV could reduce the potential for the light to
produce fading (technically known as photo bleaching) of fabrics and structures
in the lighted area. By comparison with conventional skylights, fiber optic
daylighting could significantly reduce heating and cooling loads imposed by
the daylighting systems.
With the creative application of optical filtering, fiber optic daylighting
systems offered additional degrees of freedom. As early as 1983, a fiber optic
daylighting system that also included photovoltaic (PV) conversion was pro-
posed [3]. In this system, a dichroic mirror filter would be inserted into the light
from a focusing lens to reflect the visible portion of the light into fibers for
illumination. The IR light would pass through the dichroic mirror to strike a PV
cell and be converted into electricity for other applications.
