Abstract
We present a design and optical simulation of a cost-effective
hybrid daylighting/LED system composed of mixing sunlight and
light-emitting diode (LED) illumination powered by renewable solar energy
for indoor lighting. In this approach, the sunlight collected by the
concentrator is split into visible and non-visible rays by a beam
splitter. The proposed sunlight collector consists of a Fresnel lens
array. The non-visible rays are absorbed by the solar photovoltaic devices
to provide electrical power for the LEDs. The visible rays passing through
the beam splitters are coupled to a stepped thickness waveguide (STW) by
tilted mirrors and confined by total internal reflection (TIR). LEDs are
integrated at the end of the STW to improve the lighting quality.
LEDs’ light and sunlight are mixed in the waveguide and they
are coupled into an optical fiber bundle for indoor illumination. An
optical sensor and lighting control system are used to control the LED
light flow to ensure that the total output flux for indoor lighting is a
fixed value when the sunlight is inadequate. The daylighting capacity was
modeled and simulated with a commercial ray tracing software
(LighttoolsTM). Results show that the system can
achieve 63.8% optical efficiency at geometrical concentration ratio of
630. A required accuracy of sun tracking system achieved more than
±0.5o. Therefore, our results provide an
important breakthrough for the commercialization of large scale optical
fiber daylighting systems that are faced with challenges related to high
costs.
© 2016 Optical Society of Korea
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