Trackfree Planar Solar Concentrator System

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Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa, 2012
Article de conférence

Solar concentrator systems rely on focusing a large collecting aperture onto a small one where a high efficiency solar cell is placed. The main drawback of concentrator systems is the need to track the direction of the sun. We report on the development of a trackfree planar solar concentrator which employs a self-adaptive light responsive mechanism. The working mechanism is based on optical trapping reflective particles dispersed into a liquid waveguide. The trapping effect experienced by the reflective particle at the focus of the collecting aperture effectively forces the particle to follow the direction of sunlight. The role of the reflective particle is to couple the cone of focused sunlight into a waveguide by total internal reflection (TIR) towards a solar cell placed at its edges. We report on preliminary experiments on metallic reflective particles and on gas-filled hollow glass particles that exhibit reflective properties by total internal reflection. We show promising results on vapor bubbles generated by the focused light which couple nearly 100% of the incoming light into waveguiding modes. The generated bubbles are stable and track the focal point.

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,
Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa, 2012
Article de conférence

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Efficiency of a micro-bubble reflector based, self-adaptive waveguide solar concentrator

Eric Tremblay, Volker Günter Zagolla

State of the art solar concentrators use free-space, non-imaging optics to concentrate sunlight. Mechanical actuators keep the focal spot on a small solar cell by tracking the sun's position. Planar concentrators emerged recently that employ a waveguide slab to achieve high concentration by coupling the incident sunlight into the waveguide. We report on the development of an opto-fluidic waveguide coupling mechanism for planar solar concentration. The self-adaptive mechanism is light-responsive to efficiently maintain waveguide coupling and concentration independent of incoming light's direction. By using an array of axicons and lenses, an array of vapor bubbles are generated inside a planar, liquid waveguide, one for each axicon-lens pair. The mechanism uses the infrared part of the solar spectrum on an infrared absorbing medium to provide the energy needed for bubble generation. Visible light focused onto the bubble is then reflected by total internal reflection (TIR) at the liquid-gas interface and coupled into the waveguide. Vapor bubbles inside the liquid are trapped by a thermal effect and are shown to self-track the location of the infrared focus. We show experimental results on the coupling efficiency of a single bubble and discuss the effect of angular coupling. Furthermore the effect of an array of bubbles inside the waveguide (as produced by a lensarray) onto the coupling efficiency and concentration factor is analyzed.

Spie-Int Soc Optical Engineering2013

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Demonstration and future potential of a self-tracking phase change actuator

Eric Tremblay, Volker Günter Zagolla

State-of-the-art concentrators use free-space optics to concentrate sunlight onto photovoltaic cells. To achieve high concentration factors it is necessary to track the sun's position. In current systems, mechanical actuators keep the focal spot in the solar cell. Planar concentrators have recently emerged, which use a waveguide slab to concentrate the sunlight. Here we demonstrate the development of a phase-change actuator (PCA) for self-adaptive tracking. The demonstrated mechanism is light-responsive and provides self-adaptive light concentration in a planar waveguide while maintaining efficient concentration over an angular range of +/- 16 degrees. The proposed system consists of a lens array to focus the sunlight, a waveguide slab acting as a concentrator, a dichroic prism membrane, splitting the solar spectrum into a visible (VIS) and infrared (IR) part, and the phase-change actuator. The actuator undergoes a phase change upon absorption of the IR light and vertically expands, creating a coupling feature upon contact with the waveguide. Visible light is then reflected off the prism membrane and efficiently coupled into the waveguide. As the focus spot moves, so does the coupling feature due to the light responsiveness of the actuator. We show an experimental proof-of concept prototype, highlighting the desired features of the concept. This is then further expanded by simulations of a full system achieving high effective concentrations (>100X) and first experimental results expanding the prototype to a full system.

Spie-Int Soc Optical Engineering2014

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Light induced fluidic waveguide coupling

Christophe Moser, Eric Tremblay, Volker Günter Zagolla

We report on the development of an opto-fluidic waveguide coupling mechanism for planar solar concentration. This mechanism is self-adaptive and light-responsive to efficiently maintain waveguide coupling and concentration independent of incoming light's direction. Vapor bubbles are generated inside a planar, liquid waveguide using infrared light on an infrared absorbing glass. Visible light focused onto the bubble is then reflected by total internal reflection (TIR) at the liquid-gas interface and coupled into the waveguide. Vapor bubbles inside the liquid are trapped by a thermal effect and are shown to self-track the location of the infrared focus. Experimentally we show an optical to optical waveguide coupling efficiency of 40% using laser light through a single commercial lens. Optical simulations indicate that coupling efficiency > 90% is possible with custom optics. (C) 2012 Optical Society of America

Optical Soc Amer2012

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