Semi-Transparent Energy-Harvesting Solar Concentrator Windows Employing Infrared Transmission-Enhanced Glass and Large-Area Microstructured Diffractive Elements

Abstract

We report on the study of energy-harvesting performance in medium-size (400 cm2) glass-based semitransparent solar concentrators employing edge-mounted photovoltaic modules. Systems using several different types of glazing system architecture and containing embedded diffractive structures are prepared and characterized. The technological approaches to the rapid manufacture of large-area diffractive elements suitable for use in solar window-type concentrators are described. These elements enable the internal deflection and partial trapping of light inside glass-based concentrator windows. We focus on uncovering the potential of pattern-transfer polymer-based soft lithography for enabling both the improved photon collection probability at solar cell surfaces, and the up-scaling of semitransparent solar window dimensions. Results of photovoltaic characterization of several solar concentrators employing different internal glazing-system structure and diffractive elements produced using different technologies are reported and discussed.

Recent Developments in Solar Energy-Harvesting Technologies for Building Integration and Distributed Energy Generation

“…This is because the only long-range (in the absence of glass surface imperfections or strong scattering) photon transport mechanism suitable for trapping the incident light energy within transparent waveguides is total internal reflection (TIR), which itself is enabled by the random directional character of luminescent emissions. The internal structure of LSC-type devices has also undergone rapid development, relying on the advances in areas, such as application-specific thin-film coatings, spectrally-selective transparent diffractive optics [20,77], embedded Mie scattering media [19,78], or other components designed to stimulate partial light trapping within waveguide-type glazing systems. More recently, conventional (non-transparent) PV elements, e.g., silicon or copper indium-gallium selenide (CIGS) cell modules started to merge into the design structure of transparent window-type solar concentrators, blocking a small transparent area fraction, but boosting the electric output through both the direct incident light capture and also collecting a part of light travelling within the device [40,55,[79][80][81].…”

“…The application potential, role, and purpose of embedding the light-ray deflecting microstructures into LSC-type waveguides of solar windows are illustrated in Figure 4. Detailed analysis of the potential of diffractive and scattering optics for improving the photon collection probability at solar cells is reported in [20] and [77]. The roles of spectrally-selective backside-reflector coatings and especially the waveguiding panel thickness, in ensuring the capability of longer-range transport of the incident photons within waveguides, even in the presence of significant scattering, is also illustrated in Figure 4.…”

“…Structured systems with multiple glass-air interfaces have been shown to provide mean photon path lengths somewhat in excess of that predicted by Equation 2, due to the increased probability of multiple internal reflections. Regardless of these fundamental limitations, collecting the photons efficiently at concentrator system edges, from the areas of incidence onto glass located within the range of several times the system thickness remains a valid option, which is demonstrated graphically in [77], in the presence of strong scattering at micron-scale luminophore pigment particles. The relevance of scattering as a short-range photon collection mechanism in LSC is also reported in [19,20] and discussed in [78,95].…”

Recent Developments in Solar Energy-Harvesting Technologies for Building Integration and Distributed Energy Generation

“…This is because the only long-range (in the absence of glass surface imperfections or strong scattering) photon transport mechanism suitable for trapping the incident light energy within transparent waveguides is total internal reflection (TIR), which itself is enabled by the random directional character of luminescent emissions. The internal structure of LSC-type devices has also undergone rapid development, relying on the advances in areas such as application-specific thin-film coatings, spectrally-selective transparent diffractive optics [20,77], embedded Mie scattering media [19,78], or other components designed to stimulate partial light trapping within waveguide-type glazing systems. More recently, conventional (non-transparent) PV elements, e.g.…”

“…The application potential, role, and purpose of embedding the light-ray deflecting microstructures into the LSC-type waveguides of solar windows is illustrated in Figure 4. Detailed analysis of the potential of diffractive and scattering optics for improving the photon collection probability at solar cells has been reported in [20] and [77]. The roles of spectrally-selective backsidereflector coatings and especially the waveguiding panel thickness in ensuring the capability of longer-range transport of the incident photons within waveguides, even in the presence of significant scattering, is also illustrated in Figure 4.…”