We introduce the conceptual design of the optical core for a spectral-splitting and light-guiding four-terminal (4T) photovoltaic (PV) module, with appealing features for bifacial operation. We analyze the applicability of the solution and its performance using a commercial ray-tracing software for direct and diffused solar irradiance at standard AM1.5G spectrum. The core is a right-angle transparent wedged (RAW) prism. Complementary, two dichroic mirrors are optically coupled to the rear and bottom faces of the wedge to perform the spectral-splitting (SS) function. Low-gain concentration in the visible (VIS) band is provided by combining dichroic reflections with achromatic total internal reflection (TIR) at the topmost air-dielectric interface for light guiding. The module can support 4T heterojunction connection, implemented with wide-bandgap (WG) solar cells for the VIS and silicon-based solar cells for the near infrared (NIR). At a geometrical concentration gain CG-VIS ≈ 4 and wide optical acceptance angle θA ≈ 48°, also VIS diffused light is effectively collected and a spectrally integrated optical efficiency ηo,diff = 62%, (ηo(diff,NIR) =45%, ηo(diff,VIS) = 17%) is estimated. Under direct illumination ηo,dir > 80% is obtained over the whole angular acceptance with a maximum optical efficiency ηo,dir-MAX ≈ 88.7% at θi = 37°. Low-concentrating RAW-SS can work stationary and trackless. The tilt angle for the orientation 𝛽 is set according to the latitude at the installation site, and in the northern hemisphere, it is more north-oriented with respect to standard panels. The collection of albedo irradiance from the ground is favored, since the scaling coefficient for self-shading of the module at sun elevation 𝜙 is lower than for standard flat panels of equivalent input area and normally oriented. The decrease in self-shading is therefore an asset for bifacial operation and specifically effective at lower latitudes where solar irradiance is stronger. The possible applications range from sub-watt indoor PV and Internet-of-Things power suppliers to utility-scale plants and building-integrated solutions.
An asymmetric low concentrator and spectral splitting approach to bifacial four‐terminal photovoltaic modules
Alice Carlotto;Stefano Varas;Alessandro Chiasera;
2023-01-01
Abstract
We introduce the conceptual design of the optical core for a spectral-splitting and light-guiding four-terminal (4T) photovoltaic (PV) module, with appealing features for bifacial operation. We analyze the applicability of the solution and its performance using a commercial ray-tracing software for direct and diffused solar irradiance at standard AM1.5G spectrum. The core is a right-angle transparent wedged (RAW) prism. Complementary, two dichroic mirrors are optically coupled to the rear and bottom faces of the wedge to perform the spectral-splitting (SS) function. Low-gain concentration in the visible (VIS) band is provided by combining dichroic reflections with achromatic total internal reflection (TIR) at the topmost air-dielectric interface for light guiding. The module can support 4T heterojunction connection, implemented with wide-bandgap (WG) solar cells for the VIS and silicon-based solar cells for the near infrared (NIR). At a geometrical concentration gain CG-VIS ≈ 4 and wide optical acceptance angle θA ≈ 48°, also VIS diffused light is effectively collected and a spectrally integrated optical efficiency ηo,diff = 62%, (ηo(diff,NIR) =45%, ηo(diff,VIS) = 17%) is estimated. Under direct illumination ηo,dir > 80% is obtained over the whole angular acceptance with a maximum optical efficiency ηo,dir-MAX ≈ 88.7% at θi = 37°. Low-concentrating RAW-SS can work stationary and trackless. The tilt angle for the orientation 𝛽 is set according to the latitude at the installation site, and in the northern hemisphere, it is more north-oriented with respect to standard panels. The collection of albedo irradiance from the ground is favored, since the scaling coefficient for self-shading of the module at sun elevation 𝜙 is lower than for standard flat panels of equivalent input area and normally oriented. The decrease in self-shading is therefore an asset for bifacial operation and specifically effective at lower latitudes where solar irradiance is stronger. The possible applications range from sub-watt indoor PV and Internet-of-Things power suppliers to utility-scale plants and building-integrated solutions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
