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Silicone on glass (SoG) Fresnel lenses are the reference technology in concentrator photovoltaics (CPV) because of their simplicity, cheapness, and proven long-term reliability. However, they are strongly affected by the chromatic aberration. In order to overcome this limitation, the achromatic doublet on glass (ADG) was proposed. Such technology merges the achromatic doublet concept and the simplicity and reliability of the SoG manufacturing process obtaining a cost-effective lens with highly reduced chromatic aberration. In previous works the ADG concept was experimentally demonstrated. Nevertheless, despite the achromatic behavior, the ADG has a low optical efficiency caused by both geometrical and absorption losses. In this work the authors present an alternative ADG architecture with the potential of significantly reduce the main sources of losses and to achieve a superior efficiency. Furthermore, an optimization of the ADG design parameters focused to its application with specific solar cell technologies is presented. The results demonstrated that the technology has the potential of achieving the same efficiency of the SoG technology maintaining the advantages of the achromatic design in term of spectral uniformity and reduced temperature dependency. [ABSTRACT FROM AUTHOR]

A method for misalignments characterization through image acquisition has been adapted and applied to micro-CPV. For this purpose, a measurement set-up and an image processing are proposed and explained. Two different image processing are explored: one based on conventional segmentation method, and another based on Deep Learning. The method is validated based on two measurements that determine the accuracy and the repeatability, showing that the processing based on Deep Learning improves both measurement parameters. [ABSTRACT FROM AUTHOR]

The hybrid modules developed by a Swiss startup, Insolight, consist of a micro-concentrator photovoltaic (micro-CPV) sub-module mounted on a non-concentrator Si backplane. Embedding the micro-CPV cells on top of the flat plate module complements the high efficiency of the CPV with the geographic versatility of the Si cells. Characterization of such modules should be adapted for the requirements and challenges posed by the component submodules. The top CPV layer utilizes the direct component of the incident radiation and the bottom Si layer utilizes the diffuse component. Therefore, it is necessary to test the modules under two lighting conditions. This paper demonstrates a novel solar simulator design for the indoor characterization of hybrid modules based on the collimated-light solar simulator for CPV modules developed by the Instituto de Energía Solar-UPM. The new simulator design adds provisions for testing Silicon submodules under uniform diffuse light by incorporating diffusive elements in the collimated-light path and reducing stray light. The existing CPV simulator at UPM has been refurbished to test the new design concepts. The I-V curve of a hybrid module has been characterized indoors using several configurations and compared to reference measurements obtained outdoors in order to optimize and validate the new setup. [ABSTRACT FROM AUTHOR]

A validated method for misalignments characterization through image acquisition has been adapted for measuring misalignments in micro-CPV modules with integrated tracking. Due to the tight mechanical tolerances and tiny optical elements in this type of technology, a robust image processing that reduces the detection uncertainty of the optical components position in the image is required in order to obtain a valid measurement. An image processing based on pattern recognition is presented with promising results in the accuracy of the detection. [ABSTRACT FROM AUTHOR]

Glass molded optics have a wide range of applications in commercial industry such as for secondary optical elements in concentrator photovoltaics (CPV), optics for light emitting diodes (LEDs), etc... In micro-CPV the reduction in size of all the components demands a very good optical quality of the primary lenses to achieve high concentrations and high efficiencies without the need of secondary optics. Glass for molding is a good candidate due to benefits such as a high abbe number, great mechanical properties, low coefficient of thermal expansion (CTE), low thermal coefficient of the refractive index (dn/dT), proven reliability, and manufacturing by a straight forward compression molding process. In collaboration with the company Holophane S.A.S. in France, several arrays of plano-convex concentrator lenses were manufactured using a manual compression mold. These first prototypes have shown absolute optical efficiency over 80% at 178X using a 1mm2 multi-junction (MJ) solar cell. Further results and potential improvements are discussed. [ABSTRACT FROM AUTHOR]

The possibility of using thermoplastic such as solar encapsulants as an alternative to silicone is shown for encapsulant-on-glass (EOG) lenses. This is an alternative with a respectable potential due to lower material cost, lower coefficient of thermal expansion (CTE), lower thermal coefficient of the refractive index (dn/dT) and a manufacturing process which shares many similarities to the silicone-on-glass (SOG) and flat-plane-PV fabrication. The cost of the optical component of a CPV module can be brought down with this new approach of fabricating Fresnel lenses. Measured efficiency results show optical efficiencies losses of 8% compared to state-of-the-art SOG lenses. This result is preliminary with improvements in lens design and manufacturing still pending. [ABSTRACT FROM AUTHOR]

In this paper we present a comprehensive outdoor experimental characterization of the first modules assembled using the Achromatic Doublet on Glass (ADG) Fresnel lens technology. First, only the elementary units comprising one lens and one cell are investigated: the electrical performance is measured varying the cell-lens distance in order to identify the optimal focal distance. Second, a mono-module (module composed of one lens and one solar cell) has been assembled and installed on a two-axis tracker where it has been continuously measured between June and October 2018. Also, a mono-module including conventional Silicone on Glass (SoG) Fresnel lenses has been assembled and used as benchmark. Results demonstrated that the achromatic design of the ADG lenses used as Primary Optical Elements (POE) provides a significantly reduced temperature dependency of the module performance. The performance is maintained constant throughout the whole measurement period enhancing the energy output over time. [ABSTRACT FROM AUTHOR]

Concentrator photovoltaic usually embeds multi-junction solar cells, which exhibit high spectral sensitivity due to the internal series connection of the sub-cells. The use of so-called isotype or component cells with the same spectral response as the corresponding sub-cell, is widely applied for characterizing the spectral content of the impinging irradiance. These isotype sensors can be substituted by the multi-junction cells themselves, which are inherently spectrally tuned to any evolution of the multi-junction technology. To convert a multi-junction cell in a spectral sensor, it is necessary to add bias light within the spectral response of all but one of the sub-cells to saturate the corresponding junctions, so the nonsaturated limits the current under any specified impinging spectrum. This paper shows indoor and outdoor side-by-side comparison of the so-called pseudo isotypes, based on a triple-junction solar cell, and genuine isotypes. The conditions to ensure an accurate spectral response, particularly for the bottom pseudo-isotype, are presented and discussed. [ABSTRACT FROM AUTHOR]

The manufacturing method developed to obtain Achromatic Doublet on Glass (ADG) Fresnel lenses results in an optical system with high concentration while maintains a reduced cost. Recent improvements in the manufacturing process are presented in this paper. First, an adhesion promoter has been used in order to enhance adhesion between plastic and elastomer interface. This avoids the efficiency drop caused by delamination due to changes in temperature through the day. . Second, the whole lamination process has been almost completely automatized, requiring the intervention of a human operator only to place the lens inside the laminator. Finally, a new injection mold based on nickel stamper technology has been manufactured improving the geometrical characteristics of the plastic element of the lens (lower draft angle and tip rounding). [ABSTRACT FROM AUTHOR]

Concentrator photovoltaic usually embeds multi-junction solar cells, which exhibit high spectral sensitivity due to the internal series connection of the sub-cells. The use of so-called isotype or component cells with the same spectral response as the corresponding sub-cell, is widely applied for characterizing the spectral content of the impinging irradiance. These isotype sensors can be substituted by the multi-junction cells themselves, which are inherently spectrally tuned to any evolution of the multi-junction technology. To convert a multi-junction cell in a spectral sensor, it is necessary to add bias light within the spectral response of all but one of the sub-cells to saturate the corresponding junctions, so the nonsaturated limits the current under any specified impinging spectrum. This paper shows indoor and outdoor side-by-side comparison of the so-called pseudo isotypes, based on a triple-junction solar cell, and genuine isotypes. The conditions to ensure an accurate spectral response, particularly for the bottom pseudo-isotype, are presented and discussed. [ABSTRACT FROM AUTHOR]

The manufacturing method developed to obtain Achromatic Doublet on Glass (ADG) Fresnel lenses results in an optical system with high concentration while maintains a reduced cost. Recent improvements in the manufacturing process are presented in this paper. First, an adhesion promoter has been used in order to enhance adhesion between plastic and elastomer interface. This avoids the efficiency drop caused by delamination due to changes in temperature through the day. . Second, the whole lamination process has been almost completely automatized, requiring the intervention of a human operator only to place the lens inside the laminator. Finally, a new injection mold based on nickel stamper technology has been manufactured improving the geometrical characteristics of the plastic element of the lens (lower draft angle and tip rounding). [ABSTRACT FROM AUTHOR]

The experimental method to determine the spectrally-resolved optical efficiency of concentrating optics is described in this paper. The measurement uses a multi-junction solar cell as light sensor and a series of band-pass filters to isolate the optical performance of different narrow spectral bands throughout the spectrum of interest. Additional bias light is provided to saturate the subcells whose spectral response is out of the transmittance of every band-pass filter. The method allows the characterization of the combined transmittance, reflectance and absorbance of every material composing the optics including optical couplers and thin layers such as antireflective coatings. The two application cases included illustrate the potential of this novel characterization technique. Firstly, a novel refractive concentrator, the Achromatic Doublet on Glass (ADG) Fresnel lens is measured. Secondly, the method is applied to analyze the degradation of outdoor exposed glass molded Secondary Optical Elements (SOE). [ABSTRACT FROM AUTHOR]

In this paper we present a comprehensive experimental characterization of Achromatic Doublet on Glass (ADG) Fresnel lenses. When compared to a Silicone on Glass (SoG) Fresnel lens, the ADG Fresnel lens shows higher tolerance to displacements of the lens with respect to the optimal lens-to-cell distance. Furthermore, lower sensitivity of the ADG Fresnel lens to temperature variations has been experimentally proven. [ABSTRACT FROM AUTHOR]

In this paper we present a novel manufacturing method to produce achromatic Fresnel lenses for photovoltaic application. These achromatic lenses are capable of reaching a concentration factor three times higher than that attained by a conventional Silicone-on-Glass (SOG) Fresnel lens. The manufacturing method presented to fabricate the achromatic lens, which we refer to as Achromatic Doublet on Glass (ADG) Fresnel lens, is simple, cost-effective and highly scalable. A comprehensive ray-tracing analysis and its comparison with experimental results is presented in this work. [ABSTRACT FROM AUTHOR]