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The vehicle integrated photovoltaic (VIPV) technology, which consists in integrating PV solar panels in the surfaces of electric vehicles, is a promising technology to increase car autonomy. Free-form curved PV surfaces are demanded to meet the specific design constraints of the automotive. The proper characterization of three dimensional PV surfaces requires specific methods and equipment that must be developed. This paper describes the design principles and requirements of a solar simulator for characterization of curved PV modules. Its effectiveness is demonstrated by means of ray-tracing simulations, the results show the advantages provided by the use of a collimated light source in comparison to the conventional solar simulators used for flat modules. The light beam divergence of a non-collimated light source produces a non-uniformity boost between 2% and 20% depending on the module size and curvature. The module performance will be affected by this non-uniform irradiance, but the performance loss will also depend on specific characteristics of the module such as curvature, number and size of cells, series/parallel electrical connection and number of by-pass diodes. On the contrary, the proposed collimated solar simulator reproduces the solar illumination profile over the curved surface. The Helios 3198, a solar simulator with collimated light developed for concentrator modules, has been adapted accordingly to the design proposed. A module of 1 m of curvature has been tested, the short-circuit current of the cells follows the ideal cosine response of the curvature, differences are lower than 0.5% which proves the quality of the collimated beam.

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.

To better understand the process of condensation formation in CPV modules, an experimental setup containing two Insolight mockup modules has been prepared to firstly, monitor the relevant variables involved in the internal dew point, namely the internal relative humidity and air temperature, the differential atmospheric pressure between the module and the environment and the temperatures of the front and rear parts of the modules, and secondly, to be able to modify the exchange conditions with the environment. After spending the wet season in Madrid (four months during the winter), the formation of condensation has been correlated with the monitored dew point and most of the time it disappears after a few hours. Considering that sealing the module would increase the internal pressure to the point of failure due to thermal expansion, the modules are always equalized through a breather. Hence, some preliminary mitigating actions have been studied such as the addition of desiccant and different venting configurations that seek to reduce the amount of humidity content and therefore help prevent the formation of the dew point.

Within the EU-funded project HIPERION, significant progress has been made on the Insolight solar panel: a high-efficiency rooftop compatible micro-CPV device with integrated planar microtracking and diffuse collection via additional low-cost Si solar cells. The IES-UPM and other R&D centers in the consortium have been tasked with characterizing the various generation of this technology. In this work we discuss the evolution of the module design and present the latest results for “Gen1” solar panels showing significant improvement in performance in self-tracking compared to earlier results even in the face of a 5X increase in module area.

Within the EU-funded project HIPERION, significant progress has been made on the Insolight solar panel: a high-efficiency rooftop compatible micro-CPV device with integrated planar microtracking and diffuse collection via additional low-cost Si solar cells. The IES-UPM and other R&D centers in the consortium have been tasked with characterizing the various generation of this technology. In this work we discuss the evolution of the module design and present the latest results for “Gen1” solar panels showing significant improvement in performance in self-tracking compared to earlier results even in the face of a 5X increase in module area.

A tracking‐integrated hybrid micro‐concentrator module is presented that can harvest direct, diffuse, and albedo irradiance components. It uses biconvex 180× lens arrays to concentrate direct light on high‐efficiency III–V solar cells (29% module efficiency has been demonstrated outdoors on direct sunlight at Concentrator Standard Test Conditions) and a planar micro‐tracking mechanism to allow installation in static frames. Two architectures have been developed to harvest diffuse irradiance: (1) a hybrid architecture where the backplane is covered with monofacial or bifacial Si cells; (2) a translucent architecture where diffuse light is transmitted through the module for dual‐land‐use applications, such as agrivoltaics. Simulations show that the hybrid architecture provides an excess of yearly energy production compared to 20% efficiency flat‐plate photovoltaic (PV) module in all locations studied, including those with a low direct normal irradiance (DNI) content, and up to 38% advantage in high‐DNI locations. The use of bifacial heterojunction and interdigitated back‐contact Si cells has been explored for the glass–Si–glass backplane laminate to harvest albedo light. Bifacial gains modeled can boost energy yield by about 30% in the best scenario. We discuss the perspectives of the translucent modules for dual‐land‐use applications as well, such as integration in greenhouses for agriculture‐integrated PV (agrivoltaics). This architecture can provide up to 47% excess electricity compared to a spaced reference Si array that transmits the same amount of solar photosynthetically active radiation for crop production. The HIPERION consortium funded by the European H2020 program is making an intensive effort to take this technology to the industrial scale.

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 monomodule 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.

Spectral indices can be defined to characterize how the solar spectrum affects photovoltaic devices. The use of such indices is particularly important in technologies which are highly dependent on spectral variations, such as tandem, or multijunction (MJ), solar cells. In this paper, we analyze the capability of three effective irradiance values, given by the photocurrents of the components of triple-junction solar cells, and covering different spectral bands, to define the spectrum condition. Even though these parameters will be based on a particular type of MJ solar cell, they provide enough information to accurately assess the spectral impact on other types of MJ solar cell technologies with significantly different spectral responses. Consequently, specific component cells for each MJ solar cell technology may not be necessarily needed and a reference technology could be used for all of them, providing a way for the future standardization of these devices as a mean of defining the solar spectral condition.

An inherent characteristic of high concentrator photovoltaics (HCPV) modules is a tight mechanical tolerance caused by the narrow angular transmission of the optical system, typically below or close to 1°. Misalignments in the modules caused during the assembly process in the production line will degrade not only the electrical but also the angular performance of the module. Moreover, dispersion in the electrical characteristics of the elementary units comprising a module would lead also to power loss. Quality control and data analysis on the production line is of great significance for adjusting the production line and preserving the angular tolerance and the electrical performance. This is particularly critical during the set-up and tuning of an automated production line. This paper presents the results of a pilot production line for HCPV modules carried out within the European funded ECOSOLE project. Several quality controls were established, which are the binning of the photovoltaic receivers, the measurement of misalignments among the elementary units within every module, and the indoor electrical characterization of the modules. Collected experimental data during the tuning phase of the pilot line were used to validate a module performance model based on production parameters. Monte Carlo method is lately applied to the model to assess the influence of production defects of diverse nature and the adequacy of quality controls, in several manufacturing scenarios beyond the specific constrains of the ECOSOLE experience.

The results of three CPV module round robins are presented. Ten test labs around the world participated to the round robins in total. Each round robin used a different CPV module technology (Daido Steel, Soitec, Suncore). The data gathered at the test labs was used to test CSOC power rating procedures as basis for the IEC draft standard 62670-3. The deviation between the minimum and the maximum power output rated at the test labs was in average 4.4 % with a standard deviation of 1.8 %abs. This underlines that power ratings or CPV modules are reliable and reproducible.

We present a method to characterize achromatic Fresnel lenses for photovoltaic applications. The achromatic doublet on glass (ADG) Fresnel lens is composed of two materials, a plastic and an elastomer, whose dispersion characteristics (refractive index variation with wavelength) are different. We first designed the lens geometry and then used ray-tracing simulation, based on the Monte Carlo method, to analyze its performance from the point of view of both optical efficiency and the maximum attainable concentration. Afterwards, ADG Fresnel lens prototypes were manufactured using a simple and reliable method. It consists of a prior injection of plastic parts and a consecutive lamination, together with the elastomer and a glass substrate to fabricate the parquet of ADG Fresnel lenses. The accuracy of the manufactured lens profile is examined using an optical microscope while its optical performance is evaluated using a solar simulator for concentrator photovoltaic systems. The simulator is composed of a xenon flash lamp whose emitted light is reflected by a parabolic mirror. The collimated light has a spectral distribution and an angular aperture similar to the real Sun. We were able to assess the optical performance of the ADG Fresnel lenses by taking photographs of the irradiance spot cast by the lens using a charge-coupled device (CCD) camera and measuring the photocurrent generated by several types of multi junction (MJ) solar cells, which have been previously characterized at a solar simulator for concentrator solar cells. These measurements have demonstrated the achromatic behavior of ADG Fresnel lenses and, as a consequence, the suitability of the modelling and manufacturing methods.

This article summarizes experimental methods to evaluate the performance and to assess the efficiency of a lens that will be used as primary optics in a concentrating photovoltaic system comprising multijunction solar cells. The methods are classified into two groups: those intended to quantify the transmission losses and those that estimate the size and shape of the light spot. In addition, the optical efficiency definition is reviewed and a systematic procedure to evaluate it is proposed.

Secondary optical elements (SOEs) are used in Concentrator Photovoltaic (CPV) modules to allow the concentration ratio to exceed those typically achievable by Fresnel lenses, reducing cell costs, without sacrificing tolerance to tracking errors. One option is a “dome” SOE: a simple, single surface refractive optic that images the primary lens onto the cell while immersing it. In this article, we explore the limits of this type of SOE and propose an evolved version, which we dub the Hybrid Dome Reflector (HDR), which offers advantages especially for high concentration modules with large cells, where reflective secondaries do not offer sufficient acceptance angle, but other dielectric secondaries, such as the Dielectric Totally Internally Reflecting Concentrator DTIRC, may be too large for economical manufacture. We discuss aspects of HDR design and share selected ray-tracing simulations and experimental results. We show that the new HDR design improves acceptance angle and tolerances to manufacturing error and lens temperature as compared to a reflective SOE built while offering similar efficiencies.

This article describes the procedure proposed by IES-UPM to measure the optical efficiency and the irradiance of the focused spot of a primary optic for concentrator PV (CPV). The method using a broadband source (solar simulator) with a solar cell as the sensor and analysis of the focused spot recorded by a camera is described in detail here to convey the details of the optical characterization in the emerging IEC 62989 technical specification. Special emphasis is placed in noting the main sources of error and the accuracy of the measurement method. As an example, the main outcomes attained in the characterization of a set of Fresnel lenses are reported.

This paper presents a novel Fresnel lens capable to significantly reduce chromatic aberration in solar applications. The optical performance of this achromatic lens has been analyzed through ray-tracing simulations, showing a concentration factor three times higher than that attained by a classic Silicone On Glass (SOG) Fresnel lens while maintaining the same acceptance angle. This should avoid the need for a secondary optical element, reducing the cost associated with its manufacturing and assembly and increasing the module reliability. The achromatic lens is made of inexpensive plastic and elastomer which allows a highly scalable and cost-competitive manufacturing process similar to the one currently used for the fabrication of SOG Fresnel lenses. (C)2016 Optical Society of America

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.

The tuning of the assembly line of concentrated photovoltaic (CPV) modules is an important task to ensure that the efficiency of modules made at the production line is as high as those fabricated in the development phase. A solar simulator for CPV and a module optical analyzer (MOA) are proposed to be used in production to improve the quality of the assembling process (both during the tuning of the production line and once it is completed). Moreover, the usefulness of performing a quality control based on maximum power and optical pointing of modules is discussed by performing a deep analysis of some modules manufactured in the production line and characterized both indoors and outdoors.

Secondary optical elements (SOEs) are used in Concentrator Photovoltaic (CPV) modules to allow the concentration ratio to exceed those typically achievable by Fresnel lenses, reducing cell costs, without sacrificing tolerance to tracking errors. One option is a “dome” SOE: a simple, single surface refractive optic that images the primary lens onto the cell while immersing it. In this article, we explore the limits of this type of SOE and propose an evolved version, which we dub the Hybrid Dome Reflector (HDR), which offers advantages especially for high concentration modules with large cells, where reflective secondaries do not offer sufficient acceptance angle, but other dielectric secondaries, such as the Dielectric Totally Internally Reflecting Concentrator DTIRC, may be too large for economical manufacture. We discuss aspects of HDR design and share selected ray-tracing simulations and experimental results. We show that the new HDR design improves acceptance angle and tolerances to manufacturing error and lens temperature as compared to a reflective SOE built while offering similar efficiencies.