ABSTRACT In this work the experimental results of a new concentrator PV module (named Rondine) developed by CPower s.r.l. are presented. This concentrating module has a medium concentration level (~25x) and employs silicon solar cells.... more
ABSTRACT In this work the experimental results of a new concentrator PV module (named Rondine) developed by CPower s.r.l. are presented. This concentrating module has a medium concentration level (~25x) and employs silicon solar cells. The tests have been carried out in Italy and the energy production of a prototypal Rondine module is compared with that produced by a tracking flat plate crystalline PV panel. The non-imaging optic of the concentrator allows for larger angular acceptance respect to many solar concentrators, giving the possibility to employ trackers for standard PV modules. The first results of a complete system of 4 kW of peak power installed in July 2008 are here presented.
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ABSTRACT A novel, powerful method for the optical characterization of solar concentrators is presented. It requires the reversing of light path, realized through the backward illumination of the concentrator from the receiver surface, and... more
ABSTRACT A novel, powerful method for the optical characterization of solar concentrators is presented. It requires the reversing of light path, realized through the backward illumination of the concentrator from the receiver surface, and the measuring of intensity distribution of light projected on a far, diffusive screen. If the source of back illumination is spatially uniform and has a Lambertian angular distribution, then the angle-resolved relative radiance derived from the projected light intensity perfectly coincides with the relative angle-resolved transmission efficiency of the concentrator operating in the normal, direct mode. Respect to the conventional method for deriving the angle-resolved efficiency, which requires an expensive apparatus and long measurements at different orientations of the concentrator respect to a parallel beam, the presented, inverse, method is extremely simple to apply and requires only the recording of an image, that displayed on the screen, by a camera or a CCD. The inverse method, previously validated with simple ideal, reflective non-imaging (CPC) concentrators, is here applied to real (absorbing) reflective non-imaging and refractive Fresnel lens systems.
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During the last years, because of the low cost, high crystalline perfection and sound knowledge on the handling, the use of bent silicon crystals for applications in accelerators has been intensively investigated. In particular, great... more
During the last years, because of the low cost, high crystalline perfection and sound knowledge on the handling, the use of bent silicon crystals for applications in accelerators has been intensively investigated. In particular, great attention has been paid towards improving extraction efficiency by the methods used to realize the crystals. For example, 70 GeV protons were extracted from the beam accelerator in Protvino with silicon crystal, obtaining a channeling efficiency close to 85%. The key reason for this successful operation was the use of very short bent crystals. Realization of the short bent crystal devices, as a crystalline undulator, can be difficult by traditional mechanical techniques; a possible alternative method could be the deposition of a high residual stress film onto a Si wafer. We have studied and tested two alternative methods to achieve a uniform curvature of silicon wafers: deposition of both silicon nitride films and thick aluminium films.
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Research Interests:
The development of new technologies in the field of renewable energies is becoming a key issue for economies of the next future. The worldwide exponential growth of photovoltaic installation, recently pushed up in many countries by... more
The development of new technologies in the field of renewable energies is becoming a key issue for economies of the next future. The worldwide exponential growth of photovoltaic installation, recently pushed up in many countries by feed-in tariffs, is giving a boost to the research and development of new solutions in the PV world. Huge investments have recently been made for the installation of plants for production of purified polysilicon as well as for the production of thin film solar cells. A very interesting way for reduction of costs of the photovoltaic energy production, which has the final goal to compete with the fossil fuel sources, is given by the photovoltaic concentrators; this alternative solution consists of replacing the large area of photoactive material, which is the most expensive component of the PV panels, with low cost optical structures with the function of concentrating the light on photovoltaic cell of the small area
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Rondine® photovoltaic concentrators have been developed by CPower Srl during the last 3 years; these CPV modules have a low concentration (20-25x) and use Silicon solar cells, combined with a reflective, non-imaging optics. Two systems of... more
Rondine® photovoltaic concentrators have been developed by CPower Srl during the last 3 years; these CPV modules have a low concentration (20-25x) and use Silicon solar cells, combined with a reflective, non-imaging optics. Two systems of 3.67 kWp* and 4.65kWp* have been installed in North and South Italy during 2008. The modules have been mounted on cheap 2-axis trackers for standard, flat plate PV modules, considering the high angular acceptance of the employed optics. The energy production from these systems have been compared with that forecasted by the PVGIS software for the estimation of energy production for 2-axis PV tracking systems; the obtained results have been useful employed for the development of the new Rondine module which will be produced in the low industrial volume of 5MW/y during 2010. (*rated at 850W/m2 of DNI)
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The optical collection properties of the nonimaging "Rondine" solar concentrator have been investigated by indoor measurements of the angle-resolved optical efficiency. In this paper we illustrate two different methods to draw... more
The optical collection properties of the nonimaging "Rondine" solar concentrator have been investigated by indoor measurements of the angle-resolved optical efficiency. In this paper we illustrate two different methods to draw the optical efficiency curve. The first one, called "direct method", is performed by producing a collimated beam of solar divergence (~ 0.27°) and of known flux impinging on the input aperture of the concentrator at different incidence angles, and by measuring the flux collected at the exit aperture. The second one is based on a reverse illumination procedure, from which the name of "inverse method", whereby a Lambertian diffused light source is produced at the concentrator exit aperture and the radiance of the backward beam, exiting from the input aperture, is measured at different directions in space. We obtain similar results with the two methods, though the "inverse method" be largely to be preferred for the simplicity of the experimental apparatus and the extreme quickness of execution.
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We report the development and application of a new approach to correct aberrations in GRIN microendoscopes using 3D printed polymer microlenses. Corrected microendoscopes are validated performing functional imaging experiments in the... more
We report the development and application of a new approach to correct aberrations in GRIN microendoscopes using 3D printed polymer microlenses. Corrected microendoscopes are validated performing functional imaging experiments in the mouse brain in vivo.
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Concentrating photovoltaic (CPV) systems use solar collectors to focus the incoming solar radiation onto PV receivers equipped with small area solar cells. The irradiance profile at the PV receiver plane is strongly dependent on the... more
Concentrating photovoltaic (CPV) systems use solar collectors to focus the incoming solar radiation onto PV receivers equipped with small area solar cells. The irradiance profile at the PV receiver plane is strongly dependent on the concentrator architecture and has deep influence on the performances of the solar cells. In this work we will describe an approach matching ray-tracing simulations and circuit analysis to assess the ohmic losses of the PV receiver operating under uneven illumination. In this investigation we considered three types of solar concentrator optics (Fresnel lens, parabolic mirror and freeform mirror) having different flux distribution in the focal region. The optical simulations have been carried out taking into account the real radial distribution (sunshape) of the incident solar energy. The irradiance profile at the PV cells plane has then been used as a map for the photo-generated current to be collected and drawn from the devices. The cells have been binned into a grid of generators connected between them by a resistive network simulating the metal contacts and the semiconductor layers. The current-voltage characteristics of real solar cells has been measured and modeled by an array of diodes connected in parallel to each generator. The nonlinear circuit has been solved by a simulation program with integrated circuit emphasis (SPICE).
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An overview of the achievements accomplished in the first phase of the APOLLON project, related to the optimisation of point focus (PF) and mirror based spectra splitting systems (MBS3) is presented as well as some preliminary results on... more
An overview of the achievements accomplished in the first phase of the APOLLON project, related to the optimisation of point focus (PF) and mirror based spectra splitting systems (MBS3) is presented as well as some preliminary results on the proposed innovative Concentrating Photovotaic (CPV) technologies (intelligent CPV modules).
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Rondine® photovoltaic concentrators have started in 2011 the commercial phase; the product is a 20x reflective CPV module, which can be mounted on 2-axis tracker with angular accuracy up to ±4°; this allows to mount these modules on many... more
Rondine® photovoltaic concentrators have started in 2011 the commercial phase; the product is a 20x reflective CPV module, which can be mounted on 2-axis tracker with angular accuracy up to ±4°; this allows to mount these modules on many trackers for standard PV modules without significant power losses. Moreover, the high angular acceptance permits to collect high fraction of the circumsolar light impinging the module frontal aperture, giving high efficiency on DNI during in-field operative conditions. The Rondine modules have been tested following the IEC standard procedures for CPV in order to get the certification of quality of the product.
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The optical characterization of Rondine® photovoltaic solar concentrators is discussed by comparing two "inverse" methods: the original inverse irradiation method and a method derived by the inverse luminescence method operating... more
The optical characterization of Rondine® photovoltaic solar concentrators is discussed by comparing two "inverse" methods: the original inverse irradiation method and a method derived by the inverse luminescence method operating with electroluminescent light. Both methods use lambertian sources for producing the inverse light and can be applied to any type of solar concentrator (photovoltaic, thermodynamic). Optical simulations were applied to two types of nonimaging photovoltaic concentrators, Rondine® Gen1 and Gen2. The simulations proved the equivalence of the two inverse methods to get the angular distribution of the transmission efficiency function of the concentrators, but the original inverse irradiation method proved to be more simple to configure.
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CPower Srl has been designing and developing different Mirror Based Spectrum Splitting Systems (MBS3), partially supported in the framework of European APOLLON Project, mainly to minimize the cost/performance ratio. The concentrators... more
CPower Srl has been designing and developing different Mirror Based Spectrum Splitting Systems (MBS3), partially supported in the framework of European APOLLON Project, mainly to minimize the cost/performance ratio. The concentrators employ dichroic dielectric filters working for light interference, that is an alternative respect to other spectral splitting concepts based on the refraction of the light, to spatially spread the wavelength of the spectrum. The dichroic mirrors are introduced in an intermediate plane between primary optics and the receivers. This design permits two different levels of geometrical concentration (40x and 600x), suiting well with the requirements of Si cells (primary receiver) and III-V cells, in term of economics and electrical performances. The optimization of CPower spectrum splitting systems goes through the optimization of optics components, the complete automation of receivers assembly and the designing of a dedicated tracking system. The new module...
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All PV systems have cells or groups of cells connected in series in order to build up voltage and minimise current. Because current is almost linearly dependent on the incident light, the current in a string of identical solar cells will... more
All PV systems have cells or groups of cells connected in series in order to build up voltage and minimise current. Because current is almost linearly dependent on the incident light, the current in a string of identical solar cells will be limited by the cell with the least illumination. It is therefore important to achieve a flux profile as uniform as possible. Typically for dish concentrators this is achieved through the use of secondary flux modifiers which disperse light at the centre of the receiver more evenly. However, for a facetted dish such as the Prometeo, in theory the flux profile at the focus should be uniform. In practice it is costly to achieve highly accurate optics for a dish system, due to the need for both a tightly toleranced mirror support structure and a precise solar tracking system. The aim for the Prometeo system is to lower costs by using simple materials that can be manufactured without the need for precision tooling, and at the same time, to achieve a consistent flux profile on the whole PV receiver. In this paper the measured and simulated flux profiles are compared, and the results are discussed.
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Universita di Ferrara, Dipartimento di Fisica, Via Saragat 1, 44100 Ferrara, Italy. *Phone: +39 0471 055337; Fax: +39 0471 055339; E-mail: maurizio.armani@eurac.edu ABSTRACT: This paper presents monitoring data and performance results of... more
Universita di Ferrara, Dipartimento di Fisica, Via Saragat 1, 44100 Ferrara, Italy. *Phone: +39 0471 055337; Fax: +39 0471 055339; E-mail: maurizio.armani@eurac.edu ABSTRACT: This paper presents monitoring data and performance results of 12 photovoltaic systems installed in South Tyrol, which are based on different technologies, mainly crystalline and CdTe modules, and various dimension, from few kWp to more than 800 kWp. The target of the monitoring is an evaluation of performance ratio of the different systems, under the real regional climatic condition, for the benefit of installers and final users, and the collection of data to allow a better understanding of loss mechanisms. This paper summarizes 18 months of monitoring results. The monitored data include current from the PV array, array voltage, AC power delivered, global horizontal irradiance and ambient temperature, obtained from 26 weather station scattered on the region, and array temperature. The purpose of this work is t...
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ABSTRACT In this work the experimental results of two pilot installations of 3.8 kWp and 4.9 kWp of Rondine PV concentrators installed in Italy are presented. These concentrating modules have a medium concentration level (25X) and employ... more
ABSTRACT In this work the experimental results of two pilot installations of 3.8 kWp and 4.9 kWp of Rondine PV concentrators installed in Italy are presented. These concentrating modules have a medium concentration level (25X) and employ silicon solar cells. The non-imaging optics of the concentrator allows for larger angular acceptance respect to many CPV modules, giving us the possibility to employ trackers for standard PV modules. The effect of soiling in these first installations is evaluated as well as their working conditions in different weather situations.
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Light microscopy is an essential tool in histological examination of tissue samples. However, the required equipment for a correct and rapid diagnosis is sometimes unavailable. Smartphones and mobile phone networks are widespread, and... more
Light microscopy is an essential tool in histological examination of tissue samples. However, the required equipment for a correct and rapid diagnosis is sometimes unavailable. Smartphones and mobile phone networks are widespread, and could be used for diagnostic imaging and telemedicine. Macrovesicular steatosis (MS) is a major risk factor for liver graft failure, and is only assessable by microscopic examination of a frozen tissue section. The aim of this study was to compare the microscopic assessment of MS in liver allograft biopsies by a smartphone with eyepiece adaptor (BLIPS device) to standard light microscopy. Forty liver graft biopsies were evaluated in transmitted light, using an Iphone 5s and 4 different mini-objective, add-on lenses. A significant correlation was reported between the two different approaches for graft MS assessment (Spearman's correlation coefficient: r = 0.946; p < .001). Smartphone with eyepiece adaptor had similar discriminatory power to iden...
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Graded index (GRIN) lens-based microendoscopes are widely used to perform two-photon fluorescence microscopy in deep (> 1 mm) regions of highly scattering biological tissue, such as the mammalian brain. However, GRIN microendoscopes... more
Graded index (GRIN) lens-based microendoscopes are widely used to perform two-photon fluorescence microscopy in deep (> 1 mm) regions of highly scattering biological tissue, such as the mammalian brain. However, GRIN microendoscopes are limited by intrinsic aberrations which severely restrict the usable field-of-view (FOV). The effect of aberrations is particularly relevant in ultrathin (diameter < 500 μm) microendoscopes which allow a less invasive insertion of the optical probe into the brain tissue but which are characterized by relatively small imaging FOV. Currently, there are limited commercially available solutions to correct aberrations in these ultrathin microendoscopes because of the difficulty in fabricating corrective optics at the small spatial scale corresponding to the microendoscope diameter. Here, we report the development and application of a new approach to correct aberrations in GRIN microendoscopes using microfabricated polymeric lenses. Corrective optical...
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Research Interests: Optics and Applied Optics
A fluxmeter for high flux density measurements in point-focus solar concentrators is presented. It is based on the use of two integrating spheres, coupled by an intermediate window of selected aperture area. The concentrated radiation is... more
A fluxmeter for high flux density measurements in point-focus solar concentrators is presented. It is based on the use of two integrating spheres, coupled by an intermediate window of selected aperture area. The concentrated radiation is collected by the first sphere through an input window, integrated and driven to a second sphere where it is coupled to a conventional radiometer and to a spectrometer for flux and spectral measurements, respectively. The overall attenuation factor of input radiation, from few tens up to few thousands, is controlled by selecting the area of an intermediate window. The fluxmeter can be used to measure the total flux or the flux density distribution of beams with small area focusing region, of the order of 1cm2 or less. It is particularly suitable therefore for photovoltaic applications. The response of the fluxmeter in terms of attenuation factor of flux density as function of the angular divergence of input beam showed maximum variations of the order...
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Research Interests: Mechanical Engineering, Physics, Medicine, Solar Energy, Transducers, and 11 moreRay Tracing, Applied Optics, Optical physics, Radiation Monitoring, Solar radiation, Optics and Photonics, Reproducibility of Results, Sensitivity and Specificity, Equipment Design, Equipment Failure Analysis, and Electrical And Electronic Engineering
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ABSTRACT In this work the experimental results of a new PV concentrator (named Rondine®) are presented. This concentrating module has a medium concentration level (~25X) and employs silicon solar cells. The tests have been carried out in... more
ABSTRACT In this work the experimental results of a new PV concentrator (named Rondine®) are presented. This concentrating module has a medium concentration level (~25X) and employs silicon solar cells. The tests have been carried out in Italy and the energy production of a prototype module is compared with that produced from a tracking flat plate crystalline PV panel. The non-imaging optics of the concentrator allows for larger angular acceptance with respect to many solar concentrators, giving us the possibility to employ trackers for standard PV modules. The first results of complete systems of 3.9 and 4.8 kW of peak power installed in summer 2008 are presented here.
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Imaging neuronal activity with high and homogeneous spatial resolution across the field-of-view (FOV) and limited invasiveness in deep brain regions is fundamental for the progress of neuroscience, yet is a major technical challenge. We... more
Imaging neuronal activity with high and homogeneous spatial resolution across the field-of-view (FOV) and limited invasiveness in deep brain regions is fundamental for the progress of neuroscience, yet is a major technical challenge. We achieved this goal by correcting optical aberrations in gradient index lens-based ultrathin (≤500 µm) microendoscopes using aspheric microlenses generated through 3D-microprinting. Corrected microendoscopes had extended FOV (eFOV) with homogeneous spatial resolution for two-photon fluorescence imaging and required no modification of the optical set-up. Synthetic calcium imaging data showed that, compared to uncorrected endoscopes, eFOV-microendoscopes led to improved signal-to-noise ratio and more precise evaluation of correlated neuronal activity. We experimentally validated these predictions in awake head-fixed mice. Moreover, using eFOV-microendoscopes we demonstrated cell-specific encoding of behavioral state-dependent information in distributed ...
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A concentrating photovoltaic module design incorporating a spatial spectral splitting approach with dichroic mirrors is presented. The advantages of this technology are reported, as well as a short description of the design evolution... more
A concentrating photovoltaic module design incorporating a spatial spectral splitting approach with dichroic mirrors is presented. The advantages of this technology are reported, as well as a short description of the design evolution process. The experimental results are summarised, highlighting possible improvements through the use of different production processes and components. Materials, design and assembly procedures are taken into account, keeping in mind the fundamental constrains of cost and reliability of the final product. Finally, the possibilities for market exploitation of this technology in the current photovoltaic landscape are analysed.
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The design of a specific low concentration photovoltaic module is described here, with a report of the results of the first experimental tests of its industrial version. The product is a 20× reflective concentrating photovoltaic module... more
The design of a specific low concentration photovoltaic module is described here, with a report of the results of the first experimental tests of its industrial version. The product is a 20× reflective concentrating photovoltaic module based on silicon solar cells. The optics were designed to mount these modules on 2-axis trackers with angular pointing accuracy of up to about ±4° without significant power loss. The high angular acceptance of the non-imaging optics permits the collection of a high fraction of the circumsolar light impinging on the module's frontal aperture, providing high direct normal irradiance efficiency in real operative conditions. Many technical features of the product are described here, in which features are the result of 5 years of product development in order to improve performance, reliability and cost issues.
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A method for the optical characterization of a solar concentrator, based on the reverse illumination by a Lambertian source and measurement of intensity of light projected on a far screen, has been developed. It is shown that the... more
A method for the optical characterization of a solar concentrator, based on the reverse illumination by a Lambertian source and measurement of intensity of light projected on a far screen, has been developed. It is shown that the projected light intensity is simply correlated to the angle-resolved efficiency of a concentrator, conventionally obtained by a direct illumination procedure. The method has been applied by simulating simple reflective nonimaging and Fresnel lens concentrators.
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In this paper we describe two optical characterization methods applied to photovoltaic solar concentrators. Both methods are of the 'inverse' type, where the light source is applied in place of the receiver in order to reverse the path of... more
In this paper we describe two optical characterization methods applied to photovoltaic solar concentrators. Both methods are of the 'inverse' type, where the light source is applied in place of the receiver in order to reverse the path of light inside the concentrator. The first method is the 'inverse illumination method', already known in the literature, whereas the second one is a method obtained by modifying the 'inverse luminescence method', operating with electroluminescent light. Both methods use ideal Lambertian sources for producing the inverse light and can be applied to any type of solar concentrator (photovoltaic or thermodynamic). The optical simulations show their equivalence in obtaining the angular distribution of the transmission efficiency function of Rondine® PV concentrators, but the original inverse illumination method requires a simpler configuration and significantly lower simulation times.
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The growing interest on micro-beams in recent years and the combined development of channeling technology in high-energy physics have opened the way to new concepts for micro-beams devices. Silicon micromachining technology is here... more
The growing interest on micro-beams in recent years and the combined development of channeling technology in high-energy physics have opened the way to new concepts for micro-beams devices. Silicon micromachining technology is here applied to manufacture micro-collimators in inexpensive and feasible ways. Both dry and wet etchings can be employed for the purpose, though the latter technique appears to be cheaper and easier. Two designs for micro-collimator devices have been considered and preliminary samples have been produced accordingly.
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In the last years, the research on channeling of relativistic particles has progressed considerably. A significant contribution has been provided by the development of techniques for quality improvement of the crystals. In particular, a... more
In the last years, the research on channeling of relativistic particles has progressed considerably. A significant contribution has been provided by the development of techniques for quality improvement of the crystals. In particular, a planar etching of the surfaces of the silicon crystals proved useful to remove the superficial layer, which is a region very rich in imperfections, in turn leading to greater channeling efficiency. Micro-fabrication techniques, borrowed from silicon technology, may also be useful: micro-indentation and deposition of tensile or compressive layers onto silicon samples allow one to impart an even curvature to the samples. In this way, different topologies may be envisaged, such as a bent crystal for deflection of protons and ions or an undulator to force coherent oscillations of positrons and electrons.