Papers by Luca Mercatelli
The Journal of Experimental Biology, 2020
The sandhopper Talitrus saltator relies on both the sun and the moon compasses to return to the b... more The sandhopper Talitrus saltator relies on both the sun and the moon compasses to return to the belt of damp sand on the beach in which it lives buried during the day. In addition to the sun, the gradient of radiance and the spectral distribution across the sky could provide directional information that T. saltator can potentially use to orient itself during the day even when the sun is not visible (e.g. cloudy sky). The scope of this work was (1) to determine the intensity levels of sky radiance that the sandhoppers use in their zonal recovery and (2) to investigate whether this species relies on the celestial spectral gradient in its zonal recovery. Sandhoppers were tested in the laboratory under artificial radiance or spectral gradients. Our results show that under an artificial sky simulating the natural radiance gradient on a cloudless day, sandhoppers orientated toward the correct seaward direction of their home beach; however, individuals lost their ability to use the intensity gradient as an orientation cue when the radiance was attenuated by at least 40%. Sandhoppers were also able to head in the correct seaward direction of their home beach at any time of the day by using the spectral gradient as their only source of visual orientation reference.
Science of The Total Environment
indicate that different bioplastics may have effects on T. saltator (i.e. survival rate and faeca... more indicate that different bioplastics may have effects on T. saltator (i.e. survival rate and faecal pellets structure) and confirm a potential role of amphipods in the degradation of bioplastics in supralittoral zone of marine sandy beaches, even when bioplastics are not colonized by bacterial biofilm that seems to improve palatability.
SPIE Proceedings, 2016
This article describes the works we are doing for modifying the interface between the high resolu... more This article describes the works we are doing for modifying the interface between the high resolution infrared spectrograph GIANO (0.97-2.4 micron) and the TNG telescope, passing from a fiber feed configuration to the original design of a direct light-feeding from the telescope to the spectrograph. So doing the IR spectrograph, GIANO, will work in parallel to HARPS-N spectrometer (0.38-0.70 micron), the visible high resolution spectrograph, thanks to a new telescope interface based on a dichroic window that simultaneously feeds the two instrumentes: this is GIARPS (GIAno and haRPS). The scientific aims of this project are to improve the radial velocity accuracy achievable with GIANO, down to a goal of 1 m/s, the value necessary to detect Earth-mass planets on habitable orbits around late-M stars, to implement simultaneous observations with Harps-N and GIANO optimizing the study of planets around cool stars. The very broad wavelengths range is particularly important to discriminate false radial velocity signals caused by stellar activity. We therefore include several absorption cells with different mixtures of gases and a stabilized Fabry Perot cavity, necessary to have absorption lines over the 0.97–2.4 microns range covered by GIANO. The commissioning of GIARPS is scheduled by the end of 2016.
Solar Energy, 2016
Abstract The performances of a photovoltaic system based on dye-sensitized solar cells associated... more Abstract The performances of a photovoltaic system based on dye-sensitized solar cells associated with a solar concentrator are investigated. An extensive indoor characterization is performed using both different wavelength bandwidths and concentration ratio. Starting from the acquired data, the system coupled with a solar tracking is also tested in outdoor condition. The obtained results show that it is possible to use this class of solar cells in solar concentrator systems, leading to a new class of devices with a high efficiency and a low cost.
Green Energy and Technology, 2015
The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Proceedings of SPIE, Aug 31, 2006
The problem of developing the lateral surfaces of a 3D object can arise in item inspection using ... more The problem of developing the lateral surfaces of a 3D object can arise in item inspection using automated imaging systems. In an industrial environment, these control systems typically work at high rate and they have to assure a reliable inspection of the single item. For compactness requirements it is not convenient to utilise three or four CCD cameras to control all the lateral surfaces of an object. Moreover it is impossible to mount optical components near the object if it is placed on a conveyor belt. The paper presents a system that integrates on a single CCD picture the images of both the frontal surface and the lateral surface of an object. It consists of a freeform lens mounted in front of a CCD camera with a commercial lens. The aim is to have a good magnification of the lateral surface, maintaining a low aberration level for exploiting the pictures in an image processing software. The freeform lens, made in plastics, redirects the light coming from the object to the camera lens. The final result is to obtain on the CCD: - the frontal and lateral surface images, with a selected magnification (even with two different values for the two images); - a gap between these two images, so an automatic method to analyse the images can be easily applied. A simple method to design the freeform lens is illustrated. The procedure also allows to obtain the imaging system modifying a current inspection system reducing the cost.
Proceedings of SPIE, Aug 31, 2006
Optical collectors for sunlight concentration on small surfaces have been experimentally studied ... more Optical collectors for sunlight concentration on small surfaces have been experimentally studied to evaluate their correspondence with the optical design. Measurement set-up and testing methodologies have been developed and adapted mainly to provide the optical characteristics that are fundamental for the concentration on small surfaces. The collectors are lenses of different type, with various shape and dimensions. They are optically
Energy Procedia, 2014
Linear parabolic collectors usually need profilometric control since the reflector surface can be... more Linear parabolic collectors usually need profilometric control since the reflector surface can be imperfectly manufactured. Optical profile assessment is generally addressed to detect small localised defects. The paper proposes two optical devices that were developed simulating profile measurements on linear parabolic mirrors. Solar troughs are employed in thermal plants and concentrating photovoltaic systems. The profilometer examines the reflector surface operating on a plane transversal to the linear axis of the trough collector. Then the detection is repeated displacing the optical device along the linear collector axis. The first profilometer includes a shifted laser source and a target placed at the collector focal distance. The second profilometer has a fixed target and a linear laser source, which is approximately located in the focal position of the solar mirror. Ray-tracing simulations and practical tests are illustrated for both optical devices.
Proceedings of SPIE, Jun 13, 2005
Shape detection on objects of large and huge dimensions has always represented a challenging task... more Shape detection on objects of large and huge dimensions has always represented a challenging task, mostly by the practical point of view due to the size of the related measurement equipment. When the tested object is a mirror the measurements is additionally complicated, since the classical techniques of structured light cannot be directly applied. The method proposed in this paper
Solar Energy Materials and Solar Cells, Nov 1, 2011
The optical characterization is reported of a new fluid consisting of single wall carbon nanohorn... more The optical characterization is reported of a new fluid consisting of single wall carbon nanohorns and ethylene glycol for solar energy applications. Carbon nanohorns play a significant role in enhancing sunlight absorption with respect to the pure base fluid. The obtained results are compared with those obtained for fluids suspending more conventional carbon forms, i.e. carbon-black particles. We found that nanohorn spectral features are by far more favourable than those of amorphous carbon for the specific application. This result shows that carbon-nanohorn based nanofluids can be useful for increasing the efficiency and compactness of thermal solar devices, reducing both environmental impact and costs.
ACS Sustainable Chemistry & Engineering, Jan 2, 2020
Nanofluids are colloidal systems based on the suspension of nanoparticles in a fluid. Their therm... more Nanofluids are colloidal systems based on the suspension of nanoparticles in a fluid. Their thermal properties mean they are promising heat transfer fluids with possible applications in different fields, concentrating solar energy being one of particular interest. Thus, this study presents the preparation of nanofluids based on WSe2 nanoparticles suspended in the eutectic mixture of biphenyl and diphenyl oxide, which is a heat transfer fluid widely used in concentrating solar power plants. To this end, solvothermal synthesis was used to prepare WSe2 nanosheets, which were characterized by means of scanning transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and Raman spectroscopy. The physical and chemical stability of the nanofluids was analyzed, observing that they became more stable when Triton X-100 was used as the surfactant. The presence of WSe2 nanosheets did not result in a significant increase in density or viscosity, but, by contrast, improvements were obtained in their isobaric specific heat and thermal conductivity, up to 4.7% and 64%, respectively. Spectral optical properties were investigated as well, showing a significant effect of the WSe2 nanosheets addition to the extinction coefficient of the base fluid in the wavelength range of solar spectrum, promising for direct absorption solar collectors. Finally, the efficiency of the nanofluids was analyzed in a solar collector considering the Ur parameter, obtaining a remarkable increase in the efficiency of up to 34% with respect to the pure heat transfer fluid. This proves the possibility to obtain a sustainable production of energy from the sun using these WSe2-based nanofluids.
ACS Sustainable Chemistry & Engineering, Mar 1, 2021
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Outdoor lighting and traffic signaling are emerging fields of application for the Light Emitting ... more Outdoor lighting and traffic signaling are emerging fields of application for the Light Emitting Diode technology. These sustainable power-saving illumination sources can be used thanks to the availability of high-power white LEDs that, combined with suitable lenses, permit to obtain various angular distributions of the light for many applications. The proposed LED lamp for street lighting produces high illuminance uniformity utilizing only reflective components, avoiding free-form optics: the luminous flux generated by the LEDs illuminates the roadway both directly and reflecting on the inner surface of reflectors with double curvature. It allows preventing the employment of plastic lenses, subjected to risks of yellowing and decrease of transparency. The results in terms of simulated illuminance on the road show high values of uniformity. Moreover, the optical modelling was aimed to design a configuration actually feasible from a technical point of view.
RSC Advances, 2017
Goethite (a-FeOOH) nanorods have been synthesized using two different methods, by aging at differ... more Goethite (a-FeOOH) nanorods have been synthesized using two different methods, by aging at different temperatures of ferrihydrite suspensions obtained through co-precipitation, or by fast conversion of ferrihydrite through ultrasonic irradiation. The synthesis method and parameters influenced the size and shape of nanoparticles. Stable colloidal suspensions of nanorods have been prepared by purification of the precipitates and subsequent dispersion in deionised water by sonication. The synthesized nanopowders have been characterized by Powder X-ray Diffraction and Scanning Electron Microscopy and the colloidal suspensions by Dynamic Light Scattering and z-potential measurements. The magnetic field at nuclei level has been investigated by Mössbauer spectroscopy. Moreover, since a colloidal suspension of goethite is a mineral liquid crystal and due to its peculiar magnetic properties, polarized radiation transmittance of colloids in the UV-vis-NIR range has been determined under different magnetic field directions and intensities. It has been found that the transmittance in the NIR range can be tuned by changing magnetic field direction and strength.
Solar Energy, Jul 1, 2021
Abstract In this work, for the first time, we studied the temperature-dependent spectral emittanc... more Abstract In this work, for the first time, we studied the temperature-dependent spectral emittance of highly refractory ceramics, e.g. silicon carbide (SiC) and two ultra-high temperature ceramics (tantalum diboride (TaB2), zirconium diboride (ZrB2)) to evaluate their potential for solar tower receivers applications. We measured the spectral normal emittance from 1 µm to 21 µm at temperatures up to 850 °C, in vacuum, by means of a novel experimental setup composed by an electric furnace connected to a FT-IR spectrometer. Comparison with previously published data collected with a different setup was also carried out to validate the results. In addition, the experimental spectral emittance was also compared with the values calculated from hemispherical reflectance at room temperature by means of Kirchhoff’s law. The results show that surface features play a fundamental role in the emittance of investigated ceramics.
Renewable Energy, Oct 1, 2019
The optical properties of nanofluids are peculiar and interesting for a variety of applications. ... more The optical properties of nanofluids are peculiar and interesting for a variety of applications. Among them, the high light extinction coefficient of nanofluids can be useful in linear parabolic concentrating solar systems, while their properties under high light irradiation intensities can be exploited for direct solar steam generation. The optical characterization of colloids, including the study of non-linear optical properties, is thus a needed step to design the use of such novel materials for solar energy exploitation. In this work, we analysed two different types of nanofluids, consisting of polycarboxylate chemically modified graphene nanoplatelets (P-GnP) and sulfonic acidfunctionalized graphene nanoplatelets (S-GnP) dispersed in water, at three concentrations from 0.005 wt% to 0.05 wt%. Moderately stable nanofluids were achieved with favourable light extinction properties, as well as a non-linear optical behaviour under high input solar intensities.
Solar Energy, Jun 1, 2016
Besides ultra-refractoriness and favorable mechanical and chemical characteristics, carbides of e... more Besides ultra-refractoriness and favorable mechanical and chemical characteristics, carbides of early transition metals show intrinsic spectral selectivity, making them appealing for hightemperature solar absorber applications. However these kinds of ceramics can be produced using many processing methods resulting in different compositions, density and surface finishing. Thus the present work reports on the systematic study of microstructural, mechanical and optical properties of dense zirconium, hafnium and tantalum carbides as a function of the sintering method (high pressure or pressureless), implying use of 10 or 20 vol% of MoSi 2 as sintering aid. The spectral hemispherical reflectance of Zr-, Hf-and Ta-carbides has been measured in the 0.25-16.5 µm wavelength range and correlated to the surface microstructure and roughness. Room and high temperature fracture strength has been measured as well.
Green energy and technology, Dec 30, 2014
This chapter is intended to give a general overview on characteristics of light sources, whose fu... more This chapter is intended to give a general overview on characteristics of light sources, whose function is to convert the electrical energy to visible light as efficiently as possible.
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Papers by Luca Mercatelli