Person: Navajas Hernández, David
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Navajas Hernández
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David
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Ingeniería Eléctrica, Electrónica y de Comunicación
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0000-0003-3160-3448
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811824
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Publication Open Access Desarrollo de vidrios estructurados con funcionalidades antisuciedad para módulos fotovoltaicos(2019) Navajas Hernández, David; Sanchis Gúrpide, Pablo; Bengoechea Apezteguía, Jaione; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola TeknikoaLa producción de electricidad mediante tecnología fotovoltaica puede verse afectada negativamente por la acumulación de suciedad en su cara frontal. En este sentido, el desarrollo de soluciones antisuciedad que disminuyan la adherencia del polvo y la arena a los vidrios fotovoltaicos tiene una gran importancia. El objetivo de este proyecto es el estudio de las propiedades antisuciedad de vidrios fotovoltaicos con microestructuras realizadas en su cara frontal. Con esta finalidad, en primer lugar, se estudiarán los principales mecanismos de adherencia de la suciedad a los vidrios fotovoltaicos, y se incorporarán en los modelos existentes el efecto de las microestructuras. A continuación, utilizando procesos de fotolitografía y ataque seco se fabricarán y caracterizarán varios vidrios estructurados con distintos tamaños de las estructuras. Finalmente, se probará experimentalmente, con dos tipos de suciedad artificial estandarizada, el efecto antisuciedad de estos vidrios estructurados.Publication Open Access Enhanced thermal performance of photovoltaic panels based on glass surface texturization(Elsevier, 2021) Andueza Unanua, Ángel María; Pinto Fuste, Cristina Leyre; Navajas Hernández, David; Sevilla Moróder, Joaquín; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako GobernuaPhotovoltaic module temperature is a detrimental parameter influencing the energy yield and the durability of photovoltaic systems. Among the passive strategies to reduce the operating temperature of solar cells, radiative cooling is receiving a lot of attention, as an effective mean to passively evacuate heat in systems. The existence of a wavelength window of atmospheric transparency (8–13 μm) allows sending heat to outer space. The functionalization of the glass that could help to limit or reduce the temperature of the solar cells is an interesting approach. In this paper, we explore the effect of glass surface patterns in its radiation performance, so that the radiation cooling effect could be enhanced. The study is based on numerical simulations, calculating the spectral emissivity of different geometrical configurations of structures on top of the glass. Different geometrical figures of micrometers in size have been tested to find an optimal emissivity response in the transparent atmospheric window. Periodical patterns based on cones, pyramids, or moth-eye shapes result in emissivity responses close to one along thermal wavelengths (8–25 μm) which increases the emitted power of the glass. However, when assessing the cooling power under sunlight, the evaluation wavelength band has to be expanded (0.3–25 μm). Here, we found that not all geometrical figures are effective for radiative cooling. Surfaces textured by holes and pyramids show a substantial cooling effect, providing an increase in cooling power over the flat glass ranging from 40 W/m2 to 110 W/m2 depending on the temperature of the solar devices.Publication Open Access Surface roughness effects on ENZ media IR spectra(IEEE, 2023-09-04) Navajas Hernández, David; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISCThe development of high-performance nanophotonic technologies faces challenges like material losses and surface roughness. While surface roughness has been studied in the plasmonic regime, its effect on epsilon-near-zero (ENZ) media has been less explored. Two theoretical scenarios arise regarding roughness in ENZ media: one predicts the excitation of a strong longitudinal electric field, while the other suggests minimal changes in reflection due to the large effective wavelength. This study investigates silicon carbide (SiC) as an ENZ substrate, using deep reactive ion etching (DRIE) to create significant surface roughness. The findings show that surface roughness affects the reflection spectra, induces polaritonic effects, and highlights the robustness of SiC against surface roughness. Numerical simulations and experimental measurements confirm these results, revealing that ENZ substrates maintain their reflective properties even with surface roughness on the scale of hundreds of nanometers.Publication Open Access Addressing the impact of surface roughness on epsilon-near-zero silicon carbide substrates(American Chemical Society, 2023) Navajas Hernández, David; Pérez Escudero, José Manuel; Martínez Hernández, María Elena; Goicoechea Fernández, Javier; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenEpsilon-near-zero (ENZ) media have been very actively investigated due to their unconventional wave phenomena and strengthened nonlinear response. However, the technological impact of ENZ media will be determined by the quality of realistic ENZ materials, including material loss and surface roughness. Here, we provide a comprehensive experimental study of the impact of surface roughness on ENZ substrates. Using silicon carbide (SiC) substrates with artificially induced roughness, we analyze samples whose roughness ranges from a few to hundreds of nanometer size scales. It is concluded that ENZ substrates with roughness in the few nanometer scale are negatively affected by coupling to longitudinal phonons and strong ENZ fields normal to the surface. On the other hand, when the roughness is in the hundreds of nanometers scale, the ENZ band is found to be more robust than dielectric and surface phonon polariton (SPhP) bands.Publication Open Access Spectrally stable thermal emitters enabled by material-based high-impedance surfaces(Royal Society of Chemistry, 2023) Navajas Hernández, David; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenRadiative thermal engineering with subwavelength metallic bodies is a key element for heat and energy management applications, communication and sensing. Here, we numerically and experimentally demonstrate metallic thermal emitters with narrowband but extremely stable emission spectra, whose resonant frequency does not shift with changes on the nanofilm thickness, the angle of observation and/or polarization. Our devices are based on epsilon-near-zero (ENZ) substrates acting as material-based high-impedance substrates. They do not require from complex nanofabrication processes, thus being compatible with large-area and low-cost applications.Publication Open Access Narrowband and spectrally robust thermal emission from metallic thin films on top of epsilon-near-zero substrates(IEEE, 2022) Navajas Hernández, David; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenThe absorption and emission of infrared radiation by ultra-thin metallic films is a key element in several thermal engineering applications such as heat and energy management, and thermal camouflage. However, ultra-thin metallic films are broadband and low-efficiency emitters. Here, we demonstrate numerically and experimentally that metallic films placed on top of epsilon-near-zero (ENZ) substrates become narrowband and efficient thermal emitters. Our experiments show that ENZ-based emitters feature a narrow linewidth whose frequency positioning is robust against variations in the geometry of the system and the observation angle. Moreover, since ENZ emitters are based on the material properties of the substrate, no nanofabrication processes are needed, opening the pathway towards widefield and large-scale applications.