Open Access
Shear based gap control in 2D photonic quasicrystals of dielectric cylinders
(Optica, 2021) Andueza Unanua, Ángel María; Sevilla Moróder, Joaquín; Pérez Conde, Jesús; Wang, Kang; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Zientziak; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Eléctrica, Electrónica y de Comunicación; Ciencias
2D dielectric photonic quasicrystals can be designed to show isotropic band gaps. In this work we study a quasiperiodic lattice made of silicon dielectric cylinders (ε = 12) arranged as periodic unit cell based on a decagonal approximant of a quasiperiodic Penrose lattice. We analyze the bulk properties of the resulting lattice as well as the bright states excited in the gap, which correspond to localized resonances of the electromagnetic field in specific cylinder clusters of the lattice. Then we introduce a controlled shear deformation γ which breaks the decagonal symmetry and evaluate the width reduction of the gap together with the evolution of the resonances, for all shear values compatible with physical constraints (cylinder contact). The gap width reduction reaches 18.5% while different states change their frequency in several ways. Realistic analysis of the actual transmission of the electromagnetic radiation, often missing in the literature, has been performed for a finite 'slice' of the proposed quasicrystals structure. Two calculation procedures based on MIT Photonic Bands (MPB) and Finite Integration Technique (FIT) are used for the bulk and the finite structures showing an excellent agreement between them.
Open Access
Experimental development and testing of low-cost scalable radiative cooling materials for building applications
(Elsevier, 2021) Carlosena Remírez, Laura; Andueza Unanua, Ángel María; Torres, Luis; Irulegi, Olatz; Hernández-Minguillón, Rufino J.; Sevilla Moróder, Joaquín; Santamouris, Mattheos; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua
Urban overheating has a serious impact on building energy consumption. Daytime radiative cooling materials are an interesting passive solution for refrigeration. However, their costs and complex manufacturing hinder their current application. In this study, a series of scalable and lowcost daytime radiative cooling (DTRC) materials were designed, fabricated, and tested in a moderate climate (Cfb-Köppen-Geiger classification) and compared to aluminum and Vikuiti. The methodology was: i) material selection and design, (ii) optimization, (iii) fabrication, (iv) characterization, and (v) testing. The materials were fabricated using different substrates, aluminum and Vikuiti, and two kinds of formulations for the emissive layers based on silica-derived polymer polymethylsilsesquioxane (PMSQ) with embedded silica nanoparticles. The resulting aluminum DTRC materials had a mean solar reflectivity of 0.7 and 0.34 emissivity in the atmospheric window, the samples with Vikuiti had 0.97 and 0.89, respectively. During the experiment, the samples were exposed to different ambient conditions without a convection barrier and were contained in an extruded polystyrene board to eliminate conduction. The samples reached 7.32 °C and 9.13 °C maximum surface temperature reduction (below ambient) during the day and night, respectively. The samples with the commercial substrate achieved a mean reduction of 3.72 °C below ambient temperature. Although the aluminum samples did not achieve subambient cooling throughout the entire day, the emissive layer reduced the sample's surface temperature by an average of 1.7 °C. The PMSQ radiative cooling materials show great potential for future building applications. Suitability under different climates and experimental settings should be done to test broad applicability.
Open Access
Combining radiative cooling and light trapping strategies for improved performance of PERC bifacial silicon solar cells
(Elsevier, 2023) Urdiroz Urricelqui, Unai; Itoiz Goñi, Iñigo; Sevilla Moróder, Joaquín; Andueza Unanua, Ángel María; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This work investigates the impact of combining light trapping and radiative cooling on bifacial solar panels. While several techniques have been proposed to enhance the efficiency of solar panels, their combination can lead to suboptimal results. By numerically evaluating the light absorption and thermal balance of different panel configurations, we found that each side of the bifacial solar cell can be textured independently with a cross-effect of less than 4%. However, our results also indicate that improving visible light trapping can increase infrared absorption, leading to a heating effect that may offset the benefits of radiative cooling. These findings highlight the importance of balancing the factors that influence solar panel efficiency and provide quantitative insights that guide the development of more effective solar energy systems.
Open Access
Geometry influence on the transmission spectra of dielectric single layers of spheres with different compactness
(AIP Publishing, 2010) Andueza Unanua, Ángel María; Echeverría, R.; Morales Zimmermann, Paola Andrea; Sevilla Moróder, Joaquín; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The transmission of spectra of different dielectric spheres single layer arrangements has been measured. High dielectric permittivity ε =7 spheres of several millimeters of diameter were used to build the samples whose transmission was measured in the microwave range. The behavior of lattices arranged in square and triangular geometries have been compared in a number of different compactness cases. The same patterns measured have also been calculated by finite-difference time-domain FDTD method. Spectra from different geometrical arrangements of the same compactness measured with the same filling fraction value are very similar in some cases. Based on the level of similarity we propose three compactness regions. The high compactness region, where the structure effect is important, presents spectra clearly different for the two geometries. In a medium compactness region spectra are almost identical, suggesting a dominant effect of single sphere effects. Finally, in the low compactness region, the spectra from the two geometrical configurations diverge again as the Bragg diffraction values are approached.
Open Access
Digital escape room project: engaging electronics for university students
(IEEE, 2024-08-01) Urrutia Azcona, Aitor; Ruete Ibarrola, Leyre; López Torres, Diego; Andueza Unanua, Ángel María; Elosúa Aguado, César; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PINNE2022-UPNA
This work proposes the implementation of a project-based learning methodology for the practical part of digital electronics subjects in the first years of undergraduate studies. Through the project called Digital Escape Room, a series of challenges and exercises are developed in a modular way that the students must solve in order to create a final design in Quartus software and demonstrate it on an FPGA-based device. The implementation of this project has allowed us to see that the academic results and the satisfaction and motivation of the students have improved significantly compared to previous years.
Open Access
Erratum: “Transmission spectra changes produced by decreasing compactness of opal like structures” J. Appl. Phys. 105, 024910 (2009)
(AIP Publishing, 2011) Andueza Unanua, Ángel María; Echeverría, R.; Morales Zimmermann, Paola Andrea; Sevilla Moróder, Joaquín; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Performing a systematic review of our experimental data, we have realized that we introduced a significant mistake in our abovementioned publication. Figure 3 did not correspond to the situation described, and should be changed by one here included. The corrected data do not invalidate the conclusions presented in the original publication, even more they are reinforced.
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 Gobernua
Photovoltaic 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.
Open Access
Application of active methodologies based on real cases - university-industry collaboration
(IEEE, 2024-08-01) Andueza Unanua, Ángel María; Urrutia Azcona, Aitor; Erro Betrán, María José; Ruiz Zamarreño, Carlos; Leandro González, Daniel; Elosúa Aguado, César; Socorro Leránoz, Abián Bentor; Goicoechea Fernández, Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PINNE2022-UPNA
During the last academic years, the industrial electronics specialties of the Industrial Engineering Bachelor's Degrees of the Public University of Navarra (UPNA) suffered a gradual loss of students. In order to reverse this trend, a teaching innovation project was designed based on the planned use of active learning methodologies in collaboration with Navarra's leading companies in industrial electronics. The project aims to enhance student learning by making teaching more engaging and practical, as well as boost the social visibility of electronics by improving the perception among students of this strategic industrial sector in the region of Navarra.
Open Access
Transmission spectra changes produced by decreasing compactness of opal-like structures
(AIP Publishing, 2009) Andueza Unanua, Ángel María; Echeverría, R.; Morales Zimmermann, Paola Andrea; Sevilla Moróder, Joaquín; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Artificial opal-like structures based on spheres and colloidal particles have been fabricated in a controlled way, presenting optical band-gap properties in the optical frequency range. Nonclose packed artificial opals have also been fabricated and studied recently. In order to gain a better understanding of these phenomena, we have studied macroscopic models of nonclose packed fcc lattices using glass spheres (ε = 7) of 8 mm diameter, and measuring in the microwave region from 10 to 30 GHz. The results have shown a Bragg resonance tunable with filling factor of the opal, and a strong rejected band similar, also present in close packed samples, much less affected by compactness. The relation of this high order band with spheres single layer behavior is also discussed
Open Access
Design, implementation, and evaluation of a flipped classroom and project-based learning model for industrial engineers
(IEEE, 2024-08-01) Andueza Unanua, Ángel María; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PINNE2022-UPNA
Active learning methodologies have attracted the attention of educators due to improving learning, interest, and motivation among students. In this context, the design of a model for academic training in electronic instrumentation in the Master's Degree in Industrial Engineering at the Public University of Navarra (UPNA) is presented, based on the combination of flipped classroom (FC) and project-based learning (PBL) methodologies, compared to traditional lecture-based education conducted in a control group. The results of the model do not show a significant impact on academic results compared to the control group. Furthermore, the acceptance of the FC methodology is significantly lower than PBL due to the perception that a group of students has of themselves in the course and a deficient temporal sequence in the classes. Therefore, a critical and comprehensive discussion of the dual model used, methodologies, student dynamics of the course, and the motivational factors influencing the studied group is proposed.