Test and Modelling of Solid Oxide Fuel Cell Durability: A Focus on Interconnect Role on Global Degradation

High-temperature fuel cells are a promising technology due to their high energy efficiency and low environmental impacts compared to conventional engines. Nevertheless, they have a limited lifetime which reduces the use to a few application fields. Among them, Solid Oxide Fuel Cells (SOFCs) have had a recent development at the industrial level in two possible configurations: an-ode-and electrolyte-supported design. Considering the impossibility to experimentally distinguish the effects of every degradation mechanism on global cell performance, each layer should be tested singularly through ex situ tests and then assembled into a virgin cell to evaluate its role on the whole system by in situ tests. However, this procedure results as quite complex, and some further micro-structural changes could occur during cell sintering. In order to overcome these constraints, the proposed approach paired ex situ experimental observations on a single element with modelling results on global SOFC. As a case study, CoMnO/Crofer22 APU and CuMnO/AISI 441 interconnect samples were tested, measuring their resistance variation for some hundreds of hours, followed by a detailed post-mortem microstructural analysis. Based on a previously validated local model, SIMFC (SIMulation of Fuel Cells), the durability of commercial anode-and electrolyte-supported cells was simulated, adding specific degradation functions only for the interconnects in order to highlight their influence on SOFC performance

Structural properties and thermoelectric performance of the double-filled skutterudite (Sm,Gd)y(FexNi1-x)4Sb12

The structural and thermoelectric properties of the filled skutterudite (Sm,Gd)y(FexNi1-x)4 Sb12 were investigated and critically compared to the ones in the Sm-containing system with the aim of unravelling the effect of double filling on filling fraction and thermal conductivity. Several samples (x = 0.50-0.90 and y = 0.15-0.48) were prepared by melting-sintering, and two of them were densified by spark plasma sintering in order to study their thermoelectric features. The crystallographic study enables the recognition of the role of the filler size in ruling the filling fraction and the compositional location of the p/n crossover: It has been found that the former lowers and the latter moves toward lower x values with the reduction of the filler ionic size, as a consequence of the progressively weaker interaction of the filler with the Sb12 cavity. The analysis of thermoelectric properties indicates that, despite the Sm3+/Gd3+ small mass difference, the contemporary presence of these ions in the 2a site significantly affects the thermal conductivity of both p- and n-compositions. This occurs by reducing its value with respect to the Sm-filled compound at each temperature considered, and making the overall thermoelectric performance of the system comparable to several multi-filled (Fe, Ni)-based skutterudites described in the literature

Procedimiento de automatización y control de circulación de agua de subsuelo en el condensador de un sistema de climatización por compresión de vapor

En el presente trabajo se expone un procedimiento para realizar la automatización y control del caudal de agua de subsuelo que circula por el condensador de un sistema de climatización por compresión de vapor. La innovación realizada permite conseguir una reducción del consumo de agua de subsuelo. La implementación del sistema de automatización logra un control autónomo del caudal de agua empleando un dispositivo genérico. El tiempo y esfuerzo utilizado es bajo y los conocimientos necesarios por parte del investigador son mínimos. La regulación del caudal de agua en función de la temperatura ambiente se implementa utilizando lógica difusa articulada con un programa matemático denominado MatLab. El software de automatización perteneciente al firmware del microcontrolador se desarrolló en un simulador denominado MPLAB que facilita la puesta a punto del hardware del dispositivo genérico.In this paper a method is disclosed for automation and control of the underground water flow circulating through the condenser of a vapor compression air conditioning system. Innovation made allows for achieving a reduction consumption of subsoiling water. The implementation of the automation system achieves an autonomous control over the flow of water using a generic device. The time and effort used is low and knowledge needed by the research is minimal. The regulation of the water flow according to the ambient temperature is implemented using fuzzy logic articulated with a mathematical program called MatLab. Automation software belonging to the microcontroller firmware was developed in a simulator called MPLAB that facilitates tuning the generic hardware device.Tema 8: Energías renovables, modelización y simulación.Facultad de Arquitectura y Urbanism

Andean Land Use And Biodiversity: Humanized Landscapes In A Time Of Change

Some landscapes Cannot be understood without reference., to the kinds. degrees, kinds, degrees, and history of human-caused modifications to the Earth's surface. The tropical latitudes of the Andes represent one such place, with agricultural land-use systems appearing in the Early Holocene. Current land use includes both intensive and extensive grazing and crop- or tree-based agricultural systems found across virtually the, entire range of possible elevations and humidity regimes. Biodiversity found in or adjacent to such humanized landscapes will have been altered in abundance. composition, and distribution in relation to the resiliency of the native Species to harvest, hold cover modifications, and other deliberate or inadvertent human land uses. In addition, the geometries of land cover, resulting flout difference among the shapes, sizes, connectivities, and physical structures of the patches, corridors, and matrices that compose landscape mosaics, will constrain biodiversity, often in predictable ways. This article proposes a conceptual model that alter ins that the Continued persistence of native species may depend as much oil the shifting Of Andean landscape mosaics as on species characteristics, themselves. Furthermore, mountains such as the Andes display long gradients of environmental Conditions that after in relation to latitude, soil moisture, aspect, and elevation. Global environmental change will shift these, especially temperature and humidity regimes along elevational gradients, causing Changes outside the historical range of variation for some species. Both land-use systems and Conservation efforts will need to respond spatially to these shifts in the future, at both landscape and regional scales.Geography and the Environmen

A Two-Step Approach to Tune the Micro and Nanoscale Morphology of Porous Niobium Oxide to Promote Osteointegration

We present a two-step surface modification process to tailor the micro and nano morphology of niobium oxide layers. Niobium was firstly anodized in spark regime in a Ca-and P-containing solution and subsequently treated by acid etching. The effects of anodizing time and applied potential on the surface morphology is investigated with SEM and AFM, complemented by XPS compositional analysis. Anodizing with a limiting potential of 250 V results in the fast growth of oxide layers with a homogeneous distribution of micro-sized pores. Cracks are, however, observed on 250 V grown layers. Limiting the anodizing potential to 200 V slows down the oxide growth, increasing the anodizing time needed to achieve a uniform pore coverage but produces fracture-free oxide layers. The surface nano morphology is further tuned by a subsequent acid etching process that leads to the formation of nano-sized pits on the anodically grown oxide surface. In vitro tests show that the etching-induced nanostructure effectively promotes cell adhesion and spreading onto the niobium oxide surface

Accelerated Stress Tests for Solid Oxide Cells via Artificial Aging of the Fuel Electrode

Solid Oxide Cells (SOCs) are under intensive development due to their great potential to meet the 2030 targets for decarbonization. One of their advantages is that they can work in reversible mode. However, in respect to durability, there are still some technical challenges. Although the quick development of experimental and modeling approaches gives insight into degradation mechanisms, an obligatory step that cannot be avoided is the performance of long‐term tests. Taking into account the target for a commercial lifetime is 80,000 h, experiments lasting years are not acceptable for market needs. This work aims to develop accelerated stress tests (ASTs) for SOCs by the artificial aging of the fuel electrode via redox cycling, which follows the degradation processes of calendar aging (Ni coarsening and migration). However, it can cause irreversible damage by the formation of cracks at the interface anode/electrolyte. The advantages of the developed procedure are that it offers a mild level of oxidation, which can be governed and regulated by the direct impedance monitoring of the Ni network resistance changes during oxidation/reduction on a bare anode sample. Once the redox cycling conditions are fixed and the anode/electrolyte sample is checked for cracks, the procedure is introduced for the AST in full‐cell configuration. The developed methodology is evaluated by a comparative analysis of current voltage and impedance measurements of pristine, artificially aged, and calendar‐aged button cells, combined with microstructural characterization of their anodes. It can be applied in both fuel cell and electrolyzer mode. The results obtained in this study from the electrochemical tests show that the artificially aged experimental cell corresponds to at least 3500 h of nominal operation. The number of hours is much bigger in respect to the microstructural aging of the anode. Taking into consideration that the duration of the performed 20 redox cycles is about 50 to 60 working hours, the acceleration factor in respect to experimental timing is estimated to be higher than 60, without any damaging of the sample. This result shows that the selected approach is very promising for a large decrease in testing times for SOCs

Procedimiento de automatización y control de circulación de agua de subsuelo en el condensador de un sistema de climatización por compresión de vapor

En el presente trabajo se expone un procedimiento para realizar la automatización y control del caudal de agua de subsuelo que circula por el condensador de un sistema de climatización por compresión de vapor. La innovación realizada permite conseguir una reducción del consumo de agua de subsuelo. La implementación del sistema de automatización logra un control autónomo del caudal de agua empleando un dispositivo genérico. El tiempo y esfuerzo utilizado es bajo y los conocimientos necesarios por parte del investigador son mínimos. La regulación del caudal de agua en función de la temperatura ambiente se implementa utilizando lógica difusa articulada con un programa matemático denominado MatLab. El software de automatización perteneciente al firmware del microcontrolador se desarrolló en un simulador denominado MPLAB que facilita la puesta a punto del hardware del dispositivo genérico.In this paper a method is disclosed for automation and control of the underground water flow circulating through the condenser of a vapor compression air conditioning system. Innovation made allows for achieving a reduction consumption of subsoiling water. The implementation of the automation system achieves an autonomous control over the flow of water using a generic device. The time and effort used is low and knowledge needed by the research is minimal. The regulation of the water flow according to the ambient temperature is implemented using fuzzy logic articulated with a mathematical program called MatLab. Automation software belonging to the microcontroller firmware was developed in a simulator called MPLAB that facilitates tuning the generic hardware device.Tema 8: Energías renovables, modelización y simulación.Facultad de Arquitectura y Urbanism

Procedimiento de automatización y control de circulación de agua de subsuelo en el condensador de un sistema de climatización por compresión de vapor

En el presente trabajo se expone un procedimiento para realizar la automatización y control del caudal de agua de subsuelo que circula por el condensador de un sistema de climatización por compresión de vapor. La innovación realizada permite conseguir una reducción del consumo de agua de subsuelo. La implementación del sistema de automatización logra un control autónomo del caudal de agua empleando un dispositivo genérico. El tiempo y esfuerzo utilizado es bajo y los conocimientos necesarios por parte del investigador son mínimos. La regulación del caudal de agua en función de la temperatura ambiente se implementa utilizando lógica difusa articulada con un programa matemático denominado MatLab. El software de automatización perteneciente al firmware del microcontrolador se desarrolló en un simulador denominado MPLAB que facilita la puesta a punto del hardware del dispositivo genérico.In this paper a method is disclosed for automation and control of the underground water flow circulating through the condenser of a vapor compression air conditioning system. Innovation made allows for achieving a reduction consumption of subsoiling water. The implementation of the automation system achieves an autonomous control over the flow of water using a generic device. The time and effort used is low and knowledge needed by the research is minimal. The regulation of the water flow according to the ambient temperature is implemented using fuzzy logic articulated with a mathematical program called MatLab. Automation software belonging to the microcontroller firmware was developed in a simulator called MPLAB that facilitates tuning the generic hardware device.Tema 8: Energías renovables, modelización y simulación.Facultad de Arquitectura y Urbanism

Electrochemical testing of an innovative dual membrane fuel cell design in reversible mode

Solid oxide fuel Cells (SOFC) are intrinsically reversible which makes them attractive for the development of reversible devices (rSOC). The main hurdles that have to be overcome are the higher degradation in electrolyzer (EL) mode and the slow and difficult switching form mode to mode. This work aims at the development and experimental validation of a concept for rSOC based on a new dual membrane fuel cell (dmFC) design which can overcome the existing problems of the classical SOFC. The kernel of the system is additional chamber - central membrane (CM) for water formation/evacuation in FC mode and injection in El mode. Its optimization in respect of microstructure and geometry in laboratory conditions is carried out on button cells. The electrochemical performance is evaluated based on volt-ampere characteristics (VACs) combined with impedance measurements in different working points. The influence of a catalyst in the water chamber is also examined. The VACs which give integral picture of the cell performance are in excellent agreement with the impedance studies which ensure deeper and quantitative information about the processes, including information about the rate limiting step. The results from the optimization of the water chamber show that the combination of design and material brings to important principle advantages in respect to the classical rSOC \u2013 better performance in electrolyzer mode combined with instantaneous switching

Estimación del ahorro económico en energía eléctrica obtenido en sistemas de calefacción por compresión de vapor con la implementación de agua de subsuelo en el evaporador

Se exponen los resultados obtenidos del ahorro económico en energía eléctrica en sistemas de calefacción por compresión de vapor con la implementación de agua de subsuelo en el evaporador del equipo. El estudio económico se realizó para ensayos de calefacción del sistema de climatización cuando se utiliza aire y agua de subsuelo en el evaporador. Además se realizó el análisis de amortización del equipamiento necesario para implementar la utilización del agua de subsuelo en el sistema de calefacción por compresión de vapor, para un caso específico de una escuela (caso hipotético), que posee veinte ambientes. Considerando los costos de los componentes del equipamiento auxiliar, el retorno de inversión es de 10 años, 6 meses y ocho días. Si se tiene en cuenta el posible aumento de la tarifa eléctrica en el orden del 60 %, el retorno de inversión del equipamiento auxiliar se reducirá al periodo de 6 años, 6 meses y 29 días.The results of cost savings are reported in electricity in heating systems with vapor compression implementation of subsurface water in the evaporator equipment. The economic study was conducted to test heating HVAC system when air and ground water is used in the evaporator. Besides analyzing amortization of equipment needed to implement the use of underground water in the heating system vapor compression for a specific case of a school (hypothetical case) that has made twenty environments. Considering the costs of the components of auxiliary equipment, the return on investment is 10 years, 6 months and eight days. Taking into account the possible increase in electricity tariff in the order of 60%, the return on investment of auxiliary equipment will reduce the period of 6 years, 6 months and 29 days.Tema 6: Energía eólica, geotermia, biomasa y otras energías no convencionales.Facultad de Arquitectura y Urbanism