Sustainable Biorefineries: What was Learned from the Design, Analysis and Implementation

Bioeconomies need sustainable technologies and strategies for biomass processing. One of the best ways to do that is to consider biorefineries as a practical way to achieve real developments in the industry for integral production of energy, food, feed and chemicals under an ideal dream of replacing today’s crude-oil and basically using the accessible biomass in the world as much as possible. Additionally, the existent biofuel facilities are constantly adding new processing lines without integral design strategies, and possibly repeating the past design and implementation errors in refineries based on crude-oil. In recent years, more as a fashion or tendency, these processing lines from biofuels industry have been integrated in a system called “biorefinery” and many sectors have supported this idea through policies to incentivize the development of the bio-based economies adopting this concept. The design of biorefineries is presented as a relevant topic due to the multiple processing paths that could be available to obtain a set of desirable products. However, after many scientific efforts in design through well validated methodologies the biorefineries currently are not working properly or are more close to a conventional standalone biomass processing. Some big facilities already implemented today as biorefineries are closed or working just as standalone process (biofuels plant), but not through a promising multiproduct biorefinery configuration for which the resulting design was developed. In this work, 13 biorefineries were analysed including 4 industrial cases that were implemented after specific design and different industrial plants that use different raw materials of renewable origin. To achieve this, different strategic cases were considered: raw materials with inherent logistics restrictions, technical, economic, environmental assessments together with social considerations and finally market restrictions. As a result, and based on different case studies (where these process engineering strategies where applied through conceptual design using Aspen Plus and Potential Environmental Impacts) the positive and negative lessons are discussed in detail. The main result is an overall learning from different cases of study for future design, analysis and implementation of new biorefineries with a real sustainability and avoiding a repetition of the same evolution that risky and controversial crude-oil refineries had

Impact of government incentives in the profitability of green energy production using fuel cells in Colombia

Las celdas de combustible son alternativas tecnológicas para producir energía renovable, sin embargo, los altos costos hacen a estas una opción poco rentable. Este artículo analiza el impacto de los incentivos del Gobierno de Colombia en la rentabilidad de la generación de energía eléctrica a partir de celdas de combustible. El análisis está basado en los costos totales de la operación de las celdas de combustible en tres escenarios representativos: una residencia, una oficina y un elevador de un edificio. La viabilidad económica de la generación con celdas de combustible en estos tres casos es contrastada con soluciones clásicas como generación a partir de diésel y la red eléctrica convencional. Los resultados permiten identificar que los incentivos del Gobierno de Colombia son muy efectivos para quienes generen a partir de energía renovable, como celdas de combustible, en contraste con otras opciones menos amigables con el medio ambiente, como los generadores diésel. Finalmente, nuevos incentivos son propuestos sobre la base de subsidios ofrecidos por otros países con alta penetración de las celdas de combustible en su mercado eléctrico. Todos los análisis están soportados en simulaciones realizadas con modelos matemáticos parametrizados que consideran las características de los dispositivos comerciales.Fuel cells are a technological alternative to produce green energy, however, high costs make fuel cell a non-profitable option. This paper analyses the impact of the Colombian government incentives in the profitability of fuel cells. The analysis is based on the total operation cost of the fuel cell in three representative applications: residential, office and building elevator. The economic viability of fuel cell generation in those cases is contrasted with classical solutions like diesel generators and standard grid to provide a reference framework. Such results enable to evaluate the effectiveness of the Colombian government incentives in promoting the use of fuel cells over other less environmental-friendly options such as diesel generators. Finally, new incentives are proposed by subsidies offered by other countries with higher fuel cell penetration into their electric market. All the analyses are supported in simulations performed with a mathematical model parameterized using the characteristics of commercial devices

Impact of government incentives in the profitability of green energy production using fuel cells in Colombia

Las celdas de combustible son alternativas tecnológicas para producir energía renovable, sin embargo, los altos costos hacen a estas una opción poco rentable. Este artículo analiza el impacto de los incentivos del Gobierno de Colombia en la rentabilidad de la generación de energía eléctrica a partir de celdas de combustible. El análisis está basado en los costos totales de la operación de las celdas de combustible en tres escenarios representativos: una residencia, una oficina y un elevador de un edificio. La viabilidad económica de la generación con celdas de combustible en estos tres casos es contrastada con soluciones clásicas como generación a partir de diésel y la red eléctrica convencional. Los resultados permiten identificar que los incentivos del Gobierno de Colombia son muy efectivos para quienes generen a partir de energía renovable, como celdas de combustible, en contraste con otras opciones menos amigables con el medio ambiente, como los generadores diésel. Finalmente, nuevos incentivos son propuestos sobre la base de subsidios ofrecidos por otros países con alta penetración de las celdas de combustible en su mercado eléctrico. Todos los análisis están soportados en simulaciones realizadas con modelos matemáticos parametrizados que consideran las características de los dispositivos comerciales.Fuel cells are a technological alternative to produce green energy, however, high costs make fuel cell a non-profitable option. This paper analyses the impact of the Colombian government incentives in the profitability of fuel cells. The analysis is based on the total operation cost of the fuel cell in three representative applications: residential, office and building elevator. The economic viability of fuel cell generation in those cases is contrasted with classical solutions like diesel generators and standard grid to provide a reference framework. Such results enable to evaluate the effectiveness of the Colombian government incentives in promoting the use of fuel cells over other less environmental-friendly options such as diesel generators. Finally, new incentives are proposed by subsidies offered by other countries with higher fuel cell penetration into their electric market. All the analyses are supported in simulations performed with a mathematical model parameterized using the characteristics of commercial devices

Arteriolopatía calcificante urémica, reporte de un caso tratado con tiosulfato de sodio

We describe a case of calcific uremic arteriolopathyinitially associated with skin lesions within the context of a patient with chronic kidney disease on automated peritoneal dialysis therapy. Among the most relevant findings, the patient hadhyperphosphatemia, normocalcemia and severe hyperparathyroidism without nodular hyperplasia. Clinical improvement with multimodal management of enhancement in dialysis therapy and intravenous sodium thiosulfate is highlighted. Calciphylaxis is a disorder that has a high morbidity and mortality, secondary to sepsis. It occurs more frequently in patients with chronic renal failure who are on hemodialysis. It is characterized by systemic medial calcification of the arterioles, triggering ischemia and subcutaneous necrosis of skin and soft tissues. Histopathological evaluation helps to confirm the diagnosis.Describimos un caso de arteriolopatía calcificante urémica asociada,  inicialmente, a lesiones cutáneas,en unpaciente con insuficiencia renal crónica, en terapia de diálisis peritoneal automatizada, como hallazgos másrelevantes presentaba hiperfosfatemia, normocalcemia e hiperparatiroidismo severo sin hiperplasia nodular.Se destaca la mejoría clínica con manejo multimodal de intensificación en la terapia dialítica y tiosulfato desodio intravenoso.La calcifilaxis es un trastorno que debuta con alta morbilidad ymortalidad, secundaria a sepsis, ocurre con mayor frecuencia en pacientes con insuficiencia renal crónica que se encuentran en hemodiálisis. Se caracteriza por calcificación sistémica en la media de las arteriolas, desencadenándose isquemia y necrosis subcutánea de piel y tejidos blandos. La evaluación histopatológica ayuda a confirmar el diagnóstico

Spin diffusion versus proximity effect at ferromagnet/superconductor La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7-δ) interfaces

We report on the interplay between magnetism and superconductivity in La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7) structures. We have grown heterostructures (bilayers and trilayers) with a constant thickness of the ferromagnetic layer of 40 unit cells (15 nm) and changing the thickness of the superconductor between 1 (1.2 nm) and 40 unit cells (48 nm). The critical temperature of the bilayers decreases when the thickness of the superconductor is reduced below 10 unit cells, thus providing an estimate of the length scale of superconductivity suppression by spin-polarized quasiparticles in YBa_(2)Cu_(3)O_(7-δ) (YBCO) of 10 nm, much larger than the coherence length. For thickness of the YBCO layer smaller than 4 unit cells; a second mechanism of superconductivity depression comes into play, probably related to the ferromagnetic/superconducting proximity effect. The relative importance in depressing the critical temperature of intrinsic mechanisms (quasiparticle diffusion and proximity effect) and extrinsic ones (intralayer disorder, interface roughness, or reduced dimensionality of ultrathin layers) is discussed

Strength, elastic properties and fiber–matrix interaction mechanism in geopolymer composites

The current geopolymers have limited mechanical strength against the effect of tension, which makes them susceptible to brittle failure. However, owing to their potential as a sustainable construction material, there is growing interest in improving the poor mechanical properties of geopolymers. This study experimentally investigated crucial properties of polypropylene-fiberreinforced fly ash-based geopolymer composites. The effects of polypropylene fibers (PPF) addition (0.5%, 1.0% and 1.5% by volume) on the mechanical properties of the geopolymer composites were investigated with respect to compressive and flexural strength, deformation behavior of Young’s and shear moduli, and resilience capacity. In addition, scanning electron microscopy was performed to establish the morphology of the geopolymeric matrix and the fiber–matrix interfacial interaction. The addition of PPF significantly increased the flexural strength: compared with the control, at 7 days it was 27% greater for the 0.5% PPF composite and 65% greater for the 1.0% PPF composite. By 14 days it was 31% and 61% greater, respectively. By contrast, the 1.5% PPF composite had lower strength parameters compared with the control because the fiber dispersion increased the porosity. Similar trends were seen for resilience. The SEM observations showed the dispersion of the fibers and helped elucidate the fiber–matrix interaction mechanismPeer ReviewedPostprint (published version

Subharmonic ripple analysis of an interleaved buck converter based on the Filippov method

El diseño de convertidores conmutados en gran parte de la literatura científica está realizado desde el modelo promediado, debido a la facilidad de obtener las funciones de transferencia lineales. Asimismo, la conmutación en los convertidores de potencia causa un rizado en las variables de estado que no es considerado en el modelo promediado. El componente de frecuencia de una de las variables de estado está compuesto por un espectro de potencia con un único pico de nivel DC (valor promedio), un único pico a la frecuencia de conmutación (componente de rizado) y en un número finito de picos en cada sub-armónico (inestabilidades). El método de Filippov es utilizado para la predicción de inestabilidades debidas a las dinámicas rápidas, este método predice el rango de los parámetros que evitan la primera bifurcación en las dinámicas rápidas. En el presente artículo se presenta una predicción  de un espacio de parámetros estables para el controlador PI (), estimados por el método de Filippov para un convertidor buck de dos fases con regulación de voltaje. Finalmente, los resultados presentados son validados mediante simulaciones de Matlab y Psim.In many papers, the averaged model of power switching converters is used to design the control system due to its simple manipulation, which can be approximated by linear transfer functions. Therefore, the power converter commutation causes a state variable ripple that is not considered on the averaged model. The component frequency of the state variables is composed by a power spectrum with a unique peak at the DC level (average variable), a unique peak at the switching frequency (ripple component) and a finite number of peaks in each sub-harmonic (instabilities). The Filippov method is used for instability predictions due to fast dynamics, this method predicts the parameters range that avoids the first bifurcation of the fast dynamics. In this paper a stable space of parameters (Kp, Ti) for a PI controller is presented, it estimated with the Filippov method, for a buck converter with voltage regulation. Finally, the presented results are validated using both Matlab and Psim simulations

Advances in Power and Energy Systems

Processing electrical energy is one of the most important research fields in our society. So far, tremendous efforts have been made to improve the efficiency of each step in electrical systems: generation systems have been enhanced by introducing renewable energy sources and new control systems for conventional generators, losses have been reduced, the power quality of distribution and transmission systems has been increased, the life-time and state-of-health of energy storage devices have been extended, and sections of the power grid have been isolated for intelligent energy management

Robotic Navigation based in Statics Patterns using the CMUcam3 Embedded System

Este artículo presenta un método de navegación Robótico basado en patrones estáticos usando técnicas de visión artificial implementadas sobre el sistema embebido CMUcam3, además presenta un análisis de procesamiento de cómputo para este sistema embebido. El patrón a determinar es una línea negra con cruces, guiando al agente robótico a través de ésta. Luego de la adquisición de las imágenes mediante la CMUcam3, se utiliza un algoritmo de segmentación basado en umbral, se determina el esqueleto de los patrones y luego se aplica la transformada de Hough lineal para determinar, las líneas, los ángulos y los tipos de cruces. Debido a que la transformada de Hough lineal es un método que requiere alto procesamiento, en este trabajo, se limita el rango de los ángulos y se normaliza su espacio de acumulaciones. En los resultados obtenidos se pudo determinar que el método desarrollado para la navegación es preciso y confiable, ya que en un 87% de los segmentos de decisión se pudo determinar correctamente el tipo de cruce y el ángulo de corrección. Él sistema embebido CMUcam3 logró procesar una imagen entre 0.15 y 0.28 segundos, dependiendo del tipo de cruce que encuentre.This paper presents a method based on static patterns for robotic navigation using computer vision techniques implemented on CMUcam3 embedded system, also presents an analysis of computational complexity for this embedded system. The pattern to be determined is a black line with intersections, driving the robotic agent over the line. A segmentation algorithm based in threshold is used after the images acquisition by the CMUcam3, then defines the thinning patterns and then the linear Hough transform is applied to determine the lines, the angles and the type of the intersections. Due to the linear Hough transform is a method that requires high processing, in this project, the range of the angles are limited and the accumulation space is normalized. The results showthat the method developed for the navigation is accurate and reliable, because in 87% of the decision segments it could determine correctly the type of intersection and the correction angle. The CMUcam3 embedded system succeeded to process an image between 0.15 and 0.28 seconds, depending of the type of the intersection

Origin of the inverse spin-switch behavior in manganite/cuprate/manganite trilayers

We studied ferromagnet/superconductor/ferromagnet trilayers based on La_(0.7)Ca_(0.3)MnO_(3) manganite and YBa_(2)Cu_(3)O_(7−δ) (YBCO) high-T_(c) cuprate with magnetoresistance and magnetization measurements. We find an inverse superconducting spin-switch behavior, where superconductivity is favored for parallel alignment of the magnetization in the ferromagnetic layers. We argue that this inverse superconducting spin switch originates from the transmission of spin-polarized carriers into the superconductor. In this picture, the thickness dependence of the magnetoresistance yields the spin-diffusion length in YBCO as 13 nm. A comparison of bilayers and trilayers allows ruling out the effect of the stray fields of the domain structure of the ferromagnet as the source of the inverse superconducting spin switch