Solar-plus-storage benefits for end-users placed at radial and meshed grids: An economic and resiliency analysis

[EN] A resilient photovoltaic system, which comprises from the joint use of photovoltaic solar panels and electrochemical storage that is able to operate both with and without grid connection, is capable of providing an added service both during normal grid-connected operation and when a blackout occurs (as opposed to a traditional solar system). When the conventional power grid is in normal operation, resilient photovoltaic systems are able to generate revenue and/or reduce the electricity bill. During blackouts, resilient photovoltaic systems are capable of providing critical emergency power to help backup diesel generator systems. The research presented here evaluates the technical and economic feasibility of systems based on photovoltaic solar energy and electrochemical storage in three critical infrastructures which have to account with a typical backup diesel generator. To this end, the research presented here assigns a monetary value to the cost of avoiding a blackout. Thus, the REopt Lite software has been used to optimally select and dimension different resilient schemes. For each of the cases evaluated the resilient systems were able to obtain benefits associated with the substitution of the energy use of the electricity grid, the reduction of charges for the use of energy during peak energy periods, and the modification of energy purchase periods from periods of high cost to periods of low cost. For all cases the model found the optimal combination of technologies capable of minimizing the cost of energy throughout the life cycle of the project. The obtained results show that assigning a value to the cost of blackouts can have a major impact on the economic viability of a resilient solution. For all cases the net present value of a system was always higher when a value was assigned to resilience. The values assigned to resilience were higher for users plugged to radial networks, which are more prone to blackouts, and lower for users connected to meshed grids, usually more reliable. Despite the fact that for the investigation presented here only three types of infrastructures were assessed, similar results could be expected for other critical infrastructures with similar loads and electricity tariffs. Resilient systems using photovoltaic solar installations that are limited in size could provide both economic savings during normal grid-connected operation and limited emergency power during blackouts. When these systems based on photovoltaic solar energy and electrochemical storage are used in conjunction with an emergency diesel generator, these resilient “hybrid” systems are capable of satisfying critical loads during short- and long-term blackouts.[ES] Un sistema fotovoltaico resiliente, que comprende el uso conjunto de paneles solares fotovoltaicos y un almacenamiento electroquímico que sea capaz de funcionar tanto con conexión a red como sin ella, es capaz de dar un servicio añadido tanto durante el funcionamiento normal conectado a red como cuando se produce un apagón ( a diferencia de un sistema solar tradicional). Cuando la red eléctrica convencional está en funcionamiento normal, los sistemas fotovoltaicos resilientes pueden generar ingresos y/o reducir la factura eléctrica. Durante los apagones, los sistemas fotovoltaicos resistentes son capaces de proporcionar energía de emergencia crítica para ayudar a respaldar los sistemas de generadores diésel. La investigación aquí presentada evalúa la viabilidad técnica y económica de sistemas basados en energía solar fotovoltaica y almacenamiento electroquímico en tres infraestructuras críticas que deben contar con un típico generador diésel de respaldo. Para ello, la investigación aquí presentada asigna un valor monetario al costo de evitar un apagón. Por lo tanto, el software REopt Lite se ha utilizado para seleccionar y dimensionar de manera óptima diferentes esquemas resilientes. Para cada uno de los casos evaluados los sistemas resilientes lograron obtener beneficios asociados a la sustitución del uso energético de la red eléctrica, la reducción de cargos por el uso de energía durante los períodos pico de energía y la modificación de los períodos de compra de energía de los períodos de alto costo a periodos de bajo costo. Para todos los casos el modelo encontró la combinación óptima de tecnologías capaces de minimizar el coste de la energía durante todo el ciclo de vida del proyecto. Los resultados obtenidos muestran que asignar un valor al costo de los apagones puede tener un impacto importante en la viabilidad económica de una solución resiliente. En todos los casos, el valor actual neto de un sistema siempre fue mayor cuando se asignó un valor a la resiliencia. Los valores asignados a la resiliencia fueron mayores para los usuarios conectados a redes radiales, que son más propensos a sufrir apagones, y menores para los usuarios conectados a redes malladas, generalmente más confiables. A pesar de que para la investigación aquí presentada sólo se evaluaron tres tipos de infraestructuras, se podrían esperar resultados similares para otras infraestructuras críticas con cargas y tarifas eléctricas similares. Los sistemas resilientes que utilizan instalaciones solares fotovoltaicas de tamaño limitado podrían proporcionar ahorros económicos durante el funcionamiento normal conectado a la red y energía de emergencia limitada durante los apagones. Cuando estos sistemas basados en energía solar fotovoltaica y almacenamiento electroquímico se utilizan junto con un generador diésel de emergencia, estos resistentes sistemas “híbridos” son capaces de satisfacer cargas críticas durante apagones de corto y largo plazo.S

Ecocardiografía con contraste

La ecocardiografía es una técnica de diagnóstico cardiológico que utiliza como método de estudio la emisión de haces de ultrasonido (US). Una de sus principales limitaciones es la mala propagación que tienen los US ante la presencia de grasa o aire, dificultando la visualización de las estructuras cardiacas, situación conocida como "mala ventana ecocardiográfica

An efficient synthesis of new fluorinated uracil derivatives

A series of potentially biologically active fluorinated uracil derivatives has been prepared in three steps from oxazolines and fluorinated nitriles with good chemical yields.Fustero Lardies, Santos, [email protected] ; Sanz Cervera, Juan Francisco, [email protected] ; Asensio Martinez, Amparo, [email protected]

Global sensitivity analysis of fuel-type-dependent input variables of a simplified physical fire spread model

[EN]A new global sensitivity analysis has been conducted of fuel-type-dependent input variables of the simplified physical fire spread model (PhyFire) to understand how the use of spatial averages, that is, fuel models, influences the results of PhyFire with a view to enhancing its understanding and improving its design. The model’s simplicity, the numerical techniques used, and a recent code optimisation, allow undertaking the analysis with very competitive computational times. The fuel data used correspond to grasslands, shrublands and forest in the Spanish region of Galicia. The analysis results validate the flame length sub-model proposed in the paper, which significantly improves the model’s efficiency

On a Proper Tensorial Subgrid Heat Flux Model

In this work, we aim to shed light to the following research question: can we find a nonlinear tensorial subgrid-scale (SGS) heat flux model with good physical and numerical properties, such that we can obtain satisfactory predictions for buoyancy-driven turbulent flows? This is motivated by our findings showing that the classical (linear) eddy-diffusivity assumption, q eddy ¿ ¿T, fails to provide a reasonable approximation for the actual SGS heat flux, q = uT - uT: namely, a priori analysis for airfilled Rayleigh-Bénard convection (RBC) clearly shows a strong misalignment. In the quest for more accurate models, we firstly study and confirm the suitability of the eddy-viscosity assumption for RBC carrying out a posteriori tests for different models at very low Prandtl numbers (liquid sodium, Pr = 0.005) where no heat flux SGS activity is expected. Then, different (nonlinear) tensor-diffusivity SGS heat flux models are studied a priori using DNS data of an air-filled (Pr = 0.7) RBC at Rayleigh numbers up to 1011. Apart from having good alignment trends with the actual SGS heat flux, we also restrict ourselves to models that are numerically stable per se and have the proper cubic near-wall behavior. This analysis leads to a new family of SGS heat flux models based on the symmetric positive semi-definite tensor GGT where G = ¿u, i.e. q ¿ GGT¿T, and the invariants of the GGT tensor. Finally, relevant numerical aspects regarding the implementation of this type of models are discussed in detail. A list of physical and numerical properties is identified and subsequently imposed, leading to a symmetrypreserving discretization that is based on discrete operators already available in any CFD code.F.X.T., F.D. and A.O. have been financially supported by the Ministerio de Economía y Competitividad, Spain, ANUMESOL project (ENE2017-88697-R). F.X.T. and A.O. are supported by the Generalitat de Catalunya RIS3CAT-FEDER, FusionCAT project (001-P-001722). F.D. is supported by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development, and the K1MET center for metallurgical research in Austria (www.k1-met.com). D.S. is supported by an FI AGAUR-Generalitat de Catalunya fellowship (2020FI B 00839). Calculations have been performed on the IBM MareNostrum 4 supercomputer at the BSC (PRACE 15th Call, Ref. 2016163972, “Exploring new frontiers in Rayleigh-Bénard convection” and Tier-1 RES projects IM-2020-2-0029 & IM-2020-3-0030 “Direct and Large-Eddy Simulation of buoyancy-driven turbulence in liquid metals”). The authors thankfully acknowledge these institutions.Peer ReviewedPostprint (published version

On the effect of prandtl number to subgrid-scale heat flux models

Estimations of the grid size and computational cost for direct numerical simulation (DNS) and large-eddy simulation (LES) of Rayleigh-Bénard convection (RBC) are presented in the {Ra, P r} phase space. Computational requirements to reach the so-called asymptotic Kraichnan or ultimate regime of turbulence using DNS are far too expensive. Therefore, we turn to LES to predict the large-scale behavior at very high Ra-numbers. However, a priori alignment studies clearly show why the modelization of the SGS heat flux is the main difficulty that (still) precludes reliable LES of buoyancy-driven flows at (very) high Ra-numbers. This inherent difficulty can be by-passed by carrying out simulations at low-P r numbers where no SGS heat flux activity is expected. This opens the possibility to reach the ultimate regime carrying out LES of RBC at low-P r using meshes of 1010 -1011 grid points. Nevertheless, to do so, we firstly need to combine proper numerical techniques for LES (also DNS) with an efficient use of modern hybrid supercomputers.F.X.T. and A.O. are supported by the Ministerio de Economía y Competitividad, Spain, RETOtwin project (PDC2021-120970-I00) and by the Generalitat de Catalunya RIS3CAT-FEDER, FusionCAT project (001-P-001722). D.S. and J.A.H. are supported by the FI-AGAUR predoctoral grants 2020FI B 00839 and 2022 FI B1 00204, respectively. Calculations were carried out on MareNostrum 4 supercomputer (projects IM-2022-1-0015 and IM-2022-2- 0019) at BSC. The authors thankfully acknowledge these institutions.Peer ReviewedPostprint (published version

Teaching Using Collaborative Research Projects: Experiences with Adult Learners in Distance Education

[EN] This research studies the acquisition and improvement of specific cognitive, functional, and social competencies of the students enrolled in a university module in which we applied Collaborative Research Project (CRP) strategy. The module was Research Methodology for a master’s degree in research in electrical engineering, electronics and industrial control given at the National Distance Education University (UNED) in Spain. This practice was applied to a research project in which the private sector was interested in. We have been aiming at increasing academia–industry interaction while promoting active learning; both are principles advocated by the European Higher Education Area (EHEA). Having applied this strategy, the module learning outcomes were evaluated following the guideline standards set by the National Agency for Quality Assessment of Universities (ANECA) of the Spanish Government. The results from this evaluation indicated that CRP, even when carried out by using distance learning, has encouraged the students’ interest in both research and the module. It has also fostered collaboration between students and lecturers while increasing their degree of satisfaction. We highlight the difficulties in merging all the outcomes from the students’ research as the main drawback

Optimized design method for storage systems in photovoltaic plants with delivery limitation

Versión aceptada para publicación. No contiene los cambios menores recogidos tras el proof reading.[EN] It results widely common for distribution network operators to impose restrictions on delivered solar photovoltaic generated power when the power plant rated power is greater than the maximum allowed due to the distribution network capacity. Thus, a feasible solution to maximize the performance of the solar power plant is the integration of battery energy storage systems. Although this configuration has been extensively studied in the existing literature, an optimal design method to determine the proper size and operation of the energy storage system needs to be developed. In this paper, a novel method to help power plants designers to determine the optimal battery energy storage capacity to integrate into any solar photovoltaic power plant is provided. The proposed algorithm minimizes the potential power curtailment and optimizes the utilization rate of the batteries storage system. The algorithm can be applied to any grid connected solar photovoltaic power plant under delivery power restrictions, regardless of power capacity and location. The algorithm has been implemented to a simulated power plant with delivery limitations based in a real case, and results with the optimal battery capacity show that the system would be able to recover up to the 83% of the curtailed energy and a yearly average capacity utilization of 56%. Moreover, the BESS operation has been validated with a scaled model run in Simulink and laboratory measurements, achieving 98% of curtailed energy recovery rate and a 57% of average capacity utilization.[ES] Resulta muy habitual que los operadores de las redes de distribución impongan restricciones a la potencia generada por energía solar fotovoltaica suministrada cuando la potencia nominal de la central es superior a la máxima permitida debido a la capacidad de la red de distribución. Por ello, una solución factible para maximizar el rendimiento de la central solar es la integración de sistemas de almacenamiento de energía en baterías. Aunque esta configuración ha sido ampliamente estudiada en la literatura existente, es necesario desarrollar un método de diseño óptimo para determinar el tamaño y funcionamiento adecuados del sistema de almacenamiento de energía. En este trabajo se presenta un método novedoso para ayudar a los diseñadores de centrales eléctricas a determinar la capacidad óptima de almacenamiento de energía en baterías para integrar en cualquier central solar fotovoltaica. El algoritmo propuesto minimiza el posible recorte de potencia y optimiza la tasa de utilización del sistema de almacenamiento en baterías. El algoritmo puede aplicarse a cualquier planta de energía solar fotovoltaica conectada a la red bajo restricciones de potencia de entrega, independientemente de la capacidad de potencia y la ubicación. El algoritmo se ha aplicado a una central eléctrica simulada con limitaciones de suministro basada en un caso real, y los resultados con la capacidad óptima de las baterías muestran que el sistema sería capaz de recuperar hasta el 83% de la energía restringida y una utilización media anual de la capacidad del 56%. Además, el funcionamiento del BESS se ha validado con un modelo a escala ejecutado en Simulink y mediciones de laboratorio, y se ha conseguido recuperar el 98% de la energía restringida.S

Protocolo para el diseño de una escala específica de auto-eficacia en la adherencia a una dieta sin gluten: Escala de celiaquía y auto-eficacia

Background: Celiac disease is a chronic autoimmune disorder consisting of a permanent intolerance for gluten, with a prevalence of 1%, for which the only treatment to date is to follow a strict gluten free diet for life. Lack of adherence to this treatment is related to severe health problems while compliance leads to normalization. Recently, self-efficacy has been associated with self-management behaviors in chronic disease and health status in many fields.Aims: To construct and validate a self-administered scale to measure self-efficacy in adherence to gluten free diet in the different areas a patient with celiac disease must face everyday.Material and Methods: For the validation phase, the research team aims to recruit 500 celiac individuals over 12 years of age from primary care services and patient associations. The scale will be designed to explore specific self efficacy to adhere to a gluten free diet in the following areas: purchases, eating out, eating at home with others, travelling and at work or school. An expert panel will be conducted to assure quality of the items and utility of the scale. The preliminary form will be tested in as many pilot studies as necessary. An exploratory factor analysis will be applied to study construct validity while concurrent validity will be measured with the correlation coefficient between the new instrument and the Baessler and Schwarzer General Self Efficacy Scale. The reliability of the instrument as well as that of each of the factors extracted from the prior analysis will be analyzed using Cronbach’s alpha internal consistency coefficient. Two weeks later, the scale will be administered to, at least, one third of the sample as a retest in the validation process and to allow for confirmatory factor analysis.Results: This research will design, develop and validate a questionnaire for two types of measures: A score for Self-Efficacy for the management of celiac disease, and a score of self-efficacy for each of the identified key areas. This research will result in the first scale to assess specific self efficacy while following a strict gluten free diet and will allow further research in the role that this expectation may play in patient´s adherence to the unique treatment developed to date and it may be useful in both clinical and research settings. The new scale will be easy to apply and it is expected to have a higher predictive value than instruments assessing general self-efficacy.Conclusions: This questionnaire will be the first of its kind to determine levels of self-efficacy for adherence to gluten free diet and will help to the design of self-management interventions for celiac patients.Antecedentes: La enfermedad celíaca es un trastorno autoinmune crónico, caracterizado por una intolerancia permanente al gluten, con una prevalencia del 1%, y para la que el único tratamiento hasta la fecha consiste en seguir una dieta estricta libre de gluten de por vida. La falta de adherencia a este tratamiento está relacionada con problemas de salud graves, mientras que el cumplimiento conduce a la normalización. Recientemente, la auto-eficacia se ha asociado con comportamientos de autogestión de las enfermedades crónicas y el estado de salud en muchos campos.Objetivos: Diseñar y validar una escala para medir la auto-eficacia en la adherencia a una dieta libre de gluten en los diferentes ámbitos a los que se enfrentan todos los días los pacientes con enfermedad celíaca.Material y Métodos: Para el proceso de validación, el equipo de investigación reclutará a 500 personas diagnosticadas de enfermedad celíaca, de más de 12 años de edad, a partir de los servicios de atención primaria y las asociaciones de pacientes. Se diseñará una escala para explorar la autoeficacia específica en la adherencia a una dieta sin gluten en las siguientes áreas: compras, comer fuera de casa, comer en casa con otros, viajar y comer en el trabajo o en el colegio. Se llevará a acabo un panel de expertos para asegurar la calidad de los ítems y la utilidad de la escala. Se realizarán los estudios piloto que sean necesarios para su mejora y se analizará su validez de constructo mediante un análisis factorial exploratorio mientras que la validez concurrente será medida mediante su correlación con la adaptación española del General Self Efficacy Scale de Baessler y Schwarzer. La fiabilidad del instrumento, así como de cada uno de los factores, será determinada utilizando el coeficiente alfa de Cronbach de consistencia interna. Dos semanas más tarde, la escala será administrada a, al menos, un tercio de la muestra para obtener una fiabilidad test-retest y para permitir un análisis factorial confirmatorio.Resultados: Se espera diseñar, construir y validar un cuestionario que permita producir dos tipos de medidas: una valoración especifica la auto-eficacia percibida en el manejo de la enfermedad celíaca, y una valoración de la auto-eficacia para cada una de las áreas clave identificadas. Esta investigación proporcionará la primera escala para evaluar la autoeficacia específica para la adherencia a la dieta sin gluten de importante utilidad en entornos tanto clínicos como de investigación. Se prevé que su valor predictivo sea superior a medidas generales de la expectativa de autoeficacia.Conclusiones: Este cuestionario será el primero capaz de determinar los niveles de auto-eficacia en la adherencia a la dieta libre de gluten y ayudará en el diseño de intervenciones de auto-cuidado para pacientes celíacos

An expert judgement approach to determine measures to remove institutional barriers and economic non-market failures that restrict photovoltaic self-consumption deployment in Spain

[EN] Despite the Spanish privileged geographical location and business leadership in the renewable energy field, currently is can be observed that the solar photovoltaic generation, electric self-consumption systems and net-metering policies deployment is much lower than it can be observed in other countries, even with lower energy sources for self-consumption. Energy policy experts assess as main reason the absence of a stable regulatory framework and the existence of clear disincentives. These disincentives are based on several economic non-market failures and institutional barriers. One key factor has proven to be the regulatory uncertainty created mainly by the recent national most relevant ministerial orders regarding energy generation and consumption, which suggests that, de facto, the regulatory framework is currently still under development. This paper includes first a brief but deep description of the prosumers penetration existing scenario in Spain, and then it focuses on feasible strategies to accelerate higher solar photovoltaic and self-consumption growth rates in Spain. Then, new policy measures to eliminate, or at least, mitigate, current barriers to their deployment are proposed and discussed. It is concluded that it results mandatory the urgent modernization of the energy regulatory framework promoting an active role for distributed PV generation which could have a significant positive impact in the voltage control and frequency regulation in distribution networks, among other advantages.[ES] A pesar de la privilegiada situación geográfica española y del liderazgo empresarial en el campo de las energías renovables, en la actualidad se observa que el despliegue de la generación solar fotovoltaica, de los sistemas de autoconsumo eléctrico y de las políticas de net-metering es muy inferior al que se observa en otros países, incluso con menores fuentes de energía para el autoconsumo. Los expertos en política energética valoran como razón principal la ausencia de un marco regulatorio estable y la existencia de claros desincentivos. Estos desincentivos se basan en varios fallos económicos ajenos al mercado y en barreras institucionales. Un factor clave ha resultado ser la incertidumbre regulatoria creada principalmente por las recientes órdenes ministeriales nacionales más relevantes en materia de generación y consumo de energía, lo que sugiere que, de facto, el marco regulador se encuentra actualmente en fase de desarrollo. Este trabajo incluye en primer lugar una breve pero profunda descripción del escenario de penetración de prosumidores existente en España, y a continuación se centra en las estrategias viables para acelerar mayores tasas de crecimiento de la energía solar fotovoltaica y el autoconsumo en España. A continuación, se proponen y discuten nuevas medidas políticas para eliminar, o al menos, mitigar, las barreras actuales a su despliegue. Se concluye que resulta obligatoria la urgente modernización del marco regulatorio energético promoviendo un papel activo para la generación fotovoltaica distribuida que podría tener un impacto positivo significativo en el control de la tensión y la regulación de la frecuencia en las redes de distribución.S