Assessing the contribution of microgrids to the reliability of distribution networks

The emergence of microgeneration has recently lead to the concept of microgrid, a network of LV consumers and producers able to export electric energy in some circumstances and also to work in an isolated way in emergency situations. Research on the organization of microgrids, control devices, functionalities and other technical aspects is presently being carried out, in order to establish a consistent technical framework to support the concept. The successful development of the microgrid concept implies the definition of a suitable regulation for its integration on distribution systems. In order to define such a regulation, the identification of costs and benefits that microgrids may bring is a crucial task. Actually, this is the basis for a discussion about the way global costs could be divided among the different agents that benefit from the development of microgrids. Among other aspects, the effect of microgrids on the reliability of the distribution network has been pointed out as an important advantage, due to the ability of isolated operation in emergency situations. This paper identifies the situations where the existence of a microgrid may reduce the interruption rate and duration and thus improve the reliability indices of the distribution network. The relevant expressions necessary to quantify the reliability are presented. An illustrative example is included, where the global influence of the microgrid in the reliability is commented.

Prevalencia de síntomas musculoesqueléticos en personal que labora en una Central eléctrica en las actividades de Gestión y Control de Pérdidas de Energía en Norte de Santander, 2016

Introducción: Los trastornos musculoesqueléticos de origen laboral son la primera causa de baja en los trabajadores produciendo disminución de la capacidad productiva y reducción del salario y para las empresas suponen disfunciones de la actividad y pérdidas económicas. Objetivo: Identificar la prevalencia de síntomas musculoesqueléticos del personal tanto operativo como administrativo que laboran en la central eléctrica en Norte de Santander. Metodología: Estudio de corte transversal en una población de 184 trabajadores que laboran para la sección de gestión y control de pérdidas de energía en la Central eléctrica de Norte de Santander. Se utilizó como instrumento para la recolección de información el cuestionario Nórdico de Kuorinka en su versión en español, que permite realizar la detección y análisis de síntomas musculoesqueléticos de la población expuesta, el cual consta de dos partes, la primera que incluye datos socio demográficos tales como antecedentes personales y actividad laboral y la segunda que permite registrar síntomas músculo-esqueléticos en los segmentos corporales (cuello, hombros, codos, muñecas/manos, espalda superior, espalda inferior). El análisis descriptivo incluyó el cálculo de la media y los porcentajes y para estimar asociaciones se utilizó odds ratio (OR) Resultados: El 88% de los trabajadores eran hombres, con una media de edad de 36,1(±10,5) años. El 20,7% percibía molestias en el cuello y el 17,4 % en las muñecas. Tuvieron más riesgo de percibir molestias en la región del cuello las mujeres (OR 20,54), los trabajadores que pertenecen al sector administrativo (OR 15,9), los que no realizar actividad física (OR 2,33), los que tienen menos de 1 año en el cargo (OR 2,9) y los que tenían un Índice de masa corporal mayor de 25 (OR 1,31). Conclusiones: Ser mujer y trabajar en el sector administrativo influyen en la percepción de molestias y síntomas osteomusculares con mayor prevalencia en las zonas corporales de el cuello y las muñecas o manos. De acuerdo a lo encontrado en el estudio se sugiere la realización de actividades en salud laboral que prevengan el riesgo ergonómico.

Solastalgia y conductas pro-ambientales en un conflicto socioambiental por la construcción de una hidroeléctrica

Introducción: La construcción de megaproyectos hídricos implica una reconfiguración territorial donde se ven afectadas las fuentes de agua dulce, la biodiversidad terrestre y acuática, y los asentamientos humanos que colindan con dichas construcciones. Objetivo: estimar la asociación entre las conductas proambientales con la solastalgia entre las personas que se encuentran ejerciendo un proceso de resistencia social contra la Central Hidrosogamoso en el departamento de Santander, Colombia. Metodología: se utilizó un diseño de estudio transversal en el que se entrevistaron integrantes y no integrantes de grupos ambientalistas de las zonas de influencia del proyecto. Se realizó un análisis descriptivo de las variables sociodemográficas de los dos grupos de comparación presentando frecuencias absolutas y relativas y diferencias significativas por medio de la prueba ji cuadrado, exacta de Fisher y U de Mann Whitney. Se utilizó un modelo de regresión lineal múltiple en el que la variable dependiente fue el puntaje de solastalgia y las variables independientes fueron las escalas de las conductas proambientales: altruismo, austeridad, equidad, conducta ecológica, deliberación, indignación y aprecio por lo natural, además, se ajustó por algunas variables sociodemográficas de interés. Resultados: los grupos comparados presentaron diferencias importantes en cuanto a la zona de procedencia, condiciones económicas y organización social. El incremento de 5 puntos en la escala del sentimiento de indignación incrementó 0.98 la escala de solastalgia (IC95%: 0.19; 1.78). Las personas sin pareja estable tuvieron 3.02 puntos menos de solastalgia comparadas con personas casadas o en unión libre (IC95%: -4.96; -1.44), mientras que aquellas con alto nivel educativo obtuvieron 2.02 puntos menos que las personas con primaria y bachillerato (IC95%: -3.99; -0.06). Un modelo alterno mostró que no pertenecer a un grupo ambientalista disminuye en 2.29 puntos la solastalgia, comparado con pertenecer a un grupo (IC95%: -4.31; -0.28),. Conclusión: posiblemente las motivaciones por las cuales los actores involucrados se resisten a las transformaciones territoriales ocasionadas por la construcción de las represas son más un reflejo de la condición socioeconómica que de la preocupación de los actores por el daño del medio ambiente y además, esta resistencia es un fenómeno que se limita a aquellos que están afectados directamente en el área de influencia del proyecto

SISTEMAS DE INFORMACIÓN GEOGRÁFICA COMO HERRAMIENTA PARA EVALUAR LA APORTACIÓN ANTROPICA DE MERCURIO EN SUELOS

Este trabajo evalúa el contendido y la variabilidad espacial de mercurio en suelos agrícolas de Islas Baleares y Canarias utilizando técnicas integradas en los sistemas de información geográfica. El propósito de este estudio ha sido valorar el contenido y distribución del mercurio en el suelo y distinguir la contribución considerada como natural, y procedente del aporte de la roca de origen, de la inducida por actividades humanas, considerada como contaminante. El SIG se muestra comouna tecnología capaz de localizar fuentes de contaminación y proporcionar el alcance de éstos. Los mapas generados con la relación de Hg_suelo/Hg_roca han permitido cuantificar las entradas de este metal en el suelo y evaluar el enriquecimiento de mercurio en el mismo. Valores excesivamente elevados encontrados en un área de la Isla de Mallorca son atribuibles a las emisiones de una planta eléctrica de carbón cercana.PALABRAS CLAVE: Análisis espacial, SIG, geostadística, mercurio, contaminación de suelos.ABSTRACTThis study assesses Hg concentration and the spatial variability of mercury in agricultural soils of the Balearic and Canary Islands using integrated techniques of geographic information systems. The purpose of this study was to characterize in quantitative terms the mercury concentrations and to distinguish “natural” mercury contribution from that of human-induced contamination. GIS is shown to be technologically capable of locating sources of pollution and assessing their scope. The top soil/rock mercury content maps showed a high level of mercury in the same areas. Excessively high Hg values found in an area of the island of Mallorca are attributable to emissions from a coalfired power plant nearby.KEYWORDS: Spatial analysis, GIS, geostatistic, mercury, soil contamination

Exact and heuristic algorithms for the integrated planning of multi-energy systems

The aim of this thesis is to present exact and heuristic algorithms for the integrated planning of multi-energy systems. The idea is to disaggregate the energy system, starting first with its core the Central Energy System, and then to proceed towards the Decentral part. Therefore, a mathematical model for the generation expansion operations to optimize the performance of a Central Energy System system is first proposed. To ensure that the proposed generation operations are compatible with the network, some extensions of the existing network are considered as well. All these decisions are evaluated both from an economic viewpoint and from an environmental perspective, as specific constraints related to greenhouse gases emissions are imposed in the formulation. Then, the thesis presents an optimization model for solar organic Rankine cycle in the context of transactive energy trading. In this study, the impact that this technology can have on the peer-to-peer trading application in renewable based community microgrids is inspected. Here the consumer becomes a prosumer and engages actively in virtual trading with other prosumers at the distribution system level. Moreover, there is an investigation of how different technological parameters of the solar Organic Rankine Cycle may affect the final solution. Finally, the thesis introduces a tactical optimization model for the maintenance operations’ scheduling phase of a Combined Heat and Power plant. Specifically, two types of cleaning operations are considered, i.e., online cleaning and offline cleaning. Furthermore, a piecewise linear representation of the electric efficiency variation curve is included. Given the challenge of solving the tactical management model, a heuristic algorithm is proposed. The heuristic works by solving the daily operational production scheduling problem, based on the final consumer’s demand and on the electricity prices. The aggregate information from the operational problem is used to derive maintenance decisions at a tactical level.

Formule analitiche per il calcolo delle perdite elettrodinamiche in cavi superconduttori ad alta temperatura critica.

Questo elaborato di tesi si concentra sul calcolo delle perdite che si verificano in cavi superconduttori ad alta temperatura critica per la fusione. La valutazione delle perdite riveste un ruolo di particolare importanza nella fase di progettazione di un cavo o di un avvolgimento superconduttore. Infatti, le proprietà superconduttive si manifestano a basse temperature (inferiori alla temperatura di transizione dalla fase normale alla fase superconduttiva) e di conseguenza è necessario configurare un apparato criogenico per il sistema. In tal senso, le perdite rientrano nel “budget” termico necessario a dimensionare correttamente il sistema di raffreddamento. Nel dettaglio, il lavoro verte sulla modellizzazione analitica e numerica delle perdite in una pila di nastri superconduttori in presenza sia di un campo magnetico esterno sia di una corrente di trasporto, entrambi con andamento variabile nel tempo. Gli obiettivi prefissati sono stati raggiunti grazie allo studio della letteratura e alle simulazioni numeriche, effettuate utilizzando dei software commerciali quali COMSOL Multiphysics e Matlab. Il contributo originale di questo elaborato è stato lo sviluppo di un nuovo modello analitico, che permette di calcolare le perdite per isteresi dovute a campi magnetici e correnti variabili periodicamente nel tempo. Le formule hanno carattere generale e possono essere utilizzate quando i campi e le correnti variano in fase seguendo degli andamenti periodici nel tempo di qualsiasi forma. Le simulazioni agli elementi finiti sono servite per validare le formule analitiche proposte. Le nuove relazioni ottenute sono state utilizzate per la stima delle perdite di un inserto ad alta temperatura critica del solenoide centrale di EU-DEMO (DEMOnstration Power Plant). Il modello analitico elaborato sarà pubblicato prossimamente su IEEE-Transactions on Applied Superconductivity.

Wind plant interaction with series-compensated power systems

Wind power based generation has been rapidly growing world-wide during the recent past. In order to transmit large amounts of wind power over long distances, system planners may often add series compensation to existing transmission lines owing to several benefits such as improved steady-state power transfer limit, improved transient stability, and efficient utilization of transmission infrastructure. Application of series capacitors has posed resonant interaction concerns such as through subsynchronous resonance (SSR) with conventional turbine-generators. Wind turbine-generators may also be susceptible to such resonant interactions. However, not much information is available in literature and even engineering standards are yet to address these issues. The motivation problem for this research is based on an actual system switching event that resulted in undamped oscillations in a 345-kV series-compensated, typical ring-bus power system configuration. Based on time-domain ATP (Alternative Transients Program) modeling, simulations and analysis of system event records, the occurrence of subsynchronous interactions within the existing 345-kV series-compensated power system has been investigated. Effects of various small-signal and large-signal power system disturbances with both identical and non-identical wind turbine parameters (such as with a statistical-spread) has been evaluated. Effect of parameter variations on subsynchronous oscillations has been quantified using 3D-DFT plots and the oscillations have been identified as due to electrical self-excitation effects, rather than torsional interaction. Further, the generator no-load reactance and the rotor-side converter inner-loop controller gains have been identified as bearing maximum sensitivity to either damping or exacerbating the self-excited oscillations. A higher-order spectral analysis method based on modified Prony estimation has been successfully applied to the field records identifying dominant 9.79 Hz subsynchronous oscillations. Recommendations have been made for exploring countermeasures.

From irradiance to output power fluctuations: the pv plant as a low pass filter

The power generated by large grid-connected photovoltaic (PV) plants depends greatly on the solar irradiance. This paper studies the effects of the solar irradiance variability analyzing experimental 1-s data collected throughout a year at six PV plants, totaling 18 MWp. Each PV plant was modeled as a first order filter function based on an analysis in the frequency domain of the irradiance data and the output power signals. An empiric expression which relates the filter parameters and the PV plant size has been proposed. This simple model has been successfully validated precisely determining the daily maximum output power fluctuation from incident irradiance measurements.

Patents and the CGIAR system of International Agricultural Research Centres' germplasm collections under the International Treaty on Plant Genetic Resources for Food and Agriculture

A key controversy in negotiating the International Treaty on Plant Genetic Resources for Food and Agriculture, and the likely long-term effectiveness of the agreement, is the way in which the intellectual property provisions are interpreted and applied to the key genetic resources forming the Consultative Group on International Agricultural Research (CGIAR) system of International Agricultural Research Centres' (IARC) collections. This paper reviews the intellectual property provisions in the treaty and examines the likely consequences from patenting under the Patents Act 1990 over materials derived from these collections. The consequence is argued to be significant and, over time, these practices are likely to deplete the usefulness of these collections and undermine the relevance of the treaty. The paper concludes that Australia's interests might best be served by arguing that access to these collections, and the other materials under the treaty, be subject to a non-exclusive, royalty free licence for any use of the derived materials to develop useful new plant varieties.

Antioxidant potential of two Apiaceae plant extracts: a comparative study focused on the phenolic composition

The present study aimed to characterize the extracts prepared from Pimpinella anisum L. (anise) and Coriandrum sativum L. (coriander) (Apiaceae plants) seeds in terms of phenolic composition, and to correlate the obtained profiles with the antioxidant activity. Anise gave the highest abundance in phenolic compounds (42.09± 0.11 mg/g extract), mainly flavonoids (28.08±0.17 mg/g extract) and phenolic acids (14.01±0.06 mg/g extract), and also the highest antioxidant potential, accessed for the ability to inhibit lipid peroxidation and -carotene bleaching, reducing power and free radical scavenger activity. Apigenin and luteolin derivatives, as also caffeoylquinic acid derivatives appear to be directly related with the higher in vitro antioxidant potential of the anise extract.. In contrast, the weak antioxidant potential of coriander seems to be due to their lower abundance in phenolic compounds (2.24±0.01 mg/g extract). Further studies are necessary to evaluate the in vivo antioxidant potential of the tested extracts, but the performed in vitro experiments highlight them as potential health promoters.

The Research of Increase of Channel Efficiency for IP Traffic Transmission over Digital Power Line Carrier Channels

This article is devoted to the research of channel efficiency for IP-traffic transmission over Digital Power Line Carrier channels. The application of serial WAN connections and header compression as methods to increase channel efficiency is considered. According to the results of the research an effective solution for network traffic transmission in DPLC networks was proposed.

Interpersonal Power: A Review, Critique, and Research Agenda

Power is a fundamental force in social relationships and is pervasive throughout various types of interactions. Although research has shown that the possession of power can change the powerholder, the full extent of power's consequences on individuals' decision making capabilities and social interactions within organizations is not fully understood. The goal of this paper is to review, synthesize, and critique the literature on power with a focus on its organizational and managerial implications. Specifically, we propose a definition of power that takes into account its three defining characteristics-having the discretion and means to enforce one's will-and summarize the extant literature on how power influences individuals' thoughts, emotions, and actions both in terms of prosocial and antisocial outcomes. In addition, we highlight important moderators of power and describe ways in which it can be studied in a more rigorous manner by examining methodological issues and pitfalls with regard to its measurement and manipulation. We also provide future research directions to motivate and guide the study of power by management scholars. Our desire is to present a thorough and parsimonious account of power's influence on individuals within an organizational context, as well as provide a foundation that scholars can build upon as they continue to make consequential contributions to the study of power.