Impacts of Wind Farms on Power System Stability

ilustraciones, diagramasOne of the Colombian strategies to diversify and decarbonize the energy sector is encouraging the use of non-conventional renewable resources (NCRR). For doing so the government issued in 2014 the Law 1715 to promote NCRR and energy efficiency improvements into the sector. While presumably it will help to achieve the international and national commitment to reduce the CO2 emission by 20% in 2030, this assumption cannot be tested broader without taking in account the environmental consequence that such initiatives may produce in the household sector, the greatest electricity consuming sector in Colombia This thesis measures the environmental rebound effect (ERE) when increasing the shares of wind power into the Colombian power grid in the residential (household) sector. For doing so, a process-based Life Cycle Assessment (P-LCA), an environmental extended input output (EEIO) model and re-spending models (almost ideal demand system AIDS) were applied. Direct rebound effect was measured thought the elasticity price of the electricity demand; furthermore, the environmental savings for increasing the shares of wind power into the grid were calculated via P-LCA. For doing so, a P-LCA for a wind farm in Colombia was performed, whereas the information for other energy resources (Hydro, Coal, Gas, Solar and Thermal) where collected from Ecoinvent 3.4 database. To calculate the environmental indirect rebound effect the monetary savings obtained for the environmental efficiency were calculated. For doing so, an AIDS was applied to obtain the marginal budget shares (MBS). Combining the MBS obtained with the EEIO model the monetary savings were translated into environmental indicators. The ERE is presented for ten impact categories (climate change (CC), acidification (A), ecotoxicity (E), marine eutrophication (MEUT), terrestrial eutrophication (TEUT), carcinogenic effects (CE), non-carcinogenic effects (NCE), ozone layer depletion (OD), photochemical ozone creation (POC), and respiratory effects, inorganics (RES)). Moreover, a sensitive analysis was conducted to measure the variability of the ERE to different values of the direct rebound effect and different percentages of price efficiency. The results show that the inclusion of the environmental rebound effect has generally a non-negligible impact on the overall environmental indicators across all studied years. Such impacts ranging across impact categories from 5% (eutrophication) and 6,109% (photochemical oxidant creation) for the combined model, whereas for the single model the values fall on the ranges of 1% (eutrophication) and 9,277% (photochemical oxidant creation). Further, a sensitivity analysis of the elasticity price of the electricity and the price of the electricity reveals that the ERE varies in different ways, specifically, changes in these parameters could vary the impacts, respectively, by up to about <1% and 38%. Backfire effects are present for 8 of the 10 environmental impacts studied in different magnitudes across the years, depending meanly of the savings available to re-invest.Una de las estrategias colombianas para diversificar y descarbonizar el sector energético es fomentar el uso de recursos renovables no convencionales (RNNC). Para ello, el gobierno emitió en 2014 la Ley 1715 para promover los RNNC y las mejoras de eficiencia energética en el sector. Si bien esto ayudará a cumplir el compromiso internacional y nacional de reducir las emisiones de CO2 en un 20% en 2030, este supuesto no puede ser probado de manera amplia sin tener en cuenta las consecuencias ambientales que tales iniciativas pueden producir en el sector doméstico, el mayor sector consumidor de electricidad en Colombia. Esta tesis mide el efecto rebote ambiental (ERE) de aumentar la participación de energía eólica en la red eléctrica colombiana en el sector residencial (hogares). Para ello se aplicó un modelo de evaluación del ciclo de vida basada en procesos (P-LCA), un modelo de entrada y salida ambiental extendido (EEIO) y modelos de gastos adicionales (sistema de demanda casi ideal AIDS). El efecto rebote directo se midió a través del precio de la elasticidad de la demanda de electricidad; además, el ahorro medioambiental por el aumento de la participación de energía eólica en la red se calculó a través de P-LCA. Para ello se realizó un P-LCA para un parque eólico en Colombia, mientras que la información para otros recursos energéticos (Hidro, Carbón, Gas, Solar) se tomó de la base de datos Ecoinvent 3.4. Para calcular el efecto rebote indirecto ambiental se calcularon los ahorros monetarios obtenidos por la eficiencia ambiental. Para ello se aplicó un AIDS para obtener las participaciones presupuestarias marginales (MBS). Combinando las MBS obtenidas con el modelo EEIO, el ahorro monetario se tradujo en indicadores ambientales. El ERE se presenta para diez categorías de impacto (cambio climático (CC), acidificación (A), ecotoxicidad (E), eutrofización marina (MEUT), eutrofización terrestre (TEUT), efectos cancerígenos (CE), efectos no cancerígenos (NCE), agotamiento de la capa de ozono (OD), creación fotoquímica de ozono (POC), y efectos respiratorios, inorgánicos (RES)). Además, se realizó un análisis de sensibilidad para medir la variabilidad del ERE con respecto a los diferentes valores del efecto rebote directo y los diferentes porcentajes de eficiencia de los precios. Los resultados muestran que la inclusión del efecto de rebote ambiental tiene generalmente un impacto no despreciable en los indicadores ambientales globales a lo largo de todos los años estudiados. Estos impactos oscilan entre el 5% (eutrofización) y el 6,109% (creación de oxidantes fotoquímicos) para el modelo combinado, mientras que para el modelo único los valores caen en los rangos del 1% (eutrofización) y el 9,277% (creación de oxidantes fotoquímicos). Además, un análisis de sensibilidad del precio de la elasticidad de la electricidad y del precio de la electricidad revela que la ERE varía de diferentes maneras, específicamente, los cambios en estos parámetros podrían variar los impactos, respectivamente, hasta entre un Los resultados muestran que la inclusión del efecto de rebote ambiental tiene generalmente un impacto no despreciable en los indicadores ambientales globales a lo largo de todos los años estudiados. Estos impactos oscilan entre el 5% (eutrofización) y el 6,109% (creación de oxidantes fotoquímicos) para el modelo combinado, mientras que para el modelo único los valores caen en los rangos del 1% (eutrofización) y el 9,277% (creación de oxidantes fotoquímicos). Además, un análisis de sensibilidad del precio de la elasticidad de la electricidad y del precio de la electricidad revela que la ERE varía de diferentes maneras, específicamente, los cambios en estos parámetros podrían variar los impactos, respectivamente, hasta entre un <1% y 38%. En 8 de 10 los impactos ambientales. (Texto tomado de la fuente)DoctoradoDoctor en Ingenierí

Optimum Resilient Operation and Control DC Microgrid Based Electric Vehicles Charging Station Powered by Renewable Energy Sources

This paper introduces an energy management and control method for DC microgrid supplying electric vehicles (EV) charging station. An Energy Management System (EMS) is developed to manage and control power flow from renewable energy sources to EVs through DC microgrid. An integrated approach for controlling DC microgrid based charging station powered by intermittent renewable energies. A wind turbine (WT) and solar photovoltaic (PV) arrays are integrated into the studied DC microgrid to replace energy from fossil fuel and decrease pollution from carbon emissions. Due to the intermittency of solar and wind generation, the output powers of PV and WT are not guaranteed. For this reason, the capacities of WT, solar PV panels, and the battery system are considered decision parameters to be optimized. The optimized design of the renewable energy system is done to ensure sufficient electricity supply to the EV charging station. Moreover, various renewable energy technologies for supplying EV charging stations to improve their performance are investigated. To evaluate the performance of the used control strategies, simulation is carried out in MATLAB/SIMULINK. Document type: Articl

Influence of a Hybrid MPPT Technique, SA-P&O, on PV System Performance under Partial Shading Conditions

The electricity sector has been undergoing profound transformations. In particular, the Portuguese self-consumer regime has allowed customers of the medium and low voltage electricity grid to be producers/consumers of electricity, actively contributing to greater energy efficiency. In this context, the energy that comes from the sun is not used to its maximum. In addition, photovoltaic cells have a characteristic operating curve (voltage vs. current), in which any operating point is reflected. Within this curve, there is a particular point known as the maximum power point (MPP) at which the cell supplies the maximum power output to a load. If the cell does not operate at this point, it has lower efficiency values. To harness maximum power under standard and dynamic shading conditions, there are various techniques of low complexity for capturing maximum power. We present a maximum power point tracking (MPPT) algorithm capable of dealing with the problem of partial shading. This algorithm involves modifying one of the most used algorithms within photovoltaic systems, known as P&O, using a simulated annealing (SA) algorithm. P&O is often used due to its straightforward implementation, but it is susceptible to partial shade conditions. Sampling was added to this algorithm to a better approach to the point of maximum power using the SA, and then to attain a more precise convergence with P&O. Implementing a maximum power point tracking method under partial shading was the major goal of this study

Influence of Water Aging on Microtensile Bond Strength of a Flowable and a Packable Bulk-fill Resin Composites to Dentin

AIM: Investigation of the aging effect on the microtensile bond strength (μTBS) of bulk-fill resin composite (RC) versus a conventionally incrementally applied one. MATERIALS AND METHODS: A total number of 45 sound human impacted third molars extracted molars have been selected to prepare specimens for the μTBS test. Teeth were randomly divided into three groups (C) according to type of RC material which used for restoring the teeth. Where nanohybrid RC (Grandio®SO) was used as the control Group (C1), packable bulk-fill RC (X-tra fil®) was used for restoring teeth in C2 group and flowable bulk-fill RC (X-tra base®) was used for restoring teeth in C3 group. Each group was further subdivided into 3 subgroups (n = 5) according to the water storage time, where in subgroup 1; teeth were stored for 24 h, subgroup 2; teeth were stored for 3 months while for subgroup 3; and teeth were stored for 6 months. After water storage, teeth were sectioned for preparation of μTBS testing beams. Maximum tensile stresses were recorded in megapascal (MPa). RESULTS: After 24 h of water storage, the X-tra base® showed a higher statistically significant μTBS to dentin (33.82 ± 9.84 MPa) than did the other two types of RCs. After 3 months, the X-tra fil® showed the lowest mean value of μTBS (10.90 ± 5.66 MPa), meanwhile, after 6 months of water storage Grandio®SO showed the highest mean value of μTBS (15.85 ± 6.76 MPa). Regardless of the time the X-tra fil® showed the lowest mean of μTBS (15.07 ± 11.73 MPa), while there is no significant difference between the X-tra base® and Grandio®SO. Furthermore, the water aging adversely affects μTBS values which deceased gradually by time. CONCLUSION: The packable bulk-fill RC characterized by lower μTBS to dentin in comparison to the flowable bulk fill and the incrementally applied nanohybrid RCs. Furthermore, the μTBS of the three tested materials decreased gradually by aging

The Effect of Polyacrylic Acid and Sodium Trimetaphosphate on Dentin Hybrid Layer Remineralization : an In Vitro Study

Adhesive monomers are not able to fully encapsulate collagen fibrils in hybrid layer leaving them vulnerable to time-dependent hydrolytic degradation. The current in vitro study was designed for investigation of the remineralization of the resin-dentin h

Polyunsaturated fatty acids influence offspring sex ratio in cows

Dietary polyunsaturated fatty acids (PUFAs) can influence fertility in farm animals. Some evidence in mice and sheep have suggested that PUFAs may influence offspring sex ratio, which may have significant value for cattle production. To test this hypothesis, three groups of Holstein cows were supplemented with either 0%, 3% or 5% protected fat (PF) in the form of calcium salt of fatty acids (rich in omega-6) from 14–21 days pre-partum until conception. Proven-fertile frozen semen from the same ejaculate was used for insemination. Calf sex recorded at birth was 8/19 (42.1%) male offspring in the control group, increasing to 14/20 (70%, P > 0.05) and 17/20 (85%, P < 0.05) in 3% and 5% PF, respectively. To test if this effect was caused by a direct influence on the oocyte, we supplemented bovine cumulus oocyte complexes during in vitro maturation with either omega-3 alpha-linolenic acid (ALA), omega-6 linoleic acid (LA) or trans-10, cis-12 conjugated linoleic acid (CLA). Sex ratio of the produced transferable embryos was determined using PCR of SRY gene. Similar to the in vivo results, sex ratio was skewed to the male side in the embryos derived from LA- and CLA-treated oocytes (79% and 71%) compared to control and ALA-treated oocytes (44% and 54%, respectively). These results indicate that both dietary and in vitro supplementation of omega-6 PUFAs can skew the sex ratio towards the male side in cattle. Further experiments are required to confirm this effect on a larger scale and to study the mechanisms of action that might be involved

The relationship between a new type of partogram and rate of cesarean section at Zagazig University

Background: The cesarean section (CS) rates have dramatically increased worldwide. The process of labor is associated with both maternal and fetal potential risks, regardless of the mode of delivery. Objective: The aim of this study was to investigate the value of the use of a new type of partogram and compare it with Fisher partogram in reducing the cesarean section rates. Patients and Methods: This cohort prospective study was carried out at the Department of Obstetrics and Gynecology, at Zagazig University Hospital and Menia Al-Kamh Central Hospital during the period study; year 2019. This study included 150 patients. We compared the efficacy of the two types of partograms during labor. Results: There were statistically significant differences between groups as regard newborns’ Apgar at 5th min, and as regard cesarean section rate, which in Group (A) according to Fisher partogram was 6 (5.8%) and according to new type of partogram was 3 (2.9%) while in Group (B) according to Fisher partogram it was 23 (48.9%) and according to new type of partogram was 14 (29.8%). Conclusions: The new partogram is more helpful in the recognition of the initiation of the acceleration stage during the active phase of labor and in the timely use of appropriate actions in order to achieve a safer delivery

In vivo cytogenotoxicity testing of isotretinoin by the micronucleus assay in the blood of male Sprague-Dawley rats Isotretinoin is cytotoxic and genotoxic

Isotretinoin (ISO), one of vitamin A-derived retinoids, is comparatively the most widely prescribed drug in acne vulgaris pathogenesis. Despite its excellent therapeutic success, the systemic use of this drug showed undesirable serious side effects such as teratogenesis, oxidative stress, and genotoxicity. The uses of retinoids in cancer therapy are limited due to severe adverse reactions. This has led the scientific community to ask for further studies qualifying ISO features and comparing their efficacy and safety. The purpose of this study was to evaluate the cytogenotoxicity of multiple oral doses (5, 10, 15, and 20 mg/kg, daily for seven consecutive days) of ISO in male Sprague-Dawley rats. The micronucleus assay was used to investigate genotoxicity biomarkers such as the percentage of micronucleated polychromatic erythrocytes (%MNPCEs) and the percentage of aberrant cells (%Abc). Another goal was to test the cytotoxicity of the drug by measuring the ratio between PCEs and normochromatic erythrocytes (NCEs) (PCEs/NCEs). In comparison with the control, the three cytogenetic endpoints: %MNPCEs, P/N, and %Abc significantly (P ≤ 0.0017) dose-dependent increase. This suggested genotoxicity and cytotoxicity of the tested ISO doses. Therefore, the therapeutic uses of ISO should be restricted to a very narrow range border. Further studies are needed to shed more light on the safety profile of ISO therapy

The Impact of Using Fixed and Motion Infographics on Developing the Achievement of the Eighth Basic Grade Students in Geography

The aim of the study the impact of using fixed and motion infographics on developing the achievement of the eighth basic grade students in geography and their relationship with the academic level of the student in Jordan. the semi-experimental approach was adopted. study tool achievement test. The study sample consisted of (38) students divided into three groups: the first is an experimental group of (13) students studied using motion infographics, and the second is an experimental of (12) students studied using fixed infographics, and the third is a control group of (13) students who studied in the usual method. The results showed there are statistically significant differences on the post- measurement of the results of the achievement test, and in favor of those who studied using the fixed infographics method, and there were not statistically significant differences at the level of significance (0.05 ≥α) between the averages of the grades for the eighth basic grade students, according to the variable of academic leve