Energy storage sizing for low-inertia microgrids, and lessons learned from a potential microgrid

The coordinated control of multiple distributed generators in a microgrid and the preservation of adequate system inertia in real-time operations are some of the principal technical challenges for stable microgrid operation. One issue in particular pertains to grid-tied inverters, which, as mandated by present standards, are only permitted to operate at unity power factor, thereby requiring the microgrid’s synchronous generators to operate at a low power factor. This behavior accordingly introduces ramifications by limiting the generator’s active power output, which would compromise frequency and voltage stability margins. Consideration is also given to the effect of line impedances, since interconnecting microgrid lines can be described by a variety of X/R ratios that affect the control and flow of active and reactive power. Moreover, the absence of a stiff grid presents control challenges for grid-tied inverters due to the inverters’ tendency to regulate the voltage at the point of common coupling. These same inverters also jeopardize microgrid stability due to their low equivalent inertia as traditional forms of generation (i.e., spinning sources) become displaced by inertia-less inverters. Because of this low microgrid inertia, fluctuations in the output power of renewable energy sources or changes in local load levels may lead to power quality or frequency/voltage stability concerns. Therefore, energy storage sizing is investigated in this dissertation, as it is closely related to the stability analysis of microgrids. Furthermore, an existing residential community (in Austin, TX) described by a moderate penetration of photovoltaic sources and electric vehicle charging is considered, and the implications of said community being retrofitted to a microgrid are examined.Electrical and Computer Engineerin

Formulation and In-Vitro Evaluation of Rosuvastatin Nanoemulsions

Introduction: Rosuvastatin (ROS) calcium is the latest synthetic drug in the statin group that has an anti-hyperlipidemic activity. It is available as tablets, and its poor aqueous solubility, slow dissolution rate and low-absorption extent result in less than 20% bioavailability and about 80% being excreted unchanged in the feces without absorption. The present study aimed at developing an optimal oral nanoemulsion formulation containing rosuvastatin using different proportions of oil and surfactant system for enhancing its water solubility and bioavailability. Methods and results: The solubility of ROS in different oils, surfactants and co-surfactants was tested. Based on the solubility study, liquid formulations were prepared using Arachis oil as oil phase and Tween 80 as surfactant and polyethylene 400 as co-surfactant. Pseudo-ternary phase diagrams were developed and various nanoemulsion formulations were prepared and evaluated for globule size, zeta potential, and emulsion properties. The formulations were subjected to different thermodynamic stability studies such as centrifugation, heating-cooling cycle and freeze-thaw cycle, to avoid the selection of metastable formulations. Transmittance study and in-vitro dissolution studies were carried out. An optimal nanoemulsion system was successfully developed with the droplet size of 260 nm and a composition of (Arachis oil; 20%), Tween 80 (40%) and PEG 400 (40%). The cumulative percentage drug release from optimal nanoemulsion formulation was found to be 93.29±1.11% for 50 minutes, which was significantly higher than the drug suspension (43.42±1.30%). Thus, in vitro results reveal that the prepared nanoemulsion formulations showed improved solubility of ROS. Conclusions: Nanoemulsion formulations of ROS represent a promising novel formula with a higher dissolution rate when compared to the drug in suspension. &nbsp

Ex-situ and in-situ post-photosynthesis of silver nanoparticles on polyamide fabric using daylight irradiation

Silver nanoparticles (AgNPs) have been ex-situ post-synthesized in an aqueous solution and in-situ synthesized on polyamide fabric through a simple chemical reduction method by using silver nitrate (AgNO3), stannous chloride (SnCl2) and cetyltrimethylammonium bromide (CTAB) under daylight irradiation. SnCl2 and CTAB act as reducing and stabilizing agents in the colloidal silver nanoparticles solution respectively. Post in-situ synthesis of Ag NPs have been carried out on polyamide fabric by spraying solution of AgNO3, CTAB and SnCl2 on the fabric and then irradiating under daylight for 2 h. Ag NPs solutions and Ag NPs loaded polyamide fabrics are characterized by UV-vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Appearing a strong plasmon resonance peak at 400 nm in UV-visible spectrum, XRD patterns and SEM images are found to clearly confirm the formation of silver nanoparticles. The UV-vis spectra also confirm no Ag NPs formation without daylight irradiation

Condition Assessment and End-of-Life Prediction System for Electric Machines and Their Loads

An end-of-life prediction system developed for electric machines and their loads could be used in integrated vehicle health monitoring at NASA and in other government agencies. This system will provide on-line, real-time condition assessment and end-of-life prediction of electric machines (e.g., motors, generators) and/or their loads of mechanically coupled machinery (e.g., pumps, fans, compressors, turbines, conveyor belts, magnetic levitation trains, and others). In long-duration space flight, the ability to predict the lifetime of machinery could spell the difference between mission success or failure. Therefore, the system described here may be of inestimable value to the U.S. space program. The system will provide continuous monitoring for on-line condition assessment and end-of-life prediction as opposed to the current off-line diagnoses

Multiphase induction motor drives - a technology status review

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio

Photochemical reduction of silver nitrate to nano silver using stannous chloride, ctab and daylight irradiation

Silver nanoparticles (NPs) were synthesized and stabilized by a simple method in aqueous solution, by the reduction of silver nitrate with stannous chloride (SnCl2.2H2O) and cetyl trimethyl ammonium bromide (CTAB)through day light irradiation. Thereby, the silver nanoparticles were colloidally stabilized by CTAB as a surfactant. The synthesis of silver NPs with different size were possible by changing the reaction conditions such as reagent ratio. The silver NPs were characterized by Dynamic Light Scattering (DLS) and UV-visible spectroscopy. A very strong plasmon resonance peak at 400-500 nm in the UV-visible spectra is a clear consequence of the silver NPs production. The synthesized silver NPs showed good stability by using CTAB. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2063

Učinci adheziva osjetljivih na tlak i kemijskih promotora na permeaciju fentanila kroz kožu štakora

Drug-in-adhesive patches (DIAPs) of fentanyl were formulated using various pressure sensitive adhesives (PSAs) and various chemical permeation enhancers (CPEs). The effects of the PSAs and CPEs on skin permeation of fentanyl from DIAPs were evaluated using modified jacketed Franz diffusion cells fitted with excised rat abdominal skin. It was demonstrated that permeation rate or steady state flux (Jss) of the drug through the excised rat skin was dependent on the viscosity and type of acrylic PSA as well as the type of CPE. Among different acrylic PSAs, Duro-Tak® 2054 and Duro-Tak® 2516 showed the highest Jss of 1.95 μg cm-2 h-1 and the lowest Jss of 1.43 μg cm-2 h-1, respectively. Among the various CPEs used, propylene glycol and polyethylene glycol 400 showed 1.61 and 1.18, the highest and lowest enhancement ratio (ER) on the skin permeation of fentanyl, respectively. Oleic acid and cetyl alcohol moderately increased the skin permeation of fentanyl. It was also shown that increasing the concentration of CPE led to reduction in adhesion property of PSA as measured by 180° peeling strength test. Moreover, it was found that the permeation rate increased as the fentanyl loading increased from 1 to 3%. The skin permeation rate of fentanyl did not increase significantly beyond 3% drug loading. It was concluded that PG as a CPE and cosolvent in 10% m/m with 3% fentanyl loading in Duro-Tak 2054 showed an effective monolithic DIAP for the development of a transdermal therapeutic system for fentanyl.Pripravljeni su transdermalni adhezivni flasteri fentanila (DIAPs) koristeći različite adhezive osjetljivih na tlak (PSAs) i kemijske promotore permeabilnosti (CPEs). Njihovi učinci na permeabilnost fentanila evaluirani su pomoću modificirane Franzove difuzijske ćelije s membranom od kože s abdomena štakora. Brzina permeabilnosti (Jss) ovisi o viskoznosti i vrsti akrilnih adheziva i o vrsti promotora. Najveća vrijednost Jss = 1,95 μg cm-2 h-1 postignuta je s Duro-Tak® 2054, a najmanja (Jss = 1,43 μg cm-2 h-1) s Duro-Tak® 2516. Među različitim promotorima propilen glikol i polietilen glikol 400 pokazali su najveći (1,61) i najmanji (1,18) omjer poboljšanja (ER) permeabilnosti. Oleinska kiselina i cetil alkohol umjereno su povećali permeabilnost fentanila. Za mjerenje adhezivnih svojstava upotrebljena je "metoda ljuštenja". Povećanje koncentracije CPE smanjilo je adhezivna svojstva PSA. Kada je udio fentanila u flasteru povišen s 1 na 3%, brzina permeabilnosti se povećala, dok daljnje povećanje udjela fentanila nije značajno utjecalo na brzinu. Pripravak s 10% propilen glikola i 3% fentanila u Duro-Tak 2054 pokazao se kao učinkoviti transdermalni terapijski sustav za fentanil

Učinci adheziva osjetljivih na tlak i kemijskih promotora na permeaciju fentanila kroz kožu štakora

Drug-in-adhesive patches (DIAPs) of fentanyl were formulated using various pressure sensitive adhesives (PSAs) and various chemical permeation enhancers (CPEs). The effects of the PSAs and CPEs on skin permeation of fentanyl from DIAPs were evaluated using modified jacketed Franz diffusion cells fitted with excised rat abdominal skin. It was demonstrated that permeation rate or steady state flux (Jss) of the drug through the excised rat skin was dependent on the viscosity and type of acrylic PSA as well as the type of CPE. Among different acrylic PSAs, Duro-Tak® 2054 and Duro-Tak® 2516 showed the highest Jss of 1.95 μg cm-2 h-1 and the lowest Jss of 1.43 μg cm-2 h-1, respectively. Among the various CPEs used, propylene glycol and polyethylene glycol 400 showed 1.61 and 1.18, the highest and lowest enhancement ratio (ER) on the skin permeation of fentanyl, respectively. Oleic acid and cetyl alcohol moderately increased the skin permeation of fentanyl. It was also shown that increasing the concentration of CPE led to reduction in adhesion property of PSA as measured by 180° peeling strength test. Moreover, it was found that the permeation rate increased as the fentanyl loading increased from 1 to 3%. The skin permeation rate of fentanyl did not increase significantly beyond 3% drug loading. It was concluded that PG as a CPE and cosolvent in 10% m/m with 3% fentanyl loading in Duro-Tak 2054 showed an effective monolithic DIAP for the development of a transdermal therapeutic system for fentanyl.Pripravljeni su transdermalni adhezivni flasteri fentanila (DIAPs) koristeći različite adhezive osjetljivih na tlak (PSAs) i kemijske promotore permeabilnosti (CPEs). Njihovi učinci na permeabilnost fentanila evaluirani su pomoću modificirane Franzove difuzijske ćelije s membranom od kože s abdomena štakora. Brzina permeabilnosti (Jss) ovisi o viskoznosti i vrsti akrilnih adheziva i o vrsti promotora. Najveća vrijednost Jss = 1,95 μg cm-2 h-1 postignuta je s Duro-Tak® 2054, a najmanja (Jss = 1,43 μg cm-2 h-1) s Duro-Tak® 2516. Među različitim promotorima propilen glikol i polietilen glikol 400 pokazali su najveći (1,61) i najmanji (1,18) omjer poboljšanja (ER) permeabilnosti. Oleinska kiselina i cetil alkohol umjereno su povećali permeabilnost fentanila. Za mjerenje adhezivnih svojstava upotrebljena je "metoda ljuštenja". Povećanje koncentracije CPE smanjilo je adhezivna svojstva PSA. Kada je udio fentanila u flasteru povišen s 1 na 3%, brzina permeabilnosti se povećala, dok daljnje povećanje udjela fentanila nije značajno utjecalo na brzinu. Pripravak s 10% propilen glikola i 3% fentanila u Duro-Tak 2054 pokazao se kao učinkoviti transdermalni terapijski sustav za fentanil