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Grid connected distributed generators are becoming increasingly popular owing to their reliability. In earlier days, one of the drawbacks in the solar energy sources is the need for energy storage for the system to be utilized for a significant percentage of the day. One way of overcome this disadvantages by utilizing the inverter and its controller circuits for PV based DG units during the day and night times for improving the reactive power compensation and harmonic elimination on its neighboring DG units and the grid by proper exchange of reactive power between the sources. The existing Proportional-Integral controller (PI) and predictive control methods are more dominant in current error compensation. But the conventional type PI controllers normally do not have appropriate compensation from the inverters for the grid connected applications. In this paper a composite controller design comprising of both voltage oriented control and direct power control is developed for the grid side control. The control strategy is based on generation of current reference for current controller by utilizing the separated fundamental component of power to meet the instantaneous power demand at PCC and the power availability at PV sourced inverter. The state space model for the entire scheme is presented and used for simulation. Comprehensive analysis and simulation of the scheme with variations in irradiation, wind speed and customer loads have been presented in this work. The analysis of the scheme for non linear load and three phase fault at PCC for hybrid scheme with PV array and wind generator has been attempted for the first time in this work. The adaptability of proposed controller to work in islanded mode has also been tested. The simulations have been carried out for all these variations and compared with the direct power control and the significance of the proposed work is presented.

A growing dynamic electrical demand has created an increasing interest in utilizing nonconventional energy sources like Photovoltaic (PV), wind power, etc. In this context, this paper focuses on the design and development of a composite power controller (CPC) in the decoupled double synchronous reference frame (DDSRF) combining the advantages of direct power control (DPC) and voltage oriented control (VOC) for a PV sourced grid connected inverter. In addition, a controller with the inherent active filter configuration is tested with nonlinear and unbalanced loads at the point of common coupling in both grid connected and autonomous modes of operation. Furthermore, the loss and reactive power compensation due to a non-fundamental component is also incorporated in the design, and the developed DDSRF model subsequently allows independent active and reactive power control. The proposed developed model of the controller is also implemented using MATLAB-Simulink-ISE and a Xilinx system generator which evaluate both the simulated and experimental setups. The simulation and experimental results confirm the validity of the developed model. Further, simulation results for the DPC are also presented and compared with the proposed CPC to further bring out the salient features of the proposed work.

This paper presents a new constant frequency hysteresis current controller for the grid interface of a PV-fed three-phase voltage source inverter (VSI) for a dual mode operation, feeding real power during the daytime and reactive power alone during nights, thereby acting as a STATCOM. The constant frequency is inherently achieved by means of digital implementation in a simplified manner without any complex manipulations to choose a variable band width; rather the hysteresis band varies as a natural consequence of selecting appropriate constant sampling frequency. Analytical proof is presented for the switching frequency to remain constant, without compromising on the performance indices. The design of the proposed controller for a grid-connected inverter operating in dual mode is presented, along with simulation results. The proposed controller is successfully implemented using a 1.1 kW PV array-fed inverter. The hardware results presented show the grid current harmonics complies with IEEE 1547 and has been achieved in a simpler means when compared to other existing techniques. The proposed controller is expected to be an attractive solution for grid-connected inverter applications including distributed generation, power quality, and drive applications

The effect of rhamnolipid during the formation of initial biofilm (48. h) by Pseudomonas aeruginosa CPCL on polypropylene surface was studied. This strain was isolated from a petroleum contaminated soil and it produces a mixture of rhamnolipids. The nutritional and environmental conditions necessary for optimal production of rhamnolipid, attachment of rhamnolipid and formation of thicker biofilm on the polypropylene surface were found to be different from one another. Comparatively lower pH and temperature, higher concentration of ammonium chloride and rotation velocity of the shaker were required for the biofilm formation and the attachment of rhamnolipid on the polypropylene surface. Screening design showed that the extent of viable cells and rhamnolipid attached to the polypropylene surface was positively correlated (r=0.474; p< 0.01). However, central composite design did not show any such relationship, possibly because of the different experimental ranges used in central composite design. There were considerable variations in the thickness and spatial arrangement of biofilms grown under these three different optimized conditions. Higher substratum coverage and thicker biofilm were observed under the condition optimized for biofilm formation when compared to the other two conditions. This study is essential since P. aeruginosa biofilms are found to have implication in bioremediation of recalcitrant pollutants. � 2011 Elsevier B.V.

The underground storage of carbon dioxide (CO2) requires building, sizing, and coupling the reservoir and distribution network (pipelines and wells) models. Independent designs of the pipeline network, well, and reservoir models do not account for the effects one system has on the others. Coupling the different models is necessary to effectively design the full system. This paper discusses a methodology of jointly optimizing the pipeline network, well, and storage systems. This method uses simple and fast models instead of fully coupled, complex, and integrated models. It is thus applicable in the early phases of projects, when system parameters are not fully characterized (i.e., for scenario building and sensitivity analysis). Two different projects are examined: a single well with a short pipeline and multiple wells with a long pipeline. These cases can be adapted to offshore or onshore conditions. Although vertical wells were considered for this study, the same methodology can be easily extended to deviated and horizontal wells. Depending on conditions, the constraints that will dominate the full system may come from either the reservoir model or the pipeline network and well models.

This paper highlights the effects of radiation and MHD nanofluid flowing over a permeable medium that undergoes chemical reaction in first order. The nanoparticles used in the study are copper, aluminium oxide, titanium oxide and silver. The governing partial differential equations are solved by Laplace transform technique. The influences of several values of the physical parameters on velocity, temperature, concentration profiles are analyzed in an extensive way. The derived findings are depicted in graphs. The numerical results are found for Skin friction coefficient, Nusselt and Sherwood numbers that are revealed in tabular form.

Accumulation of non-biodegradable plastics leads to increase in land and water pollution. Polyolefins includ- ing polyethylene and polypropylene are the major plastics to be dumped in the environment and due to their recalcitrant nature persist in the environment. The hydrophobicity, high molecular weight, chemical and structural composition of these polymers hinders their biodegradation. In this review current research that have been performed to understand the abiotic mechanism of the degradation process, and various physical, chemical and biochemical approaches that can be adopted to enhance their biodegradation are discussed. Genetic engineering approaches to enhance the performance of the microorganism or computational techniques to simulate the degradation pathways could be the future to speed up the deg- radation of these polymers.

We present methodologies to functionalize iron oxide (Fe3O 4) nanoparticles with biosurfactants and biocompatibility results. Positively charged Fe3O4 nanoparticles of average hydrodynamic size ~26 nm is functionalized with four different molecules of interest, viz., surfactin, rhamnolipid, polyethylene glycol (PEG) and dextran. The functionalization results in dramatic alterations in surface potential and hydrodynamic size due to the presence of coated moieties on the nanoparticle interface. The Fourier transform infrared spectroscopy and thermogravimetric analysis confirm the presence of adsorbed moieties on nanoparticles. The phase contrast microscopy studies show the formation of reversible chains of functionalized nanoparticles under an external magnetic field. Cell viability studies using L929 mouse fibroblast cell line show that pure surfactin, rhamnolipid and dextran exhibit cytotoxicity with increase in concentration, whereas, pure PEG exhibit biocompatibility at different concentrations. Accordingly, surfactin and rhamnolipid coated nanoparticles are found to be cytotoxic with increase in concentration and PEG coated nanoparticles are found to be biocompatible. Dextran coated nanoparticles do not exhibit significant increase in biocompatibility. Copyright � 2013 American Scientific Publishers All rights reserved.

Aims: To isolate and characterize the biosurfactant-producing micro-organism from petroleum-contaminated soil as well as to determine the biochemical properties of the biosurfactant. Methods and Results: A novel rhamnolipid-producing Pseudomonas aeruginosa (GenBank accession number GQ241355) strain was isolated from a petroleum-contaminated soil. Surface active compound was separated by solvent extraction of the acidified culture supernatant. The extract was able to reduce the surface tension of water from 72 to 44 mN m−1 at a critical micelle concentration of 11·27 ± 1·85 mg l−1. It showed better activity (based on microdilution method) against Gram-positive (≤ 31 mg ml−1) bacteria and filamentous fungi (≤ 50 mg ml−1) than Gram-negative bacteria (≥ 125 mg ml−1) with mild toxicity (HC50– 38 ± 8·22 μg ml−1) to red blood cells. Fourier transform infrared spectroscopy revealed the presence of aliphatic chain, hydroxyl groups, ester and glycosidic bonds. Presence of nineteen rhamnolipid homologues with variation in chain length and saturation was revealed from liquid chromatography coupled to mass spectrometry with electrospray ionization. Conclusion: The results indicate that the isolated biosurfactant has a novel combination of rhamnolipid congeners with unique properties. Significance and Impact of the Study: This study provides a biosurfactant, which can be used as a biocontrol agent against phytopathogens (Fusarium proliferatum NCIM 1105 and Aspergillus niger NCIM 596) and exploited for biomedical applications.

Unpretreated (PP-UT) and thermally pretreated (at 80 �C for 10 days) polypropylene (PP-TT) films of 0.05 mm thickness were subjected to in vitro biodegradation in minimal medium with mixed soil culture for 12 months. In this period 10.7 and 0.4% weight loss was observed with PP-TT and PP-UT, respectively. The tensile strength decreased by 51.8 and 28.3%, the crystallinity increased by 28 and 33% and isotacticity increased by 3 and 9%, respectively, over the same time period. The ester carbonyl index in PP-TT increased up to 9 months and later decreased indicating abiotic followed by biotic process. No such changes were observed with PP-UT. Methyl group index decreased in both the cases indicating oxidation at the primary carbon. Increase in surface energy indicated that the polymer became hydrophilic. Surface changes were observed by SEM and AFM. A single culture was isolated at the end of 12 months and it was identified as Bacillus flexus. The morphology of the organism was rods in a chain and it was present in the form of an endospore. � 2008 Elsevier Ltd. All rights reserved.

Biosurfactants (BS) are of recent interest due to their unique properties including structural diversity, higher biodegradability, lower toxicity and exhibit stable activity at extreme conditions including pH, temperature and ionic strength. They are found to have applications in medical and environmental fields. Some of the BS are potential antimicrobial agents and are suitable alternatives to synthetic antibiotics. In this perspective, a surfactant producing microorganism has been screened and isolated from a polymer dump site, which was characterized as Bacillus subtilis YB7. This microorganism was capable of producing 0.5 g L-1 of crude extract (dry weight) in the mineral salt medium. The FTIR and LC/MS analysis of the crude extract showed the presence of similar functional groups and six isoforms, respectively as that of the commercially available Sigma surfactin. However, the proportions of the peaks vary from sigma surfactin. Molecular mass of the major peak in the crude extract is 1023 (M+H)+ which is equivalent to C14 surfactin analog, whereas it is 1035 (C15 surfactin) in case of sigma surfactin. The crude extract reduced the surface tension of water from 72 to 30 mN m-1 at the CMC of 40 ?M. This particular strain produced unique type of cycliclipopeptide analogs. � 2009 Asian Network for Scientific Information.

Mannosylerythritol lipids (MELs) are surface active compounds that belong to the glycolipid class of biosurfactants (BSs). MELs are produced by Pseudozyma sp. as a major component while Ustilago sp. produces them as a minor component. Although MELs have been known for over five decades, they recently regained attention due to their environmental compatibility, mild production conditions, structural diversity, self-assembling properties and versatile biochemical functions. In this review, the MEL producing microorganisms, the production conditions, their applications, their diverse structures and self-assembling properties are discussed. The biosynthetic pathways and the regulatory mechanisms involved in the production of MEL are also explained here.