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A steady incompressible nanofluid flow past an inclined permeable plate is numerically studied, including radiation, viscous dissipation, and Soret and Dufour effects. A coupled non-linear simultaneous differential similarity equation is created by non-dimensionalizing the ruling partial differential equations. Then, nonlinear coupled equations with transformed boundary conditions are resolved by the shooting method based on the Runge-Kutta fourth-order method. The Prandtl number, Grashof number, Schmidt number, magnetic parameter, and Soret and Dufour effects are just a few of the controlling flow parameters for which computations are done. Graphs are used to illustrate how various flow factors affect momentum, energy, and concentration equations. The impacts of these variables on skin friction coefficients, Nusselt number, and Sherwood number are given in tabular form. The concentration profile increases with the Soret number and the reverse trend is observed with the Dufour number. It is further noted that heat-mass transfer rate reduces in the boundary layer due to an increase in the values of Soret or a decrease in the values of Dufour.

In the Malaysian context, Mandarin is taught as a foreign language. Learning the written forms can be challenging, especially for non-native speakers. Furthermore, teachers found this component to be problematic, based on learners’ classroom written tasks. In order to assist learners’ comprehension of the written form, a board game called ‘Catch Me If You Can’ was developed. The focus of this study is to find out the effectiveness of the board game in learning the written forms. The study sample consisted of 20 respondents from a local University. Data comprised the responses from questionnaires and interviews. A pre and post test was administered to gauge students’ performance in the written tasks. The findings showed the respondents enjoyed learning the written forms in a fun and engaging way. Hence, this game can be used as complementary tool in the teaching and learning of written forms.

Grid connected PV systems are becoming increasingly popular due to an exponential energy demand and also due to depletion of fossil fuels and environmental concerns. However, extraction of peak power for such system which reduce cost has always been an area of concern. Many Maximum power point tracking (MPPT) algorithms were proposed for a two stage and single stage grid connected system with some limitations in system performance. A simple strategy to extract peak power from the grid connected PV with nonlinear load at Point of common coupling (PCC) is attempted. To achieve the same task in a single stage Photovoltaic (PV) grid system, two PV emulated virtual DC voltage sources are connected in series with the PV array. The operation of this strategy is tested under low irradiation and Voltage swell at the PCC connected to the grid. A control strategy to achieve dual mode control for MPPT and to regulate DC link voltage is achieved simultaneously by the proposed control. Analysis of the control strategy is carried out using MATLAB and experimentally validated with a TMS320F28335 controller.

A time-domain design methodology for voltage regulation control of dc–dc boost and buck-boost converters based on a multi-loop controller with PI regulator for the outer loop and an inner loop with sliding mode current controller has been developed for renewable energy applications such as photovoltaic (PV)-fed dc–dc converters. This paper proposes a new method for the design of PI regulators in such multi-loop control scheme. The proposed design presents a simple analytical method for selecting controller gains and has been validated by simulation as well as hardware implementation. Also, this paper presents an illustrative example based on the proposed design for the voltage regulation control of PV-fed boost converters for off-grid applications. The simulation results for varying irradiation, temperature and load along with stability analysis have been presented in this paper. The proposed controller is implemented in hardware for a 1.1 kW PV-array-fed boost converter. Performance analysis based on field test results using real-time weather data validates the proposed design. Therefore the proposed controller could be considered as an attractive solution for off-grid renewable energy applications like PV- or fuel-cell-fed dc–dc converter, where the variations are stochastic in nature.

Isolated renewable energy systems that are based fully on renewable resources but are at the same time reliable are necessary for meeting the power demands of remote places where utility grid is not available and for which hybrid wind–solar systems play a crucial role. In this paper, a simplified control scheme has been presented for a standalone hybrid photovoltaic (PV) array-excited wind-driven induction generator (IG), considering a three-phase variable load with or without unbalance. The proposed scheme exploits the ruggedness and cost-effective IG as a viable alternative for an expensive permanent magnet synchronous generator, which is invariably used in standalone small wind turbines. Any standalone system employs a battery, however, the system is supposed to deliver power even in the absence of battery and the batteryless mode of operation is presented in this paper. The control scheme has been validated with simulation as well as hardware results. Extensive field tests have been performed using 2.4-kW PV panels, 2.2-kW wind turbine emulators, and weather stations for performance evaluation. The validation results have been presented, which show that the proposed scheme is expected to be an attractive solution for remote application where utility grid is either not feasible or not economical.

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.

In this paper, a new control algorithm for grid connected inverter fed by Photovoltaic array (PV) excited wind-driven induction generator (IG) for unbalanced nonlinear load at point of common coupling (PCC) is proposed. The proposed composite power controller comprises of multi control loops such as power, voltage and current loops. The power control loop generates positive sequence reference current based on the availability of PV power and the average power demand of the load and negative sequence reference currents to compensate the oscillating power component that appears due to the unbalanced nonlinear load at the PCC and further, drop due to non-fundamental power component is compensated by addition of virtual non-linear impedance to the current control loop. The voltage control loop generates the reactive current reference to compensate the drop due to nonlinear magnetizing reactance of IG to eliminate the machine de-rating effect. The current control loop regulates the average and suppresses the oscillating power in dual decoupled double synchronous reference frame to generate modulating signal to the PV sourced inverter. Exhaustive simulations are carried out for the proposed scheme for varying irradiations, wind speed and load variations at the PCC in MATLAB and compared with direct power control scheme.

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.

Summary Two main types of reservoirs are considered for geological storage of carbon dioxide (CO2): deep saline formations and depleted oil and gas (O&G) reservoirs. The former offers very large potential capacity and a more-even distribution at the expense of high uncertainty because of the very poor characterization of their properties to date, including their sealing capacity. The latter offers smaller overall capacity, but with a reduced risk because of better reservoir knowledge. Gas reservoirs have also provided a proven seal to pressurized gas. However, reusing depleted O&G reservoirs presents challenges that must be considered in the evaluation of performance factors and the associated risks. Depletion can cause pore collapse in the reservoir, with an associated loss of capacity and injectivity and can weaken caprock and bounding faults or even well completions, leading to possible containment losses because of mechanical failure. O&G reservoirs are also intersected by many wells, and it is likely that stricter regulatory requirements on well integrity and the quality of zonal isolation will force operators to recomplete or work over wells that will be exposed to CO2, with an obvious impact on cost. Low reservoir pressure may also mean that injection of CO2 in a dense phase would result in reservoir fracturing and very strong thermal effects that may lead to injectivity problems. In the reservoir, chemical and physical differences in behavior between CO2 and methane may adversely affect geological containment and injectivity. Analyzing the benefits and challenges with respect to all performance factors (capacity, injectivity, containment) shows that depleted O&G reservoirs and deep saline reservoirs both offer potentially attractive targets for geological storage of CO2, mostly for complementary reasons. Uncertainty on capacity and injectivity is clearly lower for depleted reservoirs, giving them a potential net economic advantage, whereas uncertainty on well containment favors saline formations, which are intersected by fewer wells. Injectivity in depleted reservoirs may be much more difficult to ensure than for saline formations or O&G reservoirs where pressure has been maintained. Saline formations have a lower, mostly unproven, safety margin between injection and fracturing pressure, resulting in a potential advantage for depleted reservoirs where repressurization will lead to a final pressure lower than or equal to the original value. Each reservoir type has a different risk profile, different advantages, and a rightful place in a portfolio of injection sites.

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.

Hybrid autonomous power plants based on wind-driven induction generators excited by a photovoltaic (PV) array has been recently found to be a reliable power source for remote locations. In such schemes, a composite controller for both maximum power point tracking and voltage control has not been attempted so far. Hence a dc–dc converter with a dual control strategy of peak power tracking when the battery is connected and in voltage control mode in the absence of the battery is proposed in this paper. The development of such a controller is also presented. A d–q axes model of the proposed scheme is given and the results of the simulation of the entire scheme are also presented. The battery charging and discharging regimes have been distinctly identified for variations in irradiations and shaft-torque conditions. Close proximity between the calculated peak power for different irradiations and the peak power observed from the simulated results brings out the significance of the proposed controller. Copyright © 2006 John Wiley & Sons, Ltd.

Grid connected PV systems is gaining popular in the recent past as a viable and attractive alternative source of power in the urban areas to meet the increasing energy demand. This paper presents a comprehensive review of Maximum Power Point Tracking (MPPT) techniques employed in such grid tied PV systems. A classification of different MPPT techniques based on topology of grid interface is presented. Also the simulation and detailed performance analysis of the incremental conductance (INC) method with d (delta) control has been presented. In this work a single stage grid tied PV system has been considered due to its advantages, for the performance analysis of the INC technique. Simulation of this single stage Grid tied PV Inverter is done using MATLAB/ Simulink. Different cases have been considered for simulation and performance indices measurement, under varying irradiation and temperature conditions. Also the MPPT control under varying grid voltages has also been analyzed. The Simulation results have been presented in detail and the results depicts that d control modified Incremental conductance MPPT works for different values of irradiations, temperature and grid parameters variation and are presented in this work.

Hybrid distributed generators are increasingly found to supply reliable power in isolated locations. In this article, a DC-DC step-up converter for maintaining a constant load voltage in a hybrid PV array excited wind-driven induction generator is proposed. A closed loop PI controller is designed to automatically vary the duty-cycle of the DC-DC converter. A dynamic d-q axes model of the entire scheme is presented. Constant voltage regimes for varying irradiation and wind speed are obtained using the developed model. Further, close agreement between the experimental and simulated waveforms is established to demonstrate the veracity of the simulation.

This paper use a suitable power converter topology and design a suitable controller for a Wind Energy Conversion system with Permanent Magnet Synchronous Generator (PMSG) for stand alone and grid integrated operations. The present work presents the system in which a PMSG feeds an isolated load through a closed loop boost converter. The output voltage and frequency of the PMSG is variable in nature due to non uniform wind velocities and is not synchronized with the grid frequency. In order to condition and feed it to grid we need power electronic interface. The variable ac output is rectified by a diode rectifier and maintained constant by a boost converter. The boost converter is provided with a closed loop feedback control, which is designed using PI controller. In this controller the output voltage is continuously sensed and duty ratio of the switch is varied to maintain the DC link voltage constant. The converter output is fed to three phase inverter which employs a sine PWM technique, the output of which is fed to the load. The power converters and together with independent control systems can effectively improve the output voltage and frequency of the wind PMSG feeding an isolated load. The whole system is simulated using MATLAB/ Simulink and the results are presented to demonstrate the veracity of the developed control scheme.

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.

The 3-Φ self-excited induction generator driven by wind energy source is suitable for stand-alone applications. For such an application, the minimum excitation capacitance required for self-excitation of 3-Φ induction generator is taken up in this work and the detailed analysis is carried out to determine the range of wind speed variation and consumer demand for the designed capacitance value. An electronic load controller is designed to maintain the load voltage constant for these variations. The excess power resulting as a consequence of rise in load voltage due to variation in load is pumped to dump load. Instead of wasting the power to the dump load, a battery is used to utilize the power. Exhaustive simulations have been carried out for such a scheme and the results have been presented in this paper.