Agnimitra Biswas

Bio: Agnimitra Biswas is an academic researcher from National Institute of Technology, Silchar. The author has contributed to research in topics: Turbine & Tip-speed ratio. The author has an hindex of 19, co-authored 76 publications receiving 1187 citations. Previous affiliations of Agnimitra Biswas include Indian Veterinary Research Institute.

Comparative study of a three-bucket savonius rotor with a combined three-bucket savonius–three-bladed darrieus rotor

Abstract: The vertical axis wind turbines are simple in construction, self-starting, inexpensive and can accept wind from any direction without orientation A combined Savonius–Darrieus type vertical axis wind rotor has got many advantages over individual Savonius or individual Darrieus wind rotor, such as better efficiency than Savonius rotor and high starting torque than Darrieus rotor But works on the combined Savonius–Darrieus wind rotor are very scare In view of the above, two types of models, one simple Savonius and the other combined Savonius–Darrieus wind rotors were designed and fabricated The Savonius rotor was a three-bucket system having provisions for overlap variations The Savonius–Darrieus rotor was a combination of three-bucket Savonius and three-bladed Darrieus rotors with the Savonius placed on top of the Darrieus rotor The overlap variation was made in the upper part, ie the Savonius rotor only These were tested in a subsonic wind tunnel available in the department The various parameters namely, power coefficients and torque coefficients were calculated for both overlap and without overlap conditions From the present investigation, it is seen that with the increase of overlap, the power coefficients start decreasing The maximum power coefficient of 51% is obtained at no overlap condition However, while comparing the power coefficients (Cp) for simple Savonius-rotor with that of the combined configuration of Savonius–Darrieus rotor, it is observed that there is a definite improvement in the power coefficient for the combined Savonius–Darrieus rotor without overlap condition Combined rotor without overlap condition provided an efficiency of 051, which is higher than the efficiency of the Savonius rotor at any overlap positions under the same test conditions

Techno-economic optimization of an off-grid hybrid renewable energy system using metaheuristic optimization approaches – Case of a radio transmitter station in India

Abstract: Development of hybrid renewable energy system has become a challenging task considering the intermittencies of renewables and multi-dimensional designing aspects (for example technical and economic aspects) of such hybrid systems. Although there are many investigations on the development of hybrid renewable energy systems, the investigations of useful models or effective methods are only a few. Metaheuristic algorithms are gaining much popularity in the optimization of complex systems like hybrid renewable energy system for their ability to give quick, accurate, and optimal solution. The objective of the present study is to obtain a techno-economic optimal design of an off-grid hybrid solar photovoltaic/biogas generator/pumped hydro energy storage/battery system with the help of metaheuristic optimization techniques for a radio transmitter station in India. Performances of two such techniques – water cycle algorithm and moth-flame optimization that have become popular in recent time are evaluated and compared with Genetic Algorithm, which was used as a benchmark metaheuristic in previous studies on hybrid renewable energy system. The objective function is a minimization of total net present cost subject to design constraints. A detailed modeling strategy has been elaborated for the optimization problem. A sensitivity analysis based on loss of load probability type reliability criteria is carried out to investigate the feasibility of the proposed design. The results show that both the considered metaheuristics are effective in finding the optimal design; however, water cycle algorithm has marginally better design solution than the other two algorithms. The optimal configuration by the water cycle algorithm is found to have solar photovoltaic panel area of 548.67 m2 (size 69.2 kW), biogas generator size of 16 kW, battery bank of 21 units, converter size of 30 kW, and upper reservoir volume of 2081.5 m3 with a total net present cost of $0.813 million. Further, on comparing the results with literature, it is found that the present metaheuristic optimization has resulted in an effective hybrid renewable energy system design with a lower techno-economic cost.

Experimental and computational evaluation of Savonius hydrokinetic turbine for low velocity condition with comparison to Savonius wind turbine at the same input power

Abstract: The extensive depletion of the conventional sources of energy has forced the mankind to explore every possibilities lying beneath the nature. The evolution and modification of the old ideas from the field of wind turbine led the mankind to explore the same technology in water. Hydrokinetic turbine, one of the most emerging technologies for power generation, has gained keen interest of the researchers because of some of the unique properties of water like higher specific weight, higher momentum than air for same velocity etc. The objective of the study is to evaluate how the conventional Savonius wind turbine performs when it rotates by the momentum of water current at low velocity from 0.3 m/s to 0.9 m/s in an open water channel. An experimental investigation along with computational fluid dynamics (CFD) study using Ansys 14.0 has been carried out to accomplish the objective of the work. To understand the significance of Savonius design in water application, the performance of the hydrokinetic turbine is experimentally compared to the identically designed wind turbine for the same input power values, showing enhanced performance of the former turbine. The purpose of using CFD is to enable a more detailed study on the velocity and torque distribution across the hydrokinetic turbine and hence to develop more insight of design information about its performance under low velocity condition. Finally the reason for enhanced performance of the hydrokinetic turbine is investigated from the computational study of flow characteristics of both the hydrokinetic and wind turbines. Smooth, stable operation and a good service life of the hydrokinetic turbine could be expected unlike the wind turbine.

Investigations on self-starting and performance characteristics of simple H and hybrid H-Savonius vertical axis wind rotors

Abstract: With recent surge in fossil fuel prices and demands for renewable energy sources, vertical axis wind turbine (VAWT) technologies have emerged out as one of the prime growing sector for small-scale power generation in the built environment. In such an environment, self-starting and high performances are of utmost importance. Amongst all VAWT designs, H-rotor, being a lift-driven device, exhibits a high power coefficient. However, it suffers from poor starting behavior due to its conventional symmetrical NACA airfoil blades. The objective of the present study is to design a VAWT rotor that possesses both self-starting and high power coefficient simultaneously. For this, a three bladed H-rotor with unsymmetrical cambered S818 airfoil blades is investigated, which shows self-starting characteristics at many of the azimuthal angles. However to make the rotor completely self-starting, the same H-rotor is incorporated in a hybrid system with Savonius rotor as its starter. It is found that the hybrid design fully exhibits self-starting capability at all azimuthal positions, signified by the positive static torque coefficient values. For improving power performance of the hybrid rotor, the same is subjected to rigorous experimentations on the wind tunnel at different Reynolds numbers (Re) between 1.44 × 10 5 and 2.31 × 10 5 for five different overlap conditions in the Savonius rotor part. The performance coefficients of the hybrid rotor are compared with the simple H-rotor. Out of all the designs investigated, the maximum Cp of 0.34 is obtained for the hybrid rotor at tip speed ratio (TSR) of 2.29 and Re of 1.92 × 10 5 for the optimum 0.15 overlap, followed by a maximum Cp of 0.28 at TSR of 2.42 and at same Re for the simple H-rotor. Furthermore insights of the performances of the optimum VAWT rotor are also obtained under different wind velocity conditions as prevail in the built environment. The optimum hybrid H-Savonius rotor demonstrates better power performance as compared to many of the existing VAWT rotors.

Investigation of self-starting and high rotor solidity on the performance of a three S1210 blade H-type Darrieus rotor

Abstract: Energy is an essential ingredient for socio-economic development and economic growth of a country. Energy is available in two different forms, fast depleting or non-renewable (coal, fuel, natural gas) and renewable (solar, wind, hydro etc). Wind is one of the potential renewable energy sources due to its abundance in the atmosphere in different scales of high, medium and low ranges. Vertical axis wind turbine (VAWT) can be installed in low wind speed regime for performing various small-scale functions ranging from electrifying a built environment to pumping water especially in remote places where grid-connected electricity is a scarce. Amongst various VAWT rotors, H-type Darrieus rotor has become more popular in the built environment for their straight blade designs and simpler construction features. However, the major problem facing such VAWT rotor is their non-self-starting characteristics due to symmetrical blade designs. Replacing VAWT's conventional blades with unsymmetrical blades and increasing rotor solidity could make potential solution to the above problem. However, there is still hardly any quantitative measure of the self-starting, torque, power coefficient etc. with increased rotor solidity so as to obtain some performance insights of high solidity unsymmetrical blade H-Darrieus rotor in low wind speed condition. In this paper a three-bladed H-type Darrieus rotor equipped with unsymmetrical S1210 blades is investigated first for its self-starting characteristics with different rotor solidities (from 0.8 to 1.2) at various azimuthal positions. Then the power coefficients (Cp) are evaluated for these solidities at various wind speeds. It will be shown that high blade solidity is in fact desirable for overall better performance of the rotor. There is an optimum rotor solidity at which power coefficient is the highest. And the maximum Cp of 0.32 is obtained for rotor solidity 1.0 and wind speed 5.7 m/s. The results are compared with some other symmetrical/unsymmetrical blade H-Darrieus rotors. Though the operating range is reduced but, for higher static and dynamic torque and comparable power coefficient with respect to existing rotors, the present rotor could be used for various small-scale applications especially that require high torque like pumping, grinding etc.

Vertical axis wind turbine-a review of various configurations and design techniques

Abstract: Increased concern for environment has led to the search for more environment friendly sources of energy. Wind energy can be a viable option in this regard. Vertical axis wind turbines offer promising solution for areas away from the integrated grid systems. However, they have certain drawbacks associated with different configurations. This paper reviews various configurations of VAWT along with their merits and demerits. Moreover, design techniques employed for VAWT design have also been reviewed along with their results. It was learned that coefficient of power (CP) for various configurations is different and can be optimized with reference to Tip Speed Ratio. Latest emerging design techniques can be helpful in this optimization. Furthermore, flow field around the blade can also be investigated with the help of these design techniques for safe operation.

Pasteurella multocida: from Zoonosis to Cellular Microbiology

Abstract: In a world where most emerging and reemerging infectious diseases are zoonotic in nature and our contacts with both domestic and wild animals abound, there is growing awareness of the potential for human acquisition of animal diseases. Like other Pasteurellaceae, Pasteurella species are highly prevalent among animal populations, where they are often found as part of the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts. Many Pasteurella species are opportunistic pathogens that can cause endemic disease and are associated increasingly with epizootic outbreaks. Zoonotic transmission to humans usually occurs through animal bites or contact with nasal secretions, with P. multocida being the most prevalent isolate observed in human infections. Here we review recent comparative genomics and molecular pathogenesis studies that have advanced our understanding of the multiple virulence mechanisms employed by Pasteurella species to establish acute and chronic infections. We also summarize efforts being explored to enhance our ability to rapidly and accurately identify and distinguish among clinical isolates and to control pasteurellosis by improved development of new vaccines and treatment regimens.

A review on recent sizing methodologies of hybrid renewable energy systems

Abstract: On account of the continuously increasing electricity consumption and concern for environmental issues, renewable energy sources have been widely utilized to generate electricity, and they present advantages such as cleanness, easy availability, low cost, and abundance. In 2017, the installed capacity of solar and wind power worldwide amounted to 903.1 GW, which represented 41.4% of the total installed capacity of renewable energy. Hybrid renewable energy systems have been proposed to overcome the variability and randomness of a single renewable energy source such as solar and wind power, and more than 80% of them are off-grid systems. Meanwhile, it is necessary to determine the size of each component to design a reliable and cost-effective hybrid renewable energy system. Therefore, this paper mainly reviews the recent classification, evaluation indicators, and sizing methodologies of hybrid renewable energy systems (stand-alone and grid-connected). Further optimization research is still required to improve the overall performance of hybrid renewable energy systems. Decision makers can explore and develop hybrid systems including hydropower and/or pumped hydro storage based on their superiority, and they should also pay attention to the development of hybrid energy storage. In addition to reliability and economic indicators, which have applications above 80%, more attention should be payed to environmental and social indicators to determine the system capacity, and some new indicators should be disseminated. The features of traditional, artificial intelligence, and hybrid methods, in additional to software tools, were assessed. Moreover, hybrid methods with high accuracy and fast convergence that can surmount the defects of single methods are the most promising sizing method compared to the other three sizing methods. This review is valuable to understand the current status and development trends of optimal sizing for hybrid renewable energy systems.

Performance investigation of H-rotor Darrieus turbine with new airfoil shapes

Abstract: Since millenaries humans have attempted to harness the wind energy through diverse means. Vertical axis wind turbines (VAWTs) were originally considered as very promising, before being superseded by the present, horizontal axis turbines. For various reasons, there is now a resurgence of interests for VAWTs, in particular Darrieus turbines. Using modern design tools and computational approaches, it should be possible to increase considerably the performance of traditional VAWTs, reaching a level almost comparable to that of horizontal axis turbines. Since VAWTs show many specific advantages (compact design, easier connection to gears/generator, easier blade control if needed, lower fatigue…), it is important to check quantitatively the efficiency of such turbines. This is the purpose of the present work, starting from the standard, straight Darrieus turbine (H-rotor). The aerodynamic investigation will be carried out for 20 different airfoils (Symmetric and Non-symmetric) by two-dimensional Computational Fluid Dynamics in order to maximize output torque coefficient and output power coefficient (efficiency). A considerable improvement of the H-rotor Darrieus turbine performance can be obtained in this manner.

Critical issues in the CFD simulation of Darrieus wind turbines

Abstract: Computational Fluid Dynamics is thought to provide in the near future an essential contribution to the development of vertical-axis wind turbines, helping this technology to rise towards a more mature industrial diffusion. The unsteady flow past rotating blades is, however, one of the most challenging applications for a numerical simulation and some critical issues have not been settled yet. In this work, an extended analysis is presented which has been carried out with the final aim of identifying the most effective simulation settings to ensure a reliable fully-unsteady, two-dimensional simulation of an H-type Darrieus turbine. Moving from an extended literature survey, the main analysis parameters have been selected and their influence has been analyzed together with the mutual influences between them; the benefits and drawbacks of the proposed approach are also discussed. The selected settings were applied to simulate the geometry of a real rotor which was tested in the wind tunnel, obtaining notable agreement between numerical estimations and experimental data. Moreover, the proposed approach was further validated by means of two other sets of simulations, based on literature study-cases.