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Maity S.K.,Indian Institute of Technology Hyderabad
Renewable and Sustainable Energy Reviews | Year: 2015

Sustainable production of energy, fuels, organic chemicals and polymers from biomass in an integrated biorefinery is extremely important to reduce enslavement on limited fossil fuels. In the present article, the biomass was classified into four general types based on their origin: energy crops, agricultural residues and waste, forestry waste and residues and industrial and municipal wastes. The article further elucidates the chemistry of various types of biomass used in the biorefinery. The biorefinery was classified into three broad categories based on the chemistry of biomass: triglyceride, sugar and starchy and lignocellulosic. The article further presents a comprehensive outlines of opportunities and recent trends of each type of biorefinery. A brief overview of original and revised list of platform chemicals, their sources from biomass and derivative potentials were also articulated. The article also provides comparisons of different types of biorefinery, broad challenges and availability of biomass. Furthermore, the article provides an overview of hydrocarbon biorefinery for production of hydrocarbon fuels and building block chemicals from biomass. ©2014 Elsevier Ltd. All rights reserved.

Srinivas S.,Indian Institute of Technology Madras | Ramachandra Sekhar K.,Indian Institute of Technology Hyderabad
IEEE Transactions on Industrial Electronics | Year: 2013

A dual two-level voltage source inverter (VSI) can synthesize a three-level voltage space vector employing an open-end winding induction motor. Space-vector-based pulsewidth modulation (PWM) variants for this dual VSI are proposed in this paper that offer the dual advantage of limiting the switching power loss to a single VSI at all instants and also reducing the switching commutations in the dual VSI by 50%. The influence of different error volt seconds (affected with different PWM variants) on the motor phase current in the dual VSI is critically analyzed. To this end, two analytical approaches (one using error-voltage trajectory information and the other using switching state information of the dual VSI) are also proposed in this paper to predict the current trajectory and the ripple content in the drive system. Expressions for rms ripple current are developed with different PWM variants. The efficacy of the proposed analytical approaches to predict the current trajectory and the ripple content is confirmed from the experimental results. All the PWM variants are first simulated using MATLAB and verified experimentally by conducting tests on a three-phase open-end winding induction motor drive controlled with volts per hertz control. The implementation of the PWM algorithms only requires instantaneous magnitudes of three-phase reference voltages and completely avoids the sector identification and lookup tables. © 1982-2012 IEEE.

Maity S.K.,Indian Institute of Technology Hyderabad
Renewable and Sustainable Energy Reviews | Year: 2015

Availability of cost-competitive biomass conversion technologies plays crucial role for successful realization of biorefinery for sustainable production of fuels and organic chemicals from biomass. The present article provides an outline of opportunities and socio-techno-economic challenges of various biomass processing technologies. The biomass processing technologies were classified into three broad categories: thermochemical, chemical and biochemical. This review article presents an overview of two potential thermochemical conversion processes, gasification and fast pyrolysis, for direct conversion of lignocellulosic biomass. The article further provides a brief review of chemical conversion of triglycerides by transesterification with methanol for production of biodiesel. The highly productive microalgae as an abundant source of triglycerides for biodiesel and various other fuels products were also reviewed. The present article also provides an outline of various steps involved in biochemical conversion of carbohydrates to alcoholic bio-fuels, bio-ethanol and bio-butanols and conversion of natures most abundant aromatic polymer, lignin, to value-added fuels and chemicals. Furthermore, an overview of production of hydrocarbon fuels through various biomass processing technologies such as hydrodeoxygenation of triglycerides, biosynthetic pathways and aqueous phase catalysis in hydrocarbon biorefinery were highlighted. The present article additionally provides economic comparisons of various biomass conversion technologies. © 2014 Elsevier Ltd. All rights reserved.

Banerjee R.,Indian Institute of Technology Hyderabad
Fuel | Year: 2013

Numerical study has been performed to analyse evaporation of a single droplet composed of a binary mixture of ethanol and iso-octane. The Navier-Stokes equations are solved in conjunction with VOF multiphase model to track the liquid/gas interface over time. Ethanol and iso-octane form a highly non-ideal mixture and therefore the UNIFAC group contribution method was used to determine the vapour-liquid equilibrium (VLE). Source terms due to interfacial mass transfer were implemented in the continuity, momentum, energy and species equations. Commercial computational fluid dynamics solver, Ansys Fluent 13.0 was used in this study. VLE, mixture transport properties and source terms due to interfacial mass transfer were implemented using user defined functions. Parametric study to analyse the effect of free stream temperature and composition, droplet temperature and composition was performed. © 2013 Elsevier Ltd. All rights reserved.

Chaudhuri D.,Indian Institute of Technology Hyderabad
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

Within the Rayleigh-Helmholtz model of active Brownian particles, activity is due to a nonlinear velocity-dependent force. In the presence of external trapping potential or constant force, the steady state of the system breaks detailed balance producing a net entropy. Using molecular dynamics simulations, we obtain the probability distributions of entropy production in these steady states. The distribution functions obey fluctuation theorems for entropy production. Using the simulation, we further show that the steady-state response function obeys a modified fluctuation-dissipation relation. © 2014 American Physical Society.

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