Faculty Publications
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Item High Thermoelectric Performance of Co-Doped Tin Telluride Due to Synergistic Effect of Magnesium and Indium(American Chemical Society service@acs.org, 2017) Bhat, D.K.; Shenoy, U.S.Thermoelectric (TE) materials are considered go-to materials lately in addressing the worldwide energy crisis. We report a study on the effect of co-doping of magnesium and indium in lead-free SnTe both experimentally and theoretically. We show how the resonant levels introduced by indium increase the Seebeck coefficient at lower temperatures and how magnesium enhances the Seebeck at higher temperatures by opening the band gap and decreasing the energy difference between the light and heavy hole valence sub-bands. Synergistically, the effects of band engineering lead to the co-doped sample having high thermoelectric figure of merit (ZT) over a wide range of temperature and record a high power factor of ?42 ?W cm-1 K-2 for SnTe based materials. For the very first time we show the effect of site occupied by the dopant on the electronic structure of the material. The resulting high ZT of 1.5 at 840 K makes SnTe a very suitable material for thermoelectric applications. (Graph Presented). © 2017 American Chemical Society.Item Enhanced thermoelectric performance of bulk tin telluride: Synergistic effect of calcium and indium co-doping(Elsevier Ltd, 2018) Bhat, D.K.; Shenoy, S.SnTe based materials are considered recently as a lead-free replacement of the well-known PbTe based thermoelectric (TE) materials in addressing the energy crisis worldwide. Herein we report both experimental and theoretical study on the effect of co-doping of calcium and indium on electronic structure and TE properties of SnTe. We show that the resonant levels introduced by indium and band gap opening caused by calcium, valence band convergence induced by both calcium and indium, synergistically increases the Seebeck coefficient for a wide range of temperatures. The co-doped SnTe with a high ZT of ?1.65 at 840 K and record high power factor of ?47 ?Wcm?1K?2 for SnTe based materials make it a promising material for TE applications. © 2018 Elsevier LtdItem Advanced control approach for shunt active power filter interfacing wind- solar hybrid renewable system to distribution grid(Engineering and Scientific Research Groups 82 Rue Baudricourt 75013 Paris, 2018) Jayasankar, V.N.; Vinatha Urundady, U.Renewable energy systems utilize the locally available energy resources and generate green energy to meet the increasing load demand. Grid integration of renewable energy systems using power electronic interfaces is the latest trend in this area of research. The non-linear loads at load centers inject current harmonics to the distribution grid at the point of common coupling and pollute the grid. The mitigation of current harmonics in the distribution grid along with the integration of renewable energy systems to the grid is the main focus of discussion in this paper. The interconnection of a hybrid solar-wind renewable energy system with the grid at the distribution level, using a voltage source inverter is presented in this paper. The inverter is controlled using the synchronous reference frame theory based control algorithm, by which the grid interfacing inverter gets additional responsibilities of shunt active power filter. Grid interfacing system consists of a 3-phase, 4-leg voltage source inverter, a dc-link capacitor and a hysteresis current controller. A self-tuning filter is designed and used in the control system for effective elimination of current harmonics. Simulation results are presented with variation in the renewable energy generation and variation in load for validating the practical application of the proposed system. All simulations are done in MATLAB-Simulink platform. The performance of 4-leg inverter in exchanging real power from renewable sources to grid along with compensating current harmonics, under balanced and unbalanced grid voltage conditions are analyzed. © JES 2018.Item Enhanced thermoelectric properties of vanadium doped SrTiO3: A resonant dopant approach(Elsevier Ltd, 2020) Shenoy, U.S.; Bhat, D.K.Development of eco-friendly thermoelectric (TE) materials to tackle global energy crisis has become the need of the day. The goal is to either improve the properties of the existing materials or to look for new materials with better TE properties which are also nontoxic, abundant and stable. SrTiO3, a perovskite material has been gaining interest recently due to its unique and tunable electronic and crystal structure. Herein, we systematically study the effect of site occupancy of vanadium doping in SrTiO3 on the electronic structure and TE properties. First principles calculations reveal that doping of V in Sr lattice site introduces resonance levels and thereby causes distortion in density of states near the Fermi level. Transport property calculations predict V doped SrTiO3 to be a potential TE material. The study is a first report on introduction of resonance states by V in Sr site in SrTiO3 and provides new insights into the doping strategy in improving the TE properties of SrTiO3. © 2020 Elsevier B.V.Item Vanadium-doped BaTiO3 as high performance thermoelectric material: role of electronic structure engineering(Elsevier Ltd, 2020) Shenoy, U.S.; Bhat, D.K.It is well known that thermoelectric (TE) materials are the most sought-after ones to mitigate energy crisis. Development of an efficient non-toxic, economic, abundant, and stable TE material is quite difficult due to its complicated traits. BaTiO3, a perovskite material shows a tremendous potential as a TE material due to its highly tunable electronic structure. Herein, for the first time we report use of dopant to improve the Seebeck coefficient of BaTiO3. We used first-principles density functional theory calculations to study the effect of vanadium doping in BaTiO3, and for the first time, we report that V acts as a resonant dopant in BaTiO3. The study on effect of site occupancy reveals that V in Ba site distorts the density of states below the conduction band by introducing resonance level at the Fermi level. The transport property calculations based on Boltzmann's relation predicts V-doped BaTiO3 to be a potential TE material. The results also provide new insights into development of BaTiO3 as a multifunctional material. © 2020 Elsevier LtdItem Consequences of ignition timing on a hydrogen-fueled engine at various equivalence ratio(Taylor and Francis Ltd., 2022) Pandey, J.K.; Gottigere Narayanappa, K.The energy crisis in the transportation sector directs researchers to look for renewable alternative energy sources. Among all available, hydrogen is one of the prominent contenders that can be renewed and available on a large scale and is carbon-free. The study suggests hydrogen is a better fuel for SI engines than CI engines. However, its feasibility still needs to be investigated. In the present experimental study, a hydrogen-fueled SI engine is tested for various equivalence ratios (ϕ) and ignition timing (IT) at a compression ratio (CR) of 14:1. The outcomes show that the brake thermal efficiency (BTE) increases by 1.07% with increasing ϕ, while a slightly retarded IT exhibits the best figure. There is an average 1.42% increase per ϕ from gasoline noticed at ϕ 0.6, which increased to 2.12% at ϕ 0.8. The cylinder pressure and net heat release rate improve and advance with retarding IT and increasing ϕ. The flame development period (CA10) continuously reduces with increasing ϕ by an average 1.93%/ϕ change and retarding IT by 2.17%/2°CA ignition retard, due to increased mass of hydrogen and increased cylinder temperature. While flame propagation period (CA10-90) reduces with increasing ϕ and reduces to a minimum with retarding IT and then increase. The maximum cylinder temperature (Tmax) and exhaust gas temperature (EGT) increase with increasing ϕ by 3.28% and 3.62%, respectively, while Tmax reduces with retarding IT, resulting in a reduction in NOx emission. The EGT increases with retarding IT. The NOx emissions increase with ϕ by an average of 4.72%; however, at higher ϕ = 0.8, the NOx emissions are 2.51% lower than gasoline for most of the retarded IT. At a retarded IT, hydrogen performs similarly to gasoline at moderate NOx emissions. The high CR helps reduce volumetric losses reflected in BTE, found above gasoline despite less fuel energy supplied than gasoline. Although NOx emissions are controlled by retarding IT, an efficiently controlling IT resulted in a severe drop in BTE. © 2022 Taylor & Francis Group, LLC.Item Solar Photovoltaic Hotspot Inspection Using Unmanned Aerial Vehicle Thermal Images at a Solar Field in South India(MDPI, 2023) Umesh, P.; Kashyap, Y.; Baxevanaki, E.; Kosmopoulos, P.The sun is an abundant source of energy, and solar energy has been at the forefront of the renewable energy sector for years. A way to convert it into electricity is by the use of solar cells. Multiple solar cells, connected to each other, create solar panels, which in their turn, are connected in a solar string, and they create solar farms. These structures are extremely efficient in electricity production, but also, cells are fragile in nature and delicate to environmental conditions, which is the reason why some of them show discrepancies and are called defective. In this research, a thermal camera mounted on a drone has been used for the first time in the solar farm operating conditions of India in order to capture images of the solar field and investigate solar panels for defective cells and create an orthomosaic image of the entire area. This procedure next year will be established on an international scale as a best practice example for commercialization, providing effortless photovoltaic monitoring and maintenance planning. For this process, an open source software WebODM has been used, and the entire field was digitized so as to identify the location of defective panels in the field. This software was the base in order to provide and analyze a digital twin of the studied area and the included photovoltaic panels. The defects on solar cells were identified with the use of thermal bands, which record and point out their temperature of them, whereas anomalies in the detected temperature in defective solar cells were captured using thermal electromagnetic waves, and these areas are mentioned as hotspots. In this research, a total number of 232.934 solar panels were identified, and 2481 defective solar panels were automatically indicated. The majority of the defects were due to manufacturing failure and normal aging, but also due to persistent shadowing and soiling from aerosols and especially dust transport, as well as from extreme weather conditions, including hail. The originality of this study relies on the application of the proposed under development technology to the specific conditions of India, including high photovoltaic panels wear rates due to extreme aerosol loads (India presents one of the highest aerosol levels worldwide) and the monsoon effects. The ability to autonomously monitor solar farms in such conditions has a strong energy and economic benefit for production management and for long-term optimization purposes. © 2023 by the authors.Item Oil price effect on asset pricing of renewable energy firms in India: a panel quantile regression approach(Emerald Publishing, 2023) Mishra, L.; Rajesh Acharya, R.H.Purpose: This study aims to investigate the relationship between oil prices and stock returns of renewable energy firms in India under different market conditions. Design/methodology/approach: The authors use the panel quantile framework with Fama–French–Carhart’s (1997) four-factor asset pricing model. All renewable energy firms listed in the National Stock Exchange of India are considered in this study. Three oil prices, such as West Texas Intermediate spot price, Europe Brent oil price and Indian basket oil price, are used in the regression. The analysis is done for the whole sample and its subgroups. Findings: In the whole sample, stock returns of renewable energy firms respond positively to oil price changes in extreme market conditions only. In the subgroups of the renewable energy firms, the relationship between stock returns and oil price is positive and more robust in higher quantiles across all subgroup firms. Originality/value: The contribution of the study is explained as follows. First, this study helps to explore the relationship between oil and stock returns of the renewable energy sector under different market conditions in the Indian context. Second, existing studies explore the effect of oil prices on stock returns of the renewable energy sector at the industry level, and most of the studies are in developed countries. To the best of the authors’ knowledge, this is the first study in the context of India. Third, this is a firm-level study. © 2022, Emerald Publishing Limited.Item Towards parity: Examining the closing gender gap on electricity access in India using data from 1998 to 2021(Elsevier B.V., 2024) Timilsina, R.R.; Jena, P.R.; Rahut, D.B.; Managi, S.Access to electricity is fundamental for human development, health, and well-being, particularly in low- and middle-income countries. Governments of several low-and middle-income countries have implemented policies and interventions to increase access to electricity over the decades. Heterogeneity in access to electricity across gender is a major aspect of this development indicator. However, little is known about the distribution of and access to electricity between male and female-headed households in countries such as India. This study aims to investigate gender parity in access to electricity using data from four waves of the National Family Health Survey (NFHS) from 1998 to 2021. The analysis employs a logit regression model and includes counterfactual analysis to comprehensively understand the determinants of electricity access across genders. The results indicate that electricity consumption is positively associated with female-headed households, education, wealth, and urban location. The study shows that the gap in access to electricity between genders is narrowing in favor of female-headed households over the four waves of national-level data spanning two decades. The difference between male and female-headed households declined from 4.73 % in 1998–2000 to 1.6 % in 2019–2021, reflecting gender parity in access to electricity in the country. Access to electricity has increased across all households, but uninterrupted supply and transition to green energy shall be the significant challenges ahead. Therefore, the government must improve access to electricity, particularly for female-headed households, and also make it affordable for households to install other renewable energy systems to increase overall electricity generation. © 2024 International Energy InitiativeItem The effect of structural oil shocks on stock returns of Indian renewable energy companies across market conditions(Emerald Publishing, 2024) Mishra, L.; Rajesh Acharya, H.Purpose: This study aims to evaluate the structural oil shocks effect on stock returns of Indian renewable energy companies across market conditions. Design/methodology/approach: This study applies the structural vector autoregression model to estimate sources of oil shocks such as oil supply shock, aggregate demand shock and oil price-specific demand shock. In the next step, the panel quantile regression model estimates the effect of these oil shocks on stock return across market conditions. Monthly data are collected from January 2009 to December 2019. All renewable energy companies listed on the National Stock Exchange of India are considered for the analysis. Findings: In the whole sample analysis, this study finds that oil shocks negatively affect stock returns in most of the market conditions except oil price-specific demand shock. In sub-groups, oil shocks driven by supply and aggregate demand also negatively affect stock return in most market conditions. This study finds the positive interaction of oil price-specific demand shock. A majority of these positive interactions happen in bearish market conditions. In the whole sample, the asymmetric effects of shocks driven from oil supply and oil price-specific demand are seen in most quantiles or market conditions. At the same time, aggregate demand shock does not affect asymmetrically. In the sub-group analysis, standalone renewable energy companies stock returns are least asymmetrically affected by these oil shocks. The asymmetries of oil supply-driven shock on stock returns of the renewable energy sub-group companies are found in most quantiles. Originality/value: First, this is a company-level study of the stock returns response to the structural oil shocks in the renewable energy sector. Second, to the best of the authors’ knowledge, this type of study is the first in the Indian context. Third using panel quantile regression model along with capital asset pricing model framework, the authors investigate these effects across market conditions. © 2024, Emerald Publishing Limited.