Currently Focused Research Activities 1. Energy and Environment 2. Fuel Technology and I. C Engine 3. Solar Energy 4. Plasma Science 5. EPRES 6. Energy Storage
All DESE faculties
Sodium metal anode battery technologies have revolutionized energy storage research. In recent years, new insights have been gained regarding the solid electrolyte interphase (SEI) on sodium metal anode; however, several questions remain to be answered, in particular, the impact of electrolyte structure on the composition and physicochemical stability of the SEI. In addition, the impact of ion-solvation chemistry on the crystallinity of the SEI warrants a more detailed understanding. This review discusses the crucial aspects of sodium-ion solvation chemistry and its impact on the stability of the SEI. The core principles guiding the design of electrolytes through additives, ion-solvent interaction, and ion-pair formation are highlighted. Future research directions necessary to design a stable sodium metal anode are also discussed.
Prof. Vipin Kumar
With the invention of the high-temperature sodium-sulfur batteries, Na metal-based chemistries remained in oblivion. However, due to increasing concerns over the safety of the high-temperature sodium-sulfur batteries, Na metal anode is revived in recent years with the ever-growing demands for high energy density and improved safety. Despite that current Na metal anode still lacks high-reversibility, efficiency, and room-temperature stability due to limited or no control over the interfacial chemistry of the Na metal anode. The electrochemical reduction of Na+ ions is accompanied by the inevitable reduction of organic species, which leads to the growth of the solid-electrolyte interphase (SEI) with Na-deposits. The SEI is inherently unstable due to the localized fluctuations in its chemical and physical properties. A deep understanding of the challenges associated with the SEI's localized interfacial chemistry is of prime importance towards developing the practical Na metal anodes for RT-Na/S batteries. This mini-review highlights critical challenges in developing a stable Na metal anode and further sheds light on its mechanistic aspects. In addition to that, novel approaches to precisely tune the interphase's physicochemical properties are highlighted to pave path for developing a stable and long-life Na-metal anode for RT-Na/S batteries.
Prof. Vipin Kumar
The increased demand for energy has prompted users to seek alternative energy storage devices. Post Li-ion battery chemistries have been considered potential contenders for the development of next-generation battery technologies. The high-specific capacity (~1675 mAh g-1) and high natural abundance (~953 ppm) of sulfur provide opportunities to meet the rigorous requirements of the market’s demands, like, high energy density and low cost. When combined with a high capacity metal anode (e.g., Na ~1165 mAh g-1, Mg ~2205 mAh g-1, and Al ~2980 mAh g-1), it leads to high-energy-density that can outperform the existing battery technologies, including high-energy Li-ion batteries. Despite the unique attributes of the sulfur-based battery system, it remains in infancy owing to the complex reaction chemistry of sulfur cathode, and the level of complexity increases with an increase in valency of metal ions. This review summarizes the unique aspects of a sulfur cathode essential to stabilizing sulfur cathode-based high-energy rechargeable batteries. Furthermore, deeper insight into the electrochemical performance of various metal-sulfur-based systems has been provided. This review may pave the path for the researchers to accelerate the development of sulfur cathode for post-Li-ion batteries.
Prof. Vipin Kumar
The study investigated the unregulated emission characteristics of a two-wheeler running on commercial gasoline (E0) and different ethanol-gasoline blends such as E10, E20, E30, E40 & E50. The physico-chemical properties of all the test fuels are presented. The two-wheeler was tested using chassis dynamometer for steady speed operation as well as transient emission test cycle. The emission species were measured using Fourier transform infra-red (FTIR) analyzer. Ethanol in gasoline enhances the fuel quality of the blend mainly octane number. The results indicate that carbonyls such as formaldehyde and acetaldehyde increased linearly with ethanol-gasoline blends. It is observed with ethanol-gasoline blend that acetaldehyde emission was three times higher than formaldehyde emission. The saturated hydrocarbon emissions (methane and ethane) increased with ethanol blends beyond E20. Aromatics (toluene), unburned ethanol emissions were higher with E30, E40 & E50 compared to neat gasoline and the blends. Ethene and propylene emissions were significantly higher with E40 & E50. All the unregulated emission components decreased with the increase in vehicle speed. The emission data and results presented in this paper could be useful to develop emission control strategies for two-wheelers.
Prof. K. A. Subramanian
The present work investigates the thermal enhancement of a binary eutectic phase change material (PCM) (150–200 °C), laden with different concentrations of COOH-functionalized Graphene nanoplatelets (f-GNP) for a multi-effect solar cooling thermal storage system. The novel nano-composite is prepared by varying the weight concentration of f-GNP from 1% to 5% in a pristine eutectic salt of LiNO3-KCl (50:50) using the standard nano synthesis protocol. The microstructure, dispersion uniformity are evaluated using scanning electron microscope (SEM) and thermophysical properties of the nano-composite are characterized using dynamic Differential scanning calorimetry (DSC). The thermal conductivity enhancement due to the doping of f-GNP is studied through a series of experimental trials conducted with Laser flash analysis (LFA). The obtained data is plotted and compared with a more robust theoretical thermal conductivity model. It is found that thermal conductivity rises by 104% with f-GNP dispersions, which reflects the improved thermal performance of the storage system. The specific heats of the solid and liquid phase show an increase of 80% & 38% respectively at f-GNP concentration of 5%. Finally, the effect of doping f-GNP on the conjugate heat transfer inside the PCM and fluid flow of HTF is investigated in a vertical shell and tube type storage system, suitable for the double effect solar cooling system. The f-GNP dispersions accelerate the heat storage process with a maximum decrease of 17.3% in the total melt duration. In addition, the role of increased viscosity on the natural convection is simultaneously studied with the increased thermal conduction due to nanoplatelets dispersions.
Prof. Dibakar Rakshit
We have investigated the carrier transport mechanisms of Ag/ITO/NixO/n-Si/LiFx/Al carrier-selective contact (CSC) silicon solar cells without and with chemically grown SiOx passivation interlayer. The carrier transport is dominated by thermionic (Schottky) emission and tunnelling at the high- (>0.4 V) and low-forward (<0.4 V) bias voltage regions, respectively, in the cell with SiOx interlayer. Without intentionally grown SiOx layer, the carrier transport is dominated by the recombination through interface/surface defect states, which is inferred from the smaller activation energy and strong temperature-dependent ideality factors in >0.4 V forward voltage bias region. The C–V analysis is also confirmed the inability to hold the excess photo-generated charge carriers because of poor interface quality of the cell without SiOx than the cell with SiOx. The NixO/c-Si junction with the SiOx is resulted in higher built-in voltage and better open-circuit voltage representing better interface passivation quality with fewer interface/surface defect states.
Prof. Vamsi K. Komarala
The present invention relates to the field of biomass based cooking and heating systems. More specifically the present invention is directed towards a clean combustion for both process heating and cooking applications having emission characteristics and thermal efficiency at par with the LPG stove. We have achieved the emission factors (kg/kg-fuel) of PM2.5 as 1/3rd and carbon monoxide (CO) as 1/11th of LPG stove, when tested using the same testing protocols (BIS). The lowest emission of PM2.5 and CO is the most important criteria for any cooking and heating device and the present model is superior to those (>500 models of improved cookstoves) available, globally
Prof. S K Tyagi
Asymmetrical cascaded bridge multilevel converters use voltage sources of different magnitudes to generate higher number of levels. However, availability of sources of different ratings feeding the bridges is a limitation. This paper overcomes such limitation by utilizing the concept of capacitor voltage-balancing using Level Doubling Network (LDN) principle in space-vector plane. With the use of optimal asymmetry, presented topology can generate 43 levels at the output line voltage by using only 12 switches per phase. Hence, the most notable attribute of the presented topology is that it does not require isolated auxiliary power-supplies to develop such high-resolution output voltage. LDNs in this topology are self-balanced, and the auxiliary full-bridges require a closed loop controller to balance their dc-bus capacitor voltage. To validate the proposed concept, MATLAB simulations and experimental results are presented in this paper.
Prof. Sumit K Chattopadhyay
In this paper we propose a one-dimensional convolutional neural network (CNN)-based state of charge estimation algorithm for electric vehicles. The CNN is trained using two publicly available battery datasets. The influence of different types of noises on the estimation capabilities of the CNN model has been studied. Moreover, a transfer learning mechanism is proposed in order to make the developed algorithm generalize better and estimate with an acceptable accuracy when a battery with different chemical characteristics than the one used for training the model, is used. It has been observed that using transfer learning, the model can learn sufficiently well with significantly less amount of battery data. The proposed method fares well in terms of estimation accuracy, learning speed and generalization capability.
Prof. Ashu Verma
An accurate, non-invasive ex situ diagnostic technique for analyzing plasma generated harmonics in radio frequency (RF) discharges is presented utilizing a broadband Dual Directional Coupler (DDC) that measures accurately both forward and reflected voltage signals in a transmission line. For usual applications such as monitoring forward and reflected power, the DDC is placed between the RF generator and the matching network (MN). However, the MN reflects all plasma generated harmonics back toward the plasma. Hence, no harmonics reach the generator side of the MN. Thus, for monitoring the harmonics, it is necessary to place the DDC between the impedance matching unit and the plasma, which was used for the first time in an asymmetric, parallel plate RF discharge at 13.56 MHz, 10 W–50 W at 200 mTorr (argon). The analysis of DDC data yields voltage, harmonic power contents, complex load impedance, plasma reflection coefficient, Voltage Standing Wave Ratio (VSWR), etc., for the fundamental frequency. For instance, at 10 W net input power, the computed plasma impedance is ZL = Rp + jXp, with Rp = 16.8 Ω and Xp = −81.9 Ω, yielding VSWR ≈11. Additionally, for 50 W input power, the third harmonic (72.31 mW) is dominant, followed by the second (8.28 mW) and fourth harmonics. In contrast, the literature states that the second harmonic is usually dominant, possibly due to the invasive nature of the diagnostics. Because harmonics are an important signature of processes taking place within the plasma, the proposed diagnostic can be effectively used for calibration and verification of theoretical models/simulations for resolving relevant physics issues.
Prof. Ramesh Narayanan
The present invention relates to the field of biomass based cooking and heating systems. More specifically the present invention is directed towards a clean combustion for both process heating and cooking applications having emission characteristics and thermal efficiency at par with the LPG stove. We have achieved the emission factors (kg/kg-fuel) of PM2.5 as 1/3rd and carbon monoxide (CO) as 1/11th of LPG stove, when tested using the same testing protocols (BIS). The lowest emission of PM2.5 and CO is the most important criteria for any cooking and heating device and the present model is superior to those (>500 models of improved cookstoves) available, globally.
Prof. S. K. Tyagi
Atmospheric Pressure Plasma: Physics and Applications
Prof. Satyananda Kar
The ultra-thin tin doped crystalline indium oxide (ITO) films (≤50 nm) were successfully deposited by a 3-dimensionally confined magnetron sputtering source (L-3DMS) at the temperature lower than 100 °C. The resistivity and the mobility of the ultra-thin ITO films deposited at a low processing temperature were about ~5 × 10−4 Ω · cm and >30 cm2/Vs, respectively, for the thickness of 30 nm. The high quality of the ultra-thin ITO films deposited by L-3DMS is believed to be related to the improved crystallinity with oxygen vacancies of the ITO films by high density plasma and low discharge voltage of the L-3DMS which enables the formation of a crystalline structure a low processing temperature.
Prof. B B Sahu
In this article, the synthesis of phase pure iron pyrite nanocubes (FeS2 NCs) and their various effects on the charge carrier dynamics and photovoltaic performances of P3HT:PC71BM based hybrid bulk-heterojunction solar cells have been studied. The optimum doping concentration of FeS2 NCs was found to be 0.3 wt%. For the optimally doped devices, the short-circuit current density was found to have improved from 5.47 to 7.99 mA cm−2 leading to an overall cell efficiency improvement from 2.10% to 3.22% as compared to the undoped reference devices. The enhancement in photovoltaic performance is mainly attributed to the formation of localized energy states near the band edges leading to higher carrier generation rate by 72% whereas carrier dissociation probability is also increased by 13%. Urbach energy estimation reveals that the optimally doped devices have achieved a relatively balanced amount of localized states resulting in reduced non-radiative recombination. Such localized defect states formation with FeS2 NCs doping was also found to have significant influence over the charge carrier dynamics of the active layer. Transient photocurrent and photovoltage studies revealed that FeS2 NCs assist in faster carrier extraction by reducing the transport time from 1.4 to 0.6 μs and by enhancing carrier recombination time from 51.7 to 78.9 μs for the reference and optimum devices respectively. Such an unorthodox approach of defect state assisted efficiency improvement demonstrates the importance of simultaneously understanding the charge carrier dynamics and photovoltaic performance for rational device optimization, and opens new prospects for developing high-efficiency solution processable hybrid devices.
Prof. Supravat Karak
In this study, the thermo-hydrodynamics of direct steam generation in the receiver of parabolic trough solar collector have been investigated using a two-fluid modeling approach. The numerical models for solving the conservation equations, turbulence parameters, phase change, boiling heat transfer, and heat loss from the receiver have been discussed in detail. The three-dimensional governing equations are solved for 12 m length of the parabolic trough solar collector using ANSYS Fluent 2020R1. The receiver is modeled with and without considering the glass envelop. The thermal-hydraulics of the direct steam generation process is studied at solar noontime and 2 h before and after solar noon with direct normal irradiance (DNI) of 750 W/m2. Further, the effect of inlet mass flow rates and operating pressures have been investigated. The simulations are performed for mass flow rates 0.3 kg/s to 0.6 kg/s and operating pressure 30 bar–100 bar. The simulation results have shown that the vapor volume fraction at the absorber outlet varies in the range of 0.30–0.58 without considering the heat losses. The absorber’s outer surface temperature reached the maximum temperature of 526.5 K, 568.1 K, and 603.4 K, respectively for operating pressures 30 bar, 60 bar, and 100 bar at solar noon. The maximum circumferential temperature difference is observed 16 K during the solar noon. The increments in mixture velocity from inlet to outlet are observed as 0.76 m/s, 0.41 m/s, and 0.26 m/s, respectively for operating pressure 30, 60, and 90 bar at the solar noon. The relative velocity between the liquid and vapor phase have been predicted. The higher pressure drops are observed at the lower operating pressures. The average heat loss from the receiver is observed as 95 W/m2 for operating pressure 30 bar and MFRs 0.3 kg/s to 0.6 kg/s and the absorber surface temperature varies between 506 K and 525 K. Further the comparison of thermal-hydraulic parameters with and without considering the glass envelop is presented. The comparison of thermal-hydraulic parameters for solar heat flux corresponding to solar noon and 2 h before and after the solar noon are presented.
Prof. K. Ravi Kumar