Satyanarayanan Seshadri

Bio: Satyanarayanan Seshadri is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Laser-induced breakdown spectroscopy & Organic Rankine cycle. The author has an hindex of 3, co-authored 15 publications receiving 33 citations.

Overview of the factors affecting the performance of vanadium redox flow batteries

Abstract: Redox flow batteries are being utilised as an attractive electrochemical energy storage technology for electricity from renewable generation. At present, the global installed capacity of redox flow battery is 1100 MWh. There are several parameters that significantly govern redox flow battery performance amongst which electrode activation, electrode material, felt compression, electrolyte additive, electrolyte temperature, membrane, and flow field design are notable. This review article presents an overview of the influence of individual components by comparing the performance of a parametrically modified cell with a default cell, which has 0% felt compression, inactivated electrode, zero electrolyte additives, and ambient condition operation. From the reviewed studies, electrode activation (thermal, chemical, laser perforation) and felt compression were identified as the most significant parameters. Electrolyte additive and flow field design were identified to be reasonably significant. Electrolyte temperature and membrane type were identified as the least significant amongst all the parameters. Based on this survey, a parametric matrix has been outlined that will aid researchers to identify appropriate parameters to focus research efforts onto improved redox flow battery performance.

Performance investigation of two stage Organic Rankine Cycle (ORC) architectures using induction turbine layouts in dual source waste heat recovery

Abstract: Improvement in performance of Organic Rankine Cycle (ORC) systems, particularly in the context of dual heat sources such as IC engines, leads to better return on investments. However, the choice of architecture to achieve the best performance is not evident from available literature. When two separate heat sources are present concurrently at different temperature levels with heat contents such as in IC engines, single stage pre-heated ORC and dual loop ORC are the two commonly deployed ORC architectures. In this study, two stage architectures: Series two stage ORC (STORC) and Parallel two stage ORC (PTORC) are analysed and their performance is compared against a single stage pre-heated ORC at sub-critical conditions in the utilization of high temperature (primary) exhaust gases (573–773 K) and low temperature (secondary) jacket water (353–393 K) representing IC engine waste heat conditions. Results show that STORC and PTORC are able to achieve the maximum net power output for an intermediate utilization of secondary heat source. The power output gains from two stage layouts improves significantly with a reduction in heat source temperature difference and for lower ratios of the heat available between the primary to secondary heat source. For a 2.9 MW natural gas IC engine operating at its design point, STORC delivers 8.5% more power output whereas PTORC delivers 0.3% less power output than pre-heated ORC. Compared to a dual–loop ORC, STORC presents a less complex and improved cycle architecture with a 13.1% increased power output and a 27.9% reduced heat exchanger requirements.

Effect of ambiance on the coal characterization using laser-induced breakdown spectroscopy (LIBS)

Abstract: The influence of surrounding gases, such as He, N2, atmospheric air, and Ar, and gas flow rate on the laser-induced breakdown spectroscopy (LIBS) characterization of coals in free space is studied. The atomic and molecular carbon (C2 and CN) emission intensities are observed to be higher in Ar and N2 ambiance. Quantitative analysis of carbon and ash content in different coal samples is carried out using the carbon bound atomic and molecular emission signals and the ash forming elements (Si, Fe, Mg, Al, Ca, Na, and K) signals. The sum of the LIBS emission of the all and major ash forming elements increased linearly with an increase in the ash content. Similarly, the ratio between the carbon signals (C I, CN, and C2) and the sum of major ash forming elements (Si, Al, Fe, and Ca) also showed a linear increase with the increase in carbon content in coal samples. The linear coefficient of regression, R2, was estimated to be 0.67, 0.58, and 0.85, and the root mean square of calibration samples was estimated to be 5.71, 5.82, and 5.57 wt% using the partial least square regression (PLSR) method for air (no flow), N2, and Ar atmosphere, respectively. The precision and accuracy of the carbon measurement in coal samples by the LIBS technique using the PLSR method were higher in the presence of Ar than air or N2 atmosphere due to the plasma shielding effect.

Laser-Induced Breakdown Spectroscopy Combined with Temporal Plasma Analysis of C2 Molecular Emission for Carbon Analysis in Coal.

Abstract: A benchtop laser-induced breakdown spectroscopy is demonstrated to determine the elemental carbon content present in raw coal used for combustion in power plants. The spectral intensities of molecular CN and C2 emission are measured together with the atomic carbon (C) and other inorganic elements (Si, Fe, Mg, Al, Ca, Na, and K) in the laser-induced breakdown spectroscopy spectrum of coal. The emission persistence time of C2 molecule emission is measured from the coal plasma generated by a nanosecond laser ablation with a wavelength of 266 nm in the Ar atmosphere. The emission persistence time of molecular C2 emission along with the spectral intensities of major ash elements (Fe, Si, Al, and Ca) and carbon emissions (atomic C, molecular CN, and C2) shows a better relationship with the carbon wt% of different coal samples. The calibration model to measure elemental carbon (wt%) is developed by combining the spectral characteristics (spectral intensity) and the temporal characteristics (emission persistence time of C2 molecule emission). The temporal characteristic studies combined with the spectroscopic data in the partial least square regression model have resulted in an improvement in the root mean square error of validation, and the relative standard deviation is reduced from 10.8% to 4.1% and from 11.3% to 6.0%, respectively.

Evaluation and optimization of a novel geothermal-driven hydrogen production system using an electrolyser fed by a two-stage organic Rankine cycle with different working fluids

Abstract: In this study, a novel system comprising of a two-stage organic Rankine cycle, driven by geothermal energy and coupled with a proton exchange membrane electrolyser, is investigated and optimized from thermodynamic and exergoeconomic viewpoints. Various working fluids are considered so as to ascertain the effects of thermophysical properties on the performance of the system. The electricity output from the two-stage organic Rankine cycle is employed to produce hydrogen through electrochemical reactions in the proton exchange membrane electrolyser. The effects are assessed on key parameters of variations in geothermal water temperature and the pressure ratio of high-pressure organic Rankine cycle turbine. Considering three distinct cases, a thorough optimization is performed utilizing a genetic algorithm. It is concluded that a 2-3 percent-point improvement in energy efficiency, as well as a 35% to 41% increase in hydrogen production and a 9.5% to 12% reduction in cost per unit exergy of hydrogen can be achieved via optimization. R123 is shown in the optimization to perform the best among the considered working fluids, with isopentane performing second best.

A review of laser-induced breakdown spectroscopy for plastic analysis

Abstract: With massive coal consumption in the industry, the increasing requirements for improving combustion efficiency and environmental protection raise widespread interests. Laser-induced breakdown spectroscopy (LIBS) shows the merits of high-speed, minimally destructive, simple preparation, etc. Combining it with the analytical chemistry methods have become a promising way for coal analysis. In this work, LIBS instruments for collecting coal spectra, pretreatment methods for coal samples, preprocessing of coal data, and analytical chemistry methods for coal analysis were summarized. Moreover, LIBS applications, including coal ranks, combustion efficiency, and environmental protection, are provided. Finally, this review proposes a description of limitations and the potential developing trend for this topic.

Vanadium redox flow batteries: Flow field design and flow rate optimization

Abstract: Vanadium redox flow battery (VRFB) has attracted much attention because it can effectively solve the intermittent problem of renewable energy power generation. However, the low energy density of VRFBs leads to high cost, which will severely restrict the development in the field of energy storage. VRFB flow field design and flow rate optimization is an effective way to improve battery performance without huge improvement costs. This review summarizes the crucial issues of VRFB development, describing the working principle, electrochemical reaction process and system model of VRFB. The process of flow field design and flow rate optimization is analyzed, and the battery attributes and metrics for evaluating VRFB performance are summarized. The focus of the research is the methods of flow field design and flow rate optimization, and the comprehensive comparison of battery performance between different flow field designs. Literature analysis shows that reasonable flow field design can improve the uniformity of electrolyte, improve battery attributes and metrics, and thus improve the overall performance of VRFB and reduce the cost.