Publications

This paper discusses the need for green energy and the critical minerals needed for green energy production and their geological occurrences with a special focus on  lithium based minerals .

Thermochemical energy storage is emerging as a promising seasonal thermal energy storage technology. Strontium Bromide has recently become one of the most used salt hydrates for the salt-hydrate and moist airbased open thermochemical energy storage system. This article suggests that radial flow fixed bed reactors offer advantageous configurations owing to their lower pressure drop without compromising thermal performance. Four possible configurations of radial flow fixed bed reactors, Inward flow Π-type, Inward flow Z-type, Outward flow Π-type, and Outward flow Z-type, are analyzed in detail. Energy efficiency, exergy efficiency, pressure drop, and non-dimensional constant named non-uniformity are used as performance metrics for comparing the proposed configurations with four different combinations of flow rates and aspect ratios. It is found that the type of the reactor configuration (Π-type or Z-type) has a negligible impact on the performance, with a maximum change of 4% in the energy efficiency during the hydration phase. The inward and outward flow arrangements exhibit considerable differences in performance, with inward flow having 3.5 times higher exergy efficiency than outward flow. The π-type configuration shows the highest non-uniformity of -0.22 for an aspect ratio of four, with a flow rate of 50 m3/h.

This study experimentally investigates the scarcely studied stratified, oil-based sensible thermal energy storage (STES) tank, to examine the heat retention capability of Hytherm-600 silicone oil during the standalone period and its heat dispatchability during the discharging process. To conduct an experimental study on the thermic oil, a vertical cylindrical tank with a helical discharging coil fitted inside is used. Three different oil charging temperatures (50, 70, and 90 °C), and three different discharging flow rates (water) through the helical coil (0.5, 1.25, and 2 L/min) have been considered. The thermal stratification phenomena in oil and the evolution of thermocline have been investigated. Results indicate the formation of a thermocline zone of 154 mm thickness in the lower portion of the tank within 3 h from the commencement of the stand-alone period. The discharging operation fluctuates the thermocline stability in the storage medium (i.e., commercial thermic oil Hytherm-600). During the discharging operation, a water flow rate of 0.5 L/min through the helical coil led to higher discharging efficiencies owing to better heat transfer attributable to the higher water residence time inside the coil. For the aforesaid water flow rate, the average discharging efficiencies are 85.6%, 75.6%, and 81.6% for the charging temperatures of 50, 70, and 90 °C, respectively. Finally, the primary thermocline thickness is found to be constant at 82 mm following the splitting of the initial thermocline during the discharging operation.

A marine section from Um Sohryngkew riverbasin, in Meghalaya,  have been studied for serach of fullerenes and associated carbon polymorphs .  This section is known for Ir-enrichment with an order of magnitude enhancement of Ir and Os, accompanied by unambiguous extinction of planktonic foraminifera, is found in a cm thicklimonitic clay layer in this section..Peak iridium concentration is found to be 13 ng/g. Os/Ir andNi/Ir are estimated to be 0.37 and 196000 respectively.  We reported here the first observation of C60 fullerenes and nano-diamonds in in the iridium-rich Cretaceous-Palaeogene (K-Pg) boundary layer from the Um-Sohryngkew river section of Meghalaya.

Book review on the book written by Professor Jagdish Sinha as a part of History of Science program of Indian National Science Academy, in which I serve as a council member. The reprint is attached herewith for ready reference.

In this study, the evaluation of carbonaceous fine particulate matter (C-PM) was conducted using the SAFAR-India regional model. Two emission inventories were utilized: the newly developed SAFAR inventory and the global EDGAR-HTAP inventory, both for the year 2018. The simulation aimed to capture the seasonal and spatial patterns of black carbon (BC) and organic carbon (OC) concentrations. To validate model results, surface meteorological parameters, and C-PM concentrations were compared with the MERRA reanalysis data for the Indian region. Model simulated surface C-PM concentration with SAFAR emission inventory is found to be slightly overestimated (1.10), whereas simulated results with EDGAR emission inventory is significantly underestimated as compared to MERRA data. Model-simulated meteorological parameters showed a better correlation with MERRA reanalysis. Simulated geographical patterns of seasonal mean C-PM with SAFAR emission inventory exhibit quite a better comparison with MERRA reanalysis as against EDGAR simulated results. However, some differences in the present results are visible, particularly over the IGP region, as compared to MERRA data, but they are mainly attributed to a significant difference in the special resolution of present results (much finer) as compared to coarser MERRA data. In the Indo-Gangetic Plain (IGP) region, the concentration of BCSF and OCSF (BC and OC with SAFAR emission, respectively) show the peak during the winter, followed by the post-monsoon season. Although the correlation coefficients of hourly time series of surface BCSF and OCSF concentrations with MERRA over India are high (0.92 and 0.88), the poor RMSE, is attributed mainly to different scales of resolution. The model simulated BC, and OC concentrations with SAFAR emission input capture the pattern of spatial distribution reasonably well. The present evolution of BC and OC will help to better quantify their impact on climate and atmospheric conditions over the Indian region.

The transition trajectory of India's two-wheeler (2W) vehicle segment is studied using a sequential modelling framework for projecting sub-segment-wise 2W fleet, energy demand, and associated CO2 emissions. Road density per capita was identified as a more significant explanatory variable than GDP per capita in estimating 2W fleet size in India. The elasticity method was used to evaluate the 2W vehicle saturation level based on five different indirect parameters. It was found that population density had the highest impact (48%), followed by urbanization (31%) and adult population share (16%). The impact of the total cost of ownership was negligible. The mean 2W vehicle saturation level was calculated to be 314 while the ownership was found to be 207, 265, and 297 vehicles per 1000 people by 2030, 2040, and 2050, respectively. Scooters were found to be leading the e-transition of 2Ws but a successful e-transition of India's 2Ws would not be achieved without transitioning the motorcycles. Two motorcycle clusters were identified that offer economies of scale towards e-transitioning. Closer scrutiny of six plausible e-transition scenarios showed that a 50% penetration of E−2Ws is unattainable before 2045. The biggest obstacle in achieving high E−2W penetration in India would be the limited capacity to supply indigenously produced vehicles. A high import dependence on battery technology and critical raw materials would limit the energy transition and diversification of the Indian road transport sector. India should follow the mass adoption-driven diffusion pathway in the short-to-medium term and the affordability-constraint diffusion pathway in the long term to achieve the best results in terms of reduction in energy demand and associated emissions for the 2W segment. The gains from the e-transition of the road transport sector would not be substantial without a simultaneous transition in the country's electricity generation mix away from coal-based thermal power.