Vaibhav Bahadur

Growing energy demands and renewable integration are stressing the aging power grid infrastructure. Lignocellulosic oil-impregnated paper is widely used in power transformers but suffers from critical limitations, such as low dielectric strength, mechanical strength, and thermal conductivity, causing premature transformer failures. Here, we demonstrate a superior electrically insulating oil-impregnated paper design using the naturally anisotropic structure of densified wood veneer to achieve nanosized channels of oil that efficiently disrupt electrical breakdown pathways. The developed oil-impregnated densified wood (ODW) creates aligned cellulose fibers with 166 ± 87-nanometer oil nanochannels, achieving record dielectric strength of 105 kilovolts per millimeter. The structure also delivers a mechanical strength of up to 384 megapascals and a thermal conductivity of 0.33 watts per meter per kelvin, enabling enhanced longevity upon thermal aging tests. The ODW could replace conventional transformer insulation to enhance power transformer performance and improve lifetime. Moreover, its anisotropic oil-filled nanochannel design offers a general strategy for hybrid dielectrics in medium- and high-voltage applications.

Global research uses nano- and microparticles to produce innovative insulation for winding insulation, electromobility, anticorona paint, transformer insulation, and bushings. Scientific, multifunctional research on materials provided the engineering data required to design manufacturable insulation. This article overviews the holistic approach needed to successfully develop insulation materials by examining specific insulation systems from recent research.

ABSTRACT This investigation addresses the effect of particulate additives on the electrical breakdown strength of the oil impregnated insulation paper system. The morphological complexity is addressed by converting data from scanning electron microscope images to a data set suitable for numerical simulation analysis. Then, by using the conventional oil‐triggered breakdown assumption, the breakdown strength of the proposed hybrid insulation system was calculated. As a result, it demonstrates that the introduction of particles can redefine the electric field distribution in the hybrid insulation system under study. Consequently, a higher applied voltage is needed for the electrical breakdown to occur in the hybrid system with proper selection and addition of particles. This analysis method builds on the existing understanding of the electrical breakdown phenomena for oil impregnated insulation paper system, explains recent experimental data and supports improvements of material design in the future.

The continuous accumulation of carbon dioxide (CO2) in the atmosphere represents one of the greatest challenges to achieving a sustainable and circular carbon economy. Traditional capture technologies based on aqueous amines are effective but suffer from high energy penalties, corrosion, and environmental toxicity. In contrast, bio-based polymers offer renewable, low-impact alternatives for CO2 capture and subsequent transformation. Chitin and its deacetylated derivative chitosan emerge as particularly promising due to their abundance in marine waste, intrinsic amine functionalities, and compatibility with mild processing routes. Their molecular structure enables reversible carbamate and bicarbonate formation, and they may also serve as precursors to nitrogen-doped carbon materials with enhanced porosity and catalytic activity. This review integrates methodological details on the transformation of chitin and chitosan into N-doped carbons, evaluates their performance relative to other biopolymers and traditional CO2 capture technologies, and discusses challenges such as moisture sensitivity, limited surface area, and scalability. Opportunities for industrial implementation and pathway integration are explored to provide a balanced, forward-looking perspective on the role of chitin-based systems in sustainable carbon capture and utilization.

Recent research shows that a five-time enhancement in through-plane thermal conductivity of the oil-paper insulation in transformers can double their life by decreasing hotspot temperatures. This can be achieved by developing novel insulation paper with improved through-plane thermal conductivity without compromising other key paper attributes such as dielectric breakdown strength, tensile strength, and thermal degradation rate. The present study broadens the design space for advanced transformer insulation paper with improved and balanced thermal, mechanical, and dielectric properties by incorporating turbostratic boron nitride (BN) particles. A simulation model based on Scanning Electron Microscopic (SEM) imaging was used to explain the dielectric breakdown strength and through-plane thermal conductivity enhancement of the proposed material. Depending on the material formulation, the proposed BN insulation paper has 2 to 3 times greater through-plane thermal conductivity, 20 %–30 % higher dielectric strength, 25 %–50 % greater tensile strength and approximately 30 % smaller relative permittivity than the commercial insulation paper with similar thermal degradation rates.

Abstract Carbon dioxide (CO2) hydrates are crystalline solids of water and CO2 that form around 0 °C and at moderate pressures (~ 400 psi) from mixtures of CO2 and water. Hydrates offer an avenue for large-scale, long-term carbon sequestration. Recent work from this group reported ultrafast formation of CO2 hydrates in a bubble column reactor using magnesium as a passive nucleation promoter. While that study utilized pure CO2, we presently study hydrate formation from a binary mixture of CO2 (90% by volume) and nitrogen (10% by volume). Additionally, we study the impact of bubble delivery via a micrometer-sized pore sparger and contrast it with bubble delivery using a straight tube. We report sequestration rates as high as 1163 g h−1 L−1 MPa−1, which is within 10% of the fastest reported rates (using pure CO2). Significantly, this rate is achieved using synthetic ocean water, which itself has an inhibiting effect on hydrate formation. We find that use of the sparger increases the density of hydrates formed and the conversion of CO2 into hydrate. Overall, the high formation rates achieved with impure CO2 vastly improve the techno-economics of CO2 hydrates-based sequestration since purification of CO2 is energy and cost intensive.

Abstract CO2 hydrates are crystalline solids of water and CO2 that form around 0°C and elevated pressures from mixtures of CO2 and water. We report the fastest-even formation rate of carbon dioxide (CO2) hydrate slurry without the use of any conventional chemical promoters or mechanical agitation. This is achieved by sparging CO2 gas as bubbles (size in the order of 100 μm) at high flowrates in a water column in a bubble column reactor. Importantly, the enhancement in the CO2 sequestration rate (based on net gas consumption) is achieved using synthetic oceanwater, which has traditionally slowed hydrate formation. Use of a 2μm-pore sized sparger results in a three orders of magnitude increase in gas-liquid interfacial area compared to our previous studies which used millimetric sized bubbles delivered by a tube into the reactor. Enhanced bubbling continuously renews the gas-water-hydrate interface and improves the heat/mass transfer. We measure CO2 gas consumption rate and hydrate slurry composition (hydrate, CO2 dissolved in water, trapped CO2 gas) as a function of the bubble delivery method, operating pressure, and gas flowrate and duration. Our best results show that hydrate slurries can be formed in 10s of seconds; we report sequestration rate of 2.4 kg h−1 L−1 MPa−1, which is 2X higher than our previous best result. Overall, these results further improve the prospects of large-scale carbon sequestration via ultrafast CO2 hydrate formation.

Abstract Ammonia is a promising carbon-free hydrogen carrier and can have a meaningful role in the emerging hydrogen economy. This study conducts technical and techno-economic modeling of an ammonia production facility, which produces ammonia from either blue or green hydrogen using the Haber-Bosch process. Three separate cases are modeled; these account for the energy consumption of ammonia production being met by natural gas (with carbon capture), renewables-based electricity and hydrogen, respectively. Process modeling is conducted using Aspen Plus® to estimate key process parameters and energy/water consumption. This modeling serves to inform the technoeconomic analysis which estimates the levelized cost of ammonia production and the economics of an ammonia producing plant. Our analysis shows that a plant purchasing hydrogen is economically viable in the current ammonia market when the cost of hydrogen is < $4.66/kg H2. Furthermore, our results indicate that renewables-based electricity powered ammonia production has the most favorable economics with low impact of unfavorable pricing conditions on project economics.

Abstract Surfactant-aided electrolysis and pool boiling systems typically exhibit premature film formation, which reduces the critical current density (CCD) and critical heat flux (CHF), respectively. Unlike the conventional Helmholtz instability, film incipience in these systems was previously formulated by equating the gas/vapor generation rate with the non-coalesced bubble advection rate from the surface. This study proposes new correlations for CCD and CHF, which address the limitations of previous studies that neglected bubble-bubble interactions and considered the drag coefficient independent of bubble Reynolds number. Presently, the drag coefficient is calculated using the drag law for a spherical bubble swarm with appropriate bubble diameters and Reynolds numbers (Re) before film formation. Correlations based on nonlinear solutions of Re and bubble diameter from experimental data are arrived at, which state that CHF is proportional to the square root of bubble diameter (<10% error), and CCD is proportional to bubble diameter to the power of 1.21 (<5% error). At higher surfactant concentrations, the accuracy of the proposed correlations improves because foaming primarily influences the film incipience phenomenon, rather than conventional bubble column instability. Overall, the proposed correlations in the present study elucidate the physics of film formation in surfactant based electrolysis and pool boiling systems.

Increasing the thermal conductivity of the oil-paper insulation system can significantly extend the thermal life of transformers by enabling effective heat removal, which reduces high temperature-induced insulation degradation. This research shows that the addition of nominally 25 µm diameter boron nitride particles can achieve sufficient increase in through-plane thermal conductivity of insulation paper to an extent that doubles the transformer thermal life. Importantly, the dielectric breakdown strength can also be enhanced by adding boron nitride particles to the developed insulation paper. Moreover, applying lignin containing cellulose microfibrils into the paper can compensate for the paper strength loss due to the disruption of hydrogen bonding by the addition of BN particles. Building on these findings, we outlined a pathway for a boron nitride-based enhanced insulation system with outstanding through-plane thermal conductivity, enhanced dielectric strength, an appropriate dielectric constant and the needed tensile strength. Additionally, thermal aging experiments showed that the proposed material can have a reasonable thermal life under transformer operating conditions. Overall, this research shows that the mix of thermal, mechanical, and dielectric properties can be successfully tuned to achieve a beneficial insulation system which can significantly enhance the transformer life. As the summary, the proposed material has three times better through-plane thermal conductivity (0.76 W/m·K vs. 0.2 W/m·K), 23 % higher dielectric strength (84.6 kV/mm vs. 65.3 kV/mm), 35 % greater tensile strength (71.26 N·m/g vs. 45.91 N·m/g) and 33 % smaller relative permittivity (3.7 vs. 5.5) than the commercial insulation paper with similar thermal degradation rates.

Hydrates are ice-like crystalline structures of hydrogen-bonded water molecules that trap a guest molecule. Hydrates have several applications, including carbon sequestration, gas separation, desalination, etc. A classical major challenge associated with artificial hydrate formation is the very long induction time to nucleate hydrates. This has spurred the development of multiple chemical, mechanical, and electrical strategies to promote nucleation. Presently, we discover that magnesium can significantly promote the nucleation of tetrahydrofuran (THF) hydrates. While magnesium has been recently shown (by our group) to promote the formation of carbon dioxide hydrates (gas-liquid system), this study discovers that the benefits of magnesium extend to liquid-liquid hydrate systems as well. Experiments show that magnesium reduces the induction time for THF hydrate nucleation with deionized (DI) water and saltwater by six and eight times, respectively. Magnesium-induced nucleation rate enhancements for hydrate formation with DI water and saltwater were 12 and 99 times, respectively. Importantly, we demonstrate near-instantaneous nucleation when magnesium is introduced after the hydrate-forming system reaches suitable thermodynamic conditions. We conduct statistically significant measurements of nucleation and XPS analysis to identify the underlying mechanisms responsible for nucleation. We discuss multiple phenomena at play, including chemical and mechanistic promotion pathways. The formation of hydrogen bubbles and the presence of magnesium ions in solution are seen as important to magnesium-based nucleation promotion. Importantly, very low amounts of Mg are consumed in this process unlike in traditional chemical promotion techniques. Overall, our discovery can enable on-demand nucleation of liquid-liquid hydrate systems, which is critical to the development of several applications.

Abstract Significant carbon sequestration capacity (up to 10 Gigatons/yr) will be needed by 2050 to limit the Earth’s temperature rise to < 1.5 °C. The current worldwide capacity is ∼40MT/yr, which highlights the need for the development of new and scalable sequestration approaches. One novel technology for long-term sequestration of CO2 is the deposition of CO2 hydrates (ice-like solids made with water and CO2) on the seabed (under marine sediments or with artificial sealing). This involves rapid formation of CO2 hydrate slurries in a bubble column reactor (BCR) by bubbling CO2 gas at high flow rates in a BCR with the unreacted CO2 being recirculated; this approach is being pioneered by the present research group. This study utilizes recent experimental results on ultra-fast hydrate formation to conduct a techno-economic analysis of the hydrate slurry-making process. All analysis is conducted for a 1 Megaton/yr sequestration project, which is expected to run for 30 years. Our analysis shows that the total cost of hydrate slurry production is $16.2/ton. Such projects would require an initial investment of $74M, and the energy requirement will be 641 MWh/day. Contributions of each part of the process to the total cost are identified. Our results show that gas recirculation in a BCR contributes minimally (0.04%) to the overall energy requirement. Furthermore, the cost of BCR is only 0.3% of the total investment cost. This suggests that a low conversion of gas into hydrates in each pass of the BCR is not detrimental from a techno-economic standpoint. The findings of this study set the stage for more detailed analysis of hydrates-based sequestration, which is essential to add this technology to the existing bank of established carbon sequestration solutions.

Abstract Novel energy efficient and scalable carbon capture and sequestration technologies are critical to meeting the goals of the Paris Agreement. In this study, we present a first-order system-level assessment of an integrated carbon capture and carbon sequestration plant that couples electrochemical CO2 capture from oceanwater with co-located long-term carbon sequestration as CO2 hydrates (ice-like solids) on the seabed. Separate recent experimental results associated with electrochemical capture and hydrate formation form the basis for this energetics-focused analysis, which evaluates power consumption of all the key components associated with capture and sequestration. Hydrates can be formed from both pure water as well as seawater, and the implications of including a desalination plant to provide pure water for hydrate formation are studied. All analysis is conducted for a 1 plant which captures and sequesters 1 megaton CO2 annually. Our results indicate the carbon capture will consume significantly more energy than carbon sequestration despite the use of a low-energy consuming electrochemical technique. From a sequestration standpoint, there are clear benefits to forming hydrates at high pressures, since the elevated formation rates reduce the number of hydrate formation reactors significantly. It is also seen that the addition of a desalination plant to provide pure water for hydrate formation (which speeds up hydrate formation) will not affect the energetics of the overall process significantly; however the CAPEX and operational aspects of including a desalination plant need to be analyzed in greater detail. Overall, this study seeds a novel CCS concept which can be deployed via decommissioned oil-gas platforms to capture CO2 from surface oceanwater and store CO2 right below on the seabed after appropriate sealing (artificial or natural).

We report ultrafast formation of carbon dioxide (CO 2 ) hydrate foam without the use of any conventional chemical promoters or mechanical agitation. Our 6× enhancement in the CO 2 sequestration rate (based on net gas consumption) results from the high flow rate sparging of CO 2 gas in water in an open system (constant gas inflow/outflow) in the presence of magnesium. This approach continuously renews the gas–water–hydrate interface, thereby increasing the growth rate. The CO 2 gas consumption rate (for hydrate foam formation) and foam composition (hydrate, CO 2 dissolved in water, trapped CO 2 gas) are experimentally quantified versus various parameters, including thermodynamic (pressure), CO 2 flow-related parameters (flow rate, duration), water composition, and quantity of magnesium. The maximum measured CO 2 sequestration rate (time-averaged) of 1276.5 g h –1 L –1 MPa –1 is 6 times higher than the fastest reported instantaneous rate. Importantly, we show rapid foam formation with saltwater, which will greatly improve the techno-economics. We develop an analytical framework to evaluate the composition of foam. We discover that the reactor pressure is a key determinant of the sequestration rate under high flow rate conditions, with magnesium playing a catalytic role. Overall, such foams enable new approaches to transport and sequester CO 2 and benefit other applications that are hindered by notoriously sluggish hydrate formation.

Degradation of insulation paper is a key contributor to the failure of power transformers. Insulation degradation accelerates at elevated temperatures, which highlights the potential for better thermal management to prolong life. While several studies have analyzed the benefits of high thermal conductivity oil for reducing temperatures inside a transformer, this study is an initial assessment of the benefits of high thermal conductivity paper on transformer life. Blending particulates with cellulosic fibers offers a pathway for high thermal conductivity paper (with good dielectric properties), which can reduce internal temperatures. Presently, life extensions that can be achieved by the use of such thermally conducting papers were estimated, with the thermal conductivity of the paper being the key parameter under study. The analytical-numerical thermal model used in this study was validated against experimental measurements in a distribution transformer, adding confidence to the utility of the model. This model was then used to provide estimates of hot-spot temperature reduction resulting from the use of papers with higher thermal conductivity than baseline. Transformer life was predicted conventionally by tracking the degree of polymerization of paper over time, based on an Arrhenius model. Results indicate that increasing the thermal conductivity of paper from 0.2 W/mK (baseline) to 1 W/mK reduces the hot spot temperature by 10 °C. While degradation significantly depends on the moisture and oxygen content, the model shows that such a temperature reduction can increase life for all conditions, by as much as a factor of three.

Abstract Gigascale carbon capture and sequestration (CCS) is increasingly seen as essential to meeting the targets of the Paris Agreement. Sequestration of CO2 as CO2 hydrates (ice-like materials of CO2 and water) has received research attention recently. CO2 hydrates form at medium pressures and temperatures close to freezing from a water-CO2 gas mixture. Bubble column reactors (BCR) are a preferred way of rapidly forming CO2 hydrates. This study uses a recently-developed and validated model to predict performance of a BCR for CO2 hydrate formation from flue gas (CO2/N2). In particular, two performance parameters are analyzed, the gas consumption rate for hydrate formation, and the fraction of CO2 that can be converted to CO2 hydrates (conversion factor). Extensive parametric analysis is conducted to study the influence of pressure, temperature, CO2 mole fraction at inlet, inlet gas flow rate, reactor height and reactor diameter on CO2 hydrate formation rate. Across the range of simulations conducted in this study, the maximum reported hydrate formation rate is 71 ton/yr and the highest conversion efficiency is 67.8%. It is seen that both the performance parameters improve with increasing pressure, decreasing temperature and increasing inlet mole fraction of CO2. Increasing gas flow rate increases the gas consumption rate (i.e., hydrate formation rate) but reduces the conversion factor. This suggests that the operation of BCR for gas separation should involve low flow rates but that high flow rates should be used to synthesize hydrates for CO2 sequestration. An increase in reactor volume by increasing the height or diameter, improves hydrate formation on both performance parameters (rate, conversion factor).

Abstract This work analyzes the techno-economic factors associated with the production of blue H2, and hydrates-based capturing of CO2 produced by sorption-enhanced steam methane reforming (SESMR) of methane from landfill gas (LFG) across various counties in Texas. The SESMR system is coupled with a hydrates-based carbon capture system, and the energy and cost of setting up and running such a hydrates-centered capture facility have been estimated. In doing so, the amount of water and energy required to compress and refrigerate the gas down to hydrate-forming conditions and the capital and operating costs involved in setting up and running such a facility are evaluated in detail. The cost of producing hydrogen (without the carbon capture system) from this analysis is estimated at $0.5/kg of H2. The total cost (CAPEX+OPEX) for capturing one metric ton of CO2 ranges from $96 (Harris County) to $145 (Brazoria County). Notably, adding a thermodynamic promoter such as Tetrabutylammonium bromide (TBAB) to the hydrate precursor mixture to achieve favorable thermodynamic formation conditions increases the overall cost ($107–$137/metric ton of CO2 captured). This can be attributed to the increased water requirement necessitating a higher number of reactors, higher refrigeration capacity, and labor costs. The minimum hydrogen cost required for a positive combined net present value (NPV) for a coupled SESMR + hydrate-based carbon capture system for a 30-year project duration is estimated at $0.9/kg and $2.4/kg of H2 for Harris and Brazoria counties, respectively. Furthermore, a 5-year payback period would require a minimum cost corresponding to $1.35/kg (Harris) and $4.95/kg (Brazoria) of H2, demonstrating that the coupled system would be economical only for counties that have a significant hydrogen production potential.