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The diesel engine process including fuel injection, fuel spray, air and fuel mixing, ignition and combustion which influences its performance and emission characteristics. The fuel injection and fuel spray are important process as they are directly related to the quality of fuel which results into fluctuating the ignition and combustion characteristics. Ignition in a diesel engine occurs at the edge of the spray depending on the in-cylinder pressure and temperature. Experiments were conducted on a modified dual-fuel diesel engine (3.5 kW power) with fuel additives, diesel and hydrogen (gaseous fuel) at a stable speed of 1500 rpm. Spray behavior and ignition delay were analyzed to determine the impact of fuel additives in neat diesel combined with hydrogen. Additionally, for dual-fuel Cases, the ignition delay correlations provided for diesel engines have been modified as per the experimental results. The injection velocity was maximized with a 15–25% hydrogen substitution range because the fuel density was reduced to a minimum, but it was decreased with the addition of fuel additives. The SMD for hydrogen with neat diesel and diesel with fuel additives both increased up to 20% hydrogen substitution, whereas for higher hydrogen substitution, the Sauter mean diameter decreased. It was found that the addition of fuel additives in diesel resulted into an increased fuel injection velocity (3.3%) with reduced sauter mean diameter of 3.4% while with the lower substitution of H 2 (15%), a maximum increment of 32% in the injection velocity was seen as compared with neat diesel operation. With 15% hydrogen substitution, the change in pressure and density of diesel along with fuel additives accommodated the optimum spray penetration equivalent to neat diesel. In all Cases of hydrogen substitution, the experimental and theoretical values obtained for the chemical ignition delay were found to be consistent with one another except for 35% H 2 showing a maximum deviation of 0.2%. • Addition of fuel additives with higher hydrogen reduced the chemical delay. • TID reduced up to 25% hydrogen, increased with higher hydrogen substitution. • Injection velocity was found optimum in the range of 15–25% hydrogen substitution. • Spray penetration and sauter diameter increased up to 20% hydrogen substitution. [ABSTRACT FROM AUTHOR]

The present study is focused on the combustion behavior, performance and emissions of a modified diesel engine working on dual fuel mode with hydrogen as a gaseous fuel by the inclusion of tri-ethylene glycol mono methyl ether and alumina nanoparticles as fuel additives. The inclusion of tri-ethylene glycol mono methyl ether, alumina and hydrogen separately and simultaneously improved the net heat release with reduced cylinder pressure at high loads as compared with neat diesel. The brake thermal efficiency increased by 22.5% and 11.6% by the inclusion of tri-ethylene glycol mono methyl ether and hydrogen respectively at 50% load, when combined together, it was improved remarkably by 28.15%. The addition of alumina was responsible for a slight reduction in NO x formation at all loads, while it was incremented by hydrogen enrichment at the highest load as compared to pure diesel. The CO formation was incremented by the addition of alumina, while the CO 2 and HC formations were reduced up to 50% load, increased at 70% load. The CO, CO 2 , HC and smoke opacity were reduced with TGME and hydrogen enrichment, while the NO x formation was reduced up to 50% load, then increased at the higher load. • The H 2 enrichment incremented NHR by 21.7% at 356°CA. • A minimum ID of 11°CA was observed in case of D + TGME @5%. • BTE increased by 28.15% at a load of 50% for D + TGME @5% +H 2@35%. • For D + TGME @5% , combustion efficiency improved by 10.4%. • The HC formation was reduced by 21.8% for D + TGME @5% at 50% load. [ABSTRACT FROM AUTHOR]

The utilization of hydrogen as a gaseous fuel in CI engines in dual fuel mode, has gained significant interest due to its clean-burning nature, high energy share, and higher availability in nature. In this experimental study, hydrogen was used as a secondary fuel along with tri-ethylene glycol mono methyl ether (TGME) as a fuel additive in diesel to investigate the effects on the engine performances and emissions using a modified duel fuel diesel engine (power of 3.5 kW at 1500 rpm). It revealed that addition of hydrogen (30–35%) enhanced the brake thermal efficiency of the engine at each load conditions, but in accordance it also reduces with the lower hydrogen (15–25%). Reduction in oxides of nitrogen was observed with the hydrogen insertion up to 50% load while carbon mono oxide, carbon dioxide and un-burnt hydrocarbon were significantly reduced at entire load conditions. Further, the addition of fuel additive (TGME) enhanced the brake thermal efficiency at each loads. A reduced ignition delay was also observed by the inclusion of TGME and hydrogen due to pre-ignition of the fresh charge. Moreover, this study concluded that addition of 1% fuel additive in diesel with 25% of hydrogen at 30% load, performance and emissions were optimum. • Addition of TGME with higher H 2 enhanced the BTE at entire loads. • NO x reduced up to 50% loads with TGME, increased at highest load. • CO and HC emission at all loads reduced with 5% TGME and 35% H 2. • Use of 1% TGME with 25% H 2 at all loads, BTE and emissions were optimum. [ABSTRACT FROM AUTHOR]

Green hydrogen, a carbon-neutral fuel, has the potential to reduce atmospheric greenhouse gas and plays a vital role in mitigating climate change. Its potential is immense in renewable-rich Asian economies, however, its production is yet to start with key factors such as safety parameters, resources, proper government incentives, and public acceptability affecting its optimal generation. This study employs three multi-criteria decision-making approach like analytic hierarchy process (AHP), decision-making trial and evaluation laboratory (DEMATEL), and Fuzzy-AHP followed by the sensitivity analysis to identify and prioritize the robustness of the five primary potentials (social, political, economic, technical, and environmental). Subsequently, categorized into 22 sub-potentials of green hydrogen and ideal renewable resource for the sustainable development objective of India. The results of the DEMATEL analysis suggest that the social is the key predictor and the last one is Technical. The Fuzzy-TOPSIS method suggests that solar is the best renewable energy resource followed by wind, small hydro, and biomass energy. Hence, the government's intervention and robust policy frameworks are required to increase its production with special emphasis on cost considering solar energy. The finding of this study will guide the governments, energy sector players, producers, environmental advocacy groups, and users to make a strategic decision regarding the choice of the most viable source of renewable energy to achieve the targets of sustainable development Goals (SDGs-7). • Potentials for Green Hydrogen (GH) in India. • Source of Renewable energy for Green Hydrogen production. • Integrated framework for prioritizing the GH potentials. [ABSTRACT FROM AUTHOR]

Gasification has the potential to convert biomass into gaseous mixtures that can be used for hydrogen production. Thermal gasification and supercritical water gasification are commonly used thermochemical methods for conversion of biomass to hydrogen. Supercritical water gasification handles wet biomass, thus eliminating the capital cost-intensive drying step. Thermal gasification is considered as an alternative means of producing hydrogen from microalgae where biomass has to be dried before gasification. The authors developed techno-economic models for assessment of the production of hydrogen through supercritical gasification and thermal gasification processes. Techno-economic assessment was based on developed process models. Equipment was sized and costs were estimated using the developed process models, and the product value was determined assuming 20 years of plant life. The economic assessment of supercritical water and thermal gasification show that 2000 dry tonnes/day plant requires total capital investments of 277.8 M$ and 215.3 M$ for hydrogen product values of $4.59 ± 0.10/kg and $5.66 ± 0.10/kg, respectively. The relatively higher yield obtained in supercritical water gasification compared to thermal gasification results in lower product value of hydrogen for supercritical water gasification, thereby making it more desirable. This cost of hydrogen is about 4 times the cost of hydrogen from natural gas. The sensitivity analysis indicates that biomass cost and yield are the most sensitive parameters in the economics of the supercritical or thermal gasification process; this signifies the importance of algal biomass availability. The techno-economic assessment helps to identify options for the production of hydrogen fuel through these novel technologies. • The production of hydrogen from thermochemical algal conversion is assessed. • Data-intensive techno economic model is developed to determine the product value. • The cost of hydrogen from algal thermochemical processing varies from 4.59 to 5.66 $/kg. • The impact of CO 2 tipping fee on cost of hydrogen was assessed. [ABSTRACT FROM AUTHOR]

The worldwide energy demand is steadily increasing and estimated to be doubled by the year 2050 due to a continuous hike in economies and population. A large part of the global energy requirement procures using traditional energy sources such as fossil fuels, which are non-renewable. Also, their excessive consumption imparts negative impacts on the environment by CO 2 , and CO emissions, which constantly increase the average global temperature. Therefore, the need for a more reliable, sustainable, inexpensive, renewable and environmentally-friendly form of energy is imperative. From these perspectives, hydrogen energy is emerging as one of the most promising alternatives to overcome rising energy demand with a zero-carbon footprint. Herein, various layered double hydroxides (LDH) nanocomposite owing to their attractive physicochemical properties and synergistic effect with other materials in the field of hydrogen production are reviewed. Why the class of LDHs materials is critical and their ideographic properties which make them promising materials in the field of water splitting via photocatalysis and electrocatalysis are also discussed. The synthetic methods of LDHs based nanocomposites fabrication are summarized. Various challenges and strategies from the viewpoint of a different method of hydrogen production through LDHs are reported. Additionally, multiple techniques like surface plasmon resonance (SPR), heterojunction formation, and doping with co-catalyst to increase the efficiency for photocatalytic hydrogen production are also presented. Hopefully, this review will help the readers explore highly efficient, inexpensive and stable LDH catalysts toward photocatalytic water splitting. • Current issues related with energy requirements and green energy sources. • Recent advancements in LDH based electrocatalysts and photocatalysts for water splitting. • Challenges in conventional photocatalysts based water splitting. • Strategies to enhance photocatalytic hydrogen evolution and oxygen evolution reactions. [ABSTRACT FROM AUTHOR]

This paper presents a model to perform energy balances and estimate hydrogen conversion efficiency from UCG-based syngas. The model was developed for H 2 production from UCG-based syngas with and without CCS, along with the co-production of electricity and steam in a conventional combined cycle plant. In this paper, at base case conditions (H 2 O-to-O 2 injection ratio of 2 and a steam-to-carbon ratio of 3), the coal-to-H 2 conversion efficiency is estimated to be 58.1% for UCG with and without CCS. For the plant configuration involving no CCS, in addition to H 2 production, approximately 4.7% of coal energy is converted to electricity that is exported to the grid. In the case of UCG–CCS, a minor energy penalty is incurred; wherein the electrical energy exported per unit coal energy is around 2.4%, with a CO 2 capture efficiency of 91.6% being achieved. The H 2 conversion efficiency decreases with rise in H 2 O-to-O 2 injection ratio, but increases with fall in steam-to-carbon ratio. Effect of ground water influx in UCG on the H 2 conversion efficiency is minor, whereas H 2 separation efficiency in the pressure swing adsorption (PSA) unit has a major effect. [ABSTRACT FROM AUTHOR]