This paper reviews the literature available concerning the energy balance of internal combustion engines operating on alternative fuels. Global warming and energy crisis are among the most important ...issues that threaten the peaceful existence of the man-kind. More usage of alternative fuels and energy loss minimization from automotive engines can be an effective solution to this issue. The energy balance analysis gives useful information on the distribution of supplied fuel energy in the engine systems and identifies the avoidable losses of the real engine process with respect to ideal process. It is a very widely used tool, mostly used for the layout of the engine components. The basic energy balance theory has been discussed in details along with the variations in energy balance approaches and terms. The wall energy loss may vary to a great extent depending on the selection of heat transfer correlations. The theoretical energy balance also explored in this paper with help of thermodynamic models. There are some significant variations observed in energy balance when the engine operating fuel is changed and devices like turbocharger, supercharger etc. are used to boost the intake air pressure. The review extends to the energy balance study of low heat rejection engines (LHR) as well as the effects of engine variables and design factors on energy balance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One ...of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen–oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M–O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for these catalysts.
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Increasing demand for fossil fuels due to the luxurious lifestyle, significant growth of population, transportation and the basic industry sectors has caused serious environmental problems. Moreover, ...a rapid decline in the fossil fuels has led scientists and researchers to look for new alternatives. In this regard, alternative fuels such as biofuels are becoming important increasingly due to environmental and energy concerns. Biofuels are commonly referred to as first generations, which are produced primarily from food crops. However, the use of edible oil to produce biodiesel in many countries is not feasible in view of a big gap in the demand and supply of such oils for dietary consumption.
This paper critically reviews the facts and prospects of biofuel utilization especially, three edible biodiesels namely soybean, rapeseed, palm and two non-edible viz. jatropha and cottonseed to reduce engine exhaust gas, noise emission and petro dependency. Based on various biofuel feedstocks, this paper generally found that biodiesel fuels are considered as offering many benefits, including sustainability, reduction of greenhouse gas emissions and many harmful pollutants along with noise emission, regional development, social structure and agriculture, and security of supply.
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Hydrogen can be transported via long distances based on Liquid Organic Hydrogen Carriers (LOHC). Such a transport is realized based on a two-step cycle: (1) loading/storage of hydrogen ...(hydrogenation) into the LOHC molecule and (2) unloading/release of hydrogen (de-hydrogenation). During the storage period, hydrogen is covalently bound to the respective LOHC. Since the (optimal) LOHC is liquid at ambient conditions and shows similar properties as crude oil based liquids (e.g. diesel, gasoline), it can easily be handled, transported and stored; thus a stepwise implementation using the existing crude oil based infrastructure would be possible. Against this background this paper reviews the current knowledge in hydrogenation and de-hydrogenation of various LOHC. Therefore, a variety of LOHC is evaluated based on their properties and compared to each other. By applying different evaluation criteria representing the requirements of the three different application areas (energy-storage, energy-transport, mobility application), the LOHCs can be assigned to a field they suit best. The analysis shows that the most promising LOHC candidates to date are dibenzyltoluene for energy-transport and energy-storage as well as N-ethylcarbazole for mobility applications. In addition, a use of toluene in the transport sector is also conceivable. Methanol can potentially be applied in all three application fields due to its properties if a compromise between de-hydrogenation temperature and gas flow can be achieved based on further R&D-activities. For future implementation phenazine and formic acid show great potential, but also additional R&D especially regarding catalysis and solvents is necessary.
•LOHC provide a sustainable solution to store and transport hydrogen.•Assessment of eight selected LOHC for using in different application areas.•Overview of important chemical and economic properties of the selected LOHC.•Topics for further research on improving LOHC storage materials.
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Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and ...production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO2 reduction, and N2 reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.
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Energy technologies have attracted great attention due to the fast development of sustainable energy. Biodiesel technologies have been identified as the sustainable route through which overdependence ...on fossil fuels can be reduced. Biodiesel has played a key role in handling the growing challenge of a global climate change policy. Biodiesel is defined as the monoalkyl esters of vegetable oils or animal fats. Biodiesel is a cost-effective, renewable, and sustainable fuel that can be made from vegetable oils and animal fats. Compared to petroleum-based diesel, biodiesel would offer a non-toxicity, biodegradability, improved air quality and positive impact on the environment, energy security, safe-to-handle, store and transport and so on. Biodiesels have been used as a replacement of petroleum diesel in transport vehicles, heavy-duty trucks, locomotives, heat oils, hydrogen production, electricity generators, agriculture, mining, construction, and forestry equipment. This book describes a comprehensive overview, covering a broad range of topics on biodiesel technologies and allied applications. Chapters cover history, properties, resources, fabrication methods, parameters, formulations, reactors, catalysis, transformations, analysis, in situ spectroscopies, key issues and applications of biodiesel technology. It also includes biodiesel methods, extraction strategies, biowaste utilization, oleochemical resources, non-edible feedstocks, heterogeneous catalysts, patents, and case-studies. Progress, challenges, future directions, and state-of-the-art biodiesel commercial technologies are discussed in detail. This book is an invaluable resource guide for professionals, faculty, students, chemical engineers, biotechnologists, and environmentalists in these research and development areas.
•Demand for transport is large, growing, powered by combustion of petroleum fuels.•All alternatives start from a low base and cannot grow rapidly or without restraint.•Forced rapid change will incur ...large environmental, economic and social costs.•Transport will be powered mostly by combustion engines/petroleum for decades to come.•Limited electrification as hybridization will help combustion engines to improve.
Transport is almost entirely powered by internal combustion engines (ICEs) burning petroleum-derived liquid fuels and the global demand for transport energy is large and is increasing. Available battery capacity will have to increase by several hundred fold for even light duty vehicles (LDVs), which account for less than half of the global transport energy demand, to be run on electricity alone. However the greenhouse gas (GHG) impact of battery electric vehicles (BEVs) would be worse than that of conventional vehicles if electricity generation and the energy used for battery production are not sufficiently decarbonized. If coal continues to be a part of the energy mix, as it will in China and India, and if power generation is near urban centers, even local urban air quality in terms of particulates, nitrogen oxides and sulfur dioxide would get worse. The human toxicity impacts associated with the mining of metals needed for batteries are very serious and will have to be addressed. Large prior investments in charging infrastructure and electricity generation will be needed for widespread forced adoption of BEVs to occur. There will be additional costs in the short term associated with various subsidies required to promote such a change and in the longer term, the loss of revenue from fuel taxes which contribute significantly to public finances in most countries. ICEs will continue to power transport, particularly commercial transport, to a large extent for decades to come and will continue to improve. There will also be a role for low-carbon and other alternative fuels where they make sense. However such alternatives also start from a low base and face constraints on rapid and unlimited growth so that they are unlikely to make up much more than 10% of the total transport energy demand by 2040. As the energy system is decarbonized and battery technology improves there will be an increasing role for BEVs and hydrogen which could replace liquid hydrocarbons in transport and the required infrastructure will evolve. Meanwhile, there will certainly be increasing electrification, particularly of LDVs in the form of hybridization to improve ICEs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
An increasingly large percentage of power is being generated from renewable energy sources with intermittent and fluctuating outputs. Therefore there is a growing need for energy storage. With ...power-to-gas, excess electricity is converted into hydrogen by water electrolysis, which can be stored and, when needed, can be reconverted into electricity with fuel cells. Besides the energy vector for electricity, mobility and heat, hydrogen can be utilized as a raw material for the chemical industry or further be used for the synthesis of various hydrocarbon fuels such as methane.
This article is an international review of numerous power-to-gas pilot plants that have either already been realized or are being planned. It provides information about their installed components and capacities as well as about operating experience that has been had with them. In many of the projects it was concluded that the design and sizing, control strategy and system integration of the power-to-gas plants have a great influence on their overall efficiency, reliability and economics.
Topics for further research are the improvement of the efficiency, reliability, lifetime and costs of electrolyzers and fuel cells and better ways of dealing with power sources. In order to improve the overall performance, the reduction of auxiliary equipment and the continuous long-term operation of power-to-gas pilot plants will be necessary. The further development of codes and standards for permits to operate, as well as of hydrogen components and control strategies, would bring additional benefits for power-to-gas systems. It is also recommended that optimum system configurations and components be determined with regard to the available infrastructure and the type of application involved.
► Evaluation and description of 41 realized and seven planned power-to-gas systems. ► Operating experience with alkaline and PEM electrolyzers and fuel cells. ► Lessons that have been learned in respect to system design, efficiency and lifetime. ► Integration of power-to-gas plants into the available infrastructure. ► Topics for further research on improving power-to-gas systems.
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•Comparative analysis of OMEn and diesel fuel blends versus individual OMEn and diesel in a combustion chamber.•Fuel optimization conducted using CFD and RSM for regression analysis, identifying the ...optimal OMEn and diesel blend.•Investigation of emission spray combustion properties of OMED and diesel using optical CVC setup..•Understanding alternative fuel combustion and emission reduction strategies, advancing sustainable energy development.
This study investigates an optimized fuel blend comprising oxymethylene ethers (OMEn = 1–5 series) with diesel aimed at simultaneously reducing soot and NOx emissions while enhancing fuel efficiency. An optimal blend was identified through rigorous experimentation and computational fluid dynamics (CFD) modeling. The study employs the response surface method (RSM) for regression analysis and integrates machine learning techniques for predictive modeling to assess various fuel compositions and optimize the mixture for improved combustion dynamics. Experimental measurements were conducted in an optical constant volume combustion chamber (CVCC) to confirm the blend’s effectiveness in reducing both soot and NOx emissions. The investigation thoroughly analyzes spray combustion properties, including injection duration, Start of Combustion (SOC), End of Combustion (EOC), Lift-Off length of fuels, spray tip penetration, and their impact on combustion efficiency. Analysis of energy densities between the blends reveals that OMED exhibits a heating value superior to OME2-5 but inferior to diesel, striking a balance in energy output. Furthermore, OMED demonstrates superior energy density compared to OME1-3 and diesel, highlighting its potential for enhanced fuel efficiency. The optimized blend achieves a significant 78.2 % reduction in soot emissions and a 31.3 % reduction in NOx emissions compared to conventional diesel, underscoring its efficacy in mitigating harmful emissions without compromising combustion performance. This research contributes valuable insights into developing sustainable fuel solutions for diesel engines, paving the way for greener automotive technologies in the future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The sluggish kinetics of Oxygen Reduction Reaction (ORR) at the cathode in proton exchange membrane fuel cells or metal-air batteries requires highly effective and stable electrocatalysts to ...boost the reaction. The low abundance and high price of Pt-based electrocatalysts hamper the widespread application of proton exchange membrane fuel cells and metal-air batteries. As promising alternatives, metal-free carbon materials, especially upon doping heteroatoms or creating defects demonstrated excellent ORR activity, which is as efficient as or even superior to commercial platinum on carbon. Significant progress on the development of advanced carbon materials as highly stable and durable catalysts has been achieved, but the catalytic mechanisms of these materials still remain undistinguished. In present review, we summarized the up-to-date progress in the studies of carbon materials, and emphasized on the combination of experiment and theory to clarify the underlying mechanisms of these materials. At last, we proposed the perspectives on the proper strategies of elucidating the mechanisms of carbon materials as electrocatalysts towards ORR.
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