Synthetic Fuels Research Articles

Synthetic methane for closing the carbon loop: Comparative study of three carbon sources for remote carbon-neutral fuel synthetization

Achieving carbon neutrality is probably one of the most important challenges of the 21st century for our societies. Part of the solution to this challenge is to leverage renewable energies. However, these energy sources are often located far away from places that need the energy, and their availability is intermittent, which makes them challenging to work with. In this paper, we build upon the concept of Remote Renewable Energy Hubs (RREHs), which are hubs located at remote places with abundant renewable energy sources whose purpose is to produce carbon-neutral synthetic fuels. More precisely, we model and study the Energy Supply Chain (ESC) that would be required to provide a constant source of carbon-neutral synthetic methane, also called e-NG (electric Natural Gas) or e-methane (electric methane), in Belgium from an RREH located in Morocco. To be carbon neutral, a synthetic fuel has to be produced from existing carbon dioxide (CO2) that needs to be captured using either Direct Air Capture (DAC) or Post Combustion Carbon Capture (PCCC). In this work, we detail the impact of three different carbon sourcing configurations on the price of the e-methane delivered in Belgium. Our results show that sourcing CO2 through a combination of DAC and PCCC is more cost-effective, resulting in a cost of 146 €/MWh for e-methane delivered in Belgium, as opposed to relying solely on DAC, which leads to a cost of 158 €/MWh. Moreover, these scenarios are compared to a scenario where CO2 is captured in Morocco from a CO2 emitting asset that allow to deliver e-methane for a cost of 136 €/MWh.

Detailed kinetic analysis of synthetic fuels containing ammonia

The imperative to adopt environmentally sustainable energy sources has propelled the exploration of zero-carbon alternatives, such as hydrogen and ammonia for energy supply. Integrating these species with methane is recognized as a viable short-term solution. However, a complete understanding of their chemical behaviour in a wide range of conditions remains elusive, especially in terms of safety parameters, limiting the applicability of this solution. To this aim, this work presents a detailed analysis of the overall reactivity, expressed either in terms of laminar burning velocity or flammability limits, of hydrogen-ammonia-containing fuels. Additional considerations were obtained by the analysis of the maximum pressure rise and maximum pressure obtained in adiabatic conditions. A spectrum of nitrogen/oxygen mixtures was scrutinized, and the influence of initial temperature within the range of 300–500 K was systematically investigated. The estimation quality of the adopted mechanism was evaluated by comparing numerical predictions with experimental measurements obtained by different systems, when available. A tendency in slightly more conservative results on the safe side was detected for the assessment of flammability limits and minimum oxygen concentration. This trend was attributed to the assumption of perfectly adiabatic conditions posed for the numerical analysis, which does not perfectly match the experimental conditions. Conversely, an excellent agreement between numerical and experimental laminar burning velocity was observed. Therefore, the collected data were used for the quantification of input parameters required by well-established correlations suitable for synthetic fuels.

Техніко-економічні передумови доцільності створення в Україні виробництва синтетичного моторного палива

The article formulates the main scenarios for organizing the supply of motor fuel to Ukraine. It is shown that a significant reduction in imports of motor fuel in the post-war period is possible only through the restoration and development of oil production and refining with the simultaneous search for options for organizing the production of synthetic motor fuel from non-oil raw materials. The article compares the technical characteristics of a full-cycle oil refinery and a plant producing synthetic motor fuels from coal. It is shown that in the USA and Western Europe, the depth of oil refining is 90-95 %. In Ukraine, these figures were much lower - only 72.1 %. In addition, the European Union's environmental standards governing the content of harmful substances in exhaust gases from cars and specialized machinery are becoming stricter, which should stimulate the development of oil refining and transport engineering technologies. When synthetic motor fuels are produced, the degree of carbon conversion of the original fossil coal into the target light products is 56.0 %, which is objectively less than the depth of oil refining. Under such conditions, the main advantages of obtaining synthetic motor fuels from coal compared to oil refining for the conditions of our country are: reduction of import dependence of the country's economy; sulphur content in the products obtained meets the requirements of modern European standards; the depth of processing of synthetic products reaches 90 % and more with the use of relatively simple equipment; favorable technological properties of synthetic oil determine its price on the world market by about 30 % higher than the best light oil ‘brent’; the obtaining of a by-products of increased demand (light hydrocarbons, thermal and electrical energy); the possibility of obtaining synthetic base oils. Keywords: fossil coal, motor fuel, synthetic fuel, oil refining, refining depth, Nelson index. Corresponding author: I.V. Shulga, e-mail: ko@ukhin.org.ua

Investigation of Substitution Energy for Engines Recovered from Synthetic Fuels Enhanced by Dimethyl Ether

Climate change and the depletion of fossil fuel reserves, it is important to utilize alternative fuels, which can help ease its impact on the environment. Besides, waste disposal is an important aspect to take into account, especially given the versatility and financial feasibility of synthetic polymers. The research in the article refers to the investigation of the synthetic fuel’s effectiveness, which is produced using waste synthetic polymer, and, due to the mixture of dimethyl ether in diesel engines, serves as an addition to this fuel. The performance and emission characteristics of biodiesel derived from synthetic rubber through the pyrolysis process are examined in this study. Furthermore, dimethyl ether is introduced as an additive at two different volume concentrations, specifically 25% and 50%, with the aim of improving the engine characteristics. The impact of these additives on the overall biodiesel performance and emissions is thoroughly investigated to provide insights into the potential benefits of utilizing synthetic rubber-derived biodiesel in combination with dimethyl ether in engine applications.

Перспективи виробництва синтетичного бензину в Україні

DOI: 10.31081/1681-309X-2024-0-1-34-40 Specialty 161. U.D.C. 662.7 PROSPECTS FOR THE PRODUCTION OF SYNTHETIC PETROL IN UKRAINE © K.V. Shevchenko, Ph.D. in Technical Sciences, A.B. Grigorov, Doctor of Technical Sciences (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine) The article analyses the possibility of using various hydrocarbon feedstocks (including secondary ones) in the technology of synthetic motor petrol production, which, together with petrol produced by classical technology (from oil or gas condensate), can satisfy the existing demand for this type of motor fuel. It is shown that, taking into account the possible production volumes and demand for raw materials, as well as the complexity (energy intensity) of their technological processing, the most promising types of raw materials are biomass, solid fossil fuels and secondary polymers. Biomass (mainly agricultural waste) is a feedstock for biogas production, which is currently being used quite successfully in the European Union. The product of this production is methane, which can be used for energy purposes or processed into petrol and biomethanol. Another promising area in biomass processing is the direct production of alcohols (biomethanol and bioethanol), which can be used as a raw material for organic synthesis and for the production of blended petrol (e.g., grades E5, E7 and E10). Given Ukraine's reserves of various grades of coal, its processing into synthetic gasoline by gasification followed by synthesis using the Fischer-Tropsch method or hydrogenation can also be considered very promising. However, to date, these processes have not been widely used in industry due to their high energy intensity. It has been determined that secondary polymers - production and consumption wastes represented by polyethylenes (HPDE and LPDE) and polypropylene (PP) - are more promising for Ukraine than other types of raw materials. The main process for their processing is thermal or thermocatalytic pyrolysis, which produces both liquid petrol fractions (boiling point 30-210 °C) and gases, represented by ethylene, propylene and butylene. Given their conversion rate (70-90 % and 100 %, respectively), propylene and butylene can be processed into polymer gasoline, which, after purification, will be suitable for use in mixed or synthetic commercial motor gasoline. Keywords: natural gas, biomass, solid fossil fuels, polymers, processing, hydrogenation, synthesis, pyrolysis, methane, propylene, butylene, synthetic petrol. Corresponding author: A.B. Grigorov, e-mail: grigorovandrey@ukr.net

Sustainable Energy Solutions for Environmental Pollution Control

With increased technological advancements, in today’s world, sustainable energy solutions are innovative and provide attractive encouragement to researchers, green chemists, scientists, leaders, and the student community. These novel solution providers focus on factors such as resiliency, reliability, redundancy, lower carbon footprints, and possible positive outcomes. For big-impacted solutions, this article will research areas such as (i) Energy Indicators and Assessment, (ii) Energy Major Developments, (iii) Self-Generation Power, (iv) Thermal Retrieval, (v) Thermic Energy Storage (vi) PV solar storage, (vii) Sustainable Batteries, (viii) Electric Vehicle Developments, (ix) Types of Fuel Storage, and (x) Centralized Micro Grids and Controllers. Soon, Sustainable Renewable energy and Alternative energy are quickly substituting fossil fuels across the globe including nuclear energy, biofuels, synthetic carbon-emissionfree fuels, and hydrogen fuel cells. The chapter will also compare the advancements of hydrogen fuel cells in India and overseas. To conclude, sustainable energy solutions will project a well-established track to a cleaner future. By working together, creating awareness among individuals, communities, businesses, and governments, will pave the way to brighter and greener innovative solutions.

Understanding the ignition process and flame structure of conventional and oxygenated fuels under engine relevant conditions – An optical study

Renewably generated synthetic fuels such as poly-oxymethylene ethers (OME) have a significant potential to effectively break the soot-NOX trade-off in compression ignition engines by using exhaust gas recirculation (EGR) to maintain low nitrogen oxide (NOX) emissions while maintaining good efficiency and simultaneously contributing to circular carbon economy. However, owing to the fundamental differences in properties of OME when compared to fossil-based diesel fuels, it is critical to fully understand its ignition and combustion phenomenology to take advantage of this fuel to its utmost potential. In this context, this work outlines the results of a systematic experimental study performed in a heavy-duty, single-cylinder, optical engine probing the spatial and temporal progression of fuel decomposition and ignition behavior of OME when compared to n-dodecane, a diesel-fuel surrogate. Thermodynamic analysis and optical diagnostics techniques including simultaneous HCHO-PLIF and OH-PLIF complemented by high-speed OH* chemiluminescence were employed along with parametric sweeps of intake temperature and EGR dilution rates. OME does not exhibit any observable low temperature heat release irrespective of the ambient oxygen concentration. Differences in the observed diffusive flame structure such as longer flame lift-off length, less pronounced combustion recession, faster premixed burn at ignition (“volumetric” ignition), non-sooting behavior suggest that the inherent presence of fuel-bound oxygen in OME can skew the air-fuel ratio (AFR) distribution within the jet thereby reducing the reliance of combustion on mixing and air entrainment. This leads to rapid late-cycle oxidation leading to shorter combustion duration and favorable combustion phasing. Results also suggest that OME exhibits relatively weak negative temperature coefficient (NTC) behavior, however, the OME fuel-decomposition kinetic-pathways produce significant concentration of HCHO, which might be erroneously interpreted as a product of cool-flames.

Hydrogen production, storage, and transportation: recent advances.

One such technology is hydrogen-based which utilizes hydrogen to generate energy without emission of greenhouse gases. The advantage of such technology is the fact that the only by-product is water. Efficient storage is crucial for the practical application of hydrogen. There are several techniques to store hydrogen, each with certain advantages and disadvantages. In gaseous hydrogen storage, hydrogen gas is compressed and stored at high pressures, requiring robust and expensive pressure vessels. In liquid hydrogen storage, hydrogen is cooled to extremely low temperatures and stored as a liquid, which is energy-intensive. Researchers are exploring advanced materials for hydrogen storage, including metal hydrides, carbon-based materials, metal-organic frameworks (MOFs), and nanomaterials. These materials aim to enhance storage capacity, kinetics, and safety. The hydrogen economy envisions hydrogen as a clean energy carrier, utilized in various sectors like transportation, industry, and power generation. It can contribute to decarbonizing sectors that are challenging to electrify directly. Hydrogen can play a role in a circular economy by facilitating energy storage, supporting intermittent renewable sources, and enabling the production of synthetic fuels and chemicals. The circular economy concept promotes the recycling and reuse of materials, aligning with sustainable development goals. Hydrogen availability depends on the method of production. While it is abundant in nature, obtaining it in a clean and sustainable manner is crucial. The efficiency of hydrogen production and utilization varies among methods, with electrolysis being a cleaner but less efficient process compared to other conventional methods. Chemisorption and physisorption methods aim to enhance storage capacity and control the release of hydrogen. There are various viable options that are being explored to solve these challenges, with one option being the use of a multilayer film of advanced metals. This work provides an overview of hydrogen economy as a green and sustainable energy system for the foreseeable future, hydrogen production methods, hydrogen storage systems and mechanisms including their advantages and disadvantages, and the promising storage system for the future. In summary, hydrogen holds great promise as a clean energy carrier, and ongoing research and technological advancements are addressing challenges related to production, storage, and utilization, bringing us closer to a sustainable hydrogen economy.

A bibliometric analysis on sustainable aviation fuels: core technologies, challenges and trends

International initiatives such as the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) have set goals for the complete de-carbonization of international aviation in this century. It motivated increasing numbers of Sustainable Aviation Fuel (SAF) research projects. The objective of this paper is to provide an overview on SAF research to point one to its foundations and recent advances. Data from the Web of Science database was collected and investigated. Important papers, cooperation networks, textual, productivity and trends analysis is provided. The most productive countries are in the global north, led by the United States and China. Big developing nations such as India and Brazil need to improve. The future of a sustainable aviation sector is heading in the direction of replacement of conventional jet fuel by synthetic hydrocarbon fuels by the end of the century. But there are still doubts about its viability both from the environmental and practical aspects, as there are concerns about feedstock availability and life cycle emissions. Fischer-Tropsch Synthesis, Alcohol-to-Jet and Hydroprocessing of Esters and Fatty Acids appear as the main SAF technologies for drop-in replacements. Longer term prospects are for the development of more efficient aircraft designed for renewables and non-hydrocarbon energy sources.

(Invited)The Role of the Catalyst Microenvironment in the Electrochemical Reduction of Carbon Monoxide

Carbon monoxide is already an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petrochemical products. This can be performed under high temperature and pressure conditions in the Fischer-Tropsch process, but electrochemical methods also offer a possible way of forming different chemicals from carbon monoxide.Because of the low solubility of carbon monoxide in water, instead of the routinely used H-cells, its reduction must be performed in gas-fed electrolyzer cells, ensuring a short diffusion length for the reactant. However, even in such devices the surface of the catalyst (nano)particles is typically surrounded by a thin water shell under operating conditions, caused by various effects such as electrowetting, or wetting by the formed products. The practical insolubility of carbon monoxide (that is ca. 30 times lower compared to the solubility of CO2) makes it vital to ensure that the thickness of this hydration layer is minimized, hence the reactant can reach the catalysts' surface in gas phase, meanwhile just enough amount of a proton source – water – is in the immediate vicinity.The phase boundary between the catalyst particles, the liquid phase and the gas reactant can be engineered by using functional catalyst layer additives. Here we will demonstrate a commercial pore sealer for this purpose, ensuring the formation of C2+ products in CORR with high selectivity and rate.1 As no specific interaction between the polymer and the CO reactant was found, we assumed that the most important role of this polymer is to increase the hydrophobicity of the catalyst layer. To challenge this theory, various, systematically chosen polymeric materials were tested as catalyst binders to reveal any possible further contribution of certain motifs (e.g., functional groups, fluorinated backbone etc.), present in these polymers. The electrochemical results are contrasted with the detailed characterization of the structure, wetting and gas adsorption properties of the catalyst layer. Reference Kormányos, B. Endrődi, Z. Zhang, A. Samu, L. Mérai, G. F. Samu, L. Janovák, & C. Janáky (2023). EES Catalysis. https://doi.org/10.1039/D3EY00006K

Electrochemical Impedance Analysis of Direct Ammonia Fuel Cell Operation and Clamping Effects

In addition to being an essential chemical for fertilizers, ammonia can also be used as a hydrogen carrier or directly as a fuel. Compared to hydrogen, the main advantages are that ammonia can be liquefied in mild conditions and the technology for ammonia shipping and pipelines already exists. Compared to carbon-based synthetic fuels, no carbon dioxide is produced by the oxidation, only water and nitrogen. The theoretical voltage of a direct ammonia fuel cell (DAFC) is 1.17 V, nearly equal to the 1.23 V of hydrogen fuel cells (HFC) but a central drawback is the slow kinetics of the ammonia oxidation reaction (AOR). The AOR is even slower than the oxygen reduction reaction (ORR) at the cathode, which in turn is the main voltage loss component in HFCs. Consequently, due to the AOR kinetics, DAFCs typically require significantly higher platinum group metal (PGM) catalyst loadings than HFCs for the same power output.To improve the performance of our aqueous-feed DAFC, especially using non-PGM catalysts, we carried out comparisons of catalysts and anion exchange membranes (AEM), and supplemented the comparison of power, voltage, and current parameters with electrochemical impedance spectroscopy (EIS). Additionally, we also compared measurements in two different test cells to try to identify the cause of measurement repeatability issues that we had when using one of the cells.Initially, we assumed that the reproducibility of catalyst deposition (or lack of it) and AEM or catalyst degradation in the ammonia-containing electrolyte had caused our repeatability problems. However, following a preliminary analysis of measurement statistics, we consider problems with the cell itself a more likely cause. The maximum power of the cell depended almost inversely on the series resistance (R S, i.e., the high-frequency resistance/real-axis intercept of the EIS spectrum), and the current at given voltage varied more than the differences in the resistance alone could explain when most measurement parameters were not varied (e.g., ammonia and hydroxide concentrations, liquid and gas flow rates). The general inverse dependence on R S remained also when measuring the same electrodes in different cells, and the performance did not necessarily degrade over time so, clearly, degradation and differences between electrodes could not explain everything. When testing different screw torques and gaskets in our AEM electrolyser, we had noticed that the voltage differences were often high compared to the R S differences, and it is known that clamping torque can affect the operation of fuel cells and electrolysers significantly. Nevertheless, more detailed analysis is ongoing to determine possible other contributing factors, to optimize the use of the cell(s) in measurements, and to guide future work.This research was done under the TELEGRAM project. This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No 101006941. The project started on the 1st of November 2020 with a duration of 42 months. The authors acknowledge support from the Federal Ministry of Education and Research in the framework of the project Catlab (03EW0015A). Figure 1

(Invited) Electrosynthesis of Long-Chain Hydrocarbons and Oxygenates

The electroreduction of CO(2), driven by renewable electricity, can be used to sustainably generate synthetic fuels and chemical feedstocks. Long carbon chain molecules are of particular interest due to their high energy densities and utilities. However, to date, most of the CO(2) reduction products formed are limited to C2 and C3. Herein, we discuss the development of electrocatalysts for the reduction of CO(2) to long-chain oxygenates and hydrocarbons, and their underlying reaction mechanisms.CO(2) electroreduction has been previously reported to yield a range of carbonaceous products including alcohols, hydrocarbons and carboxylic acids. Interestingly, esters, an important family of organic compounds, have not been formed. We show how C3–C6 acetate esters could be produced from CO reduction in a membrane electrode assembly (MEA) cell. The near water-free reaction environment and the high local pH in the MEA played key roles in forming the esters with a Faradaic efficiency of 22 % and a current density up to −55 mA cm−2. We also disclose that inorganic nickel oxygenate (INO)-derived electrocatalysts can reduce CO2 to linear and branched C3-C6 hydrocarbons with Faradaic efficiencies up to 6.5%. We identified Niδ+ active sites which bind CO moderately. Our results show that Ni atom polarization to be important in hindering CO poisoning of nickel and thus facilitating CO2 reduction to a wider pool of valuable products.Finally, we show how MgAl layered double hydroxide (LDH) nanosheets ‘House-of-cards’ structures help to disperse CuO-derived Cu (OD-Cu) catalysts. The porous structures formed enhanced CO gas percolation through the catalyst layer. OD-Cu dispersed by the ‘House-of-cards’ structures catalysed CO electroreduction to C2+ products with a partial current density that is an order of magnitude higher than that shown by the unsupported OD-Cu.

Pilot-scale study of sorption-enhanced gasification of sewage sludge

Sustainable management and disposal alternatives for sewage sludge (SS) should be pursued due to the substantial increment in its global production, as well as due to the raising interest in the renewable energy and synthetic fuels deployment. Since SS present high moisture (>95 % wt.), drying would play an essential role in SS management. In this work, SS pre-treated in a solar-drying facility has been successfully used as feedstock in a 30 kWth bubbling fluidised-bed (BFB) gasification pilot plant operating under Sorption Enhanced Gasification (SEG) conditions, i.e. using CaO as bed material and steam as gasifying agent. The influence of key operating SEG parameters (such as temperature, steam-to-carbon ratio and sorbent-to biomass proportion) in the syngas yield and composition (H2, CO, CO2, CH4, CxHy, H2S, COS, NH3 and tars) has been carefully assessed. As a matter of comparison, steam-oxygen gasification conditions have been also tested in the facility using solar-dried SS as feedstock. The results obtained demonstrate the possibility of producing a syngas with high H2 contents of 70–73 vol% and relatively low CO and CO2 contents (i.e. 2–3 vol% and 8 vol% respectively).

The role of hydrogen in synthetic fuel production strategies

This paper examines the complex relationship between the role of H2, carbon emissions and their impact on global warming and the economy. Despite improvements in energy efficiency, fossil fuel consumption continues to increase. CO2 from industrial activities at high temperatures, such as cement, iron, steel and glass production, have increased rapidly, resulting in an increase in the concentration of greenhouse gases in the atmosphere. These emissions accelerate climate change, leading to dangerous consequences such as increasing average atmospheric temperature and decreasing agricultural productivity. To combat this, it is advocated to reduce CO2 emissions by using renewable energy sources such as hydroelectricity, biomass, wind solar energy. Current study also discusses carbon reduction methods, including oxy-fuel combustion capture, pre-combustion capture, and post-combustion capture. Despite their unique advantages and disadvantages, these methods play an important role in reducing CO2 emissions from power plants. Additionally, the article highlights the importance of H2 as a cornerstone in the development of synthetic fuels and future energy systems. H2 from renewable sources holds the potential to use carbon-neutral synthetic liquid fuels and revolutionize transportation. Although traditional H2 production methods are associated with emissions, sustainable H2 production techniques can facilitate low-carbon fuel production. The article concludes by highlighting the importance of sustainable energy practices and the role of H2 in reducing carbon emissions, highlighting research efforts to improve production methods, integrate renewable energy, and develop carbon capture technologies for a sustainable future.

Potentials and limitations of battery-electric container ship propulsion systems

The defossilization of the open-sea ship traffic can most definitely only be achieved with alternative energy carriers. Besides synthetic fuels, battery-electric propulsion is a much-discussed measure, especially for smaller vessels and short passages. However, there is no consensus on quantitative ship characteristics that would allow for the application of batteries instead of a fuel-based solution. Therefore, limitations of battery propulsion systems are assessed for 45 vessels with a range of transport capacities. The most common marine battery technologies are evaluated both economically and environmentally by directly comparing their performances with state-of-the-art combustion engines. Mass and volume limitations of the ship are monitored, and emerging opportunity costs are quantified in addition to capital and operating expenses.The application of battery-electric propulsion systems is found not to be limited by the vessel size but mostly by the operated passage length. While distances of up to 15,000 km are technically achievable, economic limitations are effectively reducing the area of application to a maximum of 10,000 km. However, when comparing battery solutions with conventional diesel combustion engines, economic competitiveness is only observed for passages of up to 2,500 km when including a carbon tax and forecasting optimistic battery developments.

Study on the Effect of Bi Metal-Doped TiO2 on the Performance of Photothermal Catalytic Reduction of CO2 to Renewable Synthetic Fuels

Study on the Effect of Bi Metal-Doped TiO₂ on the Performance of Photothermal Catalytic Reduction of CO₂ to Renewable Synthetic Fuels

Spray Momentum Flux Novel Estimation Procedure through the Fuel Rate of Injection Using Hydrogenated Fuels with Single Hole Nozzle Diesel Injector.

Sustainable means of transport require the innovation or development of propulsive systems more respectful of the environment. Despite current criticism, modern compression-ignition engines are efficient alternatives also in light aviation and surveillance drones (such as small helicopters), as means of air transport. Currently, the improvement of the injection, air-fuel mixture formation, and combustion processes using sustainable synthetic fuels, produced from renewable raw materials or by carbon dioxide capture, is a reality. For improving the air-fuel mixture formation inside the combustion chamber, one of the key parameters is knowledge of the spray momentum flux because of its effect on the air entrainement. To measure this parameter is complex. However, the experimental determination of the fuel mass flow rate is a common procedure. The objective of this work is the proposal of a novel but robust methodology for the momentum flux estimation of fuel sprays from measurement of the rate of injection. In this work, single-hole nozzles of 115, 130, and 150 μm in diameter are studied. The implemented methodology is applied to three fuels: a diesel fuel without biodiesel, used as reference, and two sustainable synthetic fuels: a gas to liquid fuel and a hydrotreated vegetable oil. With the fuel injection rates and the simple model proposed, the spray momentum flux is estimated under different operating conditions of a common-rail injection system. The results of the spray momentum flux show a very good precision compared with those experimentally and previously obtained with similar fuels but with multihole nozzle. With the method proposed in this work, an adequate forecast of spray momentum flux is obtained in the case of not having an experimental setup that allows direct measurement of the momentum flux. This study can help investigators for fuel spray modeling with novel and renewable fuels in modern propulsive systems.

Driving mechanisms of high-cetane number, synthetic fuel autoignition: The case of OME[formula omitted

Oxymethylene dimethyl ethers (CH3O(CH2O)xCH3 or OMEx) are potential synthetic substitutes of diesel and jet fuel that can be acquired through CO2 recycling and have the unique “clean” feature that they do not contain C-C bonds in their atom chain, but only C-O, and therefore can combust without soot. Also, they present favourable ignition characteristics and high cetane numbers. In order to determine ignition control strategies, the dominant oxidation pathways must be identified. To this end, autoignition of OME2−4/air mixtures is studied using the tools of Computational Singular Perturbation algorithm. It is shown that as the length of the atom chain x increases, ignition delays become shorter. This is because, at the very early stages of the process, H-abstraction and fuel break-up reactions realize in a larger number of ways for larger x. The process develops first through a chemical runaway that tends to slow-down autoignition and then through a thermal runaway that tends to speed-up autoignition at a progressively stronger rate. It is shown that the total heat release is independent of x, although the ignition delay becomes shorter with increasing x. The two stable intermediates H2O2 and CH2O are shown to shorten ignition delays, when used as additives in the initial mixtures. It is demonstrated that OMEx synthetic fuels offer the capability of soot-less combustion, combined with ignition control.

The race between hydrogen and heat pumps for space and water heating: A model-based scenario analysis

This paper analyses different levels and means of the electrification of space and hot water heating using an explorative modelling approach. The analysis provides guidance to the ongoing discussion on favourable pathways for heating buildings and the role of secondary energy carriers such as hydrogen or synthetic fuels. In total, 12 different scenarios were modelled with decarbonisation pathways until 2050, which cover all 27 member states of the European Union. Two highly detailed optimisation models were combined to cover the building stock and the upstream energy supply sector. The analysis shows that decarbonisation pathways for space and water heating based on large shares of heat pumps have at least 11% lower system costs in 2050 than pathways with large shares of hydrogen or synthetic fuels. This translates into system cost savings of around €70 bn. Heat pumps are cost-efficient in decentralised systems and in centralised district heating systems. Hence, heat pumps should be the favoured option to achieve a cost-optimal solution for heating buildings. Accordingly, the paper makes a novel and significant contribution to understanding suitable and cost-efficient decarbonisation pathways for space and hot water heating via electrification. The results of the paper can provide robust guidance for policymakers.

Unlocking the potential of synthetic fuel production: Coupled optimization of heat exchanger network and operating parameters of a 1 MW power-to-liquid plant

The use of synthetic fuels is a promising way to reduce emissions significantly. To accelerate cost-effective large-scale synthetic fuel deployment, we optimize a novel 1 MW power-to-liquid (PtL) plant in terms of PtL-efficiency and fuel production costs. For numerous plants, the available waste heat and temperature level depend on the operating point. To optimize efficiency and costs, the choice of the operating point is included in the heat exchanger network synthesis. All nonlinearities are approximated using piecewise linear models and transferred to MILP. Adapting the epsilon constraint method allows us to solve the multi-criteria problem with uniformly distributed solutions on the Pareto front. We improved the lowest production costs of 1.89 €/kg and the highest efficiency of 58.08% from the conventional design process to 1.83 €/kg and 61.33%. By applying the presented method, climate-neutral synthetic fuels can be promoted and emissions can be reduced in the long term.