Search Results (15)

Logistics is becoming more cost competitive while customers and regulatory bodies pressure businesses to disclose their carbon footprints, creating interest in alternative fuels as a decarbonization strategy. This paper provides a thematic review of the role of alternative fuels in sustainable air, land, and sea logistics, their challenges, and potential mitigations. Through an extensive literature survey, we determined that biofuels, synthetic kerosene, natural gas, ammonia, alcohols, hydrogen, and electricity are the primary alternative fuels of interest in terms of environmental sustainability and techno-economic feasibility. In air logistics, synthetic kerosene from hydrogenated esters and fatty acids is the most promising route due to its high technical maturity, although it is limited by biomass sourcing. Electrical vehicles are favorable in road logistics due to cheaper green power and efficient vehicle designs, although they are constrained by recharging infrastructure deployment. In sea logistics, liquified natural gas is advantageous owing to its supply chain maturity, but it is limited by methane slip control and storage requirements. Overall, our examination indicates that alternative fuels will play a pivotal role in the logistics networks of the future. Full article

In terms of energy generation and consumption, ships are autonomous isolated systems, with power demands varying according to the type of ship: passenger or commercial. The power supply in modern ships is based on thermal engines-generators, which use fossil fuels, marine diesel oil (MDO) and liquefied natural gas (LNG). The continuous operation of thermal engines on ships during cruises results in increased emissions of polluting gases, mainly CO/CO₂. The combination of renewable energy sources (REs) and triple-fuel diesel engines (TFDEs) can reduce CO/CO₂ emissions, resulting in a “greener” interaction between ships and the ecosystem. This work presents a new control method for balancing the power generation and the load demands of a ship equipped with TFDEs, fuel cells (FCs), and REs, based on a real and accurate model of a super-tanker and simulation of its operation in real cruise conditions. The new TFDE technology engines are capable of using different fuels (marine diesel oil, heavy fuel oil and liquified natural gas), producing the power required for ship operation, as well as using compositions of other fuels based on diesel, aiming to reduce the polluting gases produced. The energy management system (EMS) of a ship is designed and implemented in the structure of a finite state machine (FSM), using the logical design of transitions from state to state. The results demonstrate that further reductions in fossil fuel consumption as well as CO₂ emissions are possible if ship power generation is combined with FC units that consume hydrogen as fuel. The hydrogen is produced locally on the ship through electrolysis using the electric power generated by the on-board renewable energy sources (REs) using photovoltaic systems (PVs) and wind energy conversion turbines (WECs). Full article

The world’s economy heavily depends on the energy resources used by various countries. India is one of the promising developing nations with very low crude reserves actively looking for new renewable energy resources to power its economy. Higher energy consumption and environmental pollution are two big global challenges for our sustainable development. The world is currently facing a dual problem of an energy crisis as well as environmental degradation. So, there is a strong need to reduce our dependency on fossil fuels and greenhouse gas emissions. This can be achieved to a great extent by universally adopting clean fuels for all daily life uses, like ethanol or liquified natural gas (LNG), as these burn very clean and do not emit many pollutants. Nowadays, green hydrogen has emerged as a new clean energy source, which is abundantly available and does not pollute much. This article explores the various benefits of green hydrogen with respect to fossil fuels, various techniques of producing it, and its possible use in different sectors such as industry, transport, and aviation, as well as in day-to-day life. Finally, it explores the use of green hydrogen as fuel in automobile engines, its blending with CNG gas, and its benefits in reducing emissions compared to fossil fuels. On combustion, green hydrogen produces only water vapours and is thus a highly clean fuel. Thus, it can potentially help humanity preserve the environment due to its ultra-low emissions and can be a consistent and reliable source of energy for generations to come, thereby ending the clean energy security debate forever. Full article

One of the main issues that has limited the use of hydrogen as an energy vector for a long time is its low energy density per unit of volume. Alternative chemical storage methods have been developed in recent years to overcome the limitations associated with compressed or liquified hydrogen storage. One of these is the Liquid Organic Hydrogen Carrier (LOHC), which utilizes organic hydrocarbons that can capture hydrogen (through an exothermic hydrogenation reaction) and release hydrogen (through an endothermic dehydrogenation reaction). In this paper, a 0D model of an internal combustion engine fueled with a mixture of hydrogen and methane was used to investigate whether the enthalpy of the exhaust gases can balance the heat rate required to self-sustain the dehydrogenation stage. Two LOHC+ compounds were considered, namely, Perhydro-dibenzyltoluene and Perhydro-N-Ethylcarbazole. Four different hydrogen-to-methane ratios were considered, assuming an engine maximum brake power ranging from 500 to 6000 RPM. An energy balance was performed, balancing the dehydrogenation heat rate and the exhaust gas cooling heat rate, in order to establish the minimum temperatures of the exhaust gases required to self-sustain the LOHC+ dehydrogenation. We demonstrated that the minimum exhaust temperatures required to self-sustain the process in different running regimes and at different hydrogen-to-methane ratios are lower than literature and experimental exhaust temperatures. Full article

Extensive decarbonisation efforts result in major changes in energy demand for the extractive industry. In 2021, the extraction and primary processing of metals and minerals accounted for 4.5 Gt of CO₂ eq. per year. The aluminium industry was responsible for 1.1 Gt CO₂ eq. direct and indirect emissions. To reach the European milestone of zero emissions by 2050, a reduction of 3% annually is essential. To this end, the industry needs to take a turn towards less impactful production practices, coupling secondary production with green energy sources. The present work aims to comprehensively compare the lifecycle energy consumption and environmental performance of a secondary aluminium smelter employing alternative thermal and electricity sources. In this frame, a comparative analysis of the environmental impact of different thermal energy sources, namely natural gas, light fuel oil, liquified petroleum gas, hydrogen and electricity, for a secondary aluminium smelter is presented. The results show that H₂ produced by renewables (green H₂) is the most environmentally beneficial option, accounting for −84.156 kg CO₂ eq. By producing thermal energy as well as electricity on site, H₂ technologies also serve as a decentralized power station for green energy production. These technologies account for a reduction of 118% compared to conventionally used natural gas. The results offer a comprehensive overview to aid decision-makers in comparing environmental impacts caused by different energy sources. Full article

Decarbonisation of the energy sector is becoming increasingly more important to the reduction in climate change. Renewable energy is an effective means of reducing CO₂ emissions, but the fluctuation in demand and production of energy is a limiting factor. Liquid hydrogen allows for long-term storage of energy. Hydrogen quality is important for the safety and efficiency of the end user. Furthermore, the quality of the hydrogen gas after liquefaction has not yet been reported. The purity of hydrogen after liquefaction was assessed against the specification of Hydrogen grade D in the ISO-14687:2019 by analysing samples taken at different locations throughout production. Sampling was carried out directly in gas cylinders, and purity was assessed using multiple analytical methods. The results indicate that the hydrogen gas produced from liquefaction is of a higher purity than the starting gas, with all impurities below the threshold values set in ISO-14687:2019. The amount fraction of water measured in the hydrogen sample increased with repeated sampling from the liquid hydrogen tank, suggesting that the sampling system used was affected by low temperatures (−253 °C). These data demonstrate for the first time the impact of liquefaction on hydrogen purity assessed against ISO-14687:2019, showing that liquified hydrogen is a viable option for long-term energy storage whilst also improving quality. Full article

Recently, hydrogen (H₂) has emerged as a superior energy carrier that has the potential to replace fossil fuel. However, storing H₂ under safe and operable conditions is still a challenging process due to the current commercial method, i.e., H₂ storage in a pressurised and liquified state, which requires extremely high pressure and extremely low temperature. To solve this problem, research on solid-state H₂ storage materials is being actively conducted. Among the solid-state H₂ storage materials, borohydride is a potential candidate for H₂ storage owing to its high gravimetric capacity (majority borohydride materials release >10 wt% of H₂). Mg(BH₄)₂, which is included in the borohydride family, shows promise as a good H₂ storage material owing to its high gravimetric capacity (14.9 wt%). However, its practical application is hindered by high thermal decomposition temperature (above 300 °C), slow sorption kinetics and poor reversibility. Currently, the general research on the use of additives to enhance the H₂ storage performance of Mg(BH₄)₂ is still under investigation. This article reviews the latest research on additive-enhanced Mg(BH₄)₂ and its impact on the H₂ storage performance. The future prospect and challenges in the development of additive-enhanced Mg(BH₄)₂ are also discussed in this review paper. To the best of our knowledge, this is the first systematic review paper that focuses on the additive-enhanced Mg(BH₄)₂ for solid-state H₂ storage. Full article

Storage is still limiting the implementation of hydrogen as an energy carrier to integrate the intermittent operation of renewable energy sources. Among different solutions to the currently used compressed or liquified hydrogen systems, physical adsorption at cryogenic temperature in porous materials is an attractive alternative due to its fast and reversible operation and the resulting reduction in storage pressure. The feasibility of cryoadsorption for hydrogen storage depends mainly on the performance of the used materials for the specific application, where metal-organic frameworks or MOFs are remarkable candidates. In this work, gravimetric and volumetric hydrogen uptakes at 77 K and up to 100 bar of commercially available MOFs were measured since these materials are made from relatively cheap and accessible building blocks. These materials also show relatively high porous properties and are currently near to large-scale production. The measuring device was calibrated at different room temperatures to calculate an average correction factor and standard deviation so that the correction deviation is included in the measurement error for better comparability with different measurements. The influence of measurement conditions was also studied, concluding that the available adsorbing area of material and the occupied volume of the sample are the most critical factors for a reproducible measurement, apart from the samples’ preparation before measurement. Finally, the actual volumetric storage density of the used powders was calculated by directly measuring their volume in the analysis cell, comparing that value with the maximum volumetric uptake considering the measured density of crystals. From this selection of commercial MOFs, the materials HKUST-1, PCN-250(Fe), MOF-177, and MOF-5 show true potential to fulfill a volumetric requirement of 40 g·L⁻¹ on a material basis for hydrogen storage systems without further packing of the powders. Full article

Hydrogen used as an energy carrier can provide an important route to the decarbonization of energy supplies, but realizing this opportunity will require both significantly increased production and transportation capacity. One route to increased transportation capacity is the shipping of liquid hydrogen, but this requires an energy-intensive liquefaction step. Recent study work has shown that the energy required in this process can be reduced through the implementation of new and improved process designs, but since all low-temperature processes are affected by the available heat-sink temperature, local ambient conditions will also have an impact. The objective of this work is to identify how the energy consumption associated with hydrogen liquefaction varies with heat-sink temperature through the optimization of design parameters for a next-generation mixed refrigerant based hydrogen liquefaction process. The results show that energy consumption increases by around 20% across the cooling temperature range 5 to 50 °C. Considering just the range 20 to 30 °C, there is a 5% increase, illustrating the significant impact ambient temperature can have on energy consumption. The implications of this work are that the modelling of different liquified hydrogen based energy supply chains should take the impact of ambient temperature into account. Full article

The maritime transportation sector (MTS) is undertaking a major global effort to reduce emissions of greenhouse gases (GHG), e.g., sulfur oxides, nitrogen oxides, and the concentration of particulates in suspension. Substantial investment is necessary to develop alternative sustainable fuels, engines, and fuel modifications. The alternative fuels considered in this study include liquified natural gas, nuclear energy, hydrogen, electricity, and biofuels. This paper focuses on biofuels, in particular fast pyrolysis bio-oil (FPBO), a serious partial alternative in MTS. There are some drawbacks, e.g., biofuels usually require land necessary to produce the feedstock and the chemical compatibility of the resulting biofuel with current engines in MTS. The demand for sustainable feedstock production for MTS can be overcome by using cellulose-based and agroforestry residues, which do not compete with food production and can be obtained in large quantities and at a reasonably low cost. The compatibility of biofuels with either bunker fuel or diesel cycle engines can also be solved by upgrading biofuels, adjusting the refining process, or modifying the engine itself. The paper examines the possibilities presented by biofuels, focusing on FPBO in Brazil, for MTS. The key issues investigated include FPBO, production, and end use of feedstocks and the most promising alternatives; thermal conversion technologies; potential applications of FPBO in Brazil; sustainability; biofuels properties; fuels under consideration in MTS, challenges, and opportunities in a rapidly changing maritime fuel sector. Although the focus is on Brazil, the findings of this paper can be replicated in many other parts of the world. Full article

One of the most effective and renewable utilization methods for lignocellulosic feedstocks is the transformation from solid materials to liquid products. In this work, corn stalk (CS) was liquified with polyethylene glycol 400 (PEG400) and glycerol as the liquefaction solvents, and sulfuric acid as the catalyst. The liquefaction conditions were optimized with the liquefaction yield of 95.39% at the reaction conditions of 150 °C and 120 min. The properties of CS and liquefaction residues (LRs) were characterized using ATR–FTIR, TG, elemental analysis and SEM. The chemical components of liquefied product (LP) were also characterized by GC–MS. The results indicated that the depolymerization and repolymerization reaction took place simultaneously in the liquefaction process. The depolymerization of CS mainly occurred at the temperature of <150 °C, and the repolymerization of biomass derivatives dominated at a higher temperature of 170 °C by the lignin derivatives repolymerization with cellulose derivatives, hemicellulose derivatives and PEG400 and self-condensation of lignin derivatives. The solvolysis liquefaction of CS could be classified into the mechanism of electrophilic substitution reaction attacked by the hydrogen cation. Full article

The performance of a commercial FCC catalyst (designated as CY) and a physically mixed hybrid catalyst (80 wt.% CY and 20 wt.% HZSM-5-based catalyst, designated as CH) have been compared in the catalytic cracking of a vacuum gasoil (VGO)/bio-oil blend (80/20 wt.%) in a simulated riser reactor (C/O, 6g_catg_feed⁻¹; t, 6 s). The effect of cracking temperature has been studied on product distribution (carbon products, water, and coke) and product lumps: CO+CO₂, dry gas, liquified petroleum gases (LPG), gasoline, light cycle oil (LCO), heavy cycle oil (HCO), and coke. Using the CH catalyst, the conversion of the bio-oil oxygenates is ca. 3 wt.% higher, while the conversion of the hydrocarbons in the mixture is lower, yielding more carbon products (83.2–84.7 wt.% on a wet basis) and less coke (3.7–4.8 wt.% on a wet basis) than the CY catalyst. The CH catalyst provides lower gasoline yields (30.7–32.0 wt.% on a dry basis) of a less aromatic and more olefinic nature. Due to gasoline overcracking, enhanced LPG yields were also obtained. The results are explained by the high activity of the HZSM-5 zeolite for the cracking of bio-oil oxygenates, the diffusional limitations within its pore structure of bulkier VGO compounds, and its lower activity towards hydrogen transfer reactions. Full article

Ni catalysts supported on ZrO₂, 5%CeO₂-ZrO₂, and 5%La₂O₃-ZrO₂ were prepared via the impregnation method and tested in the oxy-steam reforming of methane and liquified natural gas (LNG). All tested catalysts exhibited high catalytic activity in the studied process at 700 and 900 °C. The improvement of the stability of Ni catalysts after the addition of CeO₂ oxide in the studied oxy-steam reforming of LNG process was confirmed. In addition, high activity and selectivity towards hydrogen was proven in the oxy-steam reforming process at 900 °C over a 20%Ni/5%CeO₂-ZrO₂ catalyst. It was also proved that the addition of CeO₂ onto a ZrO₂ carrier leads to a decrease in the NiO and metallic Ni crystallite sizes that were detected by the X-Ray diffraction (XRD) technique. The solid solution formation between NiO and ZrO₂ and/or NiO and CeO₂ was proved. Superior reactivity in the oxy-steam reforming of CH₄ and the LNG process exhibited a 20%Ni/ZrO₂ catalyst, which showed the highest methane conversions at 500 and 600 °C, equal to 63% and 89%, respectively. In addition, also in the case of the LNG reforming reaction, the most active catalyst was the 20%Ni/ZrO₂ system, which demonstrated 46.3% and 76.9% of the methane conversion value at 500 and 600 °C and the total conversion of others hydrocarbons (ethane, propane and butane). In addition, this catalytic system exhibited the highest selectivity towards hydrogen formation in the oxy-steam reforming of the LNG reaction equal to 71.2% and 71.3% at 500 and 600 °C, respectively. The highest activity of this system can be explained by the uniform distributions of Ni species and their highest concentration compared to the rest of the monometallic Ni catalysts. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) results also confirmed a strong interaction of NiO with ZrO₂ in the case of the 20%Ni/ZrO₂ catalysts. The presence of selected NiZrO⁺ ions emitted from the investigated surface of the 20%Ni/ZrO₂ system was detected. Full article

Liquified natural gas (LNG), with its low sulphur content, its favorable hydrogen-to-carbon ratio, and the lower nitrogen oxide emission when combusted compared to conventional fuels, fulfils all International Maritime Organization (IMO) air emission regulations. For the cruise industry, with their large number of customers and their high public visibility, LNG has therefore become a tempting option for new cruise ships. However, larger well-to-tank (WTT) emissions for the LNG supply chain as well as un-combusted methane (CH₄) from the ship’s engine might more than nullify any greenhouse gas (GHG) gains. Previous studies have shown very different GHG impacts from the use of LNG as a ship fuel. With climate change potentially being the largest threat to mankind, it is important that decisions with an impact on future GHG emissions are based on the best available knowledge within a sector and across sectors. The motivation for this study has therefore been to establish comparable GHG estimates for well-to-wake (WTW) emissions for LNG and traditional fuels in a transparent way. The results show that there is a need for adopting policies that can reduce the broader GHG emissions of shipping instead of CO₂ only, including the well-to-tank emissions of ship fuels. If not, we might end up with a large number of ships with GHG savings on paper only, while the real GHG emissions increases. Full article

Alternative and innovative fuel types are being introduced to power cars. These include liquified petroleum gas (LPG) gas and hydrogen energy sources. However, they also introduce new hazards, requiring revised thinking with respect to safety within car parking environments. One of the most significant dangers is accidental gas release from a car’s system, especially in underground car parks. Jet fan systems are widely used for ventilation of such enclosures, but currently their design is most often based on computational fluid dynamics (CFD) according to computer simulations that may not be relevant for such new fuels. This paper presents the results of full-scale tests which demonstrate the operational factors of jet fan ventilation systems, and assesses the conditions which can occur in a car park when a small volume of LPG is released. On the basis of measurements undertaken, Fire Dynamics Simulator (FDS) software was validated against the air velocity flows and LPG gas dispersion patterns. Finally, the simulations were used to demonstrate the effectiveness of systems in an actual car park, in the case of an accidental LPG car tank release. Full article