China, People’s Republic
Holistic Energy Efficiency and Environmental Friendliness Model for Short-Sea Vessels with Alternative Power Systems Considering Realistic Fuel Pathways and Workloads
Apr 2022
Publication
Energy requirements push the shipping industry towards more energy-efficient ships while environmental regulations influence the development of environmentally friendly ships by replacing fossil fuels with alternatives. Current mathematical models for ship energy efficiency which set the analysis boundaries at the level of the ship power system are not able to consider alternative fuels as a powering option. In this paper the energy efficiency and emissions index are formulated for ships with alternative power systems considering three different impacts on the environment (global warming acidification and eutrophication) and realistic fuel pathways and workloads. Besides diesel applications of alternative powering options such as electricity methanol liquefied natural gas hydrogen and ammonia are considered. By extending the analysis boundaries from the ship power system to the complete fuel cycle it is possible to compare different ships within the considered fleet or a whole shipping sector from the viewpoint of energy efficiency and environmental friendliness. The applicability of the model is illustrated on the Croatian ro-ro passenger fleet. A technical measure of implementation of alternative fuels in combination with an operational measure of speed reduction results in an even greater emissions reduction and an increase in energy efficiency. Analysis of the impact of voluntary speed reduction for ships with different power systems resulted in the identification of the optimal combination of alternative fuel and speed reduction by a specific percentage from the ship design speed.
Economic and Technical Analysis of Power to Gas Factory Taking Karamay as an Example
May 2022
Publication
Power to gas (PTG) refers to the technology of converting power into energy-storage gas which can absorb excess power when there is excess power and release energy-storage gas when needed. Based on the carbon dioxide (CO2 ) emission of Karamay City in Northwest China this study designed a process flow of the CO2 absorption process and the hydrogen and CO2 methanation process in PTG technology. The results show that the efficiency of the CO2 absorption process was 91.5% and the methanation efficiency was 77.5%. The heat recovery module was set during the process and the total heat recovered was 17.85 MW. The cost of producing synthetic natural gas (SNG) in the PTG factory was 1782 USD/ton. In terms of cost the cost of hydrogen production from electrolyzed water accounted for the largest proportion. In terms of product profit the sale of pure oxygen was the largest part of the profit. At present the carbon emission reduction index profit brought by SNG production accounted for a small proportion. In the future with technological progress industrial upgrading and the improvement in the carbon trading market PTG technology is expected to become one of the ways to achieve carbon-emission-reduction targets.
Artificial Neural Network Based Optimization of a Six-step Two-bed Pressure Swing Adsorption System for Hydrogen Purification
Apr 2021
Publication
The pressure swing adsorption (PSA) system is widely applied to separate and purify hydrogen from gaseous mixtures. The extended Langmuir equation fitted from the extended Langmuir-Freundlich isotherm has been used to predict the adsorption isothermal of hydrogen and methane on the zeolite 5A adsorbent bed. A six-step two-bed PSA model for hydrogen purification is developed and validated by comparing its simulation results with other works. The effects of the adsorption pressure the P/F ratio the adsorption step time and the pressure equalization time on the performance of the hydrogen purification system are studied. A four-step two-bed PSA model is taken into consideration and the six-step PSA system shows higher about 13% hydrogen recovery than the four-step PSA system. The performance of the vacuum pressure swing adsorption (VPSA) system is compared with that of the PSA system the VPSA system shows higher hydrogen purity than the PSA system. Based on the validated PSA model a dataset has been produced to train the artificial neural network (ANN) model. The effects of the number of neurons in the hidden layer and the number of samples used for training ANN model on the predicted performance of ANN model are investigated. Then the well-trained ANN model with 6 neurons in the hidden layer is applied to predict the performance of the PSA system for hydrogen purification. Multi-objective optimization of hydrogen purification system is performed based on the trained ANN model. The artificial neural network can be considered as a very effective method for predicting and optimizing the performance of the PSA system for hydrogen purification.
Optimization of Geothermal- and Solar-driven Clean Electricity and Hydrogen Production Multi-generation Systems to Address the Energy Nexus
Jan 2022
Publication
Given the limited sources of fossil fuels mankind should find new ways to meet its energy demands. In this regard geothermal and solar energy are acknowledged as reliable safe promising and clean means for this purpose. In this research study a comparative analysis is applied on geothermal and solar-driven multi-generation systems for clean electricity and hydrogen production through energy and exergy assessments. The system consists of an organic Rankine cycle a proton electrolyte membrane electrolyzer and a thermoelectric generator subsystem. The Engineering Equation Solver software has been utilized in order to model the system and obtain the output contours sensitivity analysis and exergy destruction. The results were calculated considering the ambient temperature of Bandar Abbas city as a case study considering the geothermal system due to better performance in comparison to the solar system. According to the sensitivity analysis the turbine efficiency evaporator inlet temperature thermoelectric generator suitability criterion pump efficiency and evaporator inlet mass flow rate are the most influential parameters. Also the exergy analysis showed that the utmost system's exergy destruction is pertinent to the evaporator and the least is related to the pump. In addition the system produces 352816 kWh and 174.913 kg of electrical power and hydrogen during one year.
Recent Development of Hydrogen and Fuel Cell Technologies: A Review
Aug 2021
Publication
Hydrogen has emerged as a new energy vector beyond its usual role as an industrial feedstock primarily for the production of ammonia methanol and petroleum refining. In addition to environmental sustainability issues energy-scarce developed countries such as Japan and Korea are also facing an energy security issue and hydrogen or hydrogen carriers such as ammonia and methylcyclohexane seem to be options to address these long-term energy availability issues. China has been eagerly developing renewable energy and hydrogen infrastructure to meet their sustainability goals and the growing energy demand. In this review we focus on hydrogen electrification through proton-exchange membrane fuel cells (PEMFCs) which are widely believed to be commercially suitable for automotive applications particularly for vehicles requiring minimal hydrogen infrastructure support such as fleets of taxies buses and logistic vehicles. This review covers all the key components of PEMFCs thermal and water management and related characterization techniques. A special consideration of PEMFCs in automotive applications is the highlight of this work leading to the infrastructure development for hydrogen generation storage and transportation. Furthermore national strategies toward the use of hydrogen are reviewed thereby setting the rationale for the hydrogen economy.
Comparison of Two Energy Management Strategies Considering Power System Durability for PEMFC-LIB Hybrid Logistics Vehicle
Jun 2021
Publication
For commercial applications the durability and economy of the fuel cell hybrid system have become obstacles to be overcome which are not only affected by the performance of core materials and components but also closely related to the energy management strategy (EMS). This paper takes the 7.9 t fuel cell logistics vehicle as the research object and designed the EMS from two levels of qualitative and quantitative analysis which are the composite fuzzy control strategy optimized by genetic algorithm and Pontryagin’s minimum principle (PMP) optimized by objective function respectively. The cost function was constructed and used as the optimization objective to prolong the life of the power system as much as possible on the premise of ensuring the fuel economy. The results indicate that the optimized PMP showed a comprehensive optimal performance the hydrogen consumption was 3.481 kg/100 km and the cost was 13.042 $/h. The major contribution lies in that this paper presents a method to evaluate the effect of different strategies on vehicle performance including fuel economy and durability of the fuel cell and battery. The comparison between the two totally different strategies helps to find a better and effective solution to reduce the lifetime cost.
Hollow CdS-Based Photocatalysts
Oct 2020
Publication
In recent years photocatalytic technology driven by solar energy has been extensively investigated to ease energy crisis and environmental pollution. Nevertheless efficiency and stability of photocatalysts are still unsatisfactory. To address these issues design of advanced photocatalysts is important. Cadmium sulphide (CdS) nanomaterials are one of the promising photocatalysts. Among them hollow-structured CdS featured with enhanced light absorption ability large surface area abundant active sites for redox reactions and reduced diffusion distance of photogenerated carriers reveals a broad application prospect. Herein main synthetic strategies and formation mechanism of hollow CdS photocatalysts are summarized. Besides we comprehensively discuss the current development of hollow-structured CdS nanomaterials in photocatalytic applications including H2 production CO2 reduction and pollutant degradation. Finally brief conclusions and perspectives on the challenges and future directions for hollow CdS photocatalysts are proposed.
Research on Carbide Characteristics and Their Influence on the Properties of Welding Joints for 2.25Cr1Mo0.25V Steel
Feb 2021
Publication
The carbide characteristics of 2.25Cr1Mo0.25V steel have an extremely important influence on the mechanical properties of welding joints. In addition hydrogen resistance behavior is crucial for steel applied in hydrogenation reactors. The carbide morphology was observed by scanning electron microscopy (SEM) and the carbide microstructure was characterized by transmission electron microscopy (TEM). Tensile and impact tests were carried out and the influence of carbides on properties was studied. A hydrogen diffusion test was carried out and the hydrogen brittleness resistance of welding metal and base metal was studied by tensile testing of hydrogenated samples to evaluate the influence of hydrogen on the mechanical properties. The research results show that the strength of the welding metal was slightly higher and the Charpy impact value was significantly lower compared to the base metal. The hydrogen embrittlement resistance of the welding metal was stronger than that of the base metal. The presence of more carbides and inclusions was the main cause of the decreased impact property and hydrogen brittleness resistance of the welding metal. These conclusions have certain reference value for designing and manufacturing hydrogenation reactors. View Full-Text
Effect of α′ Martensite Content Induced by Tensile Plastic Prestrain on Hydrogen Transport and Hydrogen Embrittlement of 304L Austenitic Stainless Steel
Aug 2018
Publication
Effects of microstructural changes induced by prestraining on hydrogen transport and hydrogen embrittlement (HE) of austenitic stainless steels were studied by hydrogen precharging and tensile testing. Prestrains higher than 20% at 20 °C significantly enhance the HE of 304L steel as they induce severe α′ martensite transformation accelerating hydrogen transport and hydrogen entry during subsequent hydrogen exposure. In contrast 304L steel prestrained at 50 and 80 °C and 316L steel prestrained at 20 °C exhibit less HE due to less α′ after prestraining. The increase of dislocations after prestraining has a negligible influence on apparent hydrogen diffusivity compared with pre-existing α′. The deformation twins in heavily prestrained 304L steel can modify HE mechanism by assisting intergranular (IG) fracture. Regardless of temperature and prestrain level HE and apparent diffusivity ( Dapp ) increase monotonously with α′ volume fraction ( fα′ ). Dapp can be described as log Dapp=log(Dα′sα′/sγ)+log[fα′/(1−fα′)] for 10%<fα′<90% with Dα′ is diffusivity in α′ sα′ and sγ are solubility in α′ and austenite respectively. The two equations can also be applied to these more typical duplex materials containing both BCC and FCC phases.
Synthetic Natural Gas Production from CO2 and Renewable H2: Towards Large-scale Production of Ni–Fe Alloy Catalysts for Commercialization
Apr 2020
Publication
Synthetic natural gas (SNG) is one of the promising energy carriers for the excessive electricity generated from variable renewable energy sources. SNG production from renewable H2 and CO2 via catalytic CO2 methanation has gained much attention since CO2 emissions could be simultaneously reduced. In this study Ni–Fe/(MgAl)Ox alloy catalysts for CO2 methanation were prepared via hydrotalcite precursors using a rapid coprecipitation method. The effect of total metal concentration on the physicochemical properties and catalytic behavior was investigated. Upon calcination the catalysts showed high specific surface area of above 230 m2 g−1. Small particle sizes of about 5 nm were obtained for all catalysts even though the produced catalyst amount was increased by 10 times. The catalysts exhibited excellent space-time yield under very high gas space velocity (34000 h−1) irrespective of the metal concentration. The CO2 conversions reached 73–79% at 300 °C and CH4 selectivities were at 93–95%. Therefore we demonstrated the potential of large-scale production of earth-abundant Ni–Fe based catalysts for CO2 methanation and the Power-to-Gas technology.
Synthesizing the High Surface Area g-C3N4 for Greatly Enhanced Hydrogen Production
Jul 2021
Publication
Adjusting the structure of g-C3N4 to significantly enhance its photocatalytic activity has attracted considerable attention. Herein a novel sponge-like g-C3N4 with a porous structure is prepared from the annealing of protonated melamine under N2/H2 atmosphere (PH-CN). Compared to bulk g-C3N4 via calcination of melamine under ambient atmosphere (B-CN) PH-CN displays thinner nanosheets and a higher surface area (150.1 m2/g) which is a benefit for shortening the diffusion distance of photoinduced carriers providing more active sites and finally favoring the enhancement of the photocatalytic activity. Moreover it can be clearly observed from the UV-vis spectrum that PH-CN displays better performance for harvesting light compared to B-CN. Additionally the PH-CN is prepared with a larger band gap of 2.88 eV with the Fermi level and conduction band potential increased and valence band potential decreased which could promote the water redox reaction. The application experiment results show that the hydrogen evolution rate on PH-CN was nearly 10 times higher than that of B-CN which was roughly 4104 μmol h−1 g−1. The method shown in this work provides an effective approach to adjust the structure of g-C3N4with considerable photocatalytic hydrogen evolution activity.
Self-Supported High-Entropy Alloy Electrocatalyst for Highly Efficient H2 Evolution in Acid Condition
Jul 2020
Publication
Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction (HER) with superior stability in acidic electrolyte is of critical importance for large-scale low-cost hydrogen production from water. Herein we report a CoCrFeNiAl high-entropy alloy (HEA) electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering (SPS) consolidation. The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry (HF-HEAa2) presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm−2 and a Tafel slope of 39.7 mV dec−1. The alloy effect of Al/Cr with Co/Fe/Ni at atomic level high-temperature crystallization as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H2SO4 solution. The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.
Physicochemical Properties of Proton-conducting SmNiO3 Epitaxial Films
Mar 2019
Publication
Proton conducting SmNiO3 (SNO) thin films were grown on (001) LaAlO3 substrates for systematically investigating the proton transport properties. X-ray Diffraction and Atomic Force Microscopy studies reveal that the as-grown SNO thin films have good single crystallinity and smooth surface morphology. The electrical conductivity measurements in air indicate a peak at 473 K in the temperature dependence of the resistance of the SNO films probably due to oxygen loss on heating. A Metal-Insulator-Transition occurs at 373 K for the films after annealing at 873 K in air. In a hydrogen atmosphere (3% H2/97% N2) an anomalous peak in the resistance is found at 685 K on the first heating cycle. Electrochemical Impedance Spectroscopy studies as a function of temperature indicate that the SNO films have a high ionic conductivity (0.030 S/cm at 773 K) in a hydrogen atmosphere. The activation energy for proton conductivity was determined to be 0.23 eV at 473–773 K and 0.37 eV at 773–973 K respectively. These findings demonstrate that SNO thin films have good proton conductivity and are good candidate electrolytes for low temperature proton-conducting Solid Oxide Fuel Cells.
Modeling and Statistical Analysis of the Three-side Membrane Reactor for the Optimization of Hydrocarbon Production from CO2 Hydrogenation
Feb 2020
Publication
Direct CO2 hydrogenation to hydrocarbons is a promising method of reducing CO2 emissions along with producing value-added products. However reactor design and performance have remained a challenging issue because of low olefin efficiency and high water production as a by-product. Accordingly a one-dimensional non-isothermal mathematical model is proposed to predict the membrane reactor performance and statistical analysis is used to assess the effects of important variables such as temperatures of reactor (Tr:A) shell (Ts:B) and tube (Tt:C) as well as sweep ratio (θ:D) and pressure ratio (φ:E) and their interactions on the products yields. In addition the optimized operating conditions are also obtained to achieve maximum olefin yields. Results reveal that interacting effects comprising AB (TrTs) AC (TrTt) AE (Trφ) BC (TsTt) CE (Ttφ) CD (Ttθ) and DE (θφ) play important roles on the product yields. It is concluded that higher temperatures at low sweep and pressure ratios can maximize the yields of olefins while simultaneously the yields of paraffins are minimized. In this regard optimized values for Tr Ts Tt θ and φ are determined as 325 °C 306.96 °C 325 °C 1 and 1 respectively.
Microwave Absorption of Aluminum/Hydrogen Treated Titanium Dioxide Nanoparticles
Dec 2018
Publication
Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis solar cells optics radar detection communications information processing and transport et al. Traditional mechanisms for such interactions in the microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study we present the first report of the microwave absorption of Al/H2 treated TiO2 nanoparticles where the Al/H2 treatment not only induces structural and optical property changes but also largely improves the microwave absorption performance of TiO2 nanoparticles. Moreover the frequency of the microwave absorption can be finely controlled with the treatment temperature and the absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of microwave absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased microwave absorption properties are largely increased visible-light and IR absorptions and enhanced electrical conductivity and reduced skin-depth which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
Overview of Biomass Conversion to Electricity and Hydrogen and Recent Developments in Low-Temperature Electrochemical Approaches
Nov 2020
Publication
Biomass is plant or animal material that stores both chemical and solar energies and that is widely used for heat production and various industrial processes. Biomass contains a large amount of the element hydrogen so it is an excellent source for hydrogen production. Therefore biomass is a sustainable source for electricity or hydrogen production. Although biomass power plants and reforming plants have been commercialized it remains a difficult challenge to develop more effective and economic technologies to further improve the conversion efficiency and reduce the environmental impacts in the conversion process. The use of biomass-based flow fuel cell technology to directly convert biomass to electricity and the use of electrolysis technology to convert biomass into hydrogen at a low temperature are two new research areas that have recently attracted interest. This paper first briefly introduces traditional technologies related to the conversion of biomass to electricity and hydrogen and then reviews the new developments in flow biomass fuel cells (FBFCs) and biomass electrolysis for hydrogen production (BEHP) in detail. Further challenges in these areas are discussed.
Analysis of Strategic Directions in Sustainable Hydrogen Investment Decisions
Jun 2020
Publication
This study seeks to find the appropriate strategies necessary to make sustainable and effective hydrogen energy investments. Within this scope nine different criteria are defined regarding social managerial and financial factors. A hesitant interval-valued intuitionistic fuzzy (IVIF) decision-making trial and evaluation laboratory (DEMATEL) methodology is considered to calculate the degree of importance of the criteria. Additionally impact relation maps are also generated to visualize the causality relationship between the factors. The findings indicate that the technical dimension has the greatest importance in comparison to managerial and financial factors. Furthermore it is also concluded that storage and logistics research and development and technological infrastructure are the most significant factors to be considered when defining hydrogen energy investment strategies. Hence before investing in hydrogen energy necessary actions should be taken to minimize the storage and logistic costs. Among them building the production site close to the usage area will contribute significantly to this purpose. In this way possible losses during the transportation of hydrogen can be minimized. Moreover it is essential to identify the lowest-cost hydrogen storage method by carrying out the necessary research and development activities thereby increasing the sustainability and effectiveness of hydrogen energy investment projects.
Combined Soft Templating with Thermal Exfoliation Toward Synthesis of Porous g-C3N4 Nanosheets for Improved Photocatalytic Hydrogen Evolution
Apr 2021
Publication
Insufficient active sites and fast charge carrier recombination are detrimental to photocatalytic activity of graphitic carbon nitride (g-C3N4). In this work a combination of pore creating with thermal exfoliation was employed to prepare porous g-C3N4 nanosheets for photocatalytic water splitting into hydrogen. Hexadecyl trimethyl ammonium chloride (CTAC) as the soft template promoted the formation of porous g-C3N4 during the thermal condensation of melamine. On further post-synthesis calcination the porous g-C3N4 aggregates were exfoliated into discrete nanosheets accompanied by an increase in specific surface area and defects. Optimal porous g-C3N4 nanosheets achieved 3.6 times the photocatalytic hydrogen evolution rate for bulk counterpart. The enhanced photocatalytic activity may be ascribed to TCN-1%CTAC has larger specific surface area stronger optical absorption intensity and higher photogenerated electron–hole separation efficiency. The external quantum efficiency of TCN-1%CTAC was measured to be 3.4% at 420 nm. This work provides a simple combinatorial strategy for the preparation of porous g-C3N4 nanosheets with low cost environmental friendliness and enhanced photocatalytic activity.
On-Board Liquid Hydrogen Cold Energy Utilization System for a Heavy-Duty Fuel Cell Hybrid Truck
Aug 2021
Publication
In this paper a kind of on-board liquid hydrogen (LH2 ) cold energy utilization system for a heavy-duty fuel cell hybrid truck is proposed. Through this system the cold energy of LH2 is used for cooling the inlet air of a compressor and the coolant of the accessories cooling system sequentially to reduce the parasitic power including the air compressor water pump and radiator fan power. To estimate the cold energy utilization ratio and parasitic power saving capabilities of this system a model based on AMESim software was established and simulated under different ambient temperatures and fuel cell stack loads. The simulation results show that cold energy utilization ratio can keep at a high level except under extremely low ambient temperature and light load. Compared to the original LH2 system without cold energy utilization the total parasitic power consumption can be saved by up to 15% (namely 1.8 kW).
Enhanced Hydrogen Storage of Alanates: Recent Progress and Future Perspectives
Feb 2021
Publication
The global energy crisis and environmental pollution have caused great concern. Hydrogen is a renewable and environmentally friendly source of energy and has potential to be a major alternative energy carrier in the future. Due to its high capacity and relatively low cost of raw materials alanate has been considered as one of the most promising candidates for hydrogen storage. Among them LiAlH4 and NaAlH4 as two representative metal alanates have attracted extensive attention. Unfortunately the high desorption temperature and sluggish kinetics restrict its practical application. In this paper the basic physical and chemical properties as well as the hydrogenation/dehydrogenation reaction mechanism of LiAlH4 and NaAlH4 are briefly reviewed. The recent progress on strategic optimizations toward tuning the thermodynamics and kinetics of the alanate including nanoscaling doping catalysts and compositing modification are emphatically discussed. Finally the coming challenges and the development prospects are also proposed in this review.
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