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Modern energy systems are large distributed systems and, as a rule, contain energy storage systems and, in particular, hydrogen batteries and hydrogen production systems. The use of hydrogen for energy transportation has recently been actively studied in a number of scientific projects. To ensure continuous operation of instrumentation and control equipment on long hydrogen pipelines (gas and cryogenic), it is important to ensure constant autonomous power supply to these systems. This can be solved using micromechanical energy microgeneration systems for the uninterrupted operation of various sensors, which are installed in large numbers on almost all elements of the structure and infrastructure. In addition, an important area of scientific research is the revision of the concepts and appearance of traditional devices of modern renewable energy: windmills, solar cells, turbines, etc. Fundamentally new energy devices are on the agenda, capable of recovering mechanical energy of any power and supplying it to the consumer in the form of a given specific energy flow. Collection of chaotically distributed natural energy of the environment (mechanical energy in the form of: vibrations, acoustic vibrations, wave energy, gusts of wind, tornadoes, precipitation, vibrations of the earth's crust, etc.), as well as collection of dissipated energy from artificial sources (iron and automobile highways, airstrips, spaceports, production facilities, etc.) with the help of mechanical microgenerators will allow the recovery and conversion of mechanical energy of various powers, including low power, into a universal energy carrier - hydrogen. Mechanical vibrations of artificial origin are of particular interest due to their widespread use for domestic and industrial purposes in a wide range of vibrations. The energy of mechanical vibrations can be collected and converted into electrical energy using piezoelectric, electromagnetic, triboelectric or electrostatic (capacitive) energy converters. Electrostatic microelectromechanical energy converters are considered the most promising among other energy converters, since their manufacturing processes are based on standard technology for the production of integrated circuits and microelectromechanical systems. Energy conversion by an electrostatic converter is carried out due to an external mechanical force that does work against the force of attraction of the charged electrodes of a variable capacitor. To transfer the received electrical energy to the load of the consuming device, the electrostatic converter is connected to the corresponding electrical circuits (conditioning circuits). Such a system as a whole is a kind of microgenerator or energy collector. Microenergy flow recovery systems integrated into large energy systems will ensure the collection and recovery of significant amounts of energy for remote energy consumers. At the same time, the concept of a distributed mechanical energy recovery system is quite simple: a mechanical energy receiver - a converter into electrical energy - a preliminary electrical storage device - an energy distributor - an electric energy accumulator - an electrolyser - a hydrogen accumulator - a fuel cell. To optimize the operation of the working circuit, including preliminary electrical systems for energy storage and conversion: capacitors and electric energy accumulators, electrolyzers; To ensure their durability and reliability, flexible automatic control of electrical power distribution is necessary. The real work was done to solve that problem. In addition, for extended and large power facilities it is important to ensure widespread sensory control of system parameters. At the same time, if all sensors receive power from an autonomous energy-generating device, then the costs of creating extended communications for instrumentation will be sharply reduced. In addition, the reliability of the control system will significantly increase. The results of studying operation features of a kinetic microgenerator with reduced output voltage are presented. The performance of a multi-stage modified Bennet doubler is compared to a system including a two-stage modified Bennet doubler and a diode-capacitor voltage divider. It is shown that with an increase of the number of stages in the modified Bennet doubler, the conversion of mechanical energy into electrical energy becomes less and less efficient. At the same time, for achieving the maximum energy accumulation rate (power), a two-stage power amplifier based on the Bennet doubler is preferable. It is established that when analyzing the operation of a diode-capacitor voltage divider, it is necessary to take into account the intrinsic (reverse) capacitances of the discharging diodes affecting the divider operation significantly. The divider behavior features while changing the load resistance and the intrinsic capacitances of the discharge diodes are found and analyzed. Analytical expressions linking the main characteristics of the microgenerator as a whole with the parameters of the electronic components used are derived. It is shown that for expanding the range of the "correct" division of the divider, it is necessary to use discharge diodes with minimal intrinsic capacitances, and also that connecting a load to the Bennet doubler as a voltage divider changes the permissible capacitance modulation depth of the variable capacitor. This paper examines the concepts of creating large energy-generating flows based on arrays of micromechanical energy converters placed on optimal energy-efficient receiving surfaces and analyzes the issues of cryogenic production, storage, consumption and transportation of hydrogen. Stationary and mobile cryogenic storage systems for hydrogen are considered. Much attention is paid to the safety of large cryogenic and gas hydrogen systems. [ABSTRACT FROM AUTHOR]

Hydrogen is a clean energy in the world and by-product hydrogen is an important part of global hydrogen production. The yield of by-product hydrogen accounts for 18% of hydrogen production globally. To analyze the current stage and calculate CO 2 emissions reduction of by-product hydrogen, sources, purification technology, utilization models, comparison of by-product hydrogen and other hydrogen resources, reduction of CO 2 emissions, prospects of industrial by-product hydrogen were analyzed from the respective of industrial utilization. The resources of by-product hydrogen will get expanded further. It can facilitate the utilization of industrial by-product hydrogen to establish industrial zone with the factories producing by-product hydrogen and the downstream factories utilizing by-product hydrogen under the current technology conditions. By analyzing the relevant data, it is calculated that the utilization of industrial by-product hydrogen can reduce CO 2 emissions by 6.11x105 t per year in 2022. With the development of hydrogen purification technology, by-product hydrogen can provide an efficient and economical way to reduce CO 2 emissions for global warming migration before the completion of green hydrogen substitution for other hydrogen. [Display omitted] • CO 2 emissions reduction can reach 6.11x105 t/a through the utilization of by-product hydrogen in 2022. • Hydrogen purification technology plays a significant role in the utilization of industrial by-product hydrogen. • The resources of industrial by-product hydrogen will get expanded in the future. [ABSTRACT FROM AUTHOR]

Multigenerational energy conversion plants are one of the most promising solutions for tackling environmental challenges and making efficient use of energy sources. In this regard, a newly designed multigeneration plant integrated with a methane-based Brayton cycle, a steam Rankine cycle, a supercritical CO 2 -based Brayton cycle, a multi-effect desalination process, a PEM unit, a domestic water heater process, and two thermoelectric generators is integrated, proposed and analyzed. The thermodynamic and environmental assessments of the developed paper are conducted and examined with energy and exergy efficiencies as well as CO 2 emission rate. Similarly, a parametric study is executed and reported, by the way, to define the impact of the various significant factors on the developed plant's efficiency. In the end, the CO 2 emission rate is determined and compared according to different energy conversion plants. In light of the analysis results, the net power, hydrogen, and freshwater production capacities of the reference study are calculated to be 1336 kW, 0.002004 kgs−1, and 0.954 kgs−1, respectively. Additionally, it is found that the developed study's energetic and exergetic performances are 55.76% and 52.17%. According to emission analysis results, the multigeneration system emits 272.2 k g / M W h less CO 2 emissions than the single energy conversion system. • A newly designed multigeneration plant is suggested. • Combination of a superciritical CO 2 based Brayton cycle is proposed. • Thermodynamic and environmental analysis of the multigeneration plant is conducted. • Freshwater, hydrogen, power and heating purposes are fulfilled. • The overall energy and exergy efficiencies are 55.76% and 52.17%, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have driven great interest due to a large specific surface area to volume ratio and adjustable surface behaviors, which show huge potentials for enhancing the activity of energy conversion and property optimization. In order to regulate the physicochemical properties of photocatalyst for water splitting reaction, defect engineering on 2D materials have drawn great attention. Meanwhile, a widely used strategy to improve the H 2 evolution rate kinetics has been achieved. In this paper, we prepared AgBr/g-C 3 N 4 catalyst by chemical precipitation. The obtained photocatalyst shows a unique charge transfer pathway. In addition, a deep understanding of the proton shuttle during H 2 evolution reactions can offer profound opinion into heterostructure construction and property optimization. It is found that the enhanced performance is correlated to the superiority of the S-scheme heterojunction and defect engineering on graphitic carbon nitride 2D materials. This work offers a novel method for improving efficiency in terms of energy conversion and property optimization. [Display omitted] • Surface nitrogen vacancy is instrumental in the chemisorption and activation of H 2 O. • S-scheme band of AgBr/g-C 3 N 4 is conjectured by the experiments and DFT calculations. • The prolonged photocarrier lifetime has increased H 2 production. • The results of XPS are consistent with the mechanism of S-scheme heterojunction. [ABSTRACT FROM AUTHOR]

The core of this work is a comprehensive investigation of ethanol oxidative reforming kinetics over a Pt–Ni/CeO 2 –Al 2 O 3 catalyst in the presence of fuel grade bioethanol, which has been very rarely investigated in the past. The developed kinetic model also included the formation of solid carbon. The results show that the reaction scheme involving ethylene and acetaldehyde formation from ethanol, their subsequent decomposition, methane oxidation as well as steam reforming and water gas shift reaction is able to assure a satisfactory fitting of the experimental data. Moreover, the above formulation, deposited on a porous support (Ni–Fe foam), was employed for a very long stability test (almost 400 h) and subjected to several oxidation-reduction cycles: at 600 °C, after 170 h of time-on-stream, a stable ethanol conversion of 95% and hydrogen yield of 35% were recorded, with near-zero carbon emission during its thermochemical conversion for energy generation. • Investigation of Pt–Ni/CeO 2 –Al 2 O 3 kinetics for fuel grade ethanol reforming. • Integration of solid carbon and low-concentrated species in the kinetic model. • Very satisfactory fitting of the experimental data between 300 and 550 °C. • Considerable stability of the catalytic formulation deposited on a foam carrier. [ABSTRACT FROM AUTHOR]

The looming threat of global warming has elicited efforts to develop reliable sustainable energy resources. Hydrogen as a clean fuel is deemed a potential solution to the problem of storage of power from renewable energy technologies. Among current thermochemical hydrogen generation methods, the thermochemical copper-chlorine (Cu–Cl) cycle is of high interest owing to lower temperature requirements. Present study investigates a novel heat exchanger comprising a thermoelectric generator (TEG) to recover heat from high temperature molten CuCl exiting the thermolysis reactor. Employing casting/extrusion method, the performance of the proposed heat exchanger is numerically examined using COMSOL Multiphysics. Results indicate that maximum generated power could exceed 40 W at the matching current of 4.5 A. Maximum energy conversion efficiency yields to 7.1%. Results demonstrate that TEG performance boosts with increasing the inlet Re number, particularly at the hot end. For the molten CuCl chamber, findings denote that there is a 36% discrepancy between highest and lowest Re numbers. Similarly, the highest efficiency value pertains to the case with the highest inlet velocity. Moreover, the highest temperature difference between inlet and outlet of the cooling water is about 28 °C and 10 °C for the lowest and highest inlet Re numbers, respectively. Average deviation from anticipated friction factor and Nusselt number are 0.31% and 12.62%, respectively. [Display omitted] • Heat recovery from cuprous chloride leaving the thermolysis reactor of Cu–Cl cycle. • Thermoelectric generator is modeled numerically for heat recovery. • Apparent heat capacity method to model molten CuCl phase change. • Maximum energy conversion efficiency yields to 7.1%. • Maximum generated power could exceed 40 W at the matching current of 4.5 A. [ABSTRACT FROM AUTHOR]

Efficient energy storage from intermittent renewables can rely on the conversion of temporary energy excess by alkaline electrolysis, yielding oxygen and green hydrogen, which can be stored and used on demand. Electrodes made of laser-induced graphene (LIG) materials offer many advantages over the traditional graphene processing routes, due to inherent simplicity and low cost-benefit. Despite poorly studied, LIG electrodes are promising for water splitting when properly doped/modified with metals. However, proper design and processing optimization should be considered. The present study is devoted to the laser processing effects on the LIG electrode performance towards water splitting in alkaline media. Promising guidelines were obtained for hydrogen production, showing high electrochemical activity, while the microstructural degradation can be minimised by selecting suitable laser processing conditions, such as 3.6 W of laser power, 100 mm/s of laser scan rate, 36 mJ/mm of energy density and 2 laser scans. • Laser processing affects the LIG electrode performance during water splitting. • Effects of laser power, scan rate, energy density and laser scans were studied. • Low laser power is an essential processing parameter for the LIG's stability. [ABSTRACT FROM AUTHOR]

Outer wall temperature and exergy efficiency of micro-combustor are very essential in determining micro-thermophotovoltaic energy conversion effectiveness. In this study, a swirl rib was designed to improve the thermal efficiency of micro-combustor since a swirl flow can be formed when the hydrogen/air mixture passes through the swirl rib, which increases the residence time and turbulence intensity of the mixture. Effects of position, height, spacing, and shape of the swirl rib on the thermal performance of a cylindrical micro-combustor were investigated numerically. The thermal performance shows different trends with the variation of these geometric parameters, and an optimum mean outer wall temperature of 1260 K is obtained at the distance between the inlet and the rib of 7 mm, the rib height of 1.2 mm and the rib spacing of 0.5 mm, but this optimum setting triggers the large pressure drop that impedes further improvement of the micro-combustor performance. To minimize this effect, three rip shapes including rectangle, trapezoid and inversed trapezoid was designed. The results show that the micro-combustor with trapezoidal rib presents better thermal performance. This study provides theoretical guidance for the optimal design of the hydrogen-fueled micro-combustor. • A swirl rib was proposed to improve micro-combustor performance was proposed. • Effects of the swirl rib on micro-combustor performance were investigated. • Outer wall temperature and exergy efficiency were promoted significantly. • The induced pressure drop problem by swirl rib can be controlled by adjusting rib shape. [ABSTRACT FROM AUTHOR]

Sonochemistry is considered as one of the cleaner pathways for hydrogen production. The present paper investigates the potential of this technique based upon mass, mass to energy and energy conversion metrics, using modelling and experimental approaches. Four scenarios are examined assuming four saturating gases, namely O 2 , air, N 2 and Ar, four acoustic frequencies, i.e., 20, 210, 326 and 488 kHz, and considering common acoustic intensities then common net electric power. The study revealed that Ar is the best fitting saturating gas for the sonochemical production of hydrogen. With a common acoustic intensity of 0.48 W/cm2, an optimum ratio of H 2 molar yield to acoustic energy intensity is retrieved at 210 kHz, while with a common net electric power of 87 W, the highest ratio of hydrogen yield to electric energy was observed at 20 kHz. Results were interpreted based upon emitter surface, energy conversion and distinction of calorimetric and cavitational energies. • Sono-H 2 is examined through mass, mass to energy and energy conversion metrics. • Ar is the best fitting saturating gas for the sonochemical production of hydrogen. • At 0.48 W/cm2, the optimal frequency for H 2 yield to acoustic intensity is 210 kHz. • At 87 W e , the highest ratio for H 2 yield to electric energy is observed at 20 kHz. • The optimal frequency for electric to acoustic energy conversion is 20 kHz. [ABSTRACT FROM AUTHOR]

Designing next-generation advanced electrode materials by engineering their structural and compositional features can provide a feasible strategy to enhance the electrochemical performance of energy conversion devices. In this study, the rational pathway to design and fabricate nanotube arrays of titanium manganese phosphide via etching of titanium-manganese alloy followed by plasma phosphidation in PH 3 environment is presented and discussed. The structural and elemental analyses of the air-annealed electrodes before plasma treatment confirmed the presence of different binary oxides; TiO 2 , MnO, and Mn 2 O 3. However, the XPS fitting showed the presence of Ti3+ and higher ratio of MnO when annealed in hydrogen atmosphere. The presence of composite oxides resulted in a band gap reduction, which increased the light harvesting capability of the material. This synergetic effect resulted also in a shift in the open-circuit voltage (V OC) and almost 10-fold increase in the photocurrent density compared to the performance of the nanotubes annealed in air. Mott-Schottky analysis showed a four-orders of magnitude enhancement in the carrier density for the electrodes annealed in Hydrogen and treated in PH 3 -plasma compared to those annealed in O 2 or air, ascribed to the creation of Ti3+ defects and phosphidation. Our study thus paves the way to a new approach for creating high-performance hybrid electrodes for PEC water splitting. Image 1 • Bimetallic Ti–Mn phosphide nanotubes were fabricated via CVD plasma phosphidation. • Annealing in H 2 atmosphere enabled the defect engineering of the nanotubes. • Phosphidation of the NTs resulted in a 10-fold increase in the photocurrent density. • A four-order of magnitude enhancement in the carrier density. • Synergy between point defects and phosphidation is a promising strategy. [ABSTRACT FROM AUTHOR]

A micro-combustor is the key component of the micro thermo photovoltaic power generation system. The energy conversion efficiency of the system strongly depends on the outer wall temperature and the exergy efficiency of the micro-combustor. A novel preheater-conductor plate was designed to be inserted into a cylindrical micro-combustor to improve the outer wall temperature and the exergy efficiency by preheating premixed hydrogen/air mixture via the preheater plate and conducting out the heat in the combustion chamber via the conductor plate. The impact of the width of preheater plate, the gradually increased and decreased thickness with divergent angle and convergent angle of conductor plate, and the inserted number of conductor plate on the thermal performance of the micro-combustor were investigated. It is found that the gradually varying thickness of the conductor plate has a slight influence on micro-combustor performance compared to other factors. Inserting a preheater-conductor plate with the 0.5 mm-wide preheater plate and the three 0.5 mm-thick conductor plates improve the mean outer wall temperature and the exergy efficiency of the micro-combustor by 173 K and 22.9% respectively. It is indicated that the proposed preheater-conductor plate is capable of considerably improving the thermal performance of premixed hydrogen/air fueled cylindrical micro-combustor. • A novel preheater-conductor plate for improving micro-combustor performance was proposed. • The premixed hydrogen/air mixture can be preheated via the preheater plate. • The heat in the combustion chamber can be conducted into the wall via the conductor plate. • Outer wall temperature and exergy efficiency of micro-combustor increased significantly. [ABSTRACT FROM AUTHOR]

There have been reports of ignition of high-pressure hydrogen during its sudden release for unexplained reasons and ignition mechanism still need to be further investigated. In this paper, mechanism of spontaneous ignition of high-pressure hydrogen during its sudden release into the L-shaped tube is investigated. LES, EDC model, 10-step like opening process of burst disk and 18-step detailed hydrogen combustion mechanism are employed. Three cases with burst pressures of 2.16, 6.21, and 9.10 MPa are simulated. It is found that shock wave is strongly reflected after it hits the tube corner wall, forming a reflected-shock-affected region and an energy conversion region with higher temperature, greater pressure and lower velocity. Afterwards, the reflected shock wave moving forward is reflected several times by the tube wall until it disappears and oblique shock is generated. After the hydrogen/air mixture enters the corner, it extends downstream along inner wall and separated from the main hydrogen/air mixture. The reflected shock wave moving backward interacts with the expansion waves and increases the temperature and pressure again, but spontaneous ignition cannot be initiated. Three mechanisms of spontaneous ignition of high-pressure hydrogen in the L-shaped tube are proposed eventually. The results reproduce the experimental spontaneous ignition conditions and positions, indicating that the numerical models can be applied as a tool for hydrogen safety engineering. • Mechanism of spontaneous ignition in the L-shaped tube is numerically studied. • A reflected-shock-affected region and an energy conversion region is formed. • The results well reproduce the spontaneous ignition conditions and positions. • Three mechanisms in the L-shaped tube are proposed. [ABSTRACT FROM AUTHOR]

Climate change increases the odds of worsening drought and generating extreme weather events, being the poorest nations the most vulnerable. The emission of greenhouse gases (GHG) from anthropogenic activities have a considerable impact on climate change; in particular, the emission of carbon dioxide (CO 2) and methane (CH 4) has the weightiest and most aggressive impact on the Earth. An emergent solution is to convert those specific gases into syngas (CO + H 2) by using plasma technology; which offers reduced specific energy, and it is capable to produce very energetic species with instantaneous sequential chemical reactions. This work aims to validate the production of syngas comprising acetylene (C 2 H 2) from the treatment of Biogas samples and a mixture composed of CH 4 , CO 2 , and N 2 using warm plasma reactors. Specific energy (SE) and Energy Conversion Efficiency (ECE) were obtained in the function of experimental settings, showing the potential of the warm plasma technology on GHG treatment. Additionally, a comparison between warm plasma and thermal cracking processes has shown that H 2 is generated more than 200 times faster and in a bigger quantity (more than 8 times) in a warm plasma than for conventional heating process. • High energy transfer energy is reached, when two series plasma reactor are operated. • The Optimal Conversion, selectivity and Energy Cost are presented. • The gliding plasma discharge increases the column length enhancing the reaction time. • The H 2 generation rates is much faster than those obtained by thermal cracking. • Working at 100 kHz in plasma discharge a better molecules splitting is gained. [ABSTRACT FROM AUTHOR]

Hydrogen is recognized as zero-carbon fuel having the highest calorific value per unit mass as compared to other fuels. Butanol is also a promising biofuel having better fuel characteristics as compared to bioethanol. Thus, aim of the present study was concomitant hydrogen and n-butanol production via codigestion of organic wastewater such as cane molasses (CM), distillery effluent (DE) and starchy wastewater (SWW) and nitrogenous residues. The addition of co-substrate to organic wastewater has resulted in 12.2, 1.1 and 6.6 folds increase in hydrogen production in comparison to CM, DE and SWW, respectively as the sole substrate. Maximum energy conversion efficiency and positive net energy gain of 50.16% and 7.29 KJ gCOD−1, respectively were achieved using SWW supplemented with water hyacinth (WH). Acid pretreatment of WH leads to higher hydrogen and butanol production of 3160 mL L−1 and 4.5 g L−1, respectively with 89% energy conversion efficiency. This study shows the suitability of SWW with acid treated WH as feedstock for sustainable and efficient bioenergy generation with an additional advantage of waste management. • Codigestion of SWW and WH leads to higher hydrogen and butanol production. • Positive net energy gain of 7.29 KJ g−1COD was obtained. • Acid pretreatment of WH leads to maximum energy conversion efficiency of 89%. • H 2 and butanol production of 3.16 L L−1 and 4.5 g L−1, respectively was achieved. [ABSTRACT FROM AUTHOR]

In this study, a novel Ocean Thermal Energy Conversion (OTEC) based tri-generation system that produces ammonia, cooling and power is developed and analysed. This OTEC plant operates on the naturally existing temperature difference that exists in various depths of the ocean. The OTEC plant used in this study is operated using a single-stage ammonia Rankine cycle. The discharge seawater from the condenser in the organic Rankine cycle is used to provide district cooling. Two different operation cases of the analysed system are considered, where for the first case 50% of the power produced is stored in the form of ammonia during the off-peak hours. The second case is for complete power production proposed for peak hours. For the case where 50% of the power produced (case 1) is used to produce ammonia the highest energy and exergy efficiency is found to be 1.37% and 56.17% respectively. As for the case where, only power is produced (case 2) the maximum energy and exergy efficiency of the OTEC plant is found to be 1.83% and 78.02% respectively. The corresponding maximum power production was 6612 kW and 13,224 kW for cases 1 and 2. The maximum hydrogen and ammonia production rate is found to be 94.35 kg/h and 534.7 kg/h at peak efficiency values. The cooling duty at the peak energy and exergy efficiency is found to be 64.4 MW where the condenser temperature is 11.38 °C. • A comprehensive study for the cooling duty associated with OTEC is performed. • Energy and exergy efficiencies of the system are found to be 1.37% and 56.17% (Case 1). • Energy and exergy efficiencies of the system are found to be 1.83% and 78.02% (Case 2). • The maximum hydrogen and ammonia production rates are 94.35 kg/h and 534.7 kg/h. [ABSTRACT FROM AUTHOR]

Economic feasibility is important for the development of microalgae bioenergy industry. Dark fermentation of microalgal residue in a biorefinery context can improve the energy conversion efficiency of biomass and reduce the cost of microalgae industry. The present study proposes a promising dark fermentation model that combines thermophilic hydrogen-producing bacteria with algal residue substrates. Lipid-extracted Dunaliella residue can greatly improve hydrogen production by Thermococcus eurythermalis A501, the yields of which are more than four times higher than with algal cells as substrates. Under the optimal conditions of 2.5 g/L algal residue concentration and a 2:1 initial volume ratio of gas to liquid, the highest hydrogen yields of 192.35 and 183.02 mL/g volatile solid (VS) with algal residue of Dunaliella primolecta and D. tertiolecta are obtained, respectively, in less than 19 h without any pretreatment. This work may provide a biorefinery approach for comprehensive utilization of microalgae resources. • T. eurythermalis A501 with Dunaliella biomass is an efficient H 2 production mode. • Lipid-extracted Dunaliella algal residue can greatly improve the H 2 production. • Algal concentration at 2.5 g/L and gas-liquid ratio at 2:1 reached optimal H 2 yield. • 192.35 mL/g VS H 2 yield was obtained by T. eurythermalis A501 without pretreatment. [ABSTRACT FROM AUTHOR]

In this paper, a detailed thermodynamic equilibrium and efficiency analysis of the MnSO 4 /MnO water splitting (WS) cycle is carried out using HSC Chemistry software. By drifting the molar flow rate of inert Ar ( n ˙ A r ) and thermal reduction temperature ( T H ), the thermodynamic compositions related to both thermal reduction (TR) and WS steps are identified. Moreover, the consequence of T H , n ˙ A r , and WS temperature ( T L ) on the process parameters associated with the cycle is also inspected. The obtained results denote that this cycle can attain a solar-to-fuel energy conversion efficiency () up to 45.3% if the TR and WS steps are conducted at 1573 K and 550 K, respectively. By employing heat recuperation up to 10, 30, and 50%, the η s o l a r − t o − f u e l of the MnSO 4 /MnO WS cycle can be increased up to 47.6%, 53.1%, and 60.0%, correspondingly. Based on the η s o l a r − t o − f u e l = 45.3%, the performance of the MnSO 4 /MnO WS cycle appears to be better than the formerly probed metal oxide based WS cycles. • T H reduces from 1537 to 1338 K as the n˙ Ar upsurges from 1 to 30 mol/s. • Production of H 2 via water splitting is feasible below 560 K. • Uppermost η solar–t–fuel = 45.3% can be attained at T H = 1573 K and T L = 550 K. • η solar–t–fuel rises up to 47.6%, 53.1%, and 60.0% by employing 10, 30, and 50% HR. [ABSTRACT FROM AUTHOR]

Development of highly effective and stable electrocatalysts is urgent for various energy conversion applications. Herein, a facile co-reduction approach was developed to fabricate three-dimensional (3D) hyperbranched PtRh nanoassemblies (NAs) under solvothermal conditions, where creatinine and cetyltrimethylammonium chloride (CTAC) were employed as the structure-directing agents. The as-synthesized nanocatalyst exhibited intriguing catalytic characters for hydrogen evolution reduction (HER) with a low overpotential (20 mV) at 10 mA cm−2 and a small Tafel slope (49.01 mV dec−1). Meanwhile, the catalyst showed remarkably enlarged mass activity (MA: 2.16/2.02 A mg−1) and specific activity (SA: 4.16/3.88 mA cm−2) towards ethylene glycol and glycerol oxidation reactions (EGOR and GOR) alternative to commercial Pt black and homemade Pt 3 Rh nanodendrites (NDs), PtRh 3 NDs and Pt nanoparticles (NPs). This method offers a feasible platform to fabricate bifunctional, efficient, durable and cost-effective nanocatalysts with finely engineered structures and morphologies for renewable energy devices. Image 1 • Hyperbranched PtRh NAs were synthesized by a solvothermal method in OAm. • Creatinine and CTAC behaved as co-structure-directing agents in this synthesis. • The PtRh NAs displayed great enhancement in the catalytic performances for HER and polyhydric alcohol oxidation. [ABSTRACT FROM AUTHOR]

Hydrogen production from water splitting into photoelectrochemical cells is a promising alternative for reducing the use of fossil fuels. Here, we synthesize by spray pyrolysis a porous ZnBi 38 O 60 /γ-Bi 2 O 3 film with a surface area of 744 m2 g−1 for use as a photocathode in water-splitting cells. The film of ZnBi 38 O 60 with 3 wt% Bi 2 O 3 has 2.3 eV bandgap energy and a conduction band energy of −2.14 V vs. RHE at pH 6.99, which is thermodynamically suitable for reducing H+ to H 2. Under illumination, the film produces a current density of −1.55 mA cm−2 at 0 V vs. RHE with an onset potential of 0.84 V vs. RHE. HC-STH efficiency is 0.09% at 0.17 V vs. RHE and IPCE at 0 V vs. RHE is 3.8% at 480 nm. Under continuous operation, the ZnBi 38 O 60 /γ-Bi 2 O 3 film shows a stable photocurrent of −0.4 mA cm−2 at 0 V vs. RHE for 1800 s with 100% Faradaic efficiency. Image 1 • ZnBi 38 O 60 /Bi 2 O 3 photocathode was synthesized by spray pyrolysis. • ZnBi 38 O 60 /Bi 2 O 3 film has 2.3 eV bandgap energy and flatband potential of 0.16 V. • ZnBi 38 O 60 /Bi 2 O 3 film produced a current density of −1.55 mA cm−2 at 0 V vs. RHE. • ZnBi 38 O 60 /Bi 2 O 3 shows HC-STH of 0.09% at 0.17 V vs. RHE and IPCE of 3.8% at 480 nm. • Under continuous operation, a stable photocurrent of −0.4 mA cm−2 was observed. [ABSTRACT FROM AUTHOR]

The Mg-bearing Al-Ga-In-Sn alloy with more stable hydrogen generation rate during hydrolysis reaction was synthesized, which is great suitable for the on-board hydrogen supply applications. The test results show that the hydrogen release rate of the Mg-bearing alloys could be effectively controlled. In particular, when the Mg dosage is 0.5 wt.%, the average hydrogen generation rate can even be reduced to 2.1 ml/min·g, while the total energy conversion efficiency of Al has not been affected and still reaches to nearly 100%. Further analysis shows that the reduction of hydrogen production rate during the Al-water reaction process is closely related to the changes of the phase compositions and the microstructure of grain boundary phase (GB-phase) particles in these alloys. Moreover, the electrochemical tests further clarify the reactivity of the alloys with different Mg dosage. • Mg-doping reduces the H 2 release rate but achieves 100% energy conversion. • Mg 2 Sn and In starts to appear in GB-phase particles with Mg doping. • Mg 2 Sn and In simple substance do not co-exist in the same GB-phase particle. • Mg-doping results in a morphology change of particles from stereoscopic to linear. • The average H 2 rate even reduced to 2.1 ml/min when Mg dosage is 0.5 wt%. [ABSTRACT FROM AUTHOR]

Combustion is the primary source for exergy loss in power systems such as combustion engines. To elucidate the exergy loss behaviors in combustion and explore the principle for efficiency improvement, the second-law thermodynamic analysis was conducted to analyze the energy conversion characteristics in laminar premixed flames of methane/hydrogen binary fuels. The sources causing exergy losses in laminar premixed flames included five parts, namely heat conduction, mass diffusion, viscous dissipation, chemical reactions and incomplete combustion, respectively. The calculations were conducted at both atmospheric and elevated pressures, with the equivalence ratio varying from 0.6 to 1.5 and the hydrogen blending ratio increasing from 0% to 70%. The results indicated that the total exergy loss firstly increased and then decreased with increased equivalence ratio, and reached the minimum value at the equivalence ratio of 0.9. This was primarily due to the trade-off relation between the decreased exergy loss from entropy generation and the increased exergy loss from incomplete combustion, as equivalence ratio increased. As the hydrogen blending ratio increased from 0% to 70%, the total exergy loss decreased by 2%. Specifically, the exergy loss from heat conduction decreased, primarily due to the decreased flame thickness. Moreover, the reactions with H 2 , H and H 2 O as reactants were inhibited, leading to decreased the exergy loss from chemical reactions. As pressure increased from 1 atm to 5 atm, the total exergy loss decreased by 1%, because the exergy losses induced by heat conduction and chemical reactions decreased as the flame thickness was reduced. The exergy loss from incomplete combustion also decreased, because elevated pressure inhibited dissociations and decreased the mole fractions of incomplete combustion products. • Exergy losses in laminar premixed flames of CH 4 /H 2 blends were studied. • Minimum exergy loss occurred at the equivalence ratio of 0.9 for different blends. • Exergy losses from chemical reactions and heat conduction were dominant among all the sources. • Total exergy loss declines as the H 2 percentage or initial pressure rises. [ABSTRACT FROM AUTHOR]

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al 2 O 3 catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 °C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6–215.3 m2/g. The effect of Ni loading (5–30 wt%), reaction temperature (400–500 °C), and tar concentration (0.5–7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H 2 , were significantly enhanced with an addition of Ni/Al 2 O 3 catalysts. With 20%Ni/Al 2 O 3 , the H 2 yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al 2 O 3 had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H 2 yield of 46.8 mol/kg tar was achieved with 20%Ni/Al 2 O 3 at 500 °C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al 2 O 3 has a potential to improve H 2 production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater. • Catalytic conversion of tar to syngas in SCW (≥400 °C, >23 MPa) was investigated. • Ni/Al 2 O 3 catalysts were prepared and they could be reused for more than 3 cycles. • Gas yield at 450 °C with 20Ni/Al was comparable to that of 500 °C without catalyst. • Highest H 2 yield of 46.8 mol/kg tar was achieved with 20Ni/Al at 500 °C. [ABSTRACT FROM AUTHOR]

Among various types of energy conversion systems, hydrogen-fueled solid oxide fuel cells (SOFCs) have been acknowledged as one of the most promising technologies, thanks to the high energy density and numerous environmental and technical benefits they offer. The current study aims to provide a comprehensive review on numerical software-based modeling of these systems. The work is motivated by the increasing demand in utilization of software packages for investigating the multi-physiochemical phenomena occurring within the cell. The available software packages are introduced with the different applications being outlined. Novelty of each work as well as the corresponding drawbacks are represented through a critical approach. In the end, innovative designs and models, existing gaps in the literature, careful considerations for developing the numerical models, and recommendations for achieving further improvements in the field are provided. • Geometrically simplified models are powerful tools for SOFC modeling with fast rate of convergence. • Evaluating the failure probability rather than only temperature gradients is more accurate. • Electrolyte conductivity greatly affects the cell operating voltage and temperature. • Using adiabatic rather than isothermal boundaries yields more realistic results for single cells. [ABSTRACT FROM AUTHOR]

Abstract Algal blooms can be harvested as renewable biomass waste for gaseous biofuel production. However, the rigid cell structure of raw algae may hinder efficient microbial conversion for production of biohydrogen and biomethane. To improve the energy conversion efficiency, biomass from an algal bloom in Dianchi Lake was subjected to a hydrothermal/steam acid pretreatment prior to sequential dark hydrogen fermentation and anaerobic digestion. Results from X-ray diffraction and Fourier transform infrared spectroscopy suggest that hydrothermal acid pretreatment leads to stronger damage of the amorphous structure (including hemicellulose and amorphous cellulose) due to the acid pretreatment, as evidenced by the higher crystallinity index. Scanning electron microscopy analysis showed that smaller fragments (∼5 mm) and wider cell gaps (∼1 μm) on algal cell surfaces occurred after pretreatment. In comparison to steam acid pretreatment, hydrothermal acid pretreatment resulted in a maximum energy conversion efficiency of 44.1% as well as production of 24.96 mL H 2 /g total volatile solids (TVS) and 299.88 mL CH 4 /g TVS. Highlights • Algal bloom from Dianchi Lake was pretreated by hydrothermal/steam acid. • The microstructural changes before and after pretreatment were comparatively revealed. • Hydrothermal acid led to the highest H 2 yield (25.0 mL/g) and CH 4 yield (299.9 mL/g). • Hydrothermal acid led to the highest energy conversion efficiency of 44.1%. [ABSTRACT FROM AUTHOR]

Abstract In this study, the model food waste was gasified to hydrogen-rich syngas in a batch reactor under supercritical water condition. The model food consisted of rice, chicken, cabbage, and cooking oil. The effects of the main operating parameters including temperature (420–500 °C), residence time (20–60 min) and feedstock concentration (2–10 wt%) were investigated. Under the optimal condition at 500 °C, 2 wt% feedstock and 60 min residence time, the highest H 2 yield of 13.34 mol/kg and total gas yield of 28.27 mol/kg were obtained from non-catalytic experiments. In addition, four commercial catalysts namely FeCl 3 , K 2 CO 3 , activated carbon, and KOH were employed to investigate the catalytic effect of additives at the optimal condition. The results showed that the highest hydrogen yield of 20.37 mol/kg with H 2 selectivity of 113.19%, and the total gas yield of 38.36 mol/kg were achieved with 5 wt% KOH addition Moreover, the low heating value of gas products from catalytic experiments with KOH increased by 32.21% compared to the non-catalytic experiment. The catalytic performance of the catalysts can be ranked in descending order as KOH > activated carbon > FeCl 3 > K 2 CO 3. The supercritical water gasification (SCWG) with KOH addition can be a potential applied technology for food waste treatment with production of hydrogen-rich gases. Highlights • Energy conversion of food waste in supercritical water was investigated. • Four different catalysts were employed to catalyze the SCWG of food waste for Improving of hydrogen production. • The maximum H 2 yield (20.37 mol/kg) was achieved at 500 °C, 60 min, 2 wt% feedstock with addition of KOH. • Performance of the catalysts was ranked in the order KOH > activated carbon > FeCl 3 > K 2 CO 3. [ABSTRACT FROM AUTHOR]

Abstract N-decane decomposition with plasma to obtain prone detonation gaseous fuel is investigated by adopting fuel liquid film feeding mode at applied voltage of 10 kV and 15 kV, discharge frequency of 300–3000 Hz with interval 100 Hz. The result shows that the discharge parameters can regulate the composition and the concentration of the cracked products. When the composition of the product is unchanged, the concentration and proportion of the components can be increased as the discharge frequency becomes higher. The hydrogen concentration increases 3.4 times and 2.3 times respectively for the applied voltage of 15 kV and 10 kV as the discharge frequency is increased from 500 to 3000 Hz. However, the voltage has no effect on the proportion of the components, and increasing the voltage only increases the concentration of the species. For selectivity, raising the discharge frequency can greatly increase the species selectivity of hydrogen and acetylene that are most prone to detonate. The selectivities of hydrogen and acetylene are the highest at 15 kV and 3 kHz, reaching 18.40% and 4.22% respectively, and at this time, the selectivity of ethylene is the lowest, which is 60.4%. Besides, it is confirmed that high selectivity can be achieved at the lower specific energy input causing by low-voltage/high-frequency discharge. Through the analysis of the bond dissociation energy, there is a competitive relationship between the production of ethylene, ethane and pentane which all consume ethyl, and two possible pathways for the production of acetylene are put forward. Highlights • Plasma decomposition of n-decane liquid film was conducted in flow reactor. • Detonable gas was detected in the cracking gas. • The better cracking effect could be achieved at high frequency and low voltage. • The reaction path of n-decane decomposition was explained. • Selectivity and energy conversion ratio were analyzed. [ABSTRACT FROM AUTHOR]

Microwave-assisted ethanol decomposition over pyrolysis residue of sewage sludge (PRSS) was investigated in a multi-mode microwave (MW) oven, and was compared with ethanol decomposition over a commercial activated carbon (AC). The results indicated that PRSS showed higher MW heating performance than AC. Under the same microwave power (MP), the temperature of catalyst bed, hydrogen produc0oij9tion and ethanol conversion over PRSS were higher than that over AC. Both hydrogen production (per unit volume of ethanol) and ethanol conversion increased with the increase of MP, whereas decreased with the increase of the volumetric hourly space velocity of ethanol (VHSV eth ). Additionally, comparison between ethanol decomposition by MW and conventional heating was also conducted. Results indicated that MW heating was much more beneficial for hydrogen production than conventional heating, and the energy efficiency of hydrogen production under MW heating was much higher than conventional heating. Finally, carbon nanofilaments formation over PRSS and AC were observed under MW heating. The size and structures of carbon nanofilaments over PRSS and AC were significantly different with each other, which may be strongly correlated with the formation of micro-plasmas during MW heating. [ABSTRACT FROM AUTHOR]

Though bismuth vanadate (BiVO 4 ) is extensively used as a photoactive material, its performance in harnessing solar energy is limited by ineffective separation of photo-excited charge carriers. We demonstrate here a concept of n-n + homojunction of BiVO 4 /BiV 1-x Mn x O 4-y , which improves its charge separation efficiency. Using first-principles theoretical calculations, we determine the effect of Mn substitution on oxygen vacancy formation energies and associated changes in the electronic structure of BiVO 4 . Showing that Mn substitution pushes the Fermi level of BiVO 4 towards its conduction band, we predict that the associated enhanced bending of bands at the homojunction (BiVO 4 /BiV 1-x Mn x O 4-y ) facilitates efficient separation of charge carriers. With Mott-Schottky experiments, we verify the increased band bending at the n-n + homojunction, and show that the maximum photocurrent density measured in a sample with n-n + homojunction is ten times higher than that obtained of the pristine sample. Secondly, Mn substitution in BiVO 4 also reduces the oxygen vacancy formation energy, promoting higher concentration of O-vacancies, further enhancing the photoelectrochemical response. [ABSTRACT FROM AUTHOR]

Depressurization tests at a laboratory scale, coupled with numerical modelling, are used to determine the key parameters responsible for the polymeric liner collapse in hyperbaric type IV hydrogen storage vessels. X-ray tomography allows to determine the damages suffered by the sample during the depressurization step. Results show that the differential pressure induced during the depressurization step between the liner/composite interface and the free surface of the liner is the main factor responsible for the collapse of the liner. For a given temperature, this pressure gradient can be modified by changing the maximum H 2 pressure, the emptying rate or by adding a residual pressure plateau. Temperature is also of prime importance by influencing the yield point of the liner, the interface resistance and the amount of gas dissolved into the vessel. Thus, increasing temperature also increases the risk of liner collapse for the same gas exposure conditions. [ABSTRACT FROM AUTHOR]

The use of hydrogen to store electricity is no longer utopian nor merely theoretical. Hydrogen applications such as Power-to-Gas systems are entering the market and some of them are ready to compete with other options in the near future. This means they have indeed a potential for profitability, especially if seen as large-scale storage solutions for the electricity surplus produced by variable renewable energy sources. In this study Power-to-Industry, Power-to-Mobility and Power-to-Power applications are chosen to be investigated and compared through levelized cost of hydrogen to identify the main cost drivers and consequently understand the possible solutions to reduce costs. The feasibility of the applications is discussed and analyzed in Germany, Belgium and Iceland, with mid and long-term perspectives, focusing the analysis on the advantage of scaling up. [ABSTRACT FROM AUTHOR]

The ultrasonic-assisted solar photochemical splitting of water had been explored in recent years to enhance hydrogen production efficiency. In this study, a photon-absorption-based study was conducted to investigate the mechanism of the ultrasonic-assisted solar photochemical splitting of water. An elaborate test bench for temperature-controlled, ultrasonic-assisted solar photochemical water splitting was designed, set up, and tested. A comparison of the hydrogen production between the ultrasonic-assisted and conventional solar photochemical splitting of water was carried out. The effective nanoparticle size before and after ultrasonic vibration, as well as after solar photocatalysis, was analyzed. Furthermore, the spectral absorptivity of the nanofluids before and after ultrasonic vibration, as well as after solar photocatalysis, was investigated by both experimental and numerical methods. The investigation indicated that the improved particle dispersion in the solution prepared by ultrasonication allowed the absorbance of more incoming sunlight. The amount of hydrogen produced by the ultrasonic-assisted hydrogen production was 3.45 times that of conventional solar photochemical splitting of water without pre-ultrasonicated. Besides, an effective spectral absorptivity coefficient was proposed as a modified measure of spectral absorptivity. In addition, the optimal particle diameter was optimized using the Monte Carlo ray tracing method to identify the best light absorption performance. [ABSTRACT FROM AUTHOR]

Electricity generation by means of closed-Brayton-cycle (CBC) systems on hypersonic vehicles is strictly limited by the finite cold source, namely the onboard fuel. The influences of finite cold source on electricity generation, and the performance comparison among the CBC systems with different fuels, are worth investigating. In this article, the main factors and their effects on the electric power of CBC systems with finite cold source are analyzed. A simple recuperated CBC model has been established to evaluate the performances of power generation. Results indicate that the available temperature zones of cold source have great influence on the efficiency and power of CBC systems. The cryogenic fuels have greater potential of power generation than the hydrocarbon fuels at normal temperature, because of the advantages on the thermal efficiency (45% vs. 27%), effective enthalpy difference (5.67 MJ/kg vs. 1.06 MJ/kg) and effectiveness of primary cooler (∼0.9 vs. ∼0.85). Specifically, a higher electric power fraction (9.46%) can be achieved by the CBC system cooled by liquid hydrogen than kerosene (2.61%). This research provides the performance boundaries of onboard closed power generation systems in the view of finite cold source. [ABSTRACT FROM AUTHOR]

Ramjet engines are widely-used devices in the defence industry and have military applications. These engine types, preferred in many fields, are known to act according to the laws of thermodynamics. For this reason, exergy analysis methodology is a beneficial tool for assessing the performance of a ramjet engine, as well as other energy conversion systems. The present study aims to introduce a performance analysis of a hydrogen fueled ramjet engine within the framework of the first and second laws of thermodynamics. At the end of the study, the exergy efficiencies of inlet, combustion zone and nozzle are found to be 3.88%, 7.62%, and 0.03%, respectively, whereas the exergy efficiency of a ramjet engine is 8.85%. The introduced methodology and the results obtained from the current study may be useful for anybody who is interested in thermal sciences and aero-propulsion technologies. [ABSTRACT FROM AUTHOR]

We are in an era where everything is now requested to be smart. Here are some examples, such as smart materials smart devices, smartphones, smart grid, and smart metering. In regard to energy portfolio, we need to make it in line with these under smart energy solutions. With the developed cutting-edge technologies and artificial intelligence applications, we need to change the course of action in dealing with energy matters by covering the entire energy spectrum under five categories, namely, energy fundamentals and concepts, energy materials, energy production, energy conversion, and energy management. It is important to highlight the importance of a recent event. On 17 January 2017 a total of thirteen leading energy, transport and industry companies in the World Economic Forum in Davos (Switzerland) have launched a global initiative, so-called: Hydrogen Council, to voice a united vision and long-term ambition for hydrogen to foster the energy transition. It has aimed to join the global efforts in promoting hydrogen to help meet climate goals. This is a clear indication that smart solutions are not possible without hydrogen options. This study focuses on introducing and highlighting smart energy solutions under the portfolio pertaining to exergization, greenization, renewabilization, hydrogenization, integration, multigeneration, storagization, and intelligization. Each one of these plays a critical role within the smart energy portfolio and becomes key for a more sustainable future. This study also focuses on the newly developed smart energy systems by combining both renewable energy sources and hydrogen energy systems to provide more efficient, more cost-effective, more environmentally benign and more sustainable solutions for implementation. Furthermore, a wide range of integrated systems is presented to illustrate the feasibility and importance such a coupling to overcome several technical issues. Moreover, numerous studies from the recent literature are presented to highlight the importance of sustainable hydrogen production methods for a carbon-free economy. [ABSTRACT FROM AUTHOR]

Co-production of hydrogen and valuable carbonaceous materials by catalytic methane decomposition (CMD) is a promising process. However, nowadays it is still difficult for various carbon catalysts to make it. Here CMD with addition of some CO 2 as co-feed was proposed and evaluated by using a hybrid of K 2 CO 3 and coal char (CC). Effect of the additional CO 2 as co-feed was investigated on methane conversion, the outlet gas composition, and the deposited carbon morphology. The results show that co-production of syngas (H 2 and CO) and carbon fibers/microspheres could be obtained along with high and stable methane (around 80%) and CO 2 conversion (up to about 100%) in the process. Stable molar ratios of H 2 /CO (ranging from 0.6:1 to 5:1) as well as different carbon morphologies (amorphous, fibrous or microspherical) can be regulated and controlled by the molar ratio of CH 4 /CO 2 (from 75:10 to 75:75) in the feedstock. Quantitative and qualitative analysis of the products show that there is probably a synergy between K 2 CO 3 and CC during the reaction process. [ABSTRACT FROM AUTHOR]

Rotary engine generally sustains poor fuel economy and emissions performance at idle condition. Hydrogen has excellent physicochemical properties that can serve as an enhancer to improve the performance of the original engine. In this paper, a modified rotary engine equipped with dual fuel (hydrogen and n-butanol) port injection system and electronic ignition module was developed to explore the influence of hydrogen supplement on enhancing the idle performance of n-butanol rotary engine. In this study, the engine was run at the idle and stoichiometric with the original spark timing. Hydrogen volume percentage in the total intake was gradually increased from 0% to 7.9% by adjusting the fuel flow rate of n-butanol. The experimental results indicated that the engine instability and fuel energy flow rate were both reduced by enlarging the hydrogen supplying level. Combustion periods were shortened thanks to the enrichment of hydrogen. The peak chamber temperature was heightened as hydrogen fraction increased due to the improved combustion. HC and CO emissions were severally reduced by 50.4% and 85.8% when the hydrogen volume percentage was raised from 0% to 7.9%. However, NOx emissions were mildly increased because of the raised chamber temperature by increasing hydrogen fraction. [ABSTRACT FROM AUTHOR]

This work presents an experimental study describing a six-cylinder spark ignition engine running with a lean equivalence ratio, high compression ratio, ignition delay and used in a cogeneration system (heat and electricity production). Three types of fuels; natural gas, pure methane and methane/hydrogen blend (85% CH 4 and 15% H 2 by volume), were used for comparison purposes. Each fuel has been investigated at 1500 rpm and for various engine loads fixed by electrical power output conditions. CO, CO 2 , HC, and NOx emissions values, and exhaust gas temperature were measured. The effect of fuel composition on engine characteristics has been studied. The results show, that the hydrogen addition increased HC emissions (around 18%), as well as performance, whilst it reduced NO x (around 31%), exhaust gas temperature, CO and CO 2 . [ABSTRACT FROM AUTHOR]

Hydrogen fuel cells are a promising energy conversion technology due to its high energy density and zero greenhouse gas emission. As a result, the production of hydrogen from renewable and alternative resources has gained significant interest in recent decades. This paper demonstrates a new approach which uses a pyroelectric energy harvester for water splitting and represents a novel alternative hydrogen source. Pyroelectrics are attractive for harvesting waste heat due to their ability to convert temperature fluctuations into electrical energy. A range of pyroelectric materials and geometries for water electrolysis are analysed to determine, (i) the minimum material thickness to generate a critical potential to initialise water decomposition and, (ii) to maximize the charge and hydrogen mass production. We then successfully demonstrate that an appropriate pyroelectric material, when combined with rectification of the alternating current, can harvest heat fluctuations and generate a sufficient electric potential difference and current for water splitting. By harvesting the pyroelectric electrical energy, a continuous hydrogen bubble production was observed during thermal cycling. Practical routes to maximize the level of hydrogen production for this new concept are also explored. [ABSTRACT FROM AUTHOR]

Catalytic activity of 4–40 nm gold nanoparticles supported on γ-Al 2 O 3 in the reaction of ortho – para conversion of protium has been studied. The results of test indicate that nanoparticles exhibit a high catalytic activity and the rate of reaction, virtually does not depend on the particle size. [ABSTRACT FROM AUTHOR]

In this study, an overview has been presented a classification of the vehicles using hydrogen with different ways. The using of hydrogen in vehicles has been categorized into two main categories as designs in which hydrogen is burned and energy is generated by conversion to electricity. The designs of internal combustion vehicles with using hydrogen via burning, the designs of the fuel cell vehicles that using hydrogen by converting into electricity and their hybrid versions have been introduced. In the automotive industry, the structure and future advantages of hydrogen fuel cell electric vehicles have been handled in a separate title. Onboard storage, safety, the capital cost and operating cost of the different design of vehicles have been analyzed rigorously. [ABSTRACT FROM AUTHOR]

Issues of exhaustible natural resources, fluctuating fossil fuel prices and improvements in electric power systems motivated governments to behave positively toward the development of distributed generation. In addition, progresses in small size generation technologies and storage systems give rise to a significant diffusion in microgrids, working together with conventional power grid. Indeed, in the next future, domestic microgrids are expected to play a fundamental role in electric power networks, driving both the academic and industrial research interests in developing high efficient and reliable conversion and storage technologies. In this context, this study presents a feasible configuration of a solar-hydrogen integrated microgrid and documents the procedure to characterize the overall efficiency of a laboratory scale test facility. Experimental results highlight that the most significant inefficiencies in the solar to hydrogen conversion process are mainly attributed to the solar to electrical energy conversion process, being responsible for about 89% of losses. The overall laboratory scale solar to hydrogen chain can reach conversion efficiency up to 5.3%. [ABSTRACT FROM AUTHOR]

Experimental and computational studies on the hydrogen conversion from methane combustion were carried out in methane rich conditions. The experiments were conducted in a rapid compression machine (RCM) over conditions with varied pressures (18–24 bar), temperatures (962–1060 K) and equivalence ratios (2.0–2.6). Both major combustion products (H 2 and CO) and intermediate species (H 2 , CH 4 , C 2 H 2, C 2 H 4 , C 2 H 6 , C 3 H 6, CO, and CO 2 ) were sampled and analyzed by a fast sampling system equipped with gas chromatography (GC). Computational methods including chemical equilibrium and chemical kinetic modeling were used for comparison. The results showed that kinetic model was inadequate to predict hydrogen production at fuel rich conditions due to soot formation. The competition between chemical equilibrium and soot formation resulted in an optimal equivalence ratio at φ = 2.4, where hydrogen production is the highest. Besides, higher pressure and temperature within the test range also attributed to hydrogen formation. [ABSTRACT FROM AUTHOR]

A phase change material (PCM) open-cycle engine is a distinctive cycle that uses the ambient air as its hot reservoir and an on-board hydrogen storage as its cold reservoir. Here we present a new PCM open cycle engine, that is capable of overcoming two major problems of PCM engines: the significant energy losses at partial loads, and the power control inherent difficulties. The present new concept decouples the liquid boiling heating process from the vapors superheating stage. While this system is inherently unstable (as other PCM systems), it is shown that it can be effectively controlled with a simple proportional–integral controller. [ABSTRACT FROM AUTHOR]

Methane decomposition was conducted by using K 2 CO 3 /carbon hybrids as the catalysts, and hydrogen-rich gas (with hydrogen content of about 87%) and fibrous carbons can be simultaneously obtained together with high and stable methane conversion (up to about 90% at 850 °C). Effects of K 2 CO 3 on methane conversion, hydrogen content and fibrous carbons were investigated by changing the reaction temperature and space velocity. The results indicate that K 2 CO 3 can greatly promote methane activation and conversion, taking responsibility for the continuous formation of CO and a trace of CO 2 . The oxygen transfer from K 2 CO 3 probably provides convenience for the formation and growth of fibrous carbons. [ABSTRACT FROM AUTHOR]

Advanced energy conversion processes like photochemical and photoelectrochemical water splitting now a day plays a very important role in challenging the present energy crisis of our world. The successful utilization of this process depends on development of highly efficient, more stable, low cost and outstanding environmental benign semiconductor materials. From recent advancements, it is revealed that quantum dots (QDs) are very outstanding and promising material for the mentioned processes due to their favorable physical and chemical characteristics like high absorption co-efficient, quantum confinement effect, thermal, chemical, mechanical and optical stability, high conductivity and recyclability. In this review article, we have clearly explained the importance of QDs in water splitting along with the general mechanism involved in the process. Following that the enhancement of different materials like metal oxides, layered double hydroxides (LDH), carbonaceous materials (g-C 3 N 4 , benzene and benzene like materials) by QDs have discussed in the field of water splitting. [ABSTRACT FROM AUTHOR]

A 2-CSTRs anaerobic digestion system using molasses wastewater as a biochemical substrate for fermentative bioenergy production and substrate degradation under various ethanol recovery rates was developed. The effects of ethanol recovery rates (0%–80%) and organic loading rates (OLRs; 8, 16 and 24 kgCOD m −3 d −1 ) on bioenergy production rate ( ε T ) and bioenergy production yield were examined, respectively. Since the system produced a significant amount of biofuels (i.e. hydrogen, methane and ethanol), the process performance in terms of energy conversion derived from the combination of three biofuels was calculated according to production rates and combustion heat values. Recycle and reflux are the two reuse approaches for effluents in the system. A maximum HPR of 1.34 (±0.7) mol d −1 and a maximum EPR of 0.45 (±0.4) mol d −1 were observed at the OLR of 24 kgCOD m −3 d −1 . Linear regression of the collection between HPR and EPR can be expressed as y = 0.3182x + 0.0114 (r 2 = 0.9853). The highest MPR of 0.45 (±0.07) mol d −1 was obtained at the original OLR of 24 kgCOD m −3 d −1 , with an ethanol recover rate of 0%. Recycle resulted to a higher ε T and energy yield than reflux with the ethanol recover rate of 0% and 20%, respectively. This was equal to the ethanol recover rate of 50%, but lower than the ethanol recover rate of 80%; indicating that recycle would be more feasible for lower ethanol recover rates, and reflux may be more suitable with other kinds of ethanol recover rates. [ABSTRACT FROM AUTHOR]

The paper is dedicated to new unconventional sources of non-food renewable feedstock for third generation biofuel – microalgae biomass. Methods of lipid induction in microalgae have been considered. It represents the results of advanced microalgae strains state-of-the-art investigations – lipid producers. The paper discusses selection of stressors at two-stage culturing, where 1st stage includes culturing under most optimal conditions to produce maximum amount of biomass, and at 2nd stage biosynthesis and accumulation of lipids in biomass occurs. Types of stressors used for lipid induction have been briefly reviewed on the basis of foreign studies. Proper experimental results on isolation of new candidate microalgae strains from natural sources, as well as on selection of stressors for lipid induction have been shown and discussed. Nitrogen and phosphoric starvation, high and low illuminance, along with temperature conditions have been studied as stressors. Effectiveness of lipid-containing microalgae screening technique by fluorescent dye Nile red staining has been determined. Processible fast-growing Arhtrospira platensis microalgae/cyanobacteria use perspectiveness as a model for selection of stressors and overall lipid-containing microalgae culturing mode have been verified. Method of various microalgae heat-treated biomass conversion into biohydrogen by anaerobic acetone-butanol fermentation using cellular immobilized catalysts based on Clostridium acetobutylicum has been considered. Ultimate hydrogen efficiency has been found for Chlorococcum sp. rsemsu Ccc-7/11 strain biomass (8.4 и 6.1 mmol/l of medium/day); while hydrogen production is 23.7% and 18.6% of notionally possible level, A. platensis strains cultivated under the influence of stressors ( rsemsu 1/02-P – 5.6 mmol/l of medium/day, 32.3%; rsemsu 1/02-Т – 3.3 mmol/of medium/day, 28.8%) rank slightly below them in efficiency, outperforming in hydrogen production. [ABSTRACT FROM AUTHOR]

Methane decomposition was carried out on Rh/γ-Al 2 O 3 and Rh/γ-Al 2 O 3 –Nd 2 O 3 catalysts to produce hydrogen. γ-Al 2 O 3 –Nd 2 O 3 mixed oxides and Rh/γ-Al 2 O 3 –Nd 2 O 3 catalysts were prepared by wet impregnation using Nd(NO 3 ) 3 ·6H 2 O and RhCl 3 ·3H 2 O as precursors. The concentrations for the catalysts were 1.0 wt% for Rh and 1 and 10 wt% for Nd. The reaction was carried out from 400 to 750 °C. All catalysts showed high activity and selectivity at 700 °C, with conversions around 74–79 vol%. The activity per site (TOF) was higher on Rh crystallites size ≥2.1 nm. The Rh catalyst with 10 wt% neodymium concentration was highly selective to hydrogen, 100%. This behavior was explained by the highest interaction between Rh and γ-Al 2 O 3 –Nd 2 O 3 supports. Rh/γ-Al 2 O 3 and Rh/γ-Al 2 O 3 –Nd 2 O 3 with 1 wt% Nd showed selectivities of 89 and 65% at 700 °C respectively and ethane and ethylene products. These products come from the mobility of CHx species on the Rh surface during the reaction. The carbon produced was mainly deposited on the support. Characterization was done by XRD, N 2 adsorption isotherms, HRTEM, EDS-SEM, CO-FTIR, H 2 -TPR, XPS. [ABSTRACT FROM AUTHOR]

Concentrated photovoltaic (CPV) system provides highest solar energy conversion efficiency among all the photovoltaic technologies and provides the most suitable option to convert solar energy into hydrogen, as future sustainable energy carrier. So far, only conventional flat plate PV systems are being used for almost all of the commercial applications. However, most of the studies have only shown the maximum efficiency of hydrogen production using CPV. In actual field conditions, the performance of CPV-Hydrogen system is affected by many parameter and it changes continuously during whole day operation. In this paper, the daily average and long term performances are proposed to analyze the real field potential of the CPV-Hydrogen system, which is of main interest for designers and consumers. An experimental setup is developed and a performance model is proposed to investigate the average and long term production potential of CPV-Hydrogen system. The study is carried out in tropical weather of Singapore. The maximum CPV efficiency of 27–28% and solar to hydrogen (STH) efficiency of 18%, were recorded. In addition, the CPV-Hydrogen system showed the long term average efficiency of 15.5%, for period of one year (12-months), with electrolyser rating of 47 kWh/kg and STH production potential of 218 kWh/kg. Based upon the DNI availability, the system showed hydrogen production potential of 0.153–0.553 kg/m 2 /month, with average production of 0.43 kg/m 2 /month. However, CPV-Hydrogen system has shown annual hydrogen production potential of 5.162 kg/m 2 /year in tropical weather of Singapore. [ABSTRACT FROM AUTHOR]

The importance of methane conversion, syngas selectivity, and oxidizer conversion for efficient syngas production by the partial oxidation of methane using a metal oxide redox cycle is quantified. The operating conditions which enable high conversion of methane to syngas over cerium oxide and conversion of carbon dioxide to carbon monoxide in the subsequent oxidation reaction are identified experimentally. The parametric study considers operating temperatures of 900 and 1000 °C and methane flow rates from 1 to 15 mL min −1 g −1 in a fixed bed of porous ceria particles. The reduced ceria is reoxidized in a flow of 10 mL min −1 g −1 CO 2 to produce CO. A trade-off of achieving high methane conversion is observed. For example, at 1000 °C, the cycle-averaged methane conversion increases from 13% for reduction in 15 mL min −1 g −1 to 60% in 1 mL min −1 g −1 . For the same change in methane flow rate, the cycle-averaged selectivities decrease from 78% to 39% (CO) and 77% to 40% (H 2 ) and the oxidizer conversion decreases from 93% to 48%. The maximum projected solar-to-fuel thermal efficiency is 27% for cycling at 1000 °C with reduction in 5 mL min −1 g −1 methane. [ABSTRACT FROM AUTHOR]