Currently, pressure vessels that operate in hydrogen service and subjected to fatigue must be designed using a defect tolerant design procedure. This means that first the fracture mechanics properties of the material being considered must be measured in hydrogen at the maximum service pressure. The properties are fatigue crack propagation properties and threshold stress intensity factor for hydrogen embrittlement (KIHE). With these properties, a fatigue crack propagation life can be estimated assuming an initial crack size and geometry and growing this defect to failure. The property measurements are costly and can only be performed at a few laboratories. Furthermore, the resulting lives are usually very short because of the assumed initial crack size. These things limit the application of this design method to lower cycle or static loading applications. This work introduces a cost-effective method of design and construction of pressure vessels for high cycle use in hydrogen service at pressures below 40,000 psi that eliminates the need for determining fracture mechanics properties in hydrogen environment. The method uses shrink fit construction of a liner inside a jacket. The method requires that when the pressure is applied, the magnitude of the resultant stress at the pressure boundary of the liner is more compressive than the magnitude of the applied pressure and the maximum allowed size of defect in the jacket at the interface between the jacket and the liner is such that when the cyclic stress is applied the resultant fatigue loading of that defect at that location to be less than the threshold value for growth of that defect.

Liquid water management is critical for Proton Exchange Membrane (PEM) fuel cell operation, as excessive humidity can lead to flooding and cell performance degradation. Water is produced in the cathode catalyst layer during the electrochemical reaction. If reactant gas streams become saturated, liquid water forms and must travel through anode and cathode Gas Diffusion Layers (GDLs) to reach flow channels for removal. Understanding the dynamic behavior of the droplet is critical to improve water removal strategies for PEM fuel cells. In this study a 3D, transient, two-phase model based on the Volume of Fluid (VOF) method was developed to study a single droplet in the gas channel. The formation, growth, and breakup of the droplet is tracked numerically and analyzed. The pressure drop across the droplet is monitored over time and compared with theoretical analysis. The droplet size and shape change over time for two different pore sizes are compared. The impact of various gases including air, helium, and hydrogen on droplet dynamics is presented. The viscous force and pressure force on the droplet and the drag coefficient are calculated.

Biomass gasification is the devolatilization and incomplete combustion of biomass resulting in the production of a combustible gas mixture including carbon monoxide (CO), hydrogen (H 2 ) methane (CH 4 ), and traces of other hydrocarbons (C n H m ), and referred to as producer gas. Producer gas can be cleaned and then used in various engines or can be converted to various biofuels. This paper presents an experimental and simulation-based evaluation of producer gas quality resulting from corn kernel gasification in a two-stage downdraft gasifier. Test conditions were selected, based on the results of previous studies, to yield high conversion efficiency and low tar production. Experimental tests were performed with an air flow of 25 Nm 3 /h and with 80% of the air supplied to the first gasification stage. Simulations based on a chemical and thermal equilibrium model were carried out to examine the effect of equivalence ratio (ER) changes. Both the experimental and modelling results show that using a two-stage air supply leads to a significant reduction in the tar content of the producer gas, while maintaining a high gasification efficiency.

The purpose of this study is to investigate the dynamic behavior of a Solid Oxide Steam Electrolyzer (SOSE) system without an external heat source which uses transient photovoltaic (PV) generated power as an input to produce compressed (to 3MPa) renewable hydrogen to be injected directly into the natural gas network. A cathode-supported crossflow planar Solid Oxide Electrolysis (SOE) cell is modeled in a quasi-3D thermo-electrochemical model that spatially and temporally simulates the performance of a unit cell operating dynamically. The stack is comprised of 2500 unit cells that are assumed to be assembled into identically operating stacks, creating a 300kW electrolyzer stack module. A 15-minute resolution dataset for operation of PV generation was obtained from a database that archives PV power dynamics of systems on the University of California, Irvine campus. The dataset (comprised of data for approximately 4.1 MW of peak solar power) was scaled to a maximum of 450kW of PV generation. For the designed 300kW SOSE stack (thermoneutral voltage achieved at design steady state conditions), powered by the dynamic 0–450kW output of PV systems, thermal management and balancing of all heat supply and cooling demands is required based upon the operating voltage to enable efficient operation and prevent degradation of the SOSE stacks. The PV generation dataset was analyzed to obtain a day in which the PV generated power has its highest dynamic behavior (a cloudy day) and another day in which the PV generated power and energy is maximum (a sunny day). Dynamic system simulation results show that the SOSE system is capable of following the dynamic PV generated power for both of these days while the SOSE stack temperature gradient is always maintained below a maximum set point along the stack for both days. The system efficiency based upon lower heating value of the generated hydrogen is between 0–75% and 0–78% with daily hydrogen production of 94kg and 55kg for sunny and cloudy days, respectively.

Hydrogen has often been studied as a possible fuel of the future due to its capabilities to support zero emissions and sustainable energy conversion. Hydrogen can be used in a fuel cell to generate electricity at high efficiencies and with zero emissions. In addition, hydrogen can be renewably produced via electrolysis reactions that are powered from otherwise curtailed renewable energy. One possible means of storing and delivering renewable hydrogen is to inject it into the existing natural gas (NG) system and thus decarbonize gas end-uses. The NG system has potential to serve as a storage, transmission and distribution system for renewably produced hydrogen. Despite the potential of hydrogen to reduce the carbon intensity of the NG system, the unique characteristics of hydrogen (low molecular weight, high diffusivity, lower volumetric heating value, propensity to embrittle pipeline materials) has led to justified concerns over the safety of introducing hydrogen blends into the NG system. While many studies have attempted to quantitatively predict leakage rates of hydrogen using classical fluid mechanics theories, such as Hagen-Poiseuille flow, there have been limited studies which quantitatively assess gaseous fuel leakage to support the predictions made from theoretical analyses and computations. In this paper we present a summary of the literature related to gaseous fuel leakage and results from preliminary experiments which support the idea that entrance effects may significantly affect gaseous fuel leakage from practical leak scenarios such as NG fittings, resulting in similar leakage rates between hydrogen and NG.

Operational characteristics of an air breathing Rotating Detonation Combustor (RDC) fueled by natural gas-hydrogen blends are discussed in this paper. Experiments were performed on a 152 mm diameter uncooled RDC with a combustor to inlet area ratio of 0.2 at elevated inlet temperature and combustor pressure while varying the fuel split between natural gas and hydrogen over a range of equivalence ratios. Experimental data from short-duration (∼6sec) tests are presented with an emphasis on identifying detonability limits and exploring detonation stability with the addition of natural gas. Although the nominal combustor used in this experiment was not specifically designed for natural gas-air mixtures, significant advances in understanding conditions necessary for sustaining a stable, continuous detonation wave in a natural gas-hydrogen blended fuel were achieved. Data from the experimental study suggests that at elevated combustor pressures (2–3bar), only a small amount of natural gas added to the hydrogen is needed to alter the detonation wave operational mode. Additional observations indicate that an increase in air inlet temperature (up to 204°C) at atmospheric conditions significantly affects RDC performance by increasing deflagration losses through an increase in the number of combustion (detonation/Deflagration) regions present in the combustor. At higher backpressure levels the RDC exhibited the ability to achieve stable detonation with increasing concentrations of natural gas (with natural gas / hydrogen-air blend). However, losses tend to increase at intermediate air preheat levels (∼120°C). It was observed that combustor pressure had a first order influence on RDC stability in the presence of natural gas. Combining the results from this limited experimental study with our theoretical understanding of detonation wave fundamentals provides a pathway for developing an advanced combustor capable of replacing conventional constant pressure combustors typical of most power generation processes with one that produces a pressure gain.

Swiss Roll Combustor of 1 W capacity for micro gas turbine engine is operated with premixed hydrogen air mixture at ultra-lean equivalence ratio. The reaction zone under consideration has volume of 60 mm 3 . The reactant passage and product passage are coiled around the reaction zone facilitating the recovery of heat loss, by preheating the reactants. The reactants are entered through an increasing cross-sectional area passage from 0.6mm × 5mm inlet to 1.5mm × 5mm outlet, thereby reducing the velocity levels in the reactant passage, facilitating stable combustor operation. The combustor performance parameters, temperature levels, pattern factor and emissions are measured is operated at ultra-lean equivalence ratio of 0.12 to lean equivalence ratio of 0.43, for premixed hydrogen air combustion. The results are compared at similar (not same) equivalence ratios for constant area reactant passage. The visual inspection shows stable flame front in the combustion zone for variable area passage and extended flame front in the constant area passage combustor. However, the combustor performance deteriorates drastically above equivalence ratio of 0.43, leading to hot spots generation on walls.

The Rate-Controlled Constrained-Equilibrium (RCCE) is a model reduction scheme for chemical kinetics. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rate controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying Detailed Kinetic Model (DKM). Successful approximation of the constrained-equilibrium states requires accurate identification of the constraints. One promising procedure is the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, we propose a method, as part of our work-in-progress efforts, that could expand the applicability of the derived constraints. This method involves running DKM calculations for a wider range of initial conditions, appending the results of all these cases one after the other after normalizing, and finally running the ASVDADD method to get a set of ‘universal’ constraints applicable within that range of conditions. The effectiveness and robustness of the derived constraints is examined in hydrogen/oxygen ignition delay simulations and the results are compared with those obtained from DKM. The proof-of-concept results demonstrate the potential of the method for finding ‘universal’ constraints.

Combustion characteristics at small scales have been studied continuously due to the potential applications in portable power devices. It is known that heat release impacts at small scales result in different flame behavior as compared to conventional scales. The impacts of geometry, stoichiometry, flow rates, wall temperatures, etc. are widely studied in literature. However, dilution impacts still need to be further studied due to its important role on controlling the flame behavior and subsequent pollutants emissions at these scales. In this work, premixed hydrogen/air combustion is simulated at an axis-symmetric micro channel (with diameter D = 0.8 mm and length L = 10 mm ), where detailed chemical kinetics are implemented in simulations (32 species and 173 reactions). The heat transfer on the wall is considered by imposing a hyperbolic temperature profile on the wall, where the wall temperature increases from 300 K at the inlet to 1300 K at the outlet. With this setup, a range of equivalence ratios including a typical fuel-lean regime (ϕ = 0.7), stoichiometric regime (ϕ = 1.0) and and two cases at an ultra-rich regime (ϕ = 2.0 and ϕ = 3.0) are investigated. For each equivalence ratio, excess dilution (using N2) is introduced to the mixture and its impact is compared with other cases. With that, the impacts of dilution variations on the combustion characteristics of premixed hydrogen/air are investigated for different equivalence ratios. More specifically, several incidents such as flame dynamics, flame stabilization, extinctions and NOx emissions are studied for the aforementioned operating conditions.

Black powder (BP) is a typical contaminant usually found in sales gas pipelines. Its presence may cause major operational and maintenance issues including blockage of sensors and filters, erosion of pipeline bends and compromise the sales gas quality. There has been little known about its composition and sources of formation in the gas pipelines. Understanding its characteristics is considered crucial for appropriate mitigation planning and execution of smooth pipelines operations. Black powder samples collected from sales gas pipelines network of a Middle Eastern gas company are analyzed using scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) and x-ray diffraction (XRD) methods for surface analysis and phase identification of the crystalline material. These analyses revealed variation in size distribution and shape of the BP samples. Likewise, most of the BP particles were found agglomerated. EDX analysis of the sample has shown presence of iron as the most abundant element after sulfur. XRD patterns can be indexed with both iron oxides and sulfides suggesting presence of moisture and hydrogen sulfide in the gas.

Industrial activity of aluminum surface coating, namely by electrostatic painting with a polyester powder based resin, generates a significant array of wastes. Among these wastes, paint dust is classified as 08 01 12 on the European List of Wastes. As consequence of the inexistence of adequate treatment routes for its correct management, this waste is currently landfilled, without any energy and / or material recovery. Therefore, the development of proper waste management technologies in line with the environmental policies is imperative in order to improve the industrial competitiveness and to preserve the natural resources. In the present work, RDFs (Refused Derived Fuel) were produced, as pellets, for energetic valorization. These experimental RDF pellets were manufactured by mixing the industrial paint dust with sawdust (1.5 and 3%) and with paperboard (1.5%). They were subsequently tested on a purpose built experimental boiler and the combustion efficiency was assessed in terms of gaseous emissions and chemical composition of the bottom and fly ashes. The paint dust waste was delivered by a local surface treatment company and characterized concerning chemical, physical and eco toxicological properties, proving to be rich in Carbon (50.2%) and Hydrogen (4.73%). The obtained RDFs were characterized for mechanical durability, elemental and chemical analysis, bulk density and lower heating value. Results show that the utmost lower heating value (19670 kJ/kg) was obtained for the maximum incorporation content of paint dust waste tested (3%). Combustion trials were carried out at a fuel flow rate between 2 and 3 kg/h. The results showed that the incorporation of paint dust waste resulted in a decrease of the thermal efficiency which suggests that the air fuel ratio was not properly adjusted to the varying heat value of the fuel blend. For all the tests, the mass flow rate and the quality of the gaseous emissions were evaluated for the most relevant pollutants such as particles, SO 2 , TOC, CO and NOx. All parameters, except for particles in one single case, comply with strict environmental limits applicable. Samples of ashes have also been collected and their chemical composition correlated with the fusibility behavior. The results show that such levels of incorporation could be an effective process for paint dust waste management from both the environmental and energetic points of view.

The present work investigates the mass loss of fine wood biomass using a TA INSTRUMENTS SDT 2960 simultaneous DSC-TGA instrument. The samples of sawdust were classified according to the grain size (< 0.063, 0.063–0.125, 0.125–0.25, 0.25–0.5, 0.5–1, and > 1 mm) and the micro samples were tested with air at a constant heating rate of 10 K/min, from the room temperature up to 800°C. From the results the kinetic properties of the biomass fuel were determined using the 1st order Coats-Redfern equation. A transient thermal model of the fuel was implemented and was coupled with the biomass kinetic data in order to compute the mass loss of individual pellets and the results were compared with experimental data. The remaining mass, as fix carbon and ashes or unburnt substances, is approximately 3%. The kinetic parameters indicate that the biomass reactivity depends upon the particle size. The heating treatment of wood pellets at constant temperature and different time produced less nitrogen and more carbon and hydrogen for the short period of time.

Hydrogen can be produced from various primary resources by using different processes. The full benefits of hydrogen production can be obtained when it is produced from renewable energy resources. Among these emerging renewable energy resources, marine and hydrokinetic (MHK) energy systems lower variability in the energy production. Also, more than 50% of the total US population resides near water bodies. In this paper, a brief review of renewable energy-based hydrogen production systems is provided, the emission level of both conventional and renewable energy sources for producing the same amount of hydrogen are compared using GREET model, and research needs for further MHK-based hydrogen production systems are discussed. The results showed the significant emission reductions obtained from renewable-based hydrogen production systems. Moreover, the study showed the potential of producing the same amount of hydrogen with less resource quantity of wave energy compared to that from other renewables such as solar energy.

Wastewater treatment plants help removing organic matter from wastewater, and at the same time, generate digester gas as a useful byproduct. Digester gas is rich in methane, which can be used to generate electricity. Fuel cell systems are the cleanest technology for power recovery from digester gas, since all other technologies generate electricity by burning all the digester gas. The most commonly used type of fuel cell for power generation from digester gas in wastewater treatment plants is the molten carbonate fuel cell. This type of fuel cell can tolerate the impurities usually found in digester gas, such as CO 2 and H 2 S; however, this kind of fuel cell systems is more suitable for large wastewater treatment plants. This prevents the use of fuel cells for power generation from digester gas in wastewater treatment plants serving medium and small size cities, or even farms. This research attempts to explore solutions to make fuel cell technologies technically and economically feasible for medium and small size wastewater treatment plants. The most suitable type of fuel cells for small applications is the Proton Exchange Membrane, PEM, fuel cell. The main challenge in using PEM fuel cells for power recovery from digester gas is that they are highly sensitive to impurities in its hydrogen gas supply. Therefore, in order to use PEM fuel cells in this application, energy must be spent in cleaning the digester gas before it enters the PEM fuel cell and reformer system. Energy is also required in the form of heat by the reformer system to produce the hydrogen needed by the fuel cell. Both the energy used in the cleaning of the digester gas and the hydrogen generation process comes from burning part of the digester gas. This reduces the amount of digester gas available for hydrogen production and electricity generation, respectively. The approach followed in this investigation seeks to develop a Simulink ® model of the reformer and fuel cell so that the modeling tools of Matlab ® can be used to simulate the performance of the system under different operating conditions. A sensitivity analysis is carried out to identify critical operating parameters affecting the performance of the overall system. The results obtained in this work provide guidelines for future studies of performance optimization and optimal control using the tools available in Matlab ® , in order to get maximum electricity generation from digester gas using PEM fuel cell systems.

Low-grade Mg waste from post-consumer products and production waste cannot be recycled efficiently and economically. This work addresses this challenge by converting this waste into hydrogen. Mg waste is melt, loaded on one side of a stainless steel and solidified to form a galvanic Mg stainless steel couple. These couples are being used to generate hydrogen in 3.5% by weight CH 3 COOH solution at 15°C and 20°C respectively. The experimental results show that a mean accumulated H 2 volume of 3.17 litres was produced when Mg stainless steel couple had a weight of 48.44 grams and water bath temperature of 15°C. One gram of low grade Mg yielded 2.91 Litres of H 2 . Another sample at 20°C with a weight of 52.73 grams showed a higher H 2 volume yield of 3.21 litres per gram. This work can be expanded to a larger scale as the litres per gram volume indicates a lot more compared to what has been reported in literature.

Wastes represent nowadays, one of the major concerns for modern societies and for the environment, either by the wastage of raw materials and also by the existence of poor management systems that can originate and contaminate the ground water and air, and therefore, change the environment irreversibly. Waste management policies enhance the basic principles of prevention, which are the reduction in origin, followed by its recovery through recycling or energy recovery, in order to reduce the environmental and health impacts of wastes. Refuse Derived Fuel (RDF) is a solid fuel made after basic processing steps or techniques that increase the calorific value of municipal solid waste (MSW), commercial or industrial waste materials. Therefore, energy production from RDF can provide economic and environmental benefits, as reduces the amount of wastes sent to landfill and allows the energy recovery from a renewable source. In this work, it was studied the gasification of RDF collected in a Portuguese company, using steam and air as gasifying agents. This study intended to evaluate the effect of temperature and different molar ratios of both agents in gas production, gas composition and mass conversion of RDF. Physical and chemical composition of RDF was determined according to EN 15359:2011. Results showed that RDF has high quality for thermal valorization being registered high values of Low Heating Value (LHV) (24330 kJ/kg), carbon content (56.2%) and volatile matter content (77.2%). Experiments of RDF gasification were performed in a laboratory scale fixed bed gasifier, under different conditions. The effect of reaction temperature was studied at 750°C and 850°C. Gasification experiments with steam were executed at S/B feeding molar ratios ranging from 0.5 to 1.5 and the ones performed with air ranging from ER 0.2 to 0.6. Results showed that, for the same operational conditions, the rise of gasification temperature improved gas production ratio (Nm 3 /kg RDF), gas LHV and mass conversion. Results also proved that steam gasification achieved higher LHV values compared with gasification using air in optimal conditions, 9.4 and 9.8 MJ/m 3 , respectively. The gasification of RDF using steam at S/B ratio of 1.0 enables the production of syngas with 51% of hydrogen (H 2 ), 32% of carbon dioxide (CO 2 ), 11% of carbon monoxide (CO) and 6% of methane (CH 4 ) (in N 2 free basis). The increasing of steam to RDF molar ratio, increased the contents of H 2 and CO 2 , while the content of CO, CH 4 and heating value decreased. Regarding to gas production ratio the utilization of air, especially at ER of 0.6, induced the formation of 1.5 m 3 gas/kg RDF. Instead, steam gasification only allowed the production of 0.5 m 3 gas/kg RDF. Mass conversion and carbon conversion achieved almost 100% in air gasification at highest molar ratio.

This paper investigates the use of hydrogen along with natural gases and solar energy to power a 50 MW power plant in the United Arab Emirates. Sudden changes in the climate have shifted the focus of scientists to formulate solutions to global warming and environmental pollution. Hence, numerous researches are being carried out on various renewable energy sources, such as solar energy and hydrogen. This study examines how the power generation, carbon dioxide (CO 2 ) emission and the fuel consumption of the power plant is affected by the use of hydrogen, solar energy and natural gases. The power plant under investigation consisted of a hybrid conventional combined cycle whose bottoming cycle was allocated for the production of hydrogen during the day. The hydrogen that was produced was used at night to power the topping cycle to generate electricity. Solar energy was captured through concentrated solar power technology, while hydrogen was produced by a water electrolysis process. An extensive investigation of the performance of the power plant revealed that its annual hydrogen share was 7%, solar share 20% and natural gas share 73%. In addition, the annual CO 2 emission and fuel consumption was found to be 394.1 kgCO 2 /MWhe and 58412 tonne respectively.

Understanding the transport of hydrogen within metals is crucial for the advancement of energy storage and the mitigation of hydrogen embrittlement. Using nanosized palladium particles as a model, recent experimental studies have revealed several highly nonlinear phenomena that occur over a long period of time. The time scale of these phenomena is beyond the capability of established atomistic models. In this work, we present the application of a new model, referred to as diffusive molecular dynamics (DMD), to simulating long-term diffusive mass transport at atomistic length scale. Specifically, we validate the model for the long-term dynamics of a single hydrogen atom on palladium lattice. We show that the DMD result is in satisfactory agreement with the result of the classical random walk model. Then, we apply the DMD model to simulate the absorption of hydrogen by a palladium nanocube with an edge length of 16 nm. We show that the absorption process is dominated by the propagation of a sharp, coherent α/β hydride phase boundary. We also characterize the local lattice deformation near the dynamic phase boundary using the mean positions of the palladium and hydrogen atoms.

A nano-scale strip of graphene is known as graphene nano-ribbon (GNR). Previous studies have shown that the armchair-type GNR (aGNR) can open the electronic band gap at room temperature, and the band gap increases monotonically with the decrease in the width of aGNR. The critical width at which aGNR shows semi-conductive characteristics at room temperature is about 70 nm, when it is passivated by hydrogen on both sides. However, the electronic band structure varies frequently as a function of the number of carbon atoms along its width direction. In order to decrease the large variation of the band gap of aGNR to control the electronic properties of GNR for highly sensitive sensors and high performance devices, the electronic band structure of various dumbbell-shape structure of aGNR was analyzed by first-principles calculations based on the density functional theory using implemented in SIESTA package. It was shown that the width of aGNR had a large effect on the electronic band structure and the amplitude of the fluctuation of the band gap as a function of the number of carbon atoms decreased drastically. The electronic band structure of various GNRs under the application of uniaxial strain was also analyzed by using the first-principles calculations, in this study. It was confirmed that the effective band gap of aGNR thinner than 70 nm varies drastically under the application of uniaxial strain, and this result clearly indicates the possibility of a highly sensitive strain sensor using dumbbell-shape GNR structures.

Large-area and high-quality monolayer graphene was synthesized in order to fabricate a graphene-base highly sensitive strain sensor. A rapid LPCVD (Low Pressure Chemical vaper deposition) synthesis process of monolayer graphene was developed by using acetylene as a resource gas. To synthesize high-quality single-crystal graphene, the surface of copper substrate was strongly orientated to (111) crystallographic plane. By optimizing the concentration of acetylene gas by diluting hydrogen, the high quality of monolayer single-crystalline graphene film was successfully grown on the copper substrate. A strain sensor was fabricated using the graphene-coated Cu foils by applying the MEMS process and reactive ion etching (RIE). Then, the sensor was transferred onto a polydimethysiloxane (PDMS) substrate. Tree-dimensional bending test was performed to investigate the piezoresistive property of the patterned graphene nano-ribbon. It was confirmed that the highly sensitive strain sensor was obtained when the width of the nano-ribbon was thinner than 70 nm.