Systematic planning to optimize investments in hydrogen infrastructure deployment

The introduction of hydrogen infrastructure and fuel cell vehicles (FCVs) to gradually replace gasoline internal combustion engine vehicles can provide environment and energy security benefits. The deployment of hydrogen fueling infrastructure to support the demonstration and commercialization of FCVs remains a critical barrier to transitioning to hydrogen as a transportation fuel. This study utilizes an engineering methodology referred to as the Spatially and Temporally Resolved Energy and Environment Tool (STREET) to demonstrate how systematic planning can optimize early investments in hydrogen infrastructure in a way that supports and encourages growth in the deployment of FCVs while ensuring that the associated environment and energy security benefits are fully realized. Specifically, a case study is performed for the City of Irvine, California – a target area for FCV deployment – to determine the optimized number and location of hydrogen fueling stations required to provide a bridge to FCV commercialization, the preferred rollout strategy for those stations, and the environmental impact associated with three near-term scenarios for hydrogen production and distribution associated with local and regional sources of hydrogen available to the City. Furthermore, because the State of California has adopted legislation imposing environmental standards for hydrogen production, results of the environmental impact assessment for hydrogen production and distribution scenarios are measured against the California standards. The results show that significantly fewer hydrogen fueling stations are required to provide comparable service to the existing gasoline infrastructure, and that key community statistics are needed to inform the preferred rollout strategy for the stations. Well-to-wheel (WTW) greenhouse gas (GHG) emissions, urban criteria pollutants, energy use, and water use associated with hydrogen and FCVs can be significantly reduced in comparison to the average parc of gasoline vehicles regardless of whether hydrogen is produced and distributed with an emphasis on conventional resources (e.g., natural gas), or on local, renewable resources. An emphasis on local renewable resources to produce hydrogen further reduces emissions, energy use, and water use associated with hydrogen and FCVs compared to an emphasis on conventional resources. All three hydrogen production and distribution scenarios considered in the study meet California's standards for well-to-wheel GHG emissions, and well-to-tank emissions of urban ROG and NO_X. Two of the three scenarios also meet California's standard that 33% of hydrogen must be produced from renewable feedstocks. Overall, systematic planning optimizes both the economic and environmental impact associated with the deployment of hydrogen infrastructure and FCVs.     

How to measure and optimize the efficiency of a wave power converter

A method by which one can measure the hydrodynamic efficiency of a wave power converter is discussed. Provided one measures both the horizontal and the vertical wave motion, it is sufficient to have measurements at one point closely in front of the converter and at another point behind it. Good estimates of the efficiency can be obtained without a Fourier analysis of the waves. The method should be useful both for measurements in the laboratory and in the ocean.     

氢能知识系列讲座(3)如何把氢储存起来?

氢能体系主要包括氢的生产、储存和运输、应用三个环节。而氢能的储存是关键，也是目前氢能应用的主要技术障碍。大家知道，所有元素中氢的重量最轻，在标准状态下，它的密度为0．0899g／L，为水的密度的万分之一。在-252．7℃时，可成为液体，密度为70g／L，仅为水的十五分之一。所以，氢气可以储存，但是很难高密度地储存。     

Using AHP and binary integer programming to optimize the initial distribution of hydrogen infrastructures in Andalusia

The use of vehicles powered by hydrogen from renewable sources can be a viable alternative for Andalusia, given its accessibility to renewable energies and the problems of energy dependence and pollution resulting from the current energy model. However, the introduction of this type of technology requires an initial infrastructure that solves the classical chicken and egg problem. Given that hydrogen fueling infrastructure will require significant initial capital investment, it is reasonable to assume that a possible strategy of introduction could be the establishment of a station network that is sparse to avoid redundancy and therefore minimize costs. In this paper, we utilize Analytic Hierarchy Process to rank, on the basis of several supply, demand and environmental criteria, the more than 750 municipalities of Andalusia according to their suitability for the establishment of hydrogen fueling stations. Subsequently, we incorporate these results into an optimization problem to achieve optimal planning of the number and location of hydrogen fueling stations to provide coverage for the region.     

空调冷冻装置节能对策

从生产现状出发,通过对空调冷冻装置采取多种节能措施,以及对提高节能水平和用能水平的过程进行分析总结,从而整合优化生产工艺,降低装置能耗。     

Modeling and evaluation of designs for solid hydrogen storage beds

Mathematical models have been developed to predict the performance of metal-hydride beds used for hydrogen storage. The relative importance of heat transfer, mass transfer, chemical kinetics and equilibrium have been evaluated by comparison of the models with experimental data supplied by Brookhaven National Laboratory for a cylindrical bed containing iron-titanium (FeTi) alloy. Of these factors, only mass transfer was found to be negligible. An equilibrium model without empirical parameters produces bed pressure and temperatures that show good agreement with experimental data; however, events such as maximum pressure and centerline temperatures are predicted at times that differ from those observed. This model is used to evaluate two proposed designs for solid hydrogen storage beds in which (1) FeTi alloy is contained in tubes that are externally cooled, and (2) FeTi alloy is contained in a bed that is penetrated by cooling tubes. The model predicts that heat transfer surface area is utilised most effectively with the second cooling configuration.     

Development of a methodology to optimize the air bleed in PEMFC systems operating with low quality hydrogen

The use of hydrogen with lower quality than that specified in current regulation is an attractive option for stationary PEMFC power production. In this paper, the effect of CO is mitigated using air bleed levels up to 2% in an H₂ PEMFC fed with CO concentrations below 20 ppm. A methodology to optimize the air bleed levels is developed using a novel arrangement of cells coupled to a gas chromatograph. The methodology relies on evaluating the distributed performance of the cell and on determining the CO and CO₂ molar flow rates at the anode outlet. Furthermore, the amount of CO adsorbed onto the catalyst and the fraction of catalytic sites covered by CO are estimated. The results show that different parameters, such as the H₂ volumetric flow rate, CO concentration and air bleed level, influence both the steady state and dynamics of PEMFCs operated with low quality hydrogen.     

How to accurately determine the uptake of hydrogen in carbonaceous materials

A volumetric apparatus for adsorption measurement of hydrogen in carbonaceous materials aimed at hydrogen adsorption storage was constructed. The performance of the apparatus was assessed by helium and hydrogen adsorption in one kind of vapor-grown graphitic nanofiber (GNF). The bulk gas amounts determined by the equations of state of the Modified-Benedic-Webb-Rubin (MBWR), the ideal gas and the Soave-Redlich-Kwong (SRK) under the conditions of present study are compared. Two different methods of processing experimental data to determine the residual volume are studied. Experimental results and theoretic analysis showed that the volumetric apparatus and the data processing method described in this paper could accurately determine the Gibbs excess adsorption amount of hydrogen in carbonaceous materials. Although the vapor-grown GNF used in the present study did not show a significant storage capacity of hydrogen, the obtained results would provide favorable reference data for the development of the carbonaceous material for hydrogen adsorption storage.     

A new approach to optimize the performance of a hydrogen reservoir using activated carbon as the storing material

We have developed a new approach in order to compute the optimal way of filling as efficiently as possible an hydrogen reservoir using activated carbon as the storing material. Our approach combines finite element computation with multi objective optimization techniques based on the Fast Pareto Genetic Algorithm (FPGA) to find an ensemble of optimal solutions known as the Pareto front. We have illustrated our method by studying a small cylindrical reservoir. We were able to find a 7-point filling function (i.e. the input flow as a function of time) giving the shortest filling time to reach a stored hydrogen mass for a given heat transfer coefficient while keeping the reservoir internal temperature and pressure under their maximal safe values.     

Performance assessment study of photo-electro-chemical water-splitting reactor designs for hydrogen production

Solar water splitting is considered a greatly promising technique for producing clean hydrogen fuel. However, limited studies have paid attention to the designs of photo-electrochemical (PEC) reactors. In this regard, two different designs of PEC reactor are proposed and studied numerically in the present paper. The effects of important design parameters on the system performance are also investigated. The PEC governing equations of transport phenomena related to water splitting reactor are developed and numerically solved. According to the current results, the rate of the hydrogen volume production and the solar - to - hydrogen conversion efficiency increase as an applied solar incident flux increases for both proposed designs. The solar - to - hydrogen conversion efficiencies are calculated to be 12.65% for design 1 and 12.48% for design 2. The hydrogen volume production rate is performed to achieve 78.3 L/m² h by design 1, and 74.8 L/m² h by design 2.     

Development of autonomous solar hydrogen power plant of capacity to 5 kW

The main results of developing a pilot project concerning the water thermal decomposition cycle at 700°C in a reactor located at the concentrator focus are presented. Steam is generated and the mixture of water vapor with hydrogen is directed to a turbine with electrical generator; the turbine exhaust is used in the heat supply system, from which it enters an electrolyzer, in which pure hydrogen is separated from the mixture. Part of the electric power produced by the generator is used for the electrolysis process. This cycle was studied in the period from 2003 to 2008 as a part of the fundamental solar furnace programs in Parkent. The goal of the pilot project is to create a power plant with overall power output (electric energy, heat supply, hydrogen) up to 5 kW that is intended for the Uzbek rural regions. When implementing the project, developers will work out the design of the components, conduct pilot operations, train the servicing personnel, and conduct a feasibility study for replication of the unit.     

Recycling a hydrogen rich residual stream to the power and steam plant

The benefits of using a residual hydrogen rich stream as a clean combustion fuel in order to reduce Carbon dioxide emissions and cost is quantified. A residual stream containing 86% of hydrogen, coming from the top of the demethanizer column of the cryogenic separation sector of an ethylene plant, is recycled to be mixed with natural gas and burned in the boilers of the utility plant to generate high pressure steam and power. The main advantage is due to the fact that the hydrogen rich residual gas has a higher heating value and less CO₂ combustion emissions than the natural gas. The residual gas flowrate to be recycled is selected optimally together with other continuous and binary operating variables. A Mixed Integer Non Linear Programming problem is formulated in GAMS to select the operating conditions to minimize life cycle CO₂ emissions.     

Dispersion and behavior of hydrogen for the safety design of hydrogen production plant attached with nuclear power plant

Development of nuclear energy and hydrogen energy both as renewable energy open up a vast range of prospects. The scheme for hydrogen generation station in nuclear power plant has been carried out in china. However, Nuclear Energy is expected to encourage a safety culture that prevents serious accidents while dispersion of hydrogen from a container produces a risk of combustion. The dispersion and behavior of hydrogen production plant attached with nuclear power plant are still poorly understood. In this paper, a dispersion of hydrogen model is established and is calculated under two typical condition with corrected ideal gas state equation. The flammability of hydrogen after dispersion is studied. The range of flammability of dispersion of hydrogen production plant with different pressures, positions and temperatures is obtained. This work could contribute to the marginal hydrogen safety design for hydrogen production station and lay the foundation for the establishment of a safe distance standard that it's necessary to prevent hydrogen explosion.     

Optimization of heat exchanger designs in metal hydride based hydrogen storage systems

Design of the heat exchanger in a metal hydride based hydrogen storage system influences the storage capacity, gravimetric hydrogen storage density, and refueling time for automotive on-board hydrogen storage systems. The choice of a storage bed design incorporating the heat exchanger and the corresponding geometrical design parameters is not obvious. A systematic study is presented to optimize the heat exchanger design using computational fluid dynamics (CFD) modeling. Three different shell and tube heat exchanger designs are chosen. In the first design, metal hydride is present in the shell and heat transfer fluid flows through straight parallel cooling tubes placed inside the bed. The cooling tubes are interconnected by conducting fins. In the second design, heat transfer fluid flows through helical tubes in the bed. The helical tube design permits use of a specific maximum distance between the metal hydride and the coolant for removing heat during refueling. In the third design, the metal hydride is present in the tubes and the fluid flows through the shell. An automated tool is generated using COMSOL-MATLAB integration to arrive at the optimal geometric parameters for each design type. Using sodium alanate as the reference storage material, the relative merits of each design are analyzed and a comparison of the gravimetric and volumetric hydrogen storage densities for the three designs is presented.     

Design of an ocean thermal energy plant ship to produce ammonia via hydrogen

The 43°F (24°C) temperature difference that exists between surface water and deep water at selected sites in tropical oceans can be used to drive a heat engine to produce electric power, electrolyze water, and produce ammonia from the resulting hydrogen plus nitrogen from the air. A baseline design has been developed for a 100-MWe Ocean Thermal Energy Conversion (OTEC) plant-ship that would produce 313 tons per day of ammonia. The cost estimates for this design have been extrapolated to 500-MWe plant-ships to produce ammonia (for fertilizers and chemicals) or liquid hydrogen for shipment to the U.S. It is judged that ammonia will be producible at competitive cost ($96/short ton in 1975 dollars) by the sixth and subsequent plant-ships in the mid-1980s. This production by OTEC/ammonia plants would conserve supplies of natural gas or other fossil fuels now used to produce ammonia on shore. For the longer term (1990s), liquid hydrogen from OTEC plants should become competitive as demands for this clean fuel and efficient ways for employing it in larger markets (fuel cells, transportation, etc.) come to maturity.     

Electrolyzer-fuel cell combination for grid peak load management in a geothermal power plant: Power to hydrogen and hydrogen to power conversion

This study provides comprehensive energy, exergy, and economic evaluations and optimizations of a novel integrated fuel cell/geothermal-based energy system simultaneously generating cooling and electricity. The system is empowered by geothermal energy and the electricity is mainly produced by a dual organic cycle. A proton exchange membrane electrolyzer is employed to generate the oxygen and hydrogen consumed by a proton exchange membrane fuel cell utilized to support the network during consumption peak periods. This fuel cell can be also used for supplying the electricity demanded by the network to satisfy the loads at different times. All the simulations are conducted using Engineering Equation Solver software. To optimize the system, a multi-objective optimization method based on genetic algorithm is applied in MATLAB software. The objective functions are minimized cost rate and maximized exergy efficiency. The optimum values of exergy efficiency and cost rate are found to be 62.19% and 18.55$/h, respectively. Additionally, the results reveal that combining a fuel cell and an electrolyzer can be an effective solution when it comes to electricity consumption management during peak load and low load periods.     

Transient analysis of coupled high temperature nuclear reactor to a thermochemical hydrogen plant

A very high temperature reactor (VHTR) has been considered for generation of hydrogen by water-splitting through thermochemical processes using process heat. The development of this technology requires understanding of the coupled behavior of VHTR and the hydrogen generation plants and key safety issues during transients. A system level modeling of the coupled VHTR and sulfur-iodine hydrogen generation process is carried out where the thermal and neutronic models of the VHTR and the chemical models of the sulfur-iodine cycle were developed and benchmarked with available experimental data, models and simulation codes. Transient analysis of the possible accidents emanating either from VHTR or hydrogen plants was carried out. The results indicate that on VHTR side the response of the reactor is affected by the temperature feedback and xenon buildup feedback. On the hydrogen plant side the slowest reaction controlled the speed of the overall response of the chemical plant.     

Eight steps to optimize your strategic assets

This paper describes an eight-step process to implement portfolio management for a single power station during its operational, revenue-generating life-cycle phase. This paper also discusses how portfolio management creates additional value, from your generation, transmission, and distribution assets. Portfolio management currently offers the best opportunity for these managers and their companies to grow the return on these strategic assets. Organizations may obtain up to a 20% increase in the return on capital employed and substantial improvements in softer benefits, such as improved collaboration, faster decision making, and reduced administrative effort. However, the success of this new approach, and the value you can obtain for your own plant or network, depends heavily on strong leadership and a well thought out, systematic approach to implementation.     

Modeling of a two-step solar hydrogen production plant

The promising advances in research in two-step solar hydrogen production from water have increased interest in producing hydrogen with this technology. In this framework, the Hydrosol II Project pilot plant for producing continuous solar hydrogen from water using a ferrite-based redox technology was erected at the CIEMAT-Plataforma Solar de Almería. Two reactors allow the oxidation and reduction steps to be performed in parallel, which, sequentially switched, make hydrogen production quasi-continuous.