Optimization of low-carbon hydrogen supply chain networks in industrial clusters

This work presented an optimization-based model to aid in designing and planning a hydrogen supply chain network (HSCN) under different CO₂ emission mitigation policies. The novelty of this approach lies in simultaneously, 1) tracking the resources available in HSCN and 2) designing the spatial interaction production, storage, and transportation. The model was formulated as a Mixed Integer Linear Program (MILP) to identify the minimum cost of HSCN. A case study was solved to assess the techno-economic performance of grey, blue and green hydrogen production while accounting for transport and the full energy system. A Pareto-curve was constructed to understand the trade-off between the Levelized cost of Hydrogen and emission reduction. The model also enabled the investigation of various long-distance hydrogen transport schemes; hydrogen transported as ammonia will cost 19% less than the other alternatives (liquid hydrogen, and liquid organic hydrogen carrier).     

Synthesis of hydrogen network with hydrogen header of intermediate purity

In order to simplify the network configuration and enhance the expandability and flexibility of the hydrogen network, one or two hydrogen utility headers are typically set with the consideration of requirement of hydrogen consumers. This paper proposed a superstructure-based mathematical programming model for the synthesis of hydrogen network with intermediate hydrogen header. The comprehensive superstructure is embedded with hydrogen utility, internal hydrogen sources and sinks, hydrogen headers, fuel system, compressors, purifiers and all the feasible interconnections between them. Two case studies are utilized to illustrate the feasibility and applicability of the proposed approach. The results show that the optimal flow rate of hydrogen utility will be decreased with the increase of the total number of connections as well as the increase of the number of hydrogen headers. The minimum flow rate of hydrogen utility for direct reuse/recycle without any intermediate hydrogen header can be achieved with the emplacement of two intermediate hydrogen headers. Besides, there is no direct connection among the hydrogen sources and hydrogen sinks. The Pareto front is made for the comparison on the flowrate of hydrogen utility and number of connections. The purification reuse/recycle scheme is investigated with the installation of purifier and the flowrate of hydrogen utility is reduced further.     

Energy recovery in petrochemical complexes through heat integration retrofit analysis

This paper proposes the principles of how to define a boundary for heat integration in petrochemical complexes which are composed of several interconnected processing units. In order to obtain retrofit schemes that offer significant energy saving potential and are easy to implement, heat integration strategies are also developed in this study. Two case studies based on an aniline plant and an aromatic hydrocarbon plant, each one comprising several processing units, are presented to illustrate the application of these principles and strategies. The boundary for heat integration in each plant can be the whole plant or its individual processing units, the choice of which is determined by their energy saving potentials. Based on energy saving potential, each processing unit in the aniline plant was selected as the boundary for heat integration. The boundary for heat integration in the aromatic hydrocarbon plant, by contrast, was the whole plant. Retrofit schemes for the heat exchanger networks of the two plants, developed using pinch analysis, revealed that significant heating utility savings could be realized with a small number of network structure modifications.     

Multi-component optimisation for refinery hydrogen networks

Heavier crude oil, tighter environmental regulations and increased heavy-end upgrading in the petroleum industry are leading to the increased demand for hydrogen in oil refineries. Hence, hydrotreating and hydrocracking processes now play increasingly important roles in modern refineries. Refinery hydrogen networks are becoming more and more complicated as well. Therefore, optimisation of overall hydrogen networks is required to improve the hydrogen utilisation in oil refineries. Previous work over hydrogen management has developed methodologies for H₂ network optimisation, with a very simplistic assumption that all H₂ rich streams consist of H₂ and CH₄ only, which leads to a serious doubt of solution’s feasibility. To overcome the drawbacks in previous work, an improved modelling and optimisation approach has been developed. Light hydrocarbon production and integrated flash calculation are incorporated into a hydrogen consumer model. An optimisation framework is developed to solve the resulting NLP problem. A case study is carried out to demonstrate the effectiveness of the developed approach.     

PdCu membrane integration and lifetime in the production of hydrogen from methane

PdCu membranes prepared by sequential electroless plating were integrated into a hydrogen production and purification process. Hydrogen was produced from methane through catalytic partial oxidation and wet catalytic partial oxidation with Ni-based catalysts. Membrane permeance was measured with thermal cycles in an inert and hydrogen atmosphere at 673 and 773 K. Permeability was 1.98·10⁻³ mol/(smPa^0.5) at 673 K and 2.62·10⁻³ mol/(smPa^0.5) at 773 K. The optimum sweep gas flow required in the membrane module when operating with hydrogen-containing mixtures was selected. Peak hydrogen recovery was obtained using 15–20% of the feed to the module as sweep gas flow. Membranes were then placed downstream of the hydrogen production reactor. The CO and H₂O percentages fed to the membrane module did not have a major impact on membrane behavior. Around 60–67% of the hydrogen fed to the membrane module was separated, regardless of its composition.     

Designing future hydrogen infrastructure: Insights from analysis at different spatial scales

This paper critically reviews the growing literature optimising hydrogen infrastructure. We examine studies across spatial scales: national scale studies using energy system models; regional scale studies optimising spatially disaggregated hydrogen infrastructure; and local scale studies optimising the siting of filling stations. For the latter two types of study, we critically assess the assumptions made around hydrogen demand, a key exogenous input into these studies. We identify knowledge gaps and issues that have not been sufficiently addressed in the literature, and we suggest areas for further work.     

Comparison among various energy management strategies for reducing hydrogen consumption in a hybrid fuel cell/supercapacitor/battery system

The aim of this study is to introduce a comprehensive comparison of various energy management strategies of fuel cell/supercapacitor/battery storage systems. These strategies are utilized to manage the energy demand response of hybrid systems, in an optimal way, under highly fluctuating load condition. Two novel strategies based on salp swarm algorithm (SSA) and mine-blast optimization are proposed. The outcomes of these strategies are compared with commonly used strategies like fuzzy logic control, classical proportional integral control, the state machine, equivalent fuel consumption minimization, maximization, external energy maximization, and equivalent consumption minimization. Hydrogen fuel economy and overall efficiency are used for the comparison of these different strategies. Results demonstrate that the proposed SSA management strategy performed best compared with all other used strategies in terms of hydrogen fuel economy and overall efficiency. The minimum consumed hydrogen and maximum efficiency are found 19.4 gm and 85.61%, respectively.     

Multi-objective optimization of hydrogen production process and steam reforming reactor design

This study proposes a multi-objective optimization approach to design a steam methane reforming (SMR) reactor and maximize the efficiency of the hydrogen production process. Out of 1782 possible variable combinations, only 50 iterations were performed, identifying three Pareto optimal that resulted in reactor size reductions of 50.53%, 35.56%, and 20.69%, respectively, compared to the reference reactor. The process efficiency for each optimal design varied slightly, with one achieving a 105.05% increase in efficiency, another remaining stable at 100.48%, and a third experiencing a slight decrease to 86.66% compared to the reference case. The results offer practical insights for planning an on-site distributed hydrogen production system, demonstrating that an increase in overall process efficiency can be achieved even with a reduced reactor size. This work is the first attempt to optimize a hydrogen production system by simultaneously considering overall process efficiency and SMR reactor design.     

Evaluating hydrogen risk management policy PR: Lessons learned from three hydrogen accidents in South Korea

Hydrogen energy has become a pivotal actor in achieving carbon neutrality by 2050 in the era of the climate crisis. Regardless of its importance, three consecutive hydrogen safety accidents and their aftermath in South Korea have aggravated the public's acceptance of hydrogen. Hydrogen-induced risks have always existed in our society regardless of technical improvement. Here, the task of the government is to manage the hydrogen risk to prevent hydrogen disasters. This study included three steps in its research design; 1) selecting experts through snowball sampling, 2) conducting a qualitative email survey, and 3) analyzing the qualitative answer sheet by applying semantic network analysis. We found that experts' evaluations of the Korean hydrogen PR policy were positive regarding responsiveness but negative regarding openness, guidelines, and control tower. Therefore, we suggest practical policy recommendations; the central government should play an important role in cultivating professional crisis management PR personnel and others.     

Biomass-based hydrogen for oil refining: Integration and performances of two gasification concepts

In this work, two biomass-to-hydrogen concepts are designed and their integration with a large European refinery is investigated. One concept is based on indirect, atmospheric steam gasification while the second is based on pressurized direct oxygen-steam-blown gasification. The technologies chosen for gas cleaning, upgrading and hydrogen separation also differ in the two concepts. Heat integration and poly-generation opportunities are identified by means of process integration tools and four system configurations are identified. These are compared in terms of energy and exergy performances and potential for reduction of fossil CO₂ emissions at the refinery. It is found that the performance of the biomass-to-hydrogen concepts can be improved by up to 11% points in energy efficiency and 9% points in exergy efficiency. The design based on indirect gasification appears the most efficient according to both energy and exergy efficiencies. All configurations yield potential significant reductions of fossil CO₂ emissions at the refinery.     

Investigation of the electrocatalytic activity of metalophthalocyanine complexes for hydrogen production from water

The electrocatalytic proton reduction activity of metallophthalocyanines was investigated by using Nafion (Nf) membrane on ITO electrode embedding different metallophthalocyanine derivatives such as cobalt phthalocyanine (CoPc) and palladium phthalocyanine (PdPc) carrying tetra tricarbetoxyethyl groups. Electrocatalytic studies of CoPc indicated that the proton reduction was catalyzed by the CoPc via the electroreduced Co^IPc(−2) or Co^IPc(−1). PdPc modified ITO electrode exhibited only one cathodic wave which can be easily attributed to the proton reduction. Comparison of this wave with the bare electrode indicates that the complex does not work as a catalyst for proton reduction. Analysis of the CVs of CoPc at different pHs indicates that activity of CoPc varies arbitrarily with increasing pH. The most successful activity is at pH 2.2.     

Mathematical modeling and optimization of hydrogen distribution network used in refinery

In the present investigation, mathematical models have been developed to optimize hydrogen distribution in the refinery. Five models, Model-0, Model-1, Model-2, Model-3 and Model-4, have been formulated to determine the optimal hydrogen network. Amongst these, Model-0 and Model-1 are NLP networks, whereas the remaining three are MINLP networks. The NLP models are improved gradually to develop MINLP models which incorporate new compressor and PSA. The model considers pressure constraints, source flow balance, sink flow balance, compressor flow balance, sink purity constraint, operating cost, capital cost associated with new equipment, payback period and export cost. Amongst five models, Model-4 is predicted as optimal network which is MINLP model incorporating new compressor and PSA. It predicts reduction in hydrogen by 21.74% and annual profit of $ 16.57 million. The present work selects the optimal type of new compressor based on different capital cost functions. Further, the reliability of the present work is checked through comparison of its results with published models.     

Role of hydrogen storage in renewable energy management for Ontario

Effective energy storage and management is needed to manage intermittent renewable energy systems. Several jurisdictions around the world are planning to reduce or close their coal power plants to allow for renewable energy expansion, such as Ontario, Canada. Hydrogen storage, which is a promising energy storage option, is capable of meeting energy requirements that will arise from the shutdown of coal plants. In this paper, both economic and environmental feasibility of a hydrogen system linked with wind and hydroelectric plants in Ontario will be investigated. The Princefarm wind power plant and Beck1 hydro plant with production capacities of 189 MW and 490 MW, respectively, are analyzed in a case study for comparison purposes. The environmental analysis demonstrates the advantageous role of hydrogen storage and energy conversion. The overall system life-cycle yields 31.02 g CO₂ eq per 1 kW h power output of the system when hydrogen energy storage is adopted. The payback periods of the systems linked with the Princefarm and Beck1 are also analyzed and found to be about 17 years.     

A novel mathematical model for integrating the hydrogen network of refinery with compressor allocation considered

The allocation and cost of compressors have significant influence on hydrogen network. A novel mixed integer nonlinear programming method is proposed for optimizing hydrogen network with the allocation of compressors considered. This model considers the streams compressed stage by stage with multiple compressors and all possible compression paths. The compression power cost of multiple compressors is deduced to optimize the number of compressors in each compression process. The trade-off between the power loss and capital cost of compression is analyzed for different compression paths. The superstructure and mathematical model are built to optimize the hydrogen network in terms of minimizing the total annual cost. The proposed model is flexible and efficient. Three literature cases are studied by the proposed method, and the optimal flowsheets are identified. Compared with previous methods, the computing time is significantly reduced and the total cost of compressors is reduced by 3.38%–8.46%.     

Optimizing site selection for hydrogen production in Iceland

While the world energy demand is steadily growing, the concern for the environmental aspects of energy use and natural resource exploitation has increased. A new market has emerged for renewable energy, often referred to as “green energy”. This paper presents an optimization model developed as part of a feasibility study on the idea of exporting renewable energy in the form of hydrogen, from Iceland to the continent of Europe.     

Systematic retrofit method for refinery hydrogen network with light hydrocarbons recovery

Retrofit of the refinery hydrogen network is one of the important issues faced by modern refineries. Refinery off-gas streams are rich in hydrogen and valuable light hydrocarbons. Light hydrocarbons recovery (LHR) process can recover the valuable hydrocarbons and generate the hydrogen-rich stream for reuse and recycle. We firstly propose the systematic procedure for the retrofit of refinery hydrogen network integrated with LHR process. The approach combines the pinch analysis technique and process modelling and simulation. The typical pinch analysis technique (i.e. problem table) is used to determine the flowrate targets. Aspen HYSYS is used for the modelling and simulation of LHR process. The retrofit of an industrial refinery hydrogen network is conducted to illustrate the procedure. Results show that the benefit of retrofit scheme (Integrated Scheme 3) with LHR reaches 7.488 million CNY/y, and the investment payback period is only 8 months.     

Analyses of hydrogen energy system as a grid management tool for the Hawaiian Isles

One of the objectives of the research project at Hawaii Natural Energy Institute (HNEI) is to demonstrate long-term durability of the electrolyzer when operated under cyclic operation for frequency regulation on an Island grid system. In this paper, a Hydrogen Energy System with an electrolyzer is analyzed as a potential grid management tool. A simulation tool developed with a validated model of the hydrogen energy system and Island of Hawaii grid model is presented and employed for this investigation. The simulation study uses realistic measured solar and wind power profiles to understand what optimal electrolyzer size would be required to achieve the maximum level of grid frequency stabilization. The simulation results give insight into critical information when designing a hydrogen energy system for grid management applications and the economic impact it has when operated as a pure grid management scheme or as a limitless hydrogen production system.     

Optimization of autothermal reactor for maximum hydrogen production

Efficient generation of hydrogen is an important enabling technology for commercialization of fuel cells for homes and cars of the future. A methodology for optimization of an autothermal reactor with respect to system parameters is described. Furthermore, a framework for theoretical interpretation of reforming reactions is developed using an atomic balance approach, which is utilized to determine the reforming reaction space and maximum monolith temperature for a methane reformer.     

Optimal design of inter-plant hydrogen networks with intermediate headers of purity and pressure

This paper addresses the optimal design of inter-plant hydrogen networks with intermediate headers of purity and pressure. A superstructure for inter-plant integration of hydrogen networks is presented, where all hydrogen sources and hydrogen sinks are indirectly matched with each other through intra-plant hydrogen headers and inter-plant hydrogen headers. The corresponding mathematical programming model is constructed and a tailored two-step strategy is proposed to solve the model. In this solving method, the topology of the inter-plant hydrogen network and the purity levels of the hydrogen headers are first determined to minimize the cost of hydrogen utilities. The placements of compressors and pressure levels of hydrogen headers are then optimized to reach the lowest total annual cost of the inter-plant hydrogen network. The application of the proposed method is illustrated via a practical industrial case of inter-plant hydrogen network in China.     

Neural network based optimization for cascade filling process of on-board hydrogen tank

Compressed hydrogen storage is widely used in hydrogen fuel cell vehicles (HFCVs). Cascade filling systems can provide different pressure levels associated with various source tanks allowing for a variable mass flow rate. To meet refueling performance objectives, safe and fast filling processes must be available to HFCVs. The main objective of this paper is to establish an optimization methodology to determine the initial thermodynamic conditions of the filling system that leads to the lowest final temperature of hydrogen in the on-board storage tank with minimal energy consumption. First, a zero-dimensional lumped parameter model is established. This simplified model, implemented in Matlab/Simulink, is then used to simulate the flow of hydrogen from cascade pressure tanks to an on-board hydrogen storage tank. A neural network is then trained with model calculation results and experimental data for multi-objective optimization. It is found to have good prediction, allowing the determination of optimal filling parameters. The study shows that a cascade filling system can well refuel the on-board storage tank with constant average pressure ramp rate (APRR). Furthermore, a strong pre-cooling system can effectively lower the final temperature at a cost of larger energy consumption. By using the proposed neural network, for charging times less than 183s, the optimization procedure predicts that the inlet temperature is 259.99–266.58 K, which can effectively reduce energy consumption by about 2.5%.