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Numerical Study of Highly Turbulent Under-expanded Hydrogen Jet Flames Impinging Walls
Sep 2023
Publication
Heat flux on walls from under-expanded H2/AIR jet flames have been numerically investigated. The thermal behaviour of a plate close to different under-expanded jet flames has been compared with rear-face plate temperature measurements. In this study two straight nozzles with millimetric diameter were selected with H2 reservoir pressure in a range from 2 to 10 bar. The CFD study of these two quite different horizontal jet flames employs the Large Eddy Simulation (LES) formalism to capture the turbulent flame-wall interaction. The results demonstrated a good agreement with experimental wall heat fluxes computed from plate temperature measurements. The present study assesses the prediction capability of LES for flame-wall heat transfer.
Ammonia Decomposition in the Process Chain for a Renewable Hydrogen Supply
Jun 2022
Publication
This review article deals with the challenge to identify catalyst materials from literature studies for the ammonia decomposition reaction with potential for application in large-scale industrial processes. On the one hand the requirements on the catalyst are quite demanding. Of central importance are the conditions for the primary reaction that have to be met by the catalyst. Likewise the catalytic performance i.e. an ideally quantitative conversion and a high lifetime are critical as well as the consideration of requirements on the product properties in terms of pressure or by-products for potential follow-up processes in this case synthesis gas applications. On the other hand the evaluation of the multitude of literature studies poses difficulties due to significant varieties in catalytic testing protocols.
Influence of Capillary Threshold Pressure and Injection Well Location on the Dynamic CO2 and H2 Storage Capacity for the Deep Geological Structure
Jul 2021
Publication
The subject of this study is the analysis of influence of capillary threshold pressure and injection well location on the dynamic CO2 and H2 storage capacity for the Lower Jurassic reservoir of the Sierpc structure from central Poland. The results of injection modeling allowed us to compare the amount of CO2 and H2 that the considered structure can store safely over a given time interval. The modeling was performed using a single well for 30 different locations considering that the minimum capillary pressure of the cap rock and the fracturing pressure should not be exceeded for each gas separately. Other values of capillary threshold pressure for CO2 and H2 significantly affect the amount of a given gas that can be injected into the reservoir. The structure under consideration can store approximately 1 Mt CO2 in 31 years while in the case of H2 it is slightly above 4000 tons. The determined CO2 storage capacity is limited; the structure seems to be more prospective for underground H2 storage. The CO2 and H2 dynamic storage capacity maps are an important element of the analysis of the use of gas storage structures. A much higher fingering effect was observed for H2 than for CO2 which may affect the withdrawal of hydrogen. It is recommended to determine the optimum storage depth particularly for hydrogen. The presented results important for the assessment of the capacity of geological structures also relate to the safety of use of CO2 and H2 underground storage space.
The Trajectory of Hybrid and Hydrogen Technologies in North American Heavy Haul Operations
Jul 2021
Publication
The central aim of this paper is to provide an up-to-date snapshot of hybrid and hydrogen technology-related developments and activities in the North American heavy haul railway setting placed in the context of the transportation industry more broadly. An overview of relevant alternative propulsion technologies is provided including a discussion of applicability to the transportation sector in general and heavy haul freight rail specifically. This is followed by a discussion of current developments and research in alternative and blended fuels discussed again in both general and specific settings. Key factors and technical considerations for heavy haul applications are reviewed followed by a discussion of non-technical and human factors that motivate a move toward clean energy in North American Heavy Haul systems. Finally current project activities are described to provide a clear understanding of both the status and trajectory of hybrid and hydrogen technologies in the established context.
Hydrogen Production from Renewable Energy Resources: A Case Study
May 2024
Publication
In the face of increasing demand for hydrogen a feasibility study is conducted on its production by using Renewable Energy Resources (RERs) especially from wind and solar sources with the latter preferring photovoltaic technology. The analysis performed is based on climate data for the Province of Brindisi Apulia Italy. The various types of electrolyzers will be analyzed ultimately choosing the one that best suits the case study under consideration. The technical aspect of the land consumption for RER exploitation until 2050 is analyzed for the Italian case of study and for the Apulia Region. For both the 200 MW and 100 MW RER Power Plants an economic analysis is carried out on the opportunities for using hydrogen. In the last part of the economic analysis the trade-off between the high specific investment cost and the Capacity Factor of Wind technologies is also investigated. The results show the affordability of building high-scale Wind Farms harnessing the existing scale economies. The lowest Hydrogen selling price is achieved by the 200 MW Wind Farms equal to 222 €/MWh against 232 €/MWh of the 200 MW Photovoltaic (PV) Farm. Finally the feasibility analysis considers also the greenhouse gas emission reduction by including in the economic analysis the carbon dioxide (CO2) Average Auction Clearing Price leading for the 200 MW Wind Farms to a hydrogen selling price equal to 191.2 €/MWh against 201 €/MWh of the 200 MW Photovoltaic Farm.
Recent Advances in Alkaline Exchange Membrane Water Electrolysis and Electrode Manufacturing
Oct 2021
Publication
Water electrolysis to obtain hydrogen in combination with intermittent renewable energy resources is an emerging sustainable alternative to fossil fuels. Among the available electrolyzer technologies anion exchange membrane water electrolysis (AEMWE) has been paid much attention because of its advantageous behavior compared to other more traditional approaches such as solid oxide electrolyzer cells and alkaline or proton exchange membrane water electrolyzers. Recently very promising results have been obtained in the AEMWE technology. This review paper is focused on recent advances in membrane electrode assembly components paying particular attention to the preparation methods for catalyst coated on gas diffusion layers which has not been previously reported in the literature for this type of electrolyzers. The most successful methodologies utilized for the preparation of catalysts including co-precipitation electrodeposition sol–gel hydrothermal chemical vapor deposition atomic layer deposition ion beam sputtering and magnetron sputtering deposition techniques have been detailed. Besides a description of these procedures in this review we also present a critical appraisal of the efficiency of the water electrolysis carried out with cells fitted with electrodes prepared with these procedures. Based on this analysis a critical comparison of cell performance is carried out and future prospects and expected developments of the AEMWE are discussed.
Underground Hydrogen Storage Safety: Experimental Study of Hydrogen Diffusion through Caprocks
Jan 2024
Publication
Underground Hydrogen Storage (UHS) provides a large-scale and safe solution to balance the fluctuations in energy production from renewable sources and energy consumption but requires a proper and detailed characterization of the candidate reservoirs. The scope of this study was to estimate the hydrogen diffusion coefficient for real caprock samples from two natural gas storage reservoirs that are candidates for underground hydrogen storage. A significant number of adsorption/desorption tests were carried out using a Dynamic Gravimetric Vapor/Gas Sorption System. A total of 15 samples were tested at the reservoir temperature of 45 °C and using both hydrogen and methane. For each sample two tests were performed with the same gas. Each test included four partial pressure steps of sorption alternated with desorption. After applying overshooting and buoyancy corrections the data were then interpreted using the early time approximation of the solution to the diffusion equation. Each interpretable partial pressure step provided a value of the diffusion coefficient. In total more than 90 estimations of the diffusion coefficient out of 120 partial pressure steps were available allowing a thorough comparison between the diffusion of hydrogen and methane: hydrogen in the range of 1 × 10−10 m2 /s to 6 × 10−8 m2 /s and methane in the range of 9 × 10−10 m2 /s to 2 × 10−8 m2 /s. The diffusion coefficients measured on wet samples are 2 times lower compared to those measured on dry samples. Hysteresis in hydrogen adsorption/desorption was also observed.
Techno-economic Assessment of Blue and Green Ammonia as Energy Carriers in a Low-carbon Future
Feb 2022
Publication
Ammonia is an industrial chemical and the basic building block for the fertilizer industry. Lately attention has shifted towards using ammonia as a carbon-free energy vector due to the ease of transportation and storage in liquid state at − 33 ◦C and atmospheric pressure. This study evaluates the prospects of blue and green ammonia as future energy carriers; specifically the gas switching reforming (GSR) concept for H2 and N2 co-production from natural gas with inherent CO2 capture (blue) and H2 generation through an optimized value chain of wind and solar power electrolysers cryogenic N2 supply and various options for energy storage (green). These longer term concepts are benchmarked against conventional technologies integrating CO2 capture: the Kellogg Braun & Root (KBR) Purifier process and the Linde Ammonia Concept (LAC). All modelled plants utilize the same ammonia synthesis loop for a consistent comparison. A cash flow analysis showed that the GSR concept achieved an attractive levelized cost of ammonia (LCOA) of 332.1 €/ton relative to 385.1–385.9 €/ton for the conventional plants at European energy prices (6.5 €/GJ natural gas and 60 €/MWh electricity). Optimal technology integration for green ammonia using technology costs representative of 2050 was considerably more expensive: 484.7–772.1 €/ton when varying the location from Saudi Arabia to Germany. Furthermore the LCOA of the GSR technology drops to 192.7 €/ton when benefitting from low Saudi Arabian energy costs (2 €/GJ natural gas and 40 €/MWh electricity). This cost difference between green and blue ammonia remained robust in sensitivity analyses where input energy cost (natural gas or wind/solar power) was the most influential parameter. Given its low production costs and the techno-economic feasibility of international ammonia trade advanced blue ammonia production from GSR offers an attractive pathway for natural gas exporting regions to contribute to global decarbonization.
Split Injection Strategies for a High-pressure Hydrogen Direct Injection in a Small-bore Dual-fuel Diesel Engine
Jan 2024
Publication
Hydrogen-diesel dual direct-injection (H2DDI) engines present a promising pathway towards cleaner and more efficient transportation. In this study hydrogen split injection strategies were explored in an automotive-size single-cylinder compression ignition (CI) engine with a focus on varying the injection timings and energy fractions. The engine was operated at an intermediate load with fixed combustion phasing through adjustments of pilot diesel injection timing. An energy substitution principle guided the variation in energy fraction between the two hydrogen injections and then diesel injection while keeping the total energy input constant. The findings demonstrate that early first hydrogen injection timings lead to characteristics indicative of premixed combustion reflecting a high homogeneity of the hydrogen-air mixture. In contrast hydrogen stratification levels were predominantly influenced by later second injection timings with mixing-controlled combustion behaviour apparent for very late injections near top dead centre or when the second hydrogen injection held high energy fractions which led to decreased nitrogen oxides (NOx: NO and NO2) emissions. The carbon dioxide (CO2) emissions did not show high sensitivity to the hydrogen split injection strategies exhibiting about 77 % reduction compared to the diesel baseline due primarily to increased hydrogen energy fraction of up to 90 %
Explosion Mitigation Techniques in Tunnels and their Applicability to Scenarios of Hydrogen Tank Rupture in a Fire
Sep 2023
Publication
This paper presents a comprehensive review of existing explosion mitigation techniques for tunnels and evaluates their applicability in scenarios of hydrogen tank rupture in a fire. The study provides an overview of the current state of the art in tunnel explosion mitigation and discusses the challenges associated with hydrogen explosions in the context of fire incidents. The review shows that there are several approaches available to decrease the effects of explosions including wrapping the tunnel with a flexible and compressible barrier and introducing energy-absorbing flexible honeycomb elements. However these methods are limited to the mitigation of the action and do not consider either the mitigation of the structural response or the effects on the occupants. The study highlights how the structural response is affected by the duration of the action and the natural period of the structural elements and how an accurate design of the element stiffness can be used in order to mitigate the structural vulnerability to the explosion. The review also presents various passive and active mitigation techniques aimed at mitigating the explosion effects on the occupants. Such techniques include tunnel branching ventilation openings evacuation lanes right-angled bends drop-down perforated plates or high-performance fibre-reinforced cementitious composite (HPFRCC) panels for blast shielding. While some of these techniques can be introduced during the tunnel's construction phase others require changes to the already working tunnels. To simulate the effect of blast wave propagation and evaluate the effectiveness of these mitigation techniques a CFD-FEM study is proposed for future analysis. The study also highlights the importance of considering these mitigation techniques to ensure the safety of the public and first responders. Finally the study identifies the need for more research to understand blast wave mitigation by existing structural elements in the application for potential accidents associated with hydrogen tank rupture in a tunnel.
Thermocouple Thermal Inertia During Refuelling of Hydrogen Tanks: CFD Validation
Sep 2023
Publication
Fueling and defueling of hydrogen composite tanks is an important issue for the safe handling of hydrogen. To prevent temperature rise during refuelling (maximum allowed T=+85°C) the rate of fueling must be carefully controlled. Using Computational Fluid Dynamics (CFD) we simulate the temperature and velocity distribution inside the tank during these processes including cases where thermal stratification occurs. Simulations of two tank configurations with tilted injectors are presented along with experimental data validation. A model is proposed to account for the thermal inertia of the thermocouples making it possible to compare more reliably CFD results with experimental measurements.
Multi-Objective Optimization for Solar-Hydrogen-Battery-Integrated Electric Vehicle Charging Stations with Energy Exchange
Oct 2023
Publication
The importance of electric vehicle charging stations (EVCS) is increasing as electric vehicles (EV) become more widely used. EVCS with multiple low-carbon energy sources can promote sustainable energy development. This paper presents an optimization methodology for direct energy exchange between multi-geographic dispersed EVCSs in London UK. The charging stations (CSs) incorporate solar panels hydrogen battery energy storage systems and grids to support their operations. EVs are used to allow the energy exchange of charging stations. The objective function of the solar-hydrogen-battery storage electric vehicle charging station (SHS-EVCS) includes the minimization of both capital and operation and maintenance (O&M) costs as well as the reduction in greenhouse gas emissions. The system constraints encompass the power output limits of individual components and the need to maintain a power balance between the SHS-EVCSs and the EV charging demand. To evaluate and compare the proposed SHS-EVCSs two multi-objective optimization algorithms namely the Non-dominated Sorting Genetic Algorithm (NSGA-II) and the Multi-objective Evolutionary Algorithm Based on Decomposition (MOEA/D) are employed. The findings indicate that NSGA-II outperforms MOEA/D in terms of achieving higher-quality solutions. During the optimization process various factors are considered including the sizing of solar panels and hydrogen storage tanks the capacity of electric vehicle chargers and the volume of energy exchanged between the two stations. The application of the optimized SHS-EVCSs results in substantial cost savings thereby emphasizing the practical benefits of the proposed approach.
Analyzing the Future Potential of Defossilizing Industrial Specialty Glass Production with Hydrogen by LCA
Mar 2022
Publication
The glass industry is part of the energy-intensive industry with most of the energy needed to melt the raw materials. To produce glass temperatures between 1000 and 1600 °C are necessary. Presently mostly fossil natural gas is the dominant energy source. As direct electrification is not always possible in this paper a Life Cycle Assessment (LCA) for specialty glass production is conducted where the conventional fossil-based reference process is compared to a hydrogen-fired furnace. This hydrogen can be produced on-site in an water electrolyzer using not only the hydrogen for the combustion but also the produced oxygen. Hydrogen can be produced alternatively off-site in a large scale electrolyzer to facilitate economy of scale. For the transport and distribution of this hydrogen different options are available. A rather new option are liquid organic hydrogen carriers (LOHC) which bind the hydrogen in a chemical substance. However temperatures around 300 °C are necessary to separate the hydrogen from the LOHC after transport. At the glass trough waste heat is available at the required temperature level to facilitate the dehydrogenation. The comparison is completed by the production of off-site hydrogen transported to the glass trough as conventional liquefied hydrogen in cooling tanks by truck or in hydrogen pipelines. In this assessment to power the electrolyzers the national grid mix of Germany is used. A time frame from 2020 till 2050 and its changing energy system towards defossilisation is analyzed. Regarding climate change on-site hydrogen production causes the least impact for specialty glass production in 2050. However negative trade-offs for other environmental impact categories e.g. Metal depletion are recorded.
Hydrogen Dispersion Following Blowdown Releases into a Tunnel
Sep 2023
Publication
This paper presents work undertaken by the HSE as part of the Hytunnel-CS project a consortium investigating safety considerations for fuel cell hydrogen (FCH) vehicles in tunnels and similar confined spaces. The test programme investigating hydrogen dispersion in tunnels involved simulating releases analogous to Thermally activated Pressure Relief Devices (TPRDs) typically found on hydrogen vehicles into the HSE Tunnel facility. The releases were scaled and based upon four scenarios: cars buses and two different train designs. The basis for this scaling was the size of the tunnel and the expected initial mass flow rates of the releases scenarios. The results of the 12 tests completed have been analysed in two ways: the initial mass flow rates of the tests were calculated based upon facility measurements and the Able-Noble equations of state for comparison to the intended initial flow rate; and observations of the hydrogen dispersion in the tunnel were made based on 15 hydrogen sensors arrayed along the tunnel. The calculated mass flow rates showed reasonable agreement with the intended initial conditions showing that the scaling methodology can be used to interpret the data based on the full-scale tunnel of interest. Observations of the hydrogen dispersion show an initial turbulent mixing followed by a movement of the mixed hydrogen/air cloud down the tunnel. No vertical stratification of the cloud was observed but this effect could be possible in longer tunnels or tunnels with larger diameters. Higher ventilation rates in the tunnel resulted in a reduction of the residence time of the hydrogen and a slight increase in the dilution.
Critical Mineral Demands May Limit Scaling of Green Hydrogen Production
Jan 2024
Publication
Hydrogen (H2) is widely viewed as critical to the decarbonization of industry and transportation. Water electrolysis powered by renewable electricity commonly referred to as green H2 can be used to generate H2 with low carbon dioxide emissions. Herein we analyze the critical mineral and energy demands associated with green H2 production under three different hypothetical future demand scenarios ranging from 100–1000 Mtpa H2. For each scenario we calculate the critical mineral demands required to build water electrolyzers (i.e. electrodes and electrolyte) and to build dedicated or additional renewable electricity sources (i.e. wind and solar) to power the electrolyzers. Our analysis shows that scaling electrolyzer and renewable energy technologies that use platinum group metals and rare earth elements will likely face supply constraints. Specifically larger quantities of lanthanum yttrium or iridium will be needed to increase electrolyzer capacity and even more neodymium silicon zinc molybdenum aluminum and copper will be needed to build dedicated renewable electricity sources. We find that scaling green H2 production to meet projected netzero targets will require ~24000 TWh of dedicated renewable energy generation which is roughly the total amount of solar and wind projected to be on the grid in 2050 according to some energy transition models. In summary critical mineral constraints may hinder the scaling of green H2 to meet global net-zero emissions targets motivating the need for the research and development of alternative lowemission methods of generating H2
CFD Dispersion Simulations of Compressed Hydrogen Releases through TPRD Inside Scaled Tunnel
Sep 2023
Publication
To achieve the net zero carbon emissions goals by 2050 the transition to cleaner forms and carriers of energy should be accelerated without though jeopardizing the public safety. Although hydrogen has been deemed to play significant role in the energy transition for years now there are still concerns for its risks that hamper its widespread implementation in several applications like for instance automobile applications. Hydrogen-powered vehicles raise concerns about their safety especially inside confined spaces like tunnels and thus research on that topic has been intensified during the last years. In this context experiments have been conducted by UK HSE within the EU-funded project HyTunnel-CS to examine hydrogen dispersion and deflagration inside a scaled tunnel resulting from fuel cell car bus and train release.<br/>In this work that was also carried out within the HyTunnel-CS we present the Computational Fluid Dynamics (CFD) simulations of the HSE unignited experiments. Blowdown tests related to high-pressure hydrogen releases through Thermal Pressure Relief Device (TPRD) installed in car and in train were modeled using the ADREA-HF code. The scope of these simulations was two-fold: a) contribute to the design of the experiments (e.g. indicate sensor positioning ignition point etc.) and the interpretation of hydrogen behavior and b) validate the CFD code. For the former pre-test simulations preceded the experiments to provide design recommendations. When the experiments were conducted the measurements were used for the code validation. Overall the CFD results are in satisfactory agreement with the experiments. Finally simulations with different ventilation rates and with model vehicles inside the tunnel were conducted to examine their effect on mixture dispersion and tunnel safety.
Economic Modelling of Mixing Hydrogen with Natural Gas
Jan 2024
Publication
As global efforts intensify to transition toward cleaner and more sustainable energy sources the blending of hydrogen with natural gas emerges as a promising strategy to reduce carbon emissions and enhance energy security. This study employs a systematic approach to assess the economic viability of hydrogen blending considering factors such as gas costs and heat values. Various hydrogen blending scenarios are analyzed to determine the optimal blend ratios taking into account both technical feasibility and economic considerations. The study discusses potential economic benefits challenges and regulatory implications associated with the widespread adoption of hydrogen–natural gas mixtures. Furthermore the study explores the impact of this integration on existing natural gas infrastructure exploring the potential for enhanced energy storage and delivery. The findings of this research contribute valuable insights to policymakers industry stakeholders and researchers engaged in the ongoing energy transition by providing a nuanced understanding of the economic dimensions of hydrogen blending within the natural gas sector.
Green Fleet: A Prototype Biogas and Hydrogen Refueling Management System for Private Fleet Stations
Aug 2023
Publication
Biogas and hydrogen (H2 ) are breaking through as alternative energy sources in road transport specifically for heavy-duty vehicles. Until a public network of service stations is deployed for such vehicles the owners of large fleets will need to build and manage their own refueling facilities. Fleet refueling management and remote monitoring at these sites will become key business needs. This article describes the construction of a prototype system capable of solving those needs. During the design and development process of the prototype the standard industry protocols involved in these installations have been considered and the latest expertise in information technology systems has been applied. This prototype has been essential to determine the Strengths Challenges Opportunities and Risks (SCOR) of such a system which is the first step of a more ambitious project. A second stage will involve setting up a pilot study and developing a commercial system that can be widely installed to provide a real solution for the industry.
A Study on the Viability of Fuel Cells as an Alternative to Diesel Fuel Generators on Ships
Jul 2023
Publication
This study investigates methods for reducing air pollution in the shipping sector particularly in port areas. The study examines the use of fuel cells as an alternative to diesel generators. Environmental pollution at ports remains a critical issue so using fuel cells as an alternative to conventional energy systems warrants further research. This study compares commercial fuel cell types that can be used on a case study very large crude carrier (VLCC) vessel specifically although the technology is applicable to other vessels and requirements. Seven different fuel cell types were ranked based on five criteria to accomplish this. The proton-exchange membrane cell type was found to be the most suitable fuel cell type for the case study vessel. Based on the input fuel ammonia-based hydrogen storage has been identified as the most promising option along with using an ammonia reforming unit to produce pure hydrogen. Furthermore this study provides an integrated fuel cell module and highlights the economic environmental and maintenance aspects of implementing the proton-exchange membrane fuel cell module for this case study. It also calculates the required space as a crucial constraint of implementing fuel cell technology at sea.
Characterization of the Hydrogen Combustion Process in a Scramjet Engine
May 2024
Publication
In this paper by using a large eddy simulation we study the combustion process in the HyShot II scramjet combustor. By conducting a detailed analysis of the mass-fraction distributions of the main species such as H2 H2O and the radicals OH and HO2 of the mass source terms of these main species and of the chemical source term of the energy equation we detect the regions where chemical reactions occur through a diffusion process and the regions where auto-ignition and premixed combustion may develop. The analysis indicates that the combustion process is mainly of diffusive type along a thin shear layer enveloping the hydrogen plume whereas there could be some auto-ignition and/or premixed combustion cores inside the plume.
A Review on the Factors of Liner Collapse in Type IV Hydrogen Storage Vessels
Sep 2023
Publication
The on-board hydrogen storage of mobile applications is a key area of global industrial transformation to hydrogen technology. The research work provides an overview about the principle of hydrogen fuel cell vehicles with a focus on the widespread on-board hydrogen storage technologies. In this work type IV composite pressure vessels in particular are reviewed. The key challenges of polymeric liners are deeply investigated and liner collapse was identified as a critical failure of type IV vessels. Different factors of liner collapse were categorized and relevant material properties - such as permeability physical characteristics and surface properties - were explained in more detail to lay the foundation for further research on high barrier durable polymeric liner materials.
Energy and Environmental Costs in Transitioning to Zero and Low Emission Trucks for the Australian Truck Fleet: An Industry Perspective
May 2024
Publication
Modernising Australia’s old truck fleet and adopting a more stringent standard to reduce emissions and air pollutants is a primary objective for the Australian truck sector. Various strategies worldwide have been introduced to cut emissions and pollutants in the truck sector such as a low-emission strategy supported by strict diesel standards and a zero-emission strategy to shift to battery-electric or hydrogen trucks. The paper focuses on emissions and local air pollutants of trucks under various transition scenarios at both the tailpipe and the wider supply chain including domestic power generation and hydrogen production. In contrast for diesel we focus on tailpipe outputs following fuel standards in Australia given diesel is imported other than in some limited refineries. We compare and recommend actions that government and truck operators may take in the near to longer term in transitioning to cleaner energy. We tested a number of scenarios using a decision support system incorporating all the latest information on costs and emissions for all truck classes using diesel electric or hydrogen. A key finding from our scenario tests is that the current electricity mix has high carbon emissions and air pollutants due to fossil fuel-fired sources for power generation. Without improvement in using renewable energy sources in the future transitioning to electric trucks implies more carbon emissions and air pollutants in the atmosphere from power plants even though electric trucks generate zero tailpipe emissions. The main motivation for switching to zero-emission trucks is energy cost savings. We urge the government to decide on a clear roadmap for the truck sector before the sector is in a position to take action to shift to low or zero-emission trucks without totally relying on the likely reduction of emission intensity in electricity and renewable energy production.
Comparing Alternative Pathways for the Future Role of the Gas Grid in a Low-carbon Heating System
Aug 2023
Publication
This paper uses a whole-system approach to examine different strategies related to the future role of the gas grid in a low-carbon heat system. A novel model of integrated gas electricity and heat systems HEGIT is used to investigate four key sets of scenarios for the future of the gas grid using the UK as a case study: (a) complete electrification of heating; (b) conversion of the existing gas grid to deliver hydrogen; (c) a hybrid heat pump system; and (d) a greener gas grid. Our results indicate that although the infrastructure requirements the fuel or resource mix and the breakdown of costs vary significantly over the complete electrification to complete conversion of the gas grid to hydrogen spectrum the total system transition cost is relatively similar. This reduces the significance of total system cost as a guiding factor in policy decisions on the future of the gas grid. Furthermore we show that determining the roles of low-carbon gases and electrification for decarbonising heating is better guided by the trade-offs between short- and long-term energy security risks in the system as well as trade-offs between consumer investment in fuel switching and infrastructure requirements for decarbonising heating. Our analysis of these trade-offs indicates that although electrification of heating using heat pumps is not the cheapest option to decarbonise heat it has clear co-benefits as it reduces fuel security risks and dependency on carbon capture and storage infrastructure. Combining different strategies such as grid integration of heat pumps with increased thermal storage capacity and installing hybrid heat pumps with gas boilers on the consumer side are demonstrated to effectively moderate the infrastructure requirements consumer costs and reliability risks of widespread electrification. Further reducing demand on the electricity grid can be accomplished by complementary options at the system level such as partial carbon offsetting using negative emission technologies and partially converting the gas grid to hydrogen.
Impact of Experimentally Measured Relative Permeability Hysteresis on Reservoir-scale Performance of Undergound Hydrogen Storage (UHS)
Jan 2024
Publication
Underground Hydrogen Storage (UHS) is an emerging large-scale energy storage technology. Researchers are investigating its feasibility and performance including its injectivity productivity and storage capacity through numerical simulations. However several ad-hoc relative permeability and capillary pressure functions have been used in the literature with no direct link to the underlying physics of the hydrogen storage and production process. Recent relative permeability measurements for the hydrogen-brine system show very low hydrogen relative permeability and strong liquid phase hysteresis very different to what has been observed for other fluid systems for the same rock type. This raises the concern as to what extend the existing studies in the literature are able to reliably quantify the feasibility of the potential storage projects. In this study we investigate how experimentally measured hydrogen-brine relative permeability hysteresis affects the performance of UHS projects through numerical reservoir simulations. Relative permeability data measured during a hydrogen-water core-flooding experiment within ADMIRE project is used to design a relative permeability hysteresis model. Next numerical simulation for a UHS project in a generic braided-fluvial water-gas reservoir is performed using this hysteresis model. A performance assessment is carried out for several UHS scenarios with different drainage relative permeability curves hysteresis model coefficients and injection/production rates. Our results show that both gas and liquid relative permeability hysteresis play an important role in UHS irrespective of injection/production rate. Ignoring gas hysteresis may cause up to 338% of uncertainty on cumulative hydrogen production as it has negative effects on injectivity and productivity due to the resulting limited variation range of gas saturation and pressure during cyclic operations. In contrast hysteresis in the liquid phase relative permeability resolves this issue to some extent by improving the displacement of the liquid phase. Finally implementing relative permeability curves from other fluid systems during UHS performance assessment will cause uncertainty in terms of gas saturation and up to 141% underestimation on cumulative hydrogen production. These observations illustrate the importance of using relative permeability curves characteristic of hydrogen-brine system for assessing the UHS performances.
Comparative Exergy and Environmental Assessment of the Residual Biomass Gasification Routes for Hydrogen and Ammonia Production
Jul 2023
Publication
The need to reduce the dependency of chemicals on fossil fuels has recently motivated the adoption of renewable energies in those sectors. In addition due to a growing population the treatment and disposition of residual biomass from agricultural processes such as sugar cane and orange bagasse or even from human waste such as sewage sludge will be a challenge for the next generation. These residual biomasses can be an attractive alternative for the production of environmentally friendly fuels and make the economy more circular and efficient. However these raw materials have been hitherto widely used as fuel for boilers or disposed of in sanitary landfills losing their capacity to generate other by-products in addition to contributing to the emissions of gases that promote global warming. For this reason this work analyzes and optimizes the biomass-based routes of biochemical production (namely hydrogen and ammonia) using the gasification of residual biomasses. Moreover the capture of biogenic CO2 aims to reduce the environmental burden leading to negative emissions in the overall energy system. In this context the chemical plants were designed modeled and simulated using Aspen plus™ software. The energy integration and optimization were performed using the OSMOSE Lua Platform. The exergy destruction exergy efficiency and general balance of the CO2 emissions were evaluated. As a result the irreversibility generated by the gasification unit has a relevant influence on the exergy efficiency of the entire plant. On the other hand an overall negative emission balance of −5.95 kgCO2/kgH2 in the hydrogen production route and −1.615 kgCO2/kgNH3 in the ammonia production route can be achieved thus removing from the atmosphere 0.901 tCO2/tbiomass and 1.096 tCO2/tbiomass respectively.
Applying a 2 kW Polymer Membrane Fuel-Cell Stack to Building Hybrid Power Sources for Unmanned Ground Vehicles
Nov 2023
Publication
The novel constructions of hybrid energy sources using polymer electrolyte fuel cells (PEMFCs) and supercapacitors are developed. Studies on the energy demand and peak electrical power of unmanned ground vehicles (UGVs) weighing up to 100 kg were conducted under various conditions. It was found that the average electrical power required does not exceed ~2 kW under all conditions studied. However under the dynamic electrical load of the electric drive of mobile robots the short peak power exceeded 2 kW and the highest current load was in the range of 80–90 A. The electrical performance of a family of PEMFC stacks built in open-cathode mode was determined. A hydrogen-usage control strategy for power generation cleaning processes and humidification was analysed. The integration of a PEMFC stack with a bank of supercapacitors makes it possible to mitigate the voltage dips. These occur periodically at short time intervals as a result of short-circuit operation. In the second construction the recovery of electrical energy dissipated by a short-circuit unit (SCU) was also demonstrated in the integrated PEMFC stack and supercapacitor bank system. The concept of an energy-efficient mobile and environmentally friendly hydrogen charging unit has been proposed. It comprises (i) a hydrogen anion exchange membrane electrolyser (ii) a photovoltaic installation (iii) a battery storage (iv) a hydrogen buffer storage in a buffer tank (v) a hydrogen compression unit and (vi) composite tanks.
Assessment of a Fully Renewable System for the Total Decarbonization of the Economy with Full Demand Coverage on Islands Connected to a Central Grid: The Balearic Case in 2040
Jul 2023
Publication
The transition to clean electricity generation is a crucial focus for achieving the current objectives of economy decarbonization. The Balearic Archipelago faces significant environmental economic and social challenges in shifting from a predominantly fossil fuel-based economy to one based on renewable sources. This study proposes implementing a renewable energy mix and decarbonizing the economy of the Balearic Islands by 2040. The proposed system involves an entirely renewable generation system with interconnections between the four Balearic islands and the Spanish mainland grid via a 650 MW submarine cable. This flexible electrical exchange can cover approximately 35% of the peak demand of 1900 MW. The scenario comprises a 6 GWp solar photovoltaic system a wind system of under 1.2 GWp and a 600 MW biomass system as generation sub-systems. A vanadium redox flow battery sub-system with a storage capacity of approximately 21 GWh and 2.5 GWp power is available to ensure system manageability. This system’s levelized electricity cost (LCOE) is around 13.75 cEUR/kWh. The design also incorporates hydrogen as an alternative for difficult-to-electrify uses achieving effective decarbonization of all final energy uses. A production of slightly over 5 × 104 tH2 per year is required with 1.7 GW of electrolyzer power using excess electricity and water resources. The system enables a significant level of economy decarbonization although it requires substantial investments in both generation sources and storage.
Conditions for Profitable Operation of P2X Energy Hubs to Meet Local Demand Under Energy Market Access
Feb 2023
Publication
This paper analyzes the operation of an energy hub on a community level with an integrated P2X facility and with access to energy markets. In our case P2X allows converting power to hydrogen heat methane or back to power. We consider the energy hub as a large prosumer who can be both a producer and consumer in the markets with the novelty that P2X technology is available. We investigate how such a P2X energy hub trades optimally in the electricity market and satisfies local energy demand under the assumption of a long-term strong climate scenario in year 2050. For numerical analysis a case study of a mountain village in Switzerland is used. One of the main contributions of this paper is to quantify key conditions for profitable operations of such a P2X energy hub. In particular the analysis includes impacts of influencing factors on profits and operational patterns in terms of different degrees of self-sufficiency and different availability of local renewable resources. Moreover the access to real-time wholesale market electricity price signals and a future retail hydrogen market is assessed. The key factors for the successful operation of a P2X energy hub are identified to be sufficient local renewable resources and access to a retail market of hydrogen. The results also show that the P2X operation leads to an increased deployment of local renewables especially in the case of low initial deployment; on the other hand seasonal storage plays a subordinated role. Additionally P2X lowers for the community the wholesale electricity market trading volumes.
Hydrogen-powered Refrigeration System for Environmentally Friendly Transport and Delivery in the Food Supply Chain
Mar 2023
Publication
Urban population and the trend towards online commerce leads to an increase in delivery solution in cities. The growth of the transport sector is very harmful to the environment being responsible for approximately 40% of greenhouse gas emissions in the European Union. The problem is aggravated when transporting perishable foodstuffs as the vehicle propulsion engine (VPE) must power not only the vehicle but also the refrigeration unit. This means that the VPE must be running continuously both on the road and stationary (during delivery) as the cold chain must be preserved. The result is costly (high fuel consumption) and harmful to the environment. At present refrigerated transport does not support full-electric solutions due to the high energy consumption required which motivates the work presented in this article. It presents a turnkey solution of a hydrogen-powered refrigeration system (HPRS) to be integrated into standard light trucks and vans for short-distance food transport and delivery. The proposed solution combines an air-cooled polymer electrolyte membrane fuel cell (PEMFC) a lithium-ion battery and low-weight pressurised hydrogen cylinders to minimise cost and increase autonomy and energy density. In addition for its implementation and integration all the acquisition power and control electronics necessary for its correct management have been developed. Similarly an energy management system (EMS) has been developed to ensure continuity and safety in the operation of the electrical system during the working day while maximizing both the available output power and lifetime of the PEMFC. Experimental results on a real refrigerated light truck provide more than 4 h of autonomy in intensive intercity driving profiles which can be increased if necessary by simply increasing the pressure of the stored hydrogen from the current 200 bar to whatever is required. The correct operation of the entire HPRS has been experimentally validated in terms of functionality autonomy and safety; with fuel savings of more than 10% and more than 3650 kg of CO2/ year avoided.
Optimal Siting and Sizing of Hydrogen Production Modules in Distribution Networks with Photovoltaic Uncertainties
Nov 2023
Publication
Hydrogen production modules (HPMs) play a crucial role in harnessing abundant photovoltaic power by producing and supplying hydrogen to factories resulting in significant operational cost reductions and efficient utilization of the photovoltaic panel output. However the output of photovoltaic power is stochastic which will affect the revenue of investing in an HPM. This paper presents a comprehensive analysis of HPMs starting with the modeling of their operational process and investigating their influence on distribution system operations. Building upon these discussions a deterministic optimization model is established to address the corresponding challenges. Furthermore a two-stage stochastic planning model is proposed to determine optimal locations and sizes of HPMs in distribution systems accounting for uncertainties. The objective of the twostage stochastic planning model is to minimize the distribution system’s operational costs plus the investment costs of the HPM subject to power flow constraints. To tackle the stochastic nature of photovoltaic power a data-driven algorithm is introduced to cluster historical data into representative scenarios effectively reducing the planning model’s scale. To ensure an efficient solution a Benders’ decomposition-based algorithm is proposed which is an iterative method with a fast convergence speed. The proposed model and algorithms are validated using a widely utilized IEEE 33-bus system through numerical experiments demonstrating the optimality of the HPM plan generated by the algorithm. The proposed model and algorithms offer an effective approach for decision-makers in managing uncertainties and optimizing HPM deployment paving the way for sustainable and efficient energy solutions in distribution systems. Sensitivity analysis verifies the optimality of the HPM’s siting and sizing obtained by the proposed algorithm which also reveals immense economic and environmental benefits.
Levelised Cost of Transmission Comparison for Green Hydrogen and Ammonia in New-build Offshore Energy Infrastructure: Pipelines, Tankers, and HVDC
Mar 2024
Publication
As the global market develops for green hydrogen and ammonia derived from renewable electricity the bulk transmission of hydrogen and ammonia from production areas to demand-intensive consumption areas will increase. Repurposing existing infrastructure may be economically and technically feasible but increases in supply and demand will necessitate new developments. Bulk transmission of hydrogen and ammonia may be effected by dedicated pipelines or liquefied fuel tankers. Transmission of electricity using HVDC lines to directly power electrolysers producing hydrogen near the demand markets is another option. This paper presents and validates detailed cost models for newly-built dedicated offshore transmission methods for green hydrogen and ammonia and carries out a techno-economic comparison over a range of transmission distances and production volumes. New pipelines are economical for short distances while new HVDC interconnectors are suited to medium-large transmission capacities over a wide range of distances and liquefied gas tankers are best for long distances.
Work Efficiency and Economic Efficiency of Actual Driving Test of Proton Exchange Membrane Fuel Cell Forklift
Aug 2023
Publication
A 3.5 tonne forklift containing proton exchange membrane fuel cells (PEMFCs) and lithium-ion batteries was manufactured and tested in a real factory. The work efficiency and economic applicability of the PEMFC forklift were compared with that of a lithium-ion battery-powered forklift. The results showed that the back-pressure of air was closely related to the power density of the stack whose stability could be improved by a reasonable control strategy and membrane electrode assemblies (MEAs) with high consistency. The PEMFC powered forklift displayed 40.6% higher work efficiency than the lithium-ion battery-powered forklift. Its lower use-cost compared to internal engine-powered forklifts is beneficial to the commercialization of this product.
Populating the Hydrogen Component Reliability Database (HYCRED) with Incident Data from Hydrogen Dispensing
Sep 2023
Publication
Safety risk and reliability issues are vital to ensure the continuous and profitable operation of hydrogen technologies. Quantitative risk assessment (QRA) has been used to enable the safe deployment of engineering systems especially hydrogen fueling stations. However QRA studies require reliability data which are essential to collect to make the studies as realistic and relevant as possible. These data are currently lacking and data from other industries such as oil and gas are used in hydrogen system QRAs. This may lead to inaccurate results since hydrogen fueling stations have differences in physical properties system design and operational parameters when compared to other fueling stations thus necessitating new data sources are necessary to capture the effects of these differences. To address this gap we developed a structure for a hydrogen component reliability database (HyCReD) [1] which could be used to generate reliability data to be used in QRA studies. In this paper we demonstrate populating the HyCReD database with information extracted from new narrative reports on hydrogen fueling station incidents specifically focused on the dispensing processes. We analyze five new events and demonstrate the feasibility of populating the database and types of meaningful insights that can be obtained at this stage.
Optimal Design for a Hybrid Microgrid-hydrogen Storage Facility in Saudi Arabia
May 2022
Publication
Background: Sustainable development requires access to afordable reliable and efcient energy to lift billions of people out of poverty and improve their standard of living. The development of new and renewable forms of energy that emit less CO2 may not materialize quickly enough or at a price point that allows people to attain the standard of living they desire and deserve. As a result a parallel path to sustainability must be developed that uses both renewable and clean carbon-based methods. Hybrid microgrids are promoted to solve various electrical and energy-related issues that incorporate renewable energy sources such as photovoltaics wind diesel generation or a combination of these sources. Utilizing microgrids in electric power generation has several benefts including clean energy increased grid stability and reduced congestion. Despite these advantages microgrids are not frequently deployed because of economic concerns. To address these fnancial concerns it is necessary to explore the ideal confguration of micro-grids based on the quantity quality and availability of sustainable energy sources used to install the microgrid and the optimal design of microgrid components. These considerations are refected in net present value and levelized energy cost. Methods: HOMER was used to simulate numerous system confgurations and select the most feasible solution according to the net present value levelizied cost of energy and hydrogen operating cost and renewable fraction. HOMER performed a repeated algorithm process to determine the most feasible system configuration and parameters with the least economic costs and highest benefits to achieve a practically feasible system configuration. Results: This article aimed to construct a cost-effective microgrid system for Saudi Arabia’s Yanbu city using five configurations using excess energy to generate hydrogen. The obtained results indicate that the optimal configuration for the specified area is a hybrid photovoltaic/wind/battery/generator/fuel cell/hydrogen electrolyzer microgrid with a net present value and levelized energy cost of $10.6 billion and $0.15/kWh. Conclusion: With solar photovoltaic and wind generation costs declining building electrolyzers in locations with excellent renewable resource conditions such as Saudi Arabia could become a low-cost hydrogen supply option even when accounting for the transmission and distribution costs of transporting hydrogen from renewable resource locations to end-users. The optimum confguration can generate up to 32132 tons of hydrogen per year (tH2/year) and 380824 tons per year of CO2 emissions can be avoided.
Technoeconomic Analysis for Green Hydrogen in Terms of Production, Compression, Transportation and Storage Considering the Australian Perspective
Jul 2023
Publication
This current article discusses the technoeconomics (TE) of hydrogen generation transportation compression and storage in the Australian context. The TE analysis is important and a prerequisite for investment decisions. This study selected the Australian context due to its huge potential in green hydrogen but the modelling is applicable to other parts of the world adjusting the price of electricity and other utilities. The hydrogen generation using the most mature alkaline electrolysis (AEL) technique was selected in the current study. The results show that increasing temperature from 50 to 90 ◦C and decreasing pressure from 13 to 5 bar help improve electrolyser performance though pressure has a minor effect. The selected range for performance parameters was based on the fundamental behaviour of water electrolysers supported with literature. The levelised cost of hydrogen (LCH2 ) was calculated for generation compression transportation and storage. However the majority of the LCH2 was for generation which was calculated based on CAPEX OPEX capital recovery factor hydrogen production rate and capacity factor. The LCH2 in 2023 was calculated to be 9.6 USD/kgH2 using a base-case solar electricity price of 65–38 USD/MWh. This LCH2 is expected to decrease to 6.5 and 3.4 USD/kgH2 by 2030 and 2040 respectively. The current LCH2 using wind energy was calculated to be 1.9 USD/kgH2 lower than that of solar-based electricity. The LCH2 using standalone wind electricity was calculated to be USD 5.3 and USD 2.9 in 2030 and 2040 respectively. The LCH2 predicted using a solar and wind mix (SWM) was estimated to be USD 3.2 compared to USD 9.6 and USD 7.7 using standalone solar and wind. The LCH2 under the best case was predicted to be USD 3.9 and USD 2.1 compared to USD 6.5 and USD 3.4 under base-case solar PV in 2030 and 2040 respectively. The best case SWM offers 33% lower LCH2 in 2023 which leads to 37% 39% and 42% lower LCH2 in 2030 2040 and 2050 respectively. The current results are overpredicted especially compared with CSIRO Australia due to the higher assumption of the renewable electricity price. Currently over two-thirds of the cost for the LCH2 is due to the price of electricity (i.e. wind and solar). Modelling suggests an overall reduction in the capital cost of AEL plants by about 50% in the 2030s. Due to the lower capacity factor (effective energy generation over maximum output) of renewable energy especially for solar plants a combined wind- and solar-based electrolysis plant was recommended which can increase the capacity factor by at least 33%. Results also suggest that besides generation at least an additional 1.5 USD/kgH2 for compression transportation and storage is required.
Heat Integration of Liquid Hydrogen-Fueled Hybrid Electric Ship Propulsion System
Nov 2023
Publication
This study introduced the methodology for integrating ethylene glycol/water mixture (GW) systems which supply heat energy to the liquid hydrogen (LH2 ) fuel gas supply system (FGSS) and manage the temperature conditions of the battery system. All systems were designed and simulated based on the power demand of a 2 MW class platform supply vessel assumed as the target ship. The LH2 FGSS model is based on Aspen HYSYS V14 and the cell model that makes up the battery system is implemented based on a Thevenin model with four parameters. Through three different simulation cases the integrated GW system significantly reduced electric power consumption for the GW heater during ship operations achieving reductions of 1.38% (Case 1) 16.29% (Case 2) and 27.52% (Case 3). The energy-saving ratio showed decreases of 1.86% (Case 1) 21.01% (Case 2) and 33.80% (Case 3) in overall energy usage within the GW system. Furthermore an examination of the battery system’s thermal management in the integrated GW system demonstrated stable cell temperature control within ±3 K of the target temperature making this integration a viable solution for maintaining normal operating temperatures despite relatively higher fluctuations compared to an independent GW system.
Market-based Asset Valuation of Hydrogen Geological Storage
Jul 2023
Publication
Because of hydrogen's low energy density hydrogen storage is a critical component of the hydrogen economy particularly when large-scale and flexible hydrogen utilization is required. There is a sense of urgency to develop hydrogen geological storage projects to support large-scale yet flexible hydrogen utilization. This study aims to answer questions not yet resolved in the research literature discussing the valuation of hydrogen geological storage options for commercial development. This study establishes a net present value (NPV) evaluation framework for geological hydrogen storage that integrates the updated techno-economic analysis and market-based operations. The capital asset pricing model (CAPM) and the related finance theories are applied to determine the risk-adjusted discount rate in building the NPV evaluation framework. The NPV framework has been applied to two geological hydrogen storage projects a single-turn storage serving downstream transportation seasonal demand versus a multiturn storage as part of an integrated renewables-based hydrogen energy system providing peak electric load. From the NPV framework both projects have positive NPVs $46 560 632 and $12 457 546 respectively and International Rate of Return (IRR) values which are higher than the costs of capital. The NPV framework is also applied to the sensitivity analysis and shows that the hydrogen price spread between withdrawal and injection prices site development and well costs are the top three factors that impact both NPV and IRR the most for both projects. The established NPV framework can be used for project risk management by discovering the key cost drivers for the storage assets.
Development and Testing of a 100 kW Fuel-flexible Micro Gas Turbine Running on 100% Hydrogen
Jun 2023
Publication
Hydrogen as a carbon-free energy carrier has emerged as a crucial component in the decarbonization of the energy system serving as both an energy storage option and fuel for dispatchable power generation to mitigate the intermittent nature of renewable energy sources. However the unique physical and combustion characteristics of hydrogen which differ from conventional gaseous fuels such as biogas and natural gas present new challenges that must be addressed. To fully integrate hydrogen as an energy carrier in the energy system the development of low-emission and highly reliable technologies capable of handling hydrogen combustion is imperative. This study presents a ground-breaking achievement - the first successful test of a micro gas turbine running on 100% hydrogen with NOx emissions below the standard limits. Furthermore the combustor of the micro gas turbine demonstrates exceptional fuel flexibility allowing for the use of various blends of hydrogen biogas and natural gas covering a wide range of heating values. In addition to a comprehensive presentation of the test rig and its instrumentation this paper illuminates the challenges of hydrogen combustion and offers real-world operational data from engine operation with 100% hydrogen and its blends with methane.
Optimization of Emergency Alternatives for Hydrogen Leakage and Explosion Accidents Based on Improved VIKOR
Nov 2023
Publication
Hydrogen leakage and explosion accidents have obvious dangers ambiguity of accident information and urgency of decision-making time. These characteristics bring challenges to the optimization of emergency alternatives for such accidents. Effective emergency decision making is crucial to mitigating the consequences of accidents and minimizing losses and can provide a vital reference for emergency management in the field of hydrogen energy. An improved VIKOR emergency alternatives optimization method is proposed based on the combination of hesitant triangular fuzzy set (HTFS) and the cumulative prospect theory (CPT) termed the HTFS-CPT-VIKOR method. This method adopts the hesitant triangular fuzzy number to represent the decision information on the alternatives under the influence of multi-attributes constructs alternatives evaluation indicators and solves the indicator weights by using the deviation method. Based on CPT positive and negative ideal points were used as reference points to construct the prospect matrix which then utilized the VIKOR method to optimize the emergency alternatives for hydrogen leakage and explosion accidents. Taking an accident at a hydrogen refueling station as an example the effectiveness and rationality of the HTFS-CPT-VIKOR method were verified by comparing with the existing three methods and conducting parameter sensitivity analysis. Research results show that the HTFS-CPT-VIKOR method effectively captures the limited psychological behavior characteristics of decision makers and enhances their ability to identify filter and judge ambiguous information making the decisionmaking alternatives more in line with the actual environment which provided strong support for the optimization of emergency alternatives for hydrogen leakage and explosion accidents.
Evaluating Hydrogen-based Electricity Generation using the Concept of Total Efficiency
Aug 2023
Publication
The popularity of hydrogen has been increasing globally as a promising sustainable energy source. However hydrogen needs to be produced and processed before it can be used in the energy sector. This paper uses total efficiency to evaluate the lifecycle of hydrogen-driven power generation. Total efficiency introduces the energy requirement of fuel preparation in conventional efficiency and is a reliable method to fairly compare different energy sources. Two case studies in Spain and Germany with nine scenarios each are defined to study different hydrogen-preparation routes. The scenarios include the main colors of hydrogen production (grey turquoise yellow and green) and different combinations of processing and transportation choices. In most cases the highest energy penalty in the overall preparation process of the fuel is linked to the production step. A large difference is found between fossil fuel-based hydrogen and green hydrogen derived from excess renewable energy with fossil fuel-based hydrogen resulting in significantly lower total efficiencies compared to green hydrogen. The use of natural gas as the primary source to generate hydrogen is found to be a critical factor affecting total efficiency particularly in cases where the gas must be transported from far away. This shows the value of using excess renewable energy in the production of hydrogen instead of grid power. Even in the most efficient scenario of green hydrogen studied total efficiency was found to be 7 % lower than the respective conventional efficiency that does not account for hydrogen generation. These results emphasize the importance of considering the impact of fuel preparation stages in comparative thermodynamic analyses and evaluations.
Experimental Evaluation of Dynamic Operating Concepts for Alkaline Water Electrolyzers Powered by Renewable Energy
Dec 2021
Publication
Synthetic current density profiles with wind and photovoltaic power characteristics were calculated by autoregressive-moving-average (ARMA) models for the experimental evaluation of dynamic operating concepts for alkaline water electrolyzers powered by renewable energy. The selected operating concepts included switching between mixed and split electrolyte cycles and adapting the liquid electrolyte volume flow rate depending on the current density. All experiments were carried out at a pressure of 7 bar a temperature of 60 °C and with an aqueous potassium hydroxide solution with 32 wt.% KOH as the electrolyte. The dynamic operating concepts were compared to stationary experiments with mixed electrolyte cycles and the experimental evaluation showed that the selected operating concepts were able to reduce the gas impurity compared to the reference operating conditions without a noticeable increase of the cell potential. Therefore the overall system efficiency and process safety could be enhanced by this approach.
Additive Manufacturing for Proton Exchange Membrane (PEM) Hydrogen Technologies: Merits, Challenges, and Prospects
Jul 2023
Publication
With the growing demand for green technologies hydrogen energy devices such as Proton Exchange Membrane (PEM) fuel cells and water electrolysers have received accelerated developments. However the materials and manufacturing cost of these technologies are still relatively expensive which impedes their widespread commercialization. Additive Manufacturing (AM) commonly termed 3D Printing (3DP) with its advanced capabilities could be a potential pathway to solve the fabrication challenges of PEM parts. Herein in this paper the research studies on the novel AM fabrication methods of PEM components are thoroughly reviewed and analysed. The key performance properties such as corrosion and hydrogen embrittlement resistance of the additively manufactured materials in the PEM working environment are discussed to emphasise their reliability for the PEM systems. Additionally the major challenges and required future developments of AM technologies to unlock their full potential for PEM fabrication are identified. This paper provides insights from the latest research developments on the significance of advanced manufacturing technologies in developing sustainable energy systems to address the global energy challenges and climate change effects.
A Cost Comparison of Various Hourly-reliable and Net-zero Hydrogen Production Pathways in the United States
Nov 2023
Publication
Hydrogen (H2) as an energy carrier may play a role in various hard-to-abate subsectors but to maximize emission reductions supplied hydrogen must be reliable low-emission and low-cost. Here we build a model that enables direct comparison of the cost of producing net-zero hourly-reliable hydrogen from various pathways. To reach net-zero targets we assume upstream and residual facility emissions are mitigated using negative emission technologies. For the United States (California Texas and New York) model results indicate nextdecade hybrid electricity-based solutions are lower cost ($2.02-$2.88/kg) than fossil-based pathways with natural gas leakage greater than 4% ($2.73-$5.94/ kg). These results also apply to regions outside of the U.S. with a similar climate and electric grid. However when omitting the net-zero emission constraint and considering the U.S. regulatory environment electricity-based production only achieves cost-competitiveness with fossil-based pathways if embodied emissions of electricity inputs are not counted under U.S. Tax Code Section 45V guidance.
Electrocatalysts for the Generation of Hydrogen, Oxygen and Synthesis Gas
Sep 2016
Publication
Water electrolysis is the most promising method for efficient production of high purity hydrogen (and oxygen) while the required power input for the electrolysis process can be provided by renewable sources (e.g. solar or wind). The thus produced hydrogen can be used either directly as a fuel or as a reducing agent in chemical processes such as in Fischer–Tropsch synthesis. Water splitting can be realized both at low temperatures (typically below 100 °C) and at high temperatures (steam water electrolysis at 500– 1000 °C) while different ionic agents can be electrochemically transferred during the electrolysis process (OH− H+ O2− ). Singular requirements apply in each of the electrolysis technologies (alkaline polymer electrolyte membrane and solid oxide electrolysis) for ensuring high electrocatalytic activity and long-term stability. The aim of the present article is to provide a brief overview on the effect of the nature and structure of the catalyst–electrode materials on the electrolyzer’s performance. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The current trends limitations and perspectives for future developments are summarized for the diverse electrolysis technologies of water splitting while the case of CO2/H2O co-electrolysis (for synthesis gas production) is also discussed.
Environmental and Material Criticality Assessment of Hydrogen Production via Anion Exchange Membrane Electrolysis
Oct 2023
Publication
The need to drastically reduce greenhouse gas emissions is driving the development of existing and new technologies to produce and use hydrogen. Anion exchange membrane electrolysis is one of these rapidly developing technologies and presents promising characteristics for efficient hydrogen production. However the environmental performance and the material criticality of anion exchange membrane electrolysis must be assessed. In this work prospective life cycle assessment and criticality assessment are applied first to identify environmental and material criticality hotspots within the production of anion exchange membrane electrolysis units and second to benchmark hydrogen production against proton exchange membrane electrolysis. From an environmental point of view the catalyst spraying process heavily dominates the ozone depletion impact category while the production of the membrane represents a hotspot in terms of the photochemical ozone formation potential. For the other categories the environmental impacts are distributed across different components. The comparison of hydrogen production via anion exchange membrane electrolysis and proton exchange membrane electrolysis shows that both technologies involve a similar life-cycle environmental profile due to similar efficiencies and the leading role of electricity generation for the operation of electrolysis. Despite the fact that for proton exchange membrane electrolysis much less material is required due to a higher lifetime anion exchange membrane electrolysis shows significantly lower raw material criticality since it does not rely on platinum-group metals. Overall a promising environmental and material criticality performance of anion exchange membrane electrolysis for hydrogen production is concluded subject to the expected technical progress for this technology.
Hydrogen Quality in Used Natual Gas Pipelines: An Experimental Investigation of Contaminants According to ISO 14687:2019 Standard
Sep 2023
Publication
The transport of hydrogen in used natural gas pipelines is a strategic key element of a pan-European hydrogen infrastructure. At the same time accurate knowledge of the hydrogen quality is essential in order to be able to address a wide application range. Therefore an experimental investigation was carried out to find out which contaminants enter into the hydrogen from the used natural gas pipelines. Pipeline elements from the high pressure gas grid of Austria were exposed to hydrogen. Steel pipelines built between 1960 and 2018 which were operated with odorised and pure natural gas were examined. The hydrogen was analysed according to requirements of ISO14687: 2019 Grade D measurement standard. The results show that based on age odorization and sediments different contimenants are introduced. Odorants hydrocarbons but also sulphur compounds ammonia and halogenated hydrogen compounds were identified. Sediments are identified as the main source of impurities. However the concentrations of the introduced contaminants were low (6 nmol/mol to 10 μmol/mol). Quality monitoring with a wide range of detection options for different components (sulphur halogenated compounds hydrocarbons ammonia and atmospheric components) is crucial for real operation. The authors deduce that a Grade A hydrogen quality can be safely achieved in real operation.
Renewable Hydrogen: Modular Concepts from Production over Storage to the Consumer
Jan 2021
Publication
A simulation tool called HYDRA to optimize individual hydrogen infrastructure layouts is presented. The different electrolyzer technologies namely proton exchange membrane electrolysis anion exchange membrane electrolysis alkaline electrolysis and solid oxide electrolysis as well as hydrogen storage possibilities are described in more detail and evaluated. To illustrate the application opportunities of HYDRA three project examples are discussed. The examples include central and decentral applications while taking the usage of hydrogen into account.
A Newly Proposed Method for Hydrogen Storage in a Metal Hydride Storage Tank Intended for Maritime and Inland Shipping
Aug 2023
Publication
The utilisation of hydrogen in ships has important potential in terms of achieving the decarbonisation of waterway transport which produces approximately 3% of the world’s total emissions. However the utilisation of hydrogen drives in maritime and inland shipping is conditioned by the efficient and safe storage of hydrogen as an energy carrier on ship decks. Regardless of the type the constructional design and the purpose of the aforesaid vessels the preferred method for hydrogen storage on ships is currently high-pressure storage with an operating pressure of the fuel storage tanks amounting to tens of MPa. Alternative methods for hydrogen storage include storing the hydrogen in its liquid form or in hydrides as adsorbed hydrogen and reformed fuels. In the present article a method for hydrogen storage in metal hydrides is discussed particularly in a certified low-pressure metal hydride storage tank—the MNTZV-159. The article also analyses the 2D heat conduction in a transversal cross-section of the MNTZV-159 storage tank for the purpose of creating a final design of the shape of a heat exchanger (intensifier) that will help to shorten the total time of hydrogen absorption into the alloy i.e. the filling process. Based on the performed 3D calculations for heat conduction the optimisation and implementation of the intensifier into the internal volume of a metal hydride alloy will increase the performance efficiency of the shell heat exchanger of the MNTZV-159 storage tank. The optimised design increased the cooling power by 46.1% which shortened the refuelling time by 41% to 2351 s. During that time the cooling system which comprised the newly designed internal heat transfer intensifier was capable of eliminating the total heat from the surface of the storage tank thus preventing a pressure increase above the allowable value of 30 bar.
Prospects of Hydrogen Application as a Fuel for Large-Scale Compressed-Air Energy Storages
Jan 2024
Publication
A promising method of energy storage is the combination of hydrogen and compressed-air energy storage (CAES) systems. CAES systems are divided into diabatic adiabatic and isothermal cycles. In the diabatic cycle thermal energy after air compression is discharged into the environment and the scheme implies the use of organic fuel. Taking into account the prospects of the decarbonization of the energy industry it is advisable to replace natural gas in the diabatic CAES scheme with hydrogen obtained by electrolysis using power-to-gas technology. In this article the SENECA-1A project is considered as a high-power hybrid unit using hydrogen instead of natural gas. The results show that while keeping the 214 MW turbines powered the transition to hydrogen reduces carbon dioxide emissions from 8.8 to 0.0 kg/s while the formation of water vapor will increase from 17.6 to 27.4 kg/s. It is shown that the adiabatic CAES SENECA-1A mode compared to the diabatic has 0.0 carbon dioxide and water vapor emission with relatively higher efficiency (71.5 vs. 62.1%). At the same time the main advantage of the diabatic CAES is the possibility to produce more power in the turbine block (214 vs. 131.6 MW) having fewer capital costs. Thus choosing the technology is a subject of complex technical economic and ecological study.
Current and Future role of Haber–Bosch Ammonia in a Carbon-free Energy Landscape
Dec 2019
Publication
The future of a carbon-free society relies on the alignment of the intermittent production of renewable energy with our continuous and increasing energy demands. Long-term energy storage in molecules with high energy content and density such as ammonia can act as a buffer versus short-term storage (e.g. batteries). In this paper we demonstrate that the Haber–Bosch ammonia synthesis loop can indeed enable a second ammonia revolution as energy vector by replacing the CO2 intensive methane-fed process with hydrogen produced by water splitting using renewable electricity. These modifications demand a redefinition of the conventional Haber–Bosch process with a new optimisation beyond the current one which was driven by cheap and abundant natural gas and relaxed environmental concerns during the last century. Indeed the switch to electrical energy as fuel and feedstock to replace fossil fuels (e.g. methane) will lead to dramatic energy efficiency improvements through the use of high efficiency electrical motors and complete elimination of direct CO2 emissions. Despite the technical feasibility of the electrically-driven Haber–Bosch ammonia the question still remains whether such revolution will take place. We reveal that its success relies on two factors: increased energy efficiency and the development of small-scale distributed and agile processes that can align to the geographically isolated and intermittent renewable energy sources. The former requires not only higher electrolyser efficiencies for hydrogen production but also a holistic approach to the ammonia synthesis loop with the replacement of the condensation separation step by alternative technologies such as absorption and catalysis development. Such innovations will open the door to moderate pressure systems the development and deployment of novel ammonia synthesis catalysts and even more importantly the opportunity for integration of reaction and separation steps to overcome equilibrium limitations. When realised green ammonia will reshape the current energy landscape by directly replacing fossil fuels in transportation heating electricity etc. and as done in the last century food.
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