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Flame Visibility in Hydrogen Appliances
Sep 2023
Publication
One of the benefits of the direct use of hydrogen is its ability to be burned in a similar way to natural gas using appliances with which the community is already familiar. This is particularly true for applications where electrification is neither practicable nor desirable. One common example is domestic cooking stoves where the open flame offers numerous real and perceived benefits to the chef. Similarly many commercial and industrial appliances rely on the unique properties of combustion to achieve a desired purpose that cannot readily be replaced by an alternative to an open flame. Despite the enormous decarbonisation potential of the direct replacement of natural gas with hydrogen there are some operational constraints due to the different burning characteristics of hydrogen. One of the challenges is the low visible light emission from hydrogen flames. The change in visible radiation from the combustion of hydrogen compared with natural gas is a safety concern whereby visual observation of a flame may be difficult. This paper aims to provide clarity on the visual appearance of hydrogen flames via a series of measurements of flame visibility and emission spectra accompanied by the assessment of strategies to improve the safe use of hydrogen.
Investigation of the Suitability of Viper: Blast CFD Software for Hydrogen and Vapor Cloud Explosions
Sep 2023
Publication
Many simplified methods for estimating blast loads from a hydrogen or vapor cloud explosion are unable to take into account the accurate geometry of confining spaces obstacles or landscape that may significantly interact with the blast wave and influence the strength of blast loads. Computation fluid dynamics (CFD) software Viper::Blast which was originally developed for the simulation of the detonation of high explosives is able to quickly and easily model geometry for blast analyses however its use for vapor cloud explosions and deflagrations is not well established. This paper describes the results of an investigation into the suitability of Viper::Blast for use in modeling hydrogen deflagration and detonation events from various experiments in literature. Detonation events have been captured with a high degree of detail and relatively little uncertainty in inputs while deflagration events are significantly more complex. An approach is proposed that may allow for a reasonable bounding of uncertainty potentially leading to an approach to CFD-based Monte Carlo analyses that are able to address a problem’s true geometry while remaining reasonably pragmatic in terms of run-time and computational investment. This will allow further exploration of practical CFD application to inform hydrogen safety in the engineering design assessment and management of energy mobility and transport systems infrastructure and operations.
Mechanistic Evaluation of the Reservoir Engineering Performance for the Underground Hydrogen Storage in a Deep North Sea Aquifer
Jul 2023
Publication
Underground hydrogen storage (UHS) in aquifers salt caverns and depleted hydrocarbon reservoirs allows for the storage of larger volumes of H2 compared to surface storage in vessels. In this work we investigate the impact of aquifer-related mechanisms and parameters on the performance of UHS in an associated North Sea aquifer using 3D numerical compositional simulations. Simulation results revealed that the aquifer's permeability heterogeneity has a significant impact on the H2 recovery efficiency where a more homogenous rock would lead to improved H2 productivity. The inclusion of relative permeability hysteresis resulted in a drop in the H2 injectivity and recovery due to H2 discontinuity inside the aquifer which leads to residual H2 during the withdrawal periods. In contrast the effects of hydrogen solubility and hydrogen diffusion were negligible when studied each in isolation from other factors. Hence it is essential to properly account for hysteresis and heterogeneity when evaluating UHS in aquifers.
Optimization of a Hydrogen-based Hybrid Propulsion System Under Aircraft Performance Constraints
Aug 2021
Publication
This paper addresses the topic of the conceptual design of a regional aircraft with hybrid electric propulsion based on hydrogen fuel cells. It aims at providing an optimization-based method to design a hybrid propulsive system comprising two power sources (jet fuel and hydrogen) for the generation of the required propulsive power and at studying the impact of fuel cell technologies on the aircraft performances. Indeed by performing optimizations for two hybrid propulsive systems using either low temperature or high temperature Proton-exchange membrane fuel cells this study provides a preliminary assessment of the impact of the fuel cell operating temperature on the system design and the overall aircraft performance. First this paper gives a description of the baseline turboprop regional aircraft with a focus on its high speed and low speed flight performances which will serve as requirements for the design of the hybrid aircraft. Then the hybrid electric architecture and the sizing models of the propulsion system are presented. Finally optimizations are performed to design two parallel hybrid propulsive systems based on different fuel cells technologies and aimed at minimizing the block fuel per passenger over a mission of 200 nm. Results show how the proposed methodology and models lead to design two propulsive systems capable of reducing the fuel consumption per passenger by more than 30% compared to the baseline aircraft. The study also shows that the choice of fuel cell operating temperature has a first-order impact on the total mass of the propulsive system due to the higher cooling requirement of the low temperature fuel cells.
Assessing Techno-economic Feasibility of Cogeneration and Power to Hydrogen Plants: A Novel Dynamic Simulation Model
Aug 2023
Publication
Green hydrogen technologies are crucial for decarbonization purposes while cogeneration offers efficient heat and power generation. Integrating green hydrogen and cogeneration brings numerous benefits optimizing energy utilization reducing emissions and supporting the transition to a sustainable future. While there are numerous studies examining the integration of combined heat and power with Power to Gas certain aspects still requires a more detailed analysis especially for internal combustion engines fuelled by natural gas due to their widespread adoption as one of the primary technologies in use. Therefore this paper presents a comprehensive numerical 0-D dynamic simulation model implemented within the TRNSYS environment considering internal combustion engines fuelled by natural gas. Specifically the study focuses on capturing CO2 from exhaust gases and producing green hydrogen from electrolysis. Based on these considerations two configurations are proposed: the first involves the methanation reaction while the second entails the production of a hydromethane mixture. The aim is to evaluate the technical and economic feasibility of these configurations and compare their performance within the Power to Gas framework. Self-sufficiency from the national electricity grid has been almost achieved for the two configurations considering an industrial case. The production of hydromethane allows smaller photovoltaic plant (81 kWp) compared to the production of synthetic methane (670 kWp) where a high quantity of hydrogen is required especially if all the carbon dioxide captured is used in the methanation process. Encouraging economic results with payback times below ten years have been obtained with the use of hydromethane. Moreover hydromethane shows potential residential applications with small required photovoltaic sizes.
Economic Analysis of a Photovoltaic Hydrogen Refueling Station Based on Hydrogen Load
Sep 2023
Publication
With the goal of achieving “carbon peak in 2030 and carbon neutrality in 2060” as clearly proposed by China the transportation sector will face long–term pressure on carbon emissions and the application of hydrogen fuel cell vehicles will usher in a rapid growth period. However true “zero carbon” emissions cannot be separated from “green hydrogen”. Therefore it is of practical significance to explore the feasibility of renewable energy hydrogen production in the context of hydrogen refueling stations especially photovoltaic hydrogen production which is applied to hydrogen refueling stations (hereinafter referred to “photovoltaic hydrogen refueling stations”). This paper takes a hydrogen refueling station in Shanghai with a supply capacity of 500 kg/day as the research object. Based on a characteristic analysis of the hydrogen demand of the hydrogen refueling station throughout the day this paper studies and analyzes the system configuration operation strategy environmental effects and economics of the photovoltaic hydrogen refueling station. It is estimated that when the hydrogen price is no less than 6.23 USD the photovoltaic hydrogen refueling station has good economic benefits. Additionally compared with the conventional hydrogen refueling station it can reduce carbon emissions by approximately 1237.28 tons per year with good environmental benefits.
Improvement of MC Method in SAE J2601 Hydrogen Refuelling Protocol Using Dual-zone Dual-Temperature Model
Sep 2023
Publication
The MC method refuelling protocol in SAE J2601 has been published by the Society of Automotive Engineers (SAE) in order to safely and quickly refuel hydrogen vehicles. For the calculation method of the pressure target to control the refuelling stop we introduced a dual-zone dual-temperature model that distinguishes the hydrogen temperature in the tank from the wall temperature to replace the dual-zone single-temperature model of the original MC method. The total amount of heat transferred by convection between hydrogen and the inner tank wall during the filling process was expressed as an equation of final hydrogen temperature final wall temperature final refuelling time tank inner surface area and the correction factor. The correction factor equations were determined by fitting simulation data from the 0D1D model where hydrogen inside the tank is lumped parameter model (0D) and the tank wall is a one-dimensional model (1D). For the correction factor of the linear equation its first-order coefficient and constant term have a linear relationship with the initial pressure of the storage tank and their R2 values obtained from the fitting are greater than 0.99. Finally we derived a new equation to calculate the final hydrogen temperature which can be combined with the 100% SOC inside the vehicle tank to determine the pressure target. The simulation results show that the final SOC obtained are all greater than 96% using the modified pressure target and the correction factor of the linear equation.
Engineering Models for Refueling Protocol Development: Validation and Recommendations
Sep 2023
Publication
Fouad Ammouri,
Nicola Benvenuti,
Elena Vyazmina,
Vincent Ren,
Guillaume Lodier,
Quentin Nouvelot,
Thomas Guewouo,
Dorine Crouslé,
Rony Tawk,
Nicholas Hart,
Steve Mathison,
Taichi Kuroki,
Spencer Quong,
Antonio Ruiz,
Alexander Grab,
Alexander Kvasnicka,
Benoit Poulet,
Christopher Kutz and
Martin Zerta
The PRHYDE project (PRotocol for heavy duty HYDrogEn refueling) funded by the Clean Hydrogen partnership aims at developing recommendations for heavy-duty refueling protocols used for future standardization activities for trucks and other heavy duty transport systems applying hydrogen technologies. Development of a protocol requires a validated approach. Due to the limited time and budget the experimental data cannot cover the whole possible ranges of protocol parameters such as initial vehicle pressure and temperature ambient and precooling temperatures pressure ramp refueling time hardware specifications etc. Hence a validated numerical tool is essential for a safe and efficient protocol development. For this purpose engineering tools are used. They give good results in a very reasonable computation time of several seconds or minutes. These tools provide the heat parameters estimation in the gas (volume average temperature) and 1D temperature distribution in the tank wall. The following models were used SOFIL (Air Liquide tool) HyFill (by ENGIE) and H2Fills (open access code by NREL). The comparison of modelling results and experimental data demonstrated a good capability of codes to predict the evolution of average gas temperature in function of time. Some recommendations on model validation for the future protocol development are given.
Thermodynamic and Emission Analysis of a Hydrogen/Methane Fueled Gas Turbine
May 2023
Publication
The importance of hydrogen in the effort to decarbonize the power sector has grown immensely in recent years. Previous studies have investigated the effects of mixing hydrogen into natural gas for gas turbine combustors but limited studies have examined the resulting effects hydrogen addition has on the entire system. In this work a thermodynamic model of a gas turbine with combustion chemical kinetics integrated is created and the effects hydrogen addition (0-100 volume percent addition) has on the system performance emissions and combustion kinetics are analyzed. The maximum system performance is achieved when the maximum turbine inlet temperature is reached and the resulting optimal fuel/air equivalence ratio is determined. As hydrogen is added to the fuel mixture the optimal equivalence ratio shifts leaner causing non-linearity in emissions and system performance at optimal conditions. An analysis of variance is conducted and it is shown that isentropic efficiencies of the turbine and compressor influences the system performance the most out of any system parameter. While isentropic efficiencies of the turbine and compressor increase towards 100% an operating regime where the optimal system efficiency cannot be achieved is discovered due to the lower flammability limit of the fuel being reached. This can be overcome by mixing hydrogen into the fuel.
A Hydrogen Vision for the UK
Apr 2023
Publication
This report shows how the infrastructure that exists today can evolve from one based on the supply of fossil fuels to one providing the backbone of a clean hydrogen system. The ambitious government hydrogen targets across the UK will only be met with clarity focus and partnership. The gas networks are ready to play their part in the UK’s energy future. They have a plan know what is needed to deliver it and are taking the necessary steps to do just that.
Comprehensive Techno-economic Assessment of Power Technologies and Synthetic Fuels under Discussion for Ship Applications
Jun 2023
Publication
The decarbonization of the global ship traffic is one of the industry’s greatest challenges for the next decades and will likely only be achieved with the introduction of synthetic fuels. Until now however not one single best technology solution emerged to ideally fit this task. Instead different energy carriers including hydrogen ammonia methanol methane and synthetic diesel are subject of discussion for usage in either internal combustion engines or fuel cells. In order to drive the selection procedure a case study for the year 2030 with all eligible combinations of power technologies and fuels is conducted. The assessment quantifies the technologies’ economic performances for cost-optimized system designs and in dependence of a ship’s mission characteristics. Thereby the influence of trends for electrofuel prices and shipboard volume opportunity costs are examined. Even if gaseous hydrogen is often considered not suitable for large ship applications due to its low volumetric energy density both the comparatively small fuel price and the high efficiency of fuel cells lead to the overall smallest system costs for passages up to 21 days depending on assumed cost parameters. Only for missions longer than seven days fuel cells operating on methanol or ammonia can compete with gaseous hydrogen economically.
CO2 Emissions of Battery Electric Vehicles and Hydrogen Fuel Cell Vehicles
Jun 2023
Publication
During the last few years electric and hydrogen vehicles have become an alternative to cars that use internal combustion engines. The number of electric and hydrogen vehicles sold has increased due to support from local governments and because car manufacturers will stop the production of internal combustion engines in the near future. The emissions of these vehicles while being driven are zero but they still have an impact on the environment due to their fuel. In this article an analysis of carbon dioxide (CO2 ) emissions for two types of vehicles: battery electric vehicles (BEVs) powered by electricity and fuel cell electric vehicles (FCEVs) powered by hydrogen is presented. The analysis considers different values for the mix of power generation and hydrogen production options in comparison to other studies. The CO2 emissions were calculated and compared for the two types of vehicles. The results show that the CO2 emissions of BEVs are lower when compared to FCEVs if the hydrogen is obtained from pollutant sources and is higher if the hydrogen is obtained from nuclear power and renewable energy sources. When compared to conventional combustion engine vehicles BEVs have lower CO2 emissions while the emissions of FCEVs are dependent on the hydrogen production method.
Hydrogenerally - Episode 7: Hydrogen for Heat
Dec 2022
Publication
In this seventh episode Steffan Eldred Hydrogen Innovation Network Knowledge Transfer Manager and Jenni McDonnell MBE Heating and Cooling Knowledge Transfer Manager from Innovate UK KTN discuss why using hydrogen to generate heat is so important and explore the hydrogen economy opportunities and challenges within this sector alongside their special guest Jeff House Head of External Affairs Baxi Boilers.
The podcast can be found on their website.
The podcast can be found on their website.
How to Power the Energy–Water Nexus: Coupling Desalination and Hydrogen Energy Storage in Mini-Grids with Reversible Solid Oxide Cells
Nov 2020
Publication
Sustainable Development Goals establish the main challenges humankind is called to tackle to assure equal comfort of living worldwide. Among these the access to affordable renewable energy and clean water are overriding especially in the context of developing economies. Reversible Solid Oxide Cells (rSOC) are a pivotal technology for their sector-coupling potential. This paper aims at studying the implementation of such a technology in new concept PV-hybrid energy storage mini-grids with close access to seawater. In such assets rSOCs have a double useful effect: charge/discharge of the bulk energy storage combined with seawater desalination. Based on the outcomes of an experimental proof-of-concept on a single cell operated with salty water the operation of the novel mini-grid is simulated throughout a solar year. Simulation results identify the fittest mini-grid configuration in order to achieve energy and environmental optimization hence scoring a renewable penetration of more than 95% marginal CO2 emissions (13 g/kWh) and almost complete coverage of load demand. Sector-coupling co-production rate (desalinated water versus electricity issued from the rSOC) is 0.29 L/kWh.
Exploring the Complexity of Hydrogen Perception and Acceptance Among Key Stakeholders in Norway
Nov 2022
Publication
This article explores the complexity of factors or mechanisms that can influence hydrogen stakeholder perception and acceptance in Norway. We systematically analyze 16 semi-structured in-depth interviews with industry stakeholders at local municipal regional and national levels of interest and authority in Norway. Four empirical dimensions are identified that highlight the need for whole system approaches in hydrogen technology research: (1) several challenges incentives and synergy effects influence the hydrogen transition; (2) transport preferences are influenced by combined needs and limitations; (3) levels of knowledge and societal trust determinant to perceptions of risk and acceptance; and (4) national and international hydrogen stakeholders are crucial to building incentives and securing commitment among key actors. Our findings imply that project management planners engineers and policymakers need to apply a whole system perspective and work across local regional and national levels before proceeding with large-scale development and implementation of the hydrogen supply chain.
Blending Hydrogen from Electrolysis into the European Gas Grid
Jan 2022
Publication
In 2020 the European Commission launched a hydrogen strategy for a climate-neutral Europe setting out the conditions and actions for mainstreaming clean hydrogen along with targets for installing renewable hydrogen electrolysers by 2024 and 2030. Blending hydrogen alongside other gases into the existing gas grid is considered a possible interim first step towards decarbonising natural gas. In the present analysis we modelled electrolytic hydrogen generation as a process connecting two separate energy systems (power and gas). The analysis is based on a projection of the European power and gas systems to 2030 based on the EUCO3232.5 scenario. Multiple market configurations were introduced in order to assess the interplay between diverse power market arrangements and constraints imposed by the upper bound on hydrogen concentration. The study identifies the maximum electrolyser capacity that could be integrated in the power and gas systems the impact on greenhouse gas emissions and the level of price support that may be required for a broad range of electrolyser configurations. The study further attempts to shed some light on the potential side effects of having non-harmonised H2 blending thresholds between neighbouring Member States.
Small-Scale Hybrid and Polygeneration Renewable Energy Systems: Energy Generation and Storage Technologies, Applications, and Analysis Methodology
Dec 2022
Publication
The energy sector is nowadays facing new challenges mainly in the form of a massive shifting towards renewable energy sources as an alternative to fossil fuels and a diffusion of the distributed generation paradigm which involves the application of small-scale energy generation systems. In this scenario systems adopting one or more renewable energy sources and capable of producing several forms of energy along with some useful substances such as fresh water and hydrogen are a particularly interesting solution. A hybrid polygeneration system based on renewable energy sources can overcome operation problems regarding energy systems where only one energy source is used (solar wind biomass) and allows one to use an all-in-one integrated systems in order to match the different loads of a utility. From the point of view of scientific literature medium and large-scale systems are the most investigated; nevertheless more and more attention has also started to be given to small-scale layouts and applications. The growing diffusion of distributed generation applications along with the interest in multipurpose energy systems based on renewables and capable of matching different energy demands create the necessity of developing an overview on the topic of small-scale hybrid and polygeneration systems. Therefore this paper provides a comprehensive review of the technology operation performance and economical aspects of hybrid and polygeneration renewable energy systems in small-scale applications. In particular the review presents the technologies used for energy generation from renewables and the ones that may be adopted for energy storage. A significant focus is also given to the adoption of renewable energy sources in hybrid and polygeneration systems designs/modeling approaches and tools and main methodologies of assessment. The review shows that investigations on the proposed topic have significant potential for expansion from the point of view of system configuration hybridization and applications.
China's Hydrogen Development Strategy in the Context of Double Carbon Targets
Dec 2022
Publication
As a clean low-carbon efficient and renewable energy source hydrogen has gradually become an important energy carrier to combat climate change and achieve sustainable development in the world. China is now facing the stress of realizing the carbon peak and carbon neutrality goals where hydrogen will play a significant role. Against this backdrop to develop China's hydrogen strategy under the carbon peak and carbon neutrality goals this paper explores the hydrogen resource endowment in China presents the concepts such as Hydrogen Ethics and the Hu's Hydrogen Line and discusses the status quo and existing advantages in hydrogen production storage transport and utilization in China. Six major obstacles and challenges that China's hydrogen energy industry is facing are pointed out i.e. cost problem inadequate hydrogen infrastructures low energy efficiency mismatching the development progress of renewable energy insufficient market demand shortcomings in technology and imperfect policy system. Finally five policy suggestions for the future development of China's hydrogen energy industry are proposed as follows: (1) make an action plan as a response to the national hydrogen development plan; (2) build an international and domestic double-cycle hydrogen economic system; (3) incorporate hydrogen into the establishment of a clean low-carbon safe and efficient energy system; (4) accelerate the technological innovation to form advanced hydrogen technologies; and (5) construct hydrogen-oriented industrial clusters/parks to expand the hydrogen utilization market. It is concluded that for meeting the carbon peak and carbon neutrality goals China should leverage the dual advantages of hydrogen as an energy carrier and an industrial raw material allowing the hydrogen industry to play a synergistic role in ensuring the country's energy security promoting the socio-economic transformation and upgrading and protecting the ecological environment thereby providing a technical option and support for China to achieve the ultimate goal of carbon neutrality.
Recent Progress in Catalysts for Hydrogen-Chlorine Regenerative Fuel Cells
Oct 2020
Publication
The increasing energy demand and the subsequent climate change consequences are supporting the search for sustainable alternatives to fossil fuels. In this scenario the link between hydrogen and renewable energy is playing a key role and unitized hydrogen-chlorine (H2-Cl2) regenerative cells (RFCs) have become promising candidates for renewable energy storage. Described herein are the recent advances in cell configurations and catalysts for the different reactions that may take place in these systems that work in both modes: electrolysis and fuel cell. It has been found that platinum (Pt)-based catalysts are the best choice for the electrode where hydrogen is involved whereas for the case of chlorine ruthenium (Ru)-based catalysts are the best candidates. Only a few studies were found where the catalysts had been tested in both modes and recent advances are focused on decreasing the amount of precious metals contained in the catalysts. Moreover the durability of the catalysts tested under realistic conditions has not been thoroughly assessed becoming a key and mandatory step to evaluate the commercial viability of the H2-Cl2 RFC technology.
Net Hydrogen Consumption Minimization of Fuel Cell Hybrid Trains Using a Time-Based Co-Optimization Model
Apr 2022
Publication
With increasing concerns on transportation decarbonization fuel cell hybrid trains (FCHTs) attract many attentions due to their zero carbon emissions during operation. Since fuel cells alone cannot recover the regenerative braking energy (RBE) energy storage devices (ESDs) are commonly deployed for the recovery of RBE and provide extra traction power to improve the energy efficiency. This paper aims to minimize the net hydrogen consumption (NHC) by co-optimizing both train speed trajectory and onboard energy management using a time-based mixed integer linear programming (MILP) model. In the case with the constraints of speed limits and gradients the NHC of co-optimization reduces by 6.4% compared to the result obtained by the sequential optimization which optimizes train control strategies first and then the energy management. Additionally the relationship between NHC and employed ESD capacity is studied and it is found that with the increase of ESD capacity the NHC can be reduced by up to 30% in a typical route in urban railway transit. The study shows that ESDs play an important role for FCHTs in reducing NHC and the proposed time-based co-optimization model can maximize the energy-saving benefits for such emerging traction systems with hybrid energy sources including both fuel cells and ESD.
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