- Home
- A-Z Publications
- Publications
Publications
CFD Analysis of Fast Filling Strategies for Hydrogen Tanks and their Effects on Key-parameters
Nov 2014
Publication
A major requirement for the filling of hydrogen tanks is the maximum gas temperature within the vessels during the process. Different filling strategies in terms of pressure and temperature of the gas injected into the cylinder and their effects on key parameters like maximum temperature state of charge and energy cooling demand are investigated. It is shown that pre-cooling of the gas is required but is not necessary for the whole duration of the filling. Relevant energy savings can be achieved with pre-cooling over a fraction of the time. The most convenient filling strategy from the cooling energy point of view is identified: with an almost linear pressure rise and pre-cooling in the second half of the process a 60% reduction of the cooling energy demand is achieved compared to the case of pre-cooling for the whole filling.
Thermodynamic Modeling of Hydrogen Refueling for Heavy-duty Fuel Cell Buses and Comparison with Aggregated Real Data
Apr 2021
Publication
The foreseen uptake of hydrogen mobility is a fundamental step towards the decarbonization of the transport sector. Under such premises both refuelling infrastructure and vehicles should be deployed together with improved refuelling protocols. Several studies focus on refuelling the light-duty vehicles with 10 kgH2 up to 700 bar however less known effort is reported for refuelling heavy-duty vehicles with 30–40 kgH2 at 350 bar. The present study illustrates the application of a lumped model to a fuel cell bus tank-to-tank refuelling event tailored upon the real data acquired in the 3Emotion Project. The evolution of the main refuelling quantities such as pressure temperature and mass flow are predicted dynamically throughout the refuelling process as a function of the operating parameters within the safety limits imposed by SAE J2601/2 technical standard. The results show to refuel the vehicle tank from half to full capacity with an Average Pressure Ramp Rate (APRR) equal to 0.03 MPa/s are needed about 10 min. Furthermore it is found that the effect of varying the initial vehicle tank pressure is more significant than changing the ambient temperature on the refuelling performances. In conclusion the analysis of the effect of different APRR from 0.03 to 0.1 MPa/s indicate that is possible to safely reduce the duration of half-to-full refuelling by 62% increasing the APRR value from 0.03 to 0.08 MPa/s.
Overview of Current Development in Electrical Energy Storage Technologies and the Application Potential in Power System Operation
Oct 2014
Publication
Electrical power generation is changing dramatically across the world because of the need to reduce greenhouse gas emissions and to introduce mixed energy sources. The power network faces great challenges in transmission and distribution to meet demand with unpredictable daily and seasonal variations. Electrical Energy Storage (EES) is recognized as underpinning technologies to have great potential in meeting these challenges whereby energy is stored in a certain state according to the technology used and is converted to electrical energy when needed. However the wide variety of options and complex characteristic matrices make it difficult to appraise a specific EES technology for a particular application. This paper intends to mitigate this problem by providing a comprehensive and clear picture of the state-of-the-art technologies available and where they would be suited for integration into a power generation and distribution system. The paper starts with an overview of the operation principles technical and economic performance features and the current research and development of important EES technologies sorted into six main categories based on the types of energy stored. Following this a comprehensive comparison and an application potential analysis of the reviewed technologies are presented.
In the Green? Perceptions of Hydrogen Production Methods Among the Norwegian Public
Feb 2023
Publication
This article presents findings from a representative survey fielded through the Norwegian Citizen Panel examining public perceptions of hydrogen fuel and its different production methods. Although several countries including Norway have strategies to increase the production of hydrogen fuel our results indicate that hydrogen as an energy carrier and its different production methods are still unknown to a large part of the public. A common misunderstanding seems to be confusing ‘hydrogen fuel’ in general with environmentally friendly ‘green hydrogen’. Results from a survey experiment (N = 1906) show that production method is important for public acceptance. On a five-point acceptance scale respondents score on average 3.9 for ‘green’ hydrogen which is produced from renewable energy sources. The level of acceptance is significantly lower for ‘blue’ (3.2) and ‘grey’ (2.3) hydrogen when respondents are informed that these are produced from coal oil or natural gas. Public support for hydrogen fuel in general as well as the different production methods is also related to their level of worry about climate change gender and political affiliation. Widespread misunderstandings regarding ‘green’ hydrogen production could potentially fuel public resistance as new ‘blue’ or ‘grey’ projects develop. Our results indicate a need for clearer communication from the government and developers regarding production methods to avoid distrust and potential public backfire.
Evaluation of a Hydrogen Powered Scooter Toy Prototype
Nov 2022
Publication
Electric scooters are used as alternative ways of transport because they easily make travel faster. However the batteries can take around 5 h to charge and have an autonomy of 30 km. With the presence of the hydrogen cell a hybrid system reduces the charging times and increases the autonomy of the vehicle by using two types of fuel. An increase of up to 80% in maximum distance and of 34% in operating times is obtained with a 1:10 scale prototype with the hydrogen cell; although more energy is withdrawn the combined fuel efficiency increases too. This suggests the cell that is used has the same behavior as some official reported vehicles which have a long range but low power. This allows concluding that use of the cell is functional for load tests and that the comparison factor obtained works as input for real-scale scooter prototypes to compete with the traditional electric scooters.
Recent Advances in Hybrid Water Electrolysis for Energy-saving Hydrogen Production
Nov 2022
Publication
Electricity-driven water splitting to convert water into hydrogen (H2) has been widely regarded as an efficient approach for H2 production. Nevertheless the energy conversion efficiency of it is greatly limited due to the disadvantage of the sluggish kinetic of oxidation evolution reaction (OER). To effectively address the issue a novel concept of hybrid water electrolysis has been developed for energy– saving H2 production. This strategy aims to replace the sluggish kinetics of OER by utilizing thermodynamically favorable organics oxidation reaction to replace OER. Herein recent advances in such water splitting system for boosting H2 evolution under low cell voltage are systematically summarized. Some notable progress of different organics oxidation reactions coupled with hydrogen evolution reaction (HER) are discussed in detail. To facilitate the development of hybrid water electrolysis the major challenges and perspectives are also proposed.
Efficiency, Economic and Environmental Impact Assessment of a Newly Developed Rail Engine using Hydrogen and Other Sustainable Fuel Blends
Jan 2023
Publication
Locomotives still use antiqued engines such as internal combustion engines operated by fossil fuels which cause global warming due to their significant emissions. This paper continues investigating the newly hybridized locomotive engine containing a gas turbine system solid oxide fuel cell system energy saving system and on-board hydrogen production system. This new engine is operated using five fuel blends composed of five alternative fuels such as hydrogen methane methanol ethanol and dimethyl ether. The current investigation involves exergy analysis exergo-economic analysis and exergo-environmental analysis to assess the engine from three perspectives: efficiency/irreversibility cost and environmental impact. The study results show that the net power of this new engine is 4948.6 kW and it has an exergetic efficiency of 62.7% according to the fuel and product principle. This engine weighs about 9 tons and costs about $10.2M with a levelized cost rate of 147 $/h and 14.06 mPt/h of overall component-related environmental rate. The average overall specific fuel and product exergy costs are about 37 $/GJ and 60 $/GJ and the minimum values are 13.3 $/GJ and 21.8 $/GJ using methane and hydrogen blend respectively. Also the average overall specific fuel and product exergo-environmental impact are about 15 and 23 mPt/MJ respectively. The on-board hydrogen production has an average exergy cost of 274 $/GJ and an environmental impact of 52 mPt/MJ. Hydrogen blended with methane or methanol is found to be more economic and has less environmental impact.
Pore-scale Dynamics for Underground Porous Media Hydrogen Storage
Mar 2022
Publication
Underground hydrogen storage (UHS) has been launched as a catalyst to the low-carbon energy transitions. The limited understanding of the subsurface processes is a major obstacle for rapid and widespread UHS implementation. We use microfluidics to experimentally describe pore-scale multiphase hydrogen flow in an aquifer storage scenario. In a series of drainage-imbibition experiments we report the effect of capillary number on hydrogen saturations displacement/trapping mechanisms dissolution kinetics and contact angle hysteresis. We find that the hydrogen saturation after injection (drainage) increases with increasing capillary number. During hydrogen withdrawal (imbibition) two distinct mechanisms control the displacement and residual trapping – I1 and I2 imbibition mechanisms respectively. Local hydrogen dissolution kinetics show dependency on injection rate and hydrogen cluster size. Dissolved global hydrogen concentration corresponds up to 28 % of reported hydrogen solubility indicating pore-scale non-equilibrium dissolution. Contact angles show hysteresis and vary between 17 and 56°. Our results provide key UHS experimental data to improve understanding of hydrogen multiphase flow behavior.
Hydrogen Storage Assessment in Depleted Oil Reservoir and Saline Aquifer
Oct 2022
Publication
Hydrogen (H2 ) is an attractive energy carrier to move store and deliver energy in a form that can be easily used. Field proven technology for underground hydrogen storage (UHS) is essential for a successful hydrogen economy. Options for this are manmade caverns salt domes/caverns saline aquifers and depleted oil/gas fields where large quantities of gaseous hydrogen have been stored in caverns for many years. The key requirements intrinsic of a porous rock formation for seasonal storage of hydrogen are: adequate capacity ability to contain H2 capability to inject/extract high volumes of H2 and a reliable caprock to prevent leakage. We have carefully evaluated a commercial non-isothermal compositional gas reservoir simulator and its suitability for hydrogen storage and withdrawal from saline aquifers and depleted oil/gas reservoirs. We have successfully calibrated the gas equation of state model against published laboratory H2 density and viscosity data as a function of pressure and temperature. Comparisons between the H2 natural gas and CO2 storage in real field models were also performed. Our numerical models demonstrated more lateral spread of the H2 when compared to CO2 and natural gas with a need for special containment in H2 projects. It was also observed that the experience with CO2 and natural gas storage cannot be simply replicated with H2 .
Simulation of Turbulent Combustion in a Small-scale Obstructed Chamber Using Flamefoam
Sep 2021
Publication
Dynamic overpressures achieved during the combustion are related to the acceleration experienced by the propagating flame. In the case of premixed turbulent combustion in an obstructed geometry obstacles in the direction of flow result in a complex flame front interaction with the turbulence generated ahead of it. The interaction of flame front and vortex significantly affect the burning rate the rate of pressure rise and achieved overpressure the geometry of accelerating flame front and resulting structures in the flow field. Laboratory-scale premixed turbulent combustion experiments are convenient for the study of flame acceleration by obstacles in higher resolution. This paper presents numerical simulations of hydrogenair mixture combustion experiments performed in the University of Sydney small-scale combustion chamber. The simulations were performed using flameFoam – an open-source premixed turbulent combustion solver based on OpenFOAM. The experimental and numerical pressure evolutions are compared. Furthermore flow structures which develop due to the interaction between the obstacles and the flow are investigated with different obstacle configurations.
Hydrogen Embrittlement of a Boiler Water Wall Tube in a District Heating System
Jul 2022
Publication
A district heating system is an eco-friendly power generation facility with high energy efficiency. The boiler water wall tube used in the district heating system is exposed to extremely harsh conditions and unexpected fractures often occur during operation. In this study a corrosion failure analysis of the boiler water wall tube was performed to elucidate the failure mechanisms. The study revealed that overheating by flames was the cause of the failure of the boiler water wall tube. With an increase in temperature in a localized region the microstructure not only changed from ferrite/pearlite to martensite/bainite which made it more susceptible to brittleness but it also developed tensile residual stresses in the water-facing side by generating cavities or microcracks along the grain boundaries inside the tube. High-temperature hydrogen embrittlement combined with stress corrosion cracking initiated many microcracks inside the tube and created an intergranular fracture.
Renewable Hydrogen Supply Chains: A Planning Matrix and an Agenda for Future Research
Oct 2022
Publication
Worldwide energy systems are experiencing a transition to more sustainable systems. According to the Hydrogen Roadmap Europe (FCH EU 2019) hydrogen will play an important role in future energy systems due to its ability to support sustainability goals and will account for approximately 13% of the total energy mix in the coming future. Correct hydrogen supply chain (HSC) planning is therefore vital to enable a sustainable transition. However due to the operational characteristics of the HSC its planning is complicated. Renewable hydrogen supply can be diverse: Hydrogen can be produced de-centrally with renewables such as wind and solar energy or centrally by using electricity generated from a hydro power plant with a large volume. Similarly demand for hydrogen can also be diverse with many new applications such as fuels for fuel cell electrical vehicles and electricity generation feedstocks in industrial processes and heating for buildings. The HSC consists of various stages (production storage distribution and applications) in different forms with strong interdependencies which further increase HSC complexity. Finally planning of an HSC depends on the status of hydrogen adoption and market development and on how mature technologies are and both factors are characterised by high uncertainties. Directly adapting the traditional approaches of supply chain planning for HSCs is insufficient. Therefore in this study we develop a planning matrix with related planning tasks leveraging a systematic literature review to cope with the characteristics of HSCs. We focus only on renewable hydrogen due to its relevance to the future low-carbon economy. Furthermore we outline an agenda for future research from the supply chain management perspective in order to support HSC development considering the different phases of HSCs adoption and market development.
Nuclear Cogeneration: Civil Nuclear Energy in a Low-carbon Future
Oct 2020
Publication
This policy briefing considers how the use of nuclear energy could be expanded to make the most of the energy produced and also to have the flexibility to complement an energy system with a growing input of intermittent renewable energy.<br/>What is nuclear cogeneration?<br/>Nuclear cogeneration is where the heat generated by a nuclear power station is used not only to generate electricity but to address some of the ‘difficult to decarbonise’ energy demands such as domestic heating and hydrogen production. It also enables a nuclear plant to be used more flexibly by switching between electricity generation and cogeneration applications.<br/>Applications for nuclear cogeneration<br/>Heat generated by civil nuclear reactors can be extracted at two different points for applications requiring either low-temperature or high-temperature heat. Each application differs in many aspects of operation and have different challenges.<br/>Low-temperature cogeneration<br/>Applications for the lower temperature ‘waste’ heat include:<br/>District heating<br/>Seawater desalination<br/>Low-temperature industrial process heating<br/>High-temperature cogeneration<br/>Higher temperature heat can be accessed earlier and used for:<br/>High-temperature industrial process heating<br/>Hydrogen production<br/>Sustainable synthetic fuel production<br/>Direct air capture<br/>Thermal energy storage<br/>Challenges of cogeneration systems<br/>Whilst some nuclear cogeneration applications have been employed in many countries the economic benefit of widescale nuclear cogeneration needs to be determined. However if the construction cost reductions for small modular reactors (SMRs) can be realised and the regulation and licencing processes streamlined then the additional revenue benefits of cogeneration could be material for SMRs and for the future of nuclear generation in the UK.<br/>Other outstanding issues include the ownership of reactors the future demand for hydrogen and other cogeneration products at a regional national and international level and the cost of carbon and dependable power.
An Overview on Safety Issues Related to Hydrogen and Methane Blend Applications in Domestic and Industrial Use
Sep 2017
Publication
The share of electrical energy hailing from renewable sources in the European electricity mix is increasing. The match between renewable power supply and demand has become the greatest challenge to cope with. Gas infrastructure can accommodate large volumes of electricity converted into gas whenever this supply of renewable power is larger than the grid capacity or than the electricity demand. The Power-to-Gas (P2G) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable hydrogen via electrolysis and subsequent methanation. The aim of this paper is to provide an overview of the required technical adaptations of the most common devices for end users such as heating plants CHP systems home gas furnaces and cooking surfaces wherever these are fuelled with methane and hydrogen blends in variable percentages by volume. Special attention will be given to issues related to essential safety standards firstly comparing existing Italian and European regulations in this regard and secondly highlighting the potential need for legislation to regulate the suitability of hydrogen methane blends. Finally a list of foreseeable technical solutions will be provided and discussed thoroughly
System Dynamic Model for the Accumulation of Renewable Electricity using Power-to-Gas and Power-to-Liquid Concepts
Feb 2016
Publication
When the renewable energy is used the challenge is match the supply of intermittent energy with the demand for energy therefore the energy storage solutions should be used. This paper is dedicated to hydrogen accumulation from wind sources. The case study investigates the conceptual system that uses intermitted renewable energy resources to produce hydrogen (power-to-gas concept) and fuel (power-to-liquid concept). For this specific case study hydrogen is produced from surplus electricity generated by wind power plant trough electrolysis process and fuel is obtained by upgrading biogas to biomethane using hydrogen. System dynamic model is created for this conceptual system. The developed system dynamics model has been used to simulate 2 different scenarios. The results show that in both scenarios the point at which the all electricity needs of Latvia are covered is obtained. Moreover the methodology of system dynamics used in this paper is white-box model that allows to apply the developed model to other case studies and/or to modify model based on the newest data. The developed model can be used for both scientific research and policy makers to better understand the dynamic relation within the system and the response of system to changes in both internal and external factors.
Optimized Configuration and Operating Plan for Hydrogen Refueling Station with On-Site Electrolytic Production
Mar 2022
Publication
Hydrogen refueling stations (HRSs) are critical for the popularity of hydrogen vehicles (fuel cell electric vehicles—FCEVs). However due to high installation investment and operating costs the proliferation of HRSs is difficult. This paper studies HRSs with on-site electrolytic production and hydrogen storage devices and proposes an optimization method to minimize the total costs including both installation investment and operating costs (OPT-ISL method). Moreover to acquire the optimization constraints of hydrogen demand this paper creatively develops a refueling behavior simulation method for different kinds of FCEVs and proposes a hydrogen-demand estimation model to forecast the demand with hourly intervals for HRS. The Jensen–Shannon divergence is applied to verify the accuracy of the hydrogen-demand estimation. The result: 0.029 is much smaller than that of the estimation method in reference. Based on the estimation results and peak-valley prices of electricity from the grid a daily hydrogen generation plan is obtained as well as the optimal capacities of electrolyzers and storage devices. As for the whole costs compared with previous configuration methods that only consider investment costs or operating costs the proposed OPT-ISL method has the least 8.1 and 10.5% less respectively. Moreover the proposed OPT-ISL method shortens the break-even time for HRS from 11.1 years to 7.8 years a decrease of 29.7% so that the HRS could recover its costs in less time.
New Control Strategy for Heating Portable Fuel Cell Power Systems for Energy-Efficient and Reliable Operation
Dec 2022
Publication
Using hydrogen fuel cells for power systems temperature conditions are important for efficient and reliable operations especially in low-temperature environments. A heating system with an electrical energy buffer is therefore required for reliable operation. There is a research gap in finding an appropriate control strategy regarding energy efficiency and reliable operations for different environmental conditions. This paper investigates heating strategies for the subfreezing start of a fuel cell for portable applications at an early development stage to enable frontloading in product engineering. The strategies were investigated by simulation and experiment. A prototype for such a system was built and tested for subfreezing start-ups and non-subfreezing start-ups. This was done by heating the fuel cell system with different control strategies to test their efficiency. It was found that operating strategies to heat up the fuel cell system can ensure a more reliable and energy efficient operation. The heating strategy needs to be adjusted according to the ambient conditions as this influences the required heating energy efficiency and reliable operation of the system. A differentiation in the control strategy between subfreezing and non-subfreezing temperatures is recommended due to reliability reasons.
A Review on Hydrogen-Based Hybrid Microgrid System: Topologies for Hydrogen Energy Storage, Integration, and Energy Management with Solar and Wind Energy
Oct 2022
Publication
Hydrogen is acknowledged as a potential and appealing energy carrier for decarbonizing the sectors that contribute to global warming such as power generation industries and transportation. Many people are interested in employing low-carbon sources of energy to produce hydrogen by using water electrolysis. Additionally the intermittency of renewable energy supplies such as wind and solar makes electricity generation less predictable potentially leading to power network incompatibilities. Hence hydrogen generation and storage can offer a solution by enhancing system flexibility. Hydrogen saved as compressed gas could be turned back into energy or utilized as a feedstock for manufacturing building heating and automobile fuel. This work identified many hydrogen production strategies storage methods and energy management strategies in the hybrid microgrid (HMG). This paper discusses a case study of a HMG system that uses hydrogen as one of the main energy sources together with a solar panel and wind turbine (WT). The bidirectional AC-DC converter (BAC) is designed for HMGs to maintain power and voltage balance between the DC and AC grids. This study offers a control approach based on an analysis of the BAC’s main circuit that not only accomplishes the function of bidirectional power conversion but also facilitates smooth renewable energy integration. While implementing the hydrogen-based HMG the developed control technique reduces the reactive power in linear and non-linear (NL) loads by 90.3% and 89.4%.
Fuel Cell Power Systems for Maritime Applications: Progress and Perspectives
Jan 2021
Publication
Fuel cells as clean power sources are very attractive for the maritime sector which is committed to sustainability and reducing greenhouse gas and atmospheric pollutant emissions from ships. This paper presents a technological review on fuel cell power systems for maritime applications from the past two decades. The available fuels including hydrogen ammonia renewable methane and methanol for fuel cells under the context of sustainable maritime transportation and their pre-processing technologies are analyzed. Proton exchange membrane molten carbonate and solid oxide fuel cells are found to be the most promising options for maritime applications once energy efficiency power capacity and sensitivity to fuel impurities are considered. The types layouts and characteristics of fuel cell modules are summarized based on the existing applications in particular industrial or residential sectors. The various research and demonstration projects of fuel cell power systems in the maritime industry are reviewed and the challenges with regard to power capacity safety reliability durability operability and costs are analyzed. Currently power capacity costs and lifetime of the fuel cell stack are the primary barriers. Coupling with batteries modularization mass production and optimized operating and control strategies are all important pathways to improve the performance of fuel cell power systems.
Investigation on Green Hydrogen Generation Devices Dedicated for Integrated Renewable Energy Farm: Solar and Wind
Oct 2022
Publication
This study presents a comprehensive methodology to evaluate plants that integrate renewable energy sources and hydrogen generation devices. The paper focuses on presenting the methods for devices’ operation assessment taking into account the annual operation. Multiple effectiveness indices have been presented. On the basis of experimental investigation with the hydrogen generator the methods for assessing its operation during start-up phase and sudden change in the supply current were proposed. The results of the experiments and the provided mathematical models show that dynamics of the hydrogen generator should be taken into account when selecting the suitable device for cooperation with variable renewable energy. It is especially important for multiple start-ups throughout the day due to significant differences in the amount of hydrogen produced by devices characterized by the same efficiency yet various time constants. Methodology for selecting the optimal nominal power for hydrogen generator to cooperate with given renewable sources was developed. It was proven the optimal power depends on the type of the renewable source and minimal load of the hydrogen generator. Several case studies including the integration of wind and solar energy farms to yield a 10 MW renewable energy farm were considered and the minimal load of the hydrogen generator impacts the annual operation of the device has been presented. The paper provides a set of tools to contribute to the development of sustainable energy plants. The methods proposed in this paper are universal and can be used for various renewable energy sources.
No more items...