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Proton Exchange Membrane Electrolyzer Emulator for Power Electronics Testing Applications
Mar 2021
Publication
This article aims to develop a proton exchange membrane (PEM) electrolyzer emulator. This emulator is realized through an equivalent electrical scheme. It allows taking into consideration the dynamic operation of PEM electrolyzers which is generally neglected in the literature. PEM electrolyzer dynamics are reproduced by the use of supercapacitors due to the high value of the equivalent double-layer capacitance value. Steady-state and dynamics operations are investigated in this work. The design criteria are addressed. The PEM electrolyzer emulator is validated by using a 400-W commercial PEM electrolyzer. This emulator is conceived to test new DC-DC converters to supply the PEM ELs and their control as well avoiding the risk to damage a real electrolyzer for experiment purposes. The proposed approach is valid both for a single cell and for the whole stack emulation.
Assessment of Hydrogen Fuel for Rotorcraft Applications
Jun 2022
Publication
This paper presents the application of a multidisciplinary approach for the preliminary design and evaluation of the potential improvements in performance and environmental impact through the utilization of compressed (CGH2) and liquefied (LH2) hydrogen fuel for a civil tilt-rotor modelled after the NASA XV-15. The methodology deployed comprises models for rotorcraft flight dynamics engine performance flight path analysis hydrogen tank and thermal management system sizing. Trade-offs between gravimetric efficiency energy consumption fuel burn CO2 emissions and cost are quantified and compared to the kerosene-fuelled rotorcraft. The analysis carried out suggests that for these vehicle scales gravimetric efficiencies of the order of 13% and 30% can be attained for compressed and liquid hydrogen storage respectively leading to reduced range capability relative to the baseline tilt-rotor by at least 40%. At mission level it is shown that the hydrogen-fuelled configurations result in increased energy consumption by at least 12% (LH2) and 5% (CGH2) but at the same time significantly reduced life-cycle carbon emissions compared to the kerosene counterpart. Although LH2 storage at cryogenic conditions has a higher gravimetric efficiency than CGH2 (at 700 bar) it is shown that for this class of rotorcraft the latter is more energy efficient when the thermal management system for fuel pressurization and heating prior to combustion is accounted for.
Sector Coupling and Migration towards Carbon-Neutral Power Systems
Feb 2023
Publication
There is increasing interest in migrating to a carbon-neutral power system that relies on renewable energy due to concerns about greenhouse gas emissions energy shortages and global warming. However the increasing share of renewable energy has added volatility and uncertainty to power system operations. Introducing new devices and using flexible resources may help solve the problem but expanding the domain of the problem can be another solution. Sector coupling which integrates production consumption conversion and storage by connecting various energy domains could potentially meet the needs of each energy sector. It can also reduce the generation of surplus energy and unnecessary carbon emissions. As a result sector coupling an integrated energy system increases the acceptance of renewable energy in the traditional power system and makes it carbon neutral. However difficulties in large-scale integration low conversion efficiency and economic feasibility remain obstacles. This perspective paper discusses the background definition and components of sector coupling as well as its functions and examples in rendering power systems carbon-neutral. The current limitations and outlook of sector coupling are also examined.
Optimising Onshore Wind with Energy Storage Considering Curtailment
May 2022
Publication
Operating energy storage alongside onshore wind can improve its economics whilst providing a pathway for otherwise curtailed generation. In this work we present a framework to evaluate the economic potential of onshore wind co-located with battery storage (BS) and a hydrogen electrolyser (HE). This model is applied to a case study in Great Britain using historic data and considering local network charges and the cost of using curtailed power capturing an often neglected element of competition. We use a Markov Chain to model wind curtailment and determine the optimised scheduling of the storage as we vary price parameters and storage sizing. Finally by considering storage CAPEX and comparing against the case with no storage we can determine the value added (or lost) by different sized BS and HE for an onshore wind owner as a function of power purchase agreement (PPA) and green hydrogen market price. Results show that value added increases when HE is increased and when BS is decreased. Additionally a 10 MW electrolysers uses 27% more curtailed wind than 10 MW BS.
Everything About Hydrogen Podcast: Flying Hy!
Feb 2021
Publication
Decarbonizing aviation is a big challenge. It is one of the most carbon intensive business sectors in the modern world and change comes slowly to the aviation industry. Hydrogen and fuel cell technologies offer a pathway to decarbonize regional flights in the not-so-distant future and big names are looking at potential solutions for long-haul flights in the longer term. But even if we build the aircraft that can use hydrogen as a fuel how do we get the fuel to them in a timely reliable and cost-efficient way?
The podcast can be found on their website
The podcast can be found on their website
Study on the Effect of Second Injection Timing on the Engine Performances of a Gasoline/Hydrogen SI Engine with Split Hydrogen Direct Injecting
Oct 2020
Publication
Split hydrogen direct injection (SHDI) has been proved capable of better efficiency and fewer emissions. Therefore to investigate SHDI deeply a numerical study on the effect of second injection timing was presented at a gasoline/hydrogen spark ignition (SI) engine with SHDI. With an excess air ratio of 1.5 five different second injection timings achieved five kinds of hydrogen mixture distribution (HMD) which was the main factor affecting the engine performances. With SHDI since the HMD is manageable the engine can achieve better efficiency and fewer emissions. When the second injection timing was 105◦ crank angle (CA) before top dead center (BTDC) the Pmax was the highest and the position of the Pmax was the earliest. Compared with the single hydrogen direct injection (HDI) the NOX CO and HC emissions with SHDI were reduced by 20% 40% and 72% respectively.
Hydrogen Refueling Process: Theory, Modeling, and In-Force Applications
Mar 2023
Publication
Among the alternative fuels enabling the energy transition hydrogen-based transportation is a sustainable and efficient choice. It finds application both in light-duty and heavy-duty mobility. However hydrogen gas has unique qualities that must be taken into account when employed in such vehicles: high-pressure levels up to 900 bar storage in composite tanks with a temperature limit of 85 ◦C and a negative Joule–Thomson coefficient throughout a wide range of operational parameters. Moreover to perform a refueling procedure that is closer to the driver’s expectations a fast process that requires pre-cooling the gas to −40 ◦C is necessary. The purpose of this work is to examine the major phenomena that occur during the hydrogen refueling process by analyzing the relevant theory and existing modeling methodologies.
Risk Assessment and Mitigation Evaluation for Hydrogen Vehicles in Private Garages. Experiments and Modelling
Sep 2021
Publication
Governments and local authorities introduce new incentives and regulations for cleaner mobility as part of their environmental strategies to address energy challenges. Fuel cell electric vehicles (FCEVs) are becoming increasingly important and will extend beyond captive fleets reaching private users. Research on hydrogen safety issues is currently led in several projects in order to highlight and manage risks of FCEVs in confined spaces such as tunnels underground parkings repair garages etc. But what about private garages - that involve specific geometries volumes congestion ventilation? This study has been carried out in the framework of PRHyVATE JIP project which aims at better understanding hydrogen build-up and distribution in a private garage. The investigation went through different rates and modes of ventilation. As first step an HAZID (Hazard Identification) has been realized for a generic FCEV. This preliminary work allowed to select and prioritize accidental release scenarios to be explored experimentally with helium in a 40-m3 garage. Several configurations of release ventilation modes and congestion – in transient regime and at steady state – have been tested. Then analytical and numerical calculation approaches have been applied and adjusted to develop a simplified methodology. This methodology takes into account natural ventilation for assessment of hydrogen accumulation and mitigation means optimization. Finally a global risk evaluation – including ignition of a flammable hydrogen-air mixture – has been performed to account for the mostly feared events and to evaluate their consequences in a private garage. Thus preliminary recommendations good practices and safety features for safely parking FCEVs in private garages can be proposed.
An Analysis on the Compressed Hydrogen Storage System for the Fast-Filling Process of Hydrogen Gas at the Pressure of 82 MPa
May 2021
Publication
During the fast-filling of a high-pressure hydrogen tank the temperature of hydrogen would rise significantly and may lead to failure of the tank. In addition the temperature rise also reduces hydrogen density in the tank which causes mass decrement into the tank. Therefore it is of practical significance to study the temperature rise and the amount of charging of hydrogen for hydrogen safety. In this paper the change of hydrogen temperature in the tank according to the pressure rise during the process of charging the high-pressure tank in the process of a 82-MPa hydrogen filling system the final temperature the amount of filling of hydrogen gas and the change of pressure of hydrogen through the pressure reducing valve and the performance of heat exchanger for cooling high-temperature hydrogen were analyzed by theoretical and numerical methods. When high-pressure filling began in the initial vacuum state the condition was called the “First cycle”. When the high-pressure charging process began in the remaining condition the process was called the “Second cycle”. As a result of the theoretical analysis the final temperatures of hydrogen gas were calculated to be 436.09 K for the first cycle of the high-pressure tank and 403.55 for the second cycle analysis. The internal temperature of the buffer tank increased by 345.69 K and 32.54 K in the first cycle and second cycles after high-pressure filling. In addition the final masses were calculated to be 11.58 kg and 12.26 kg for the first cycle and second cycle of the high-pressure tank respectively. The works of the paper can provide suggestions for the temperature rise of 82 MPa compressed hydrogen storage system and offer necessary theory and numerical methods for guiding safe operation and construction of a hydrogen filling system.
Impacts of Renewable Energy Resources on Effectiveness of Grid-Integrated Systems: Succinct Review of Current Challenges and Potential Solution Strategies
Sep 2020
Publication
This study is aimed at a succinct review of practical impacts of grid integration of renewable energy systems on effectiveness of power networks as well as often employed state-of-the-art solution strategies. The renewable energy resources focused on include solar energy wind energy biomass energy and geothermal energy as well as renewable hydrogen/fuel cells which although not classified purely as renewable resources are a famous energy carrier vital for future energy sustainability. Although several world energy outlooks have suggested that the renewable resources available worldwide are sufficient to satisfy global energy needs in multiples of thousands the different challenges often associated with practical exploitation have made this assertion an illusion to date. Thus more research efforts are required to synthesize the nature of these challenges as well as viable solution strategies hence the need for this review study. First brief overviews are provided for each of the studied renewable energy sources. Next challenges and solution strategies associated with each of them at generation phase are discussed with reference to power grid integration. Thereafter challenges and common solution strategies at the grid/electrical interface are discussed for each of the renewable resources. Finally expert opinions are provided comprising a number of aphorisms deducible from the review study which reveal knowledge gaps in the field and potential roadmap for future research. In particular these opinions include the essential roles that renewable hydrogen will play in future energy systems; the need for multi-sectoral coupling specifically by promoting electric vehicle usage and integration with renewable-based power grids; the need for cheaper energy storage devices attainable possibly by using abandoned electric vehicle batteries for electrical storage and by further development of advanced thermal energy storage systems (overviews of state-of-the-art thermal and electrochemical energy storage are also provided); amongst others.
Numerical Simulation of Hydrogen Leakage from Fuel Cell Vehicle in an Outdoor Parking Garage
Aug 2021
Publication
It is significant to assess the hydrogen safety of fuel cell vehicles (FCVs) in parking garages with a rapidly increased number of FCVs. In the present work a Flame Acceleration Simulator (FLACS) a computational fluid dynamics (CFD) module using finite element calculation was utilized to predict the dispersion process of flammable hydrogen clouds which was performed by hydrogen leakage from a fuel cell vehicle in an outdoor parking garage. The effect of leakage diameter (2 mm 3 mm and 4 mm) and parking configurations (vertical and parallel parking) on the formation of flammable clouds with a range of 4–75% by volume was considered. The emission was assumed to be directed downwards from a Thermally Activated Pressure Relief Device (TPRD) of a 70 MPa storage tank. The results show that the 0.7 m parking space stipulated by the current regulations is less than the safety space of fuel cell vehicles. Compared with a vertical parking configuration it is safer to park FCVs in parallel. It was also shown that release through a large TPRD orifice should be avoided as the proportion of the larger hydrogen concentration in the whole flammable domain is prone to more accidental severe consequences such as overpressure.
Influence of Hydrogen Enrichment Strategy on Performance Characteristics, Combustion and Emissions of a Rotary Engine for Unmanned Aerial Vehicles (UAVs)
Dec 2022
Publication
In recent years there has been great interest in Wankel-type rotary engines which are one of the most suitable power sources for unmanned aerial vehicle (UAV) applications due to their high power-to-size and power-to-weight ratios. The purpose of the present study was to investigate the potential of a hydrogen enrichment strategy for the improvement of the performance and reduction of the emissions of Wankel engines. The main motivation behind this study was to make Wankel engines which are already very advantageous for UAV applications even more advantageous by applying the hydrogen enrichment technique. In this study hydrogen addition was implemented in a spark-ignition rotary engine model operating at a constant engine speed of 6000 rpm. The mass fraction of hydrogen in the intake gradually increased from 0% to 10%. Simulation results revealed that addition of hydrogen to the fuel accelerated the flame propagation and increased the burning speed of the fuel the combustion temperature and the peak pressure in the working chamber. These phenomena had a very positive effect on the performance and emissions of the Wankel engine. The indicated mean effective pressure (IMEP) increased by 8.18% and 9.68% and the indicated torque increased by 6.15% and 7.99% for the 5% and 10% hydrogen mass fraction cases respectively compared to those obtained with neat gasoline. In contrast CO emissions were reduced by 33.35% and 46.21% and soot emissions by 11.92% and 20.06% for 5% and 10% hydrogen additions respectively. NOx emissions increased with the application of the hydrogen enrichment strategy for the Wankel engine.
Thermodynamic Performance and Creep Life Assessment Comparing Hydrogen- and Jet-Fueled Turbofan Aero Engine
Apr 2021
Publication
There is renewed interest in hydrogen as an alternative fuel for aero engines due to their perceived environmental and performance benefits compared to jet fuel. This paper presents a cycle thermal performance energy and creep life assessment of hydrogen compared with jet fuel using a turbofan aero engine. The turbofan cycle performance was simulated using a code developed by the authors that allows hydrogen and jet fuel to be selected as fuel input. The exergy assessment uses both conservations of energy and mass and the second law of thermodynamics to understand the impact of the fuels on the exergy destruction exergy efficiency waste factor ratio environmental effect factor and sustainability index for a turbofan aero engine. Finally the study looks at a top-level creep life assessment on the high-pressure turbine hot section influenced by the fuel heating values. This study shows performance (64% reduced fuel flow rate better SFC) and more extended blade life (15% increase) benefits using liquefied hydrogen fuel which corresponds with other literary work on the benefits of LH2 over jet fuel. This paper also highlights some drawbacks of hydrogen fuel based on previous research work and gives recommendations for future work aimed at maturing the hydrogen fuel concept in aviation.
Quantitative Risk Analysis of Scaled-up Hydrogen Facilities
Sep 2021
Publication
Development of hydrogen facilities such as hydrogen refuelling stations (HRS) at scale is a fine balance between economy and safety where an optimal solution would both prevent showstoppers due to cost of increased safety measures and prevent showstoppers due to hydrogen accidents. A detailed Quantitative Risk Analysis (QRA) methodology is presented where the aim is to establish the total risk of the facility and use it to find the right level of safety features such as blast walls and layout. With upscaled hydrogen facilities comes larger area footprints and more potential leak points. These effects will cause increased possible consequence in terms of vapour cloud explosions and increased leak frequencies. Both effects contributing negative to the total risk of the hydrogen facility. At the same time as the number of such facilities is increasing rapidly the frequency of incidents can also increase. A risk-based approach is employed where inherently safe solutions is investigated and cost efficient and acceptable solutions can be established. The present QRA uses well established tools such as SAFETI FLACS and Express which are fitted for hydrogen risks. By using the established Explosion Risk Analysis tool Express the explosion risk inside the station can be found. By using CFD tools actively one can point at physical risk drivers such as equipment layout that can minimize gas cloud build-up on the station. The explosion simulations are further used to find the effects of e.g. blast wall on the pressures affecting on people on the other side of the wall. This is used together with the results from the SAFETI analysis to develop risk contours around the facility. Current standardized safety distances are discussed by considering the effects of scaling and risk drivers on the safety distances. The methodology can be used to develop certain requirement for how hydrogen facilities should be built inherently safe and in cost-efficient ways.
Reliability Analysis of Pyrotechnic Igniter for Hydrogen-Oxygen Rocket Engine with Low Temperature Combustion Instability Failure Mode
Mar 2022
Publication
To evaluate the functional reliability of the pyrotechnic igniter in the failure mode of unstable combustion at low temperature a reliability and reliability sensitivity analysis method based on the combination of an interior ballistic model and Kriging reliability method is proposed. Through the deterministic interior ballistic simulation the failure mode of low temperature unstable combustion of the pyrotechnic igniter is examined while the random variables are introduced to establish the ignition nonlinear implicit function of the pyrotechnic igniter. The ignition display function of the pyrotechnic igniter is established by the Kriging model which avoids the repeated calculation of true limit state function values. This study provides an efficient approach to evaluate the ignition reliability of the pyrotechnic igniter and compared with the traditional Monte Carlo method to verify the accuracy of the results. Finally reliability-based sensitivity indices are presented to quantify the significance of random parameters. It is shown that the influence of the uncertainties can be precisely described and the diameter of the nozzle plays a dominant role in ignition reliability. Additionally ignition experiments of nozzles with different diameters were performed to verify the result of sensitivity. This can further support the detailed design of the pyrotechnic igniter
Research & Innovation for Climate Neutrality 2050: Challenges, Opportunities & the Path Forward
Jan 2024
Publication
Transforming Europe into a climate neutral economy and society by 2050 requires extraordinary efforts and the mobilisation of all sectors and economic actors coupled with all the creative and brain power one can imagine. Each sector has to fundamentally rethink the way it operates to ensure it can be transformed towards this new net-zero paradigm without jeopardising other environmental and societal objectives both within the EU and globally. Given the scale of the transformation ahead our ability to meet climate neutrality targets directly depends on our ability to innovate. In this context Research & Innovation programmes have a key role to play and it is crucial to ensure they are fit for purpose and well equipped to support the next wave of breakthrough innovations that will be required to achieve climate neutrality in the EU and globally by 2050. The objective of this study is to contribute to these strategic planning discussions by not only identifying high-risk and high-impact climate mitigation solutions but most importantly look beyond individual solutions and consider how systemic interactions of climate change mitigation approaches can be integrated in the development of R&I agendas.
Numerical Simulation of the Transport and the Thermodynamic Properties of Imported Natural Gas Inected with Hydrogen in the Manifold
Nov 2023
Publication
Blending hydrogen with natural gas (NG) is an efficient method for transporting hydrogen on a large scale at a low cost. The manifold at the NG initial station is an important piece of equipment that enables the blending of hydrogen with NG. However there are differences in the components and component contents of imported NG from different countries. The components of hydrogen-blended NG can affect the safety and efficiency of transportation through pipeline systems. Therefore numerical simulations were performed to investigate the blending process and changes in the thermodynamic properties of four imported NGs and hydrogen in the manifold. The higher the heavy hydrocarbon content in the imported NG the longer the distance required for the gas to mix uniformly with hydrogen in the pipeline. Hydrogen blending reduces the temperature and density of NG. The gas composition is the main factor affecting the molar calorific value of a gas mixture and hydrogen blending reduces the molar calorific value of NG. The larger the content of high-molar calorific components in the imported NG the higher the molar calorific value of the gas after hydrogen blending. Increasing both the temperature and hydrogen mixing ratio reduces the Joule-Thomson coefficient of the hydrogen-blended NG. The results of this study provide technical references for the transport of hydrogen-blended NG.
Optimization of Renewable Energy Supply Chain for Sustainable Hydrogen Energy Production from Plastic Waste
Dec 2023
Publication
Disposing of plastic waste through burial or burning leads to air pollution issues while also contributing to gas emissions and plastic waste spreading underground into seas via springs. Henceforth this research aims at reducing plastic waste volume while simultaneously generating clean energy. Hydrogen energy is a promising fuel source that holds great value for humanity. However achieving clean hydrogen energy poses challenges including high costs and complex production processes especially on a national scale. This research focuses on Iran as a country capable of producing this energy examining the production process along with related challenges and the general supply chain. These challenges encompass selecting appropriate raw materials based on chosen technologies factory capacities storage methods and transportation flow among different provinces of the country. To deal with these challenges a mixed-integer linear programming model is developed to optimize the hydrogen supply chain and make optimal decisions about the mentioned problems. The supply chain model estimates an average cost—IRR 4 million (approximately USD 8)—per kilogram of hydrogen energy that is available in syngas during the initial period; however subsequent periods may see costs decrease to IRR 1 million (approximately USD 2) factoring in return-on-investment rates.
Optimal Expansion of a Multi-domain Virtual Power Plant for Green Hydrogen Production to Decarbonise Seaborne Passenger Transportation
Nov 2023
Publication
Many industrialised nations recently concentrated their focus on hydrogen as a viable option for the decarbonisation of fossil-intensive sectors including maritime transportation. A sustainable alternative to the conventional production of hydrogen based on fossil hydrocarbons is water electrolysis powered by renewable energy sources. This paper presents a detailed techno-economic optimisation model for sizing an electrolyser and a hydrogen storage embedded in a multi-domain virtual power plant to produce green hydrogen for seaborne passenger transportation. We base our numerical analysis on three years of historical data from a renewable-dominated 60/10 kV substation on the Danish island of Bornholm and on data for ferries to the mainland of Sweden. Our analysis shows that an electrolyser system serves as a valuable flexibility asset on the electrical demand side while supporting the thermal management of the district heating system and contributing to meeting the ferries hydrogen demand. With a sized electrolyser of 9.63 MW and a hydrogen storage of 1.45 t the hydrogen assets are able to take up a large share of the local excess electricity generation. The waste heat of the electrolyser delivers a significant share of 21.4% of the annual district heating demand. Moreover the substation can supply 26% of the hydrogen demand of the ferries from local resources. We further examine the sensitivity of the asset sizing towards investment costs electrolyser efficiency and hydrogen market prices.
Total Cost of Ownership Analysis of Fuel Cell Electric Bus with Different Hydrogen Supply Alternatives
Dec 2023
Publication
In the transition to sustainable public transportation with zero-emission buses hydrogen fuel cell electric buses have emerged as a promising alternative to traditional diesel buses. However assessing their economic viability is crucial for widespread adoption. This study carries out a comprehensive examination encompassing both sensitivity and probabilistic analyses to assess the total cost of ownership (TCO) for the bus fleet and its corresponding infrastructure. It considers various hydrogen supply options encompassing on-site electrolysis on-site steam methane reforming and off-site hydrogen procurement with both gaseous and liquid delivery methods. The analysis covers critical cost elements encompassing bus acquisition costs infrastructure capital expenses and operational and maintenance costs for both buses and infrastructure. This paper conducted two distinct case studies: one involving a current small bus fleet of five buses and another focusing on a larger fleet set to launch in 2028. For the current small fleet the off-site gray hydrogen purchase with a gaseous delivery option is the most cost-effective among hydrogen alternatives but it still incurs a 26.97% higher TCO compared to diesel buses. However in the case of the expanded 2028 fleet the steam methane-reforming method without carbon capture emerges as the most likely option to attain the lowest TCO with a high probability of 99.5%. Additionally carbon emission costs were incorporated in response to the growing emphasis on environmental sustainability. The findings indicate that although diesel buses currently represent the most economical option in terms of TCO for the existing small fleet steam methane reforming with carbon capture presents a 69.2% likelihood of being the most cost-effective solution suggesting it is a strong candidate for cost efficiency for the expanded 2028 fleet. Notably substantial investments are required to increase renewable energy integration in the power grid and to enhance electrolyzer efficiency. These improvements are essential to make the electrolyzer a more competitive alternative to steam methane reforming. Overall the findings in this paper underscore the substantial impact of the hydrogen supply chain and carbon emission costs on the TCO of zero-emission buses.
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