Italy
Fuel Cell Systems for Maritime: A Review of Research Development, Commercial Products, Applications, and Perspectives
Dec 2022
Publication
The ambitious targets set by the International Maritime Organization for reducing greenhouse gas emissions from shipping require radical actions by all relevant stakeholders. In this context the interest in high efficiency and low emissions (even zero in the case of hydrogen) fuel cell technology for maritime applications has been rising during the last decade pushing the research developed by academia and industries. This paper aims to present a comparative review of the fuel cell systems suitable for the maritime field focusing on PEMFC and SOFC technologies. This choice is due to the spread of these fuel cell types concerning the other ones in the maritime field. The following issues are analyzed in detail: (i) the main characteristics of fuel cell systems; (ii) the available technology suppliers; (iii) international policies for fuel cells onboard ships; (iv) past and ongoing projects at the international level that aim to assess fuel cell applications in the maritime industry; (v) the possibility to apply fuel cell systems on different ship types. This review aims to be a reference and a guide to state both the limitations and the developing potential of fuel cell systems for different maritime applications.
Industrial Decarbonization through Blended Combustion of Natural Gas and Hydrogen
Aug 2024
Publication
The transition to cleaner energy sources particularly in hard-to-abate industrial sectors often requires the gradual integration of new technologies. Hydrogen crucial for decarbonization is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen theoretical support is lacking. A novel thermodynamic analysis methodology is introduced evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume necessitating a shift to “totally hydrogen” combustion. Blended combustion can be proposed as a medium-term strategy acknowledging hydrogen’s limited penetration. Higher percentages require burner and infrastructure redesign.
On-site Solar Powered Refueling Stations for Green Hydrogen Production and Distribution: Performances and Costs
Jan 2022
Publication
Today the hydrogen is considered an essential element in speeding up the energy transition and generate important environmental benefits. Not all hydrogen is the same though. The “green hydrogen” which is produced using renewable energy and electrolysis to split water is really and completely sustainable for stationary and mobile applications. This paper is focused on the techno-economic analysis of an on-site hydrogen refueling station (HRS) in which the green hydrogen production is assured by a PV plant that supplies electricity to an alkaline electrolyzer. The hydrogen is stored in low pressure tanks (200 bar) and then is compressed at 900 bar for refueling FCHVs by using the innovative technology of the ionic compressor. From technical point of view the components of the HRS have been sized for assuring a maximum capacity of 450 kg/day. In particular the PV plant (installed in the south of Italy) has a size of 8MWp and supplies an alkaline electrolyzer of 2.1 MW. A Li-ion battery system (size 3.5 MWh) is used to store the electricity surplus and the grid-connection of the PV plant allows to export the electricity excess that cannot be stored in the battery system. The economic analysis has been performed by estimating the levelized cost of hydrogen (LCOH) that is an important economic indicator based on the evaluation of investment operational & maintenance and replacement costs. Results highlighted that the proposed on-site configuration in which the green hydrogen production is assured is characterized by a LCOH of 10.71 €/kg.
Review of Reforming Processes for the Production of Green Hydrogen from Landfill Gas
Dec 2024
Publication
The growing challenges of climate change the depletion of fossil fuel reserves and the urgent need for carbon-neutral energy solutions have intensified the focus on renewable energy. In this perspective the generation of green hydrogen from renewable sources like biogas/landfill gas (LFG) offers an intriguing option providing the dual benefits of a sustainable hydrogen supply and enhanced waste management through energy innovation and valorization. Thus this review explores the production of green hydrogen from biogas/LFG through four conventional reforming processes specifically dry methane reforming (DMR) steam methane reforming (SMR) partial oxidation reforming (POX) and autothermal reforming (ATR) focusing on their mechanisms operating parameters and the role of catalysts in hydrogen production. This review further delves into both the environmental aspects specifically GWP (CO2 eq·kg−1 H2) emissions and the economic aspects of these processes examining their efficiency and impact. Additionally this review also explores hydrogen purification in biogas/LFG reforming and its integration into the CO2 capture utilization and storage roadmap for net-negative emissions. Lastly this review highlights future research directions focusing on improving SMR and DMR biogas/LFG reforming technologies through simulation and modeling to enhance hydrogen production efficiency thereby advancing understanding and informing future research and policy initiatives for sustainable energy solutions.
Hydrogen Application as a Fuel in Internal Combustion Engines
Mar 2023
Publication
Hydrogen is the energy vector that will lead us toward a more sustainable future. It could be the fuel of both fuel cells and internal combustion engines. Internal combustion engines are today the only motors characterized by high reliability duration and specific power and low cost per power unit. The most immediate solution for the near future could be the application of hydrogen as a fuel in modern internal combustion engines. This solution has advantages and disadvantages: specific physical chemical and operational properties of hydrogen require attention. Hydrogen is the only fuel that could potentially produce no carbon carbon monoxide and carbon dioxide emissions. It also allows high engine efficiency and low nitrogen oxide emissions. Hydrogen has wide flammability limits and a high flame propagation rate which provide a stable combustion process for lean and very lean mixtures. Near the stoichiometric air–fuel ratio hydrogen-fueled engines exhibit abnormal combustions (backfire pre-ignition detonation) the suppression of which has proven to be quite challenging. Pre-ignition due to hot spots in or around the spark plug can be avoided by adopting a cooled or unconventional ignition system (such as corona discharge): the latter also ensures the ignition of highly diluted hydrogen–air mixtures. It is worth noting that to correctly reproduce the hydrogen ignition and combustion processes in an ICE with the risks related to abnormal combustion 3D CFD simulations can be of great help. It is necessary to model the injection process correctly and then the formation of the mixture and therefore the combustion process. It is very complex to model hydrogen gas injection due to the high velocity of the gas in such jets. Experimental tests on hydrogen gas injection are many but never conclusive. It is necessary to have a deep knowledge of the gas injection phenomenon to correctly design the right injector for a specific engine. Furthermore correlations are needed in the CFD code to predict the laminar flame velocity of hydrogen–air mixtures and the autoignition time. In the literature experimental data are scarce on air–hydrogen mixtures particularly for engine-type conditions because they are complicated by flame instability at pressures similar to those of an engine. The flame velocity exhibits a non-monotonous behavior with respect to the equivalence ratio increases with a higher unburnt gas temperature and decreases at high pressures. This makes it difficult to develop the correlation required for robust and predictive CFD models. In this work the authors briefly describe the research path and the main challenges listed above.
Environmental Assessment of Hydrogen Utilization in Various Applications and Alternative Renewable Sources for Hydrogen Production: A Review
May 2023
Publication
Rapid industrialization is consuming too much energy and non-renewable energy resources are currently supplying the world’s majority of energy requirements. As a result the global energy mix is being pushed towards renewable and sustainable energy sources by the world’s future energy plan and climate change. Thus hydrogen has been suggested as a potential energy source for sustainable development. Currently the production of hydrogen from fossil fuels is dominant in the world and its utilization is increasing daily. As discussed in the paper a large amount of hydrogen is used in rocket engines oil refining ammonia production and many other processes. This paper also analyzes the environmental impacts of hydrogen utilization in various applications such as iron and steel production rocket engines ammonia production and hydrogenation. It is predicted that all of our fossil fuels will run out soon if we continue to consume them at our current pace of consumption. Hydrogen is only ecologically friendly when it is produced from renewable energy. Therefore a transition towards hydrogen production from renewable energy resources such as solar geothermal and wind is necessary. However many things need to be achieved before we can transition from a fossil-fuel-driven economy to one based on renewable energy
Energy and Economic Advantages of Using Solar Stills for Renewable Energy-Based Multi-Generation of Power and Hydrogen for Residential Buildings
Apr 2024
Publication
The multi-generation systems with simultaneous production of power by renewable energy in addition to polymer electrolyte membrane electrolyzer and fuel cell (PEMFC-PEMEC) energy storage have become more and more popular over the past few years. The fresh water provision for PEMECs in such systems is taken into account as one of the main challenges for them where conventional desalination technologies such as reverse osmosis (RO) and mechanical vapor compression (MVC) impose high electricity consumption and costs. Taking this point into consideration as a novelty solar still (ST) desalination is applied as an alternative to RO and MVC for better techno-economic justifiability. The comparison made for a residential building complex in Hawaii in the US as the case study demonstrated much higher technical and economic benefits when using ST compared with both MVC and RO. The photovoltaic (PV) installed capacity decreased by 11.6 and 7.3 kW compared with MVC and RO while the size of the electrolyzer declined by 9.44 and 6.13% and the hydrogen storage tank became 522.1 and 319.3 m3 smaller respectively. Thanks to the considerable drop in the purchase price of components the payback period (PBP) dropped by 3.109 years compared with MVC and 2.801 years compared with RO which is significant. Moreover the conducted parametric study implied the high technical and economic viability of the system with ST for a wide range of building loads including high values.
Energy Consumption and Saved Emissions of a Hydrogen Power System for Ultralight Aviation: A Case Study
Jul 2024
Publication
The growing concern about climate change and the contemporary increase in mobility requirements call for faster cheaper safer and cleaner means of transportation. The retrofitting of fossil-fueled piston engine ultralight aerial vehicles to hydrogen power systems is an option recently proposed in this direction. The goal of this investigation is a comparative analysis of the environmental impact of conventional and hydrogen-based propulsive systems. As a case study a hybrid electric configuration consisting of a fuel cell with a nominal power of about 30 kW a 6 kWh LFP battery and a pressurized hydrogen vessel is proposed to replace a piston prop configuration for an ultralight aerial vehicle. Both power systems are modeled with a backward approach that allows the efficiency of the main components to be evaluated based on the load and altitude at every moment of the flight with a time step of 1 s. A typical 90 min flight mission is considered for the comparative analysis which is performed in terms of direct and indirect emissions of carbon dioxide water and pollutant substances. For the hydrogen-based configuration two possible strategies are adopted for the use of the battery: charge sustaining and charge depleting. Moreover the effect of the altitude on the parasitic power of the fuel cell compressor and consequently on the net efficiency of the fuel cell system is taken into account. The results showed that even if the use of hydrogen confines the direct environmental impact to the emission of water (in a similar quantity to the fossil fuel case) the indirect emissions associated with the production transportation and delivery of hydrogen and electricity compromise the desired achievement of pollutant-free propulsion in terms of equivalent emissions of CO2 and VOCs if hydrogen is obtained from natural gas reforming. However in the case of green hydrogen from electrolysis with wind energy the total (direct and indirect) emissions of CO2 can be reduced up to 1/5 of the fossil fuel case. The proposed configuration has the additional advantage of eliminating the problem of lead which is used as an additive in the AVGAS 100LL.
Flashback Propensity due to Hydrogen Blending in Natural Gas: Sensitivity to Operating and Geometrical Parameters
Jan 2024
Publication
Hydrogen has emerged as a promising option for promoting decarbonization in various sectors by serving as a replacement for natural gas while retaining the combustion-based conversion system. However its higher reactivity compared to natural gas introduces a significant risk of flashback. This study investigates the impact of operating and geometry parameters on flashback phenomena in multi-slit burners fed with hydrogenmethane-air mixtures. For this purpose transient numerical simulations which take into account conjugate heat transfer between the fluid and the solid walls are coupled with stochastic sensitivity analysis based on Generalized Polynomial Chaos. This allows deriving comprehensive maps of flashback velocities and burner temperatures within the parameter space of hydrogen content equivalence ratio and slit width using a limited number of numerical simulations. Moreover we assess the influence of different parameters and their interactions on flashback propensity. The ranges we investigate encompass highly H2 -enriched lean mixtures ranging from 80% to 100% H2 by volume with equivalence ratios ranging from 0.5 to 1.0. We also consider slit widths that are typically encountered in burners for end-user devices ranging from 0.5 mm to 1.2 mm. The study highlights the dominant role of preferential diffusion in affecting flashback physics and propensity as parameters vary including significant enrichment close to the burner plate due to the Soret effect. These findings hold promise for driving the design and optimization of perforated burners enabling their safe and efficient operation in practical end-user applications.
Hydrogen Consumption and Durability Assessment of Fuel Cell Vehicles in Realistic Driving
Jan 2024
Publication
This study proposes a predictive equivalent consumption minimization strategy (P-ECMS) that utilizes velocity prediction and considers various dynamic constraints to mitigate fuel cell degradation assessed using a dedicated sub-model. The objective is to reduce fuel consumption in real-world conditions without prior knowledge of the driving mission. The P-ECMS incorporates a velocity prediction layer into the Energy Management System. Comparative evaluations with a conventional adaptive-ECMS (A-ECMS) a standard ECMS with a well-tuned constant equivalence factor and a rule-based strategy (RBS) are conducted across two driving cycles and three fuel cell dynamic restrictions (|∕| ≤ 0.1 0.01 and 0.001 A∕cm2 ). The proposed strategy achieves H2 consumption reductions ranging from 1.4% to 3.0% compared to A-ECMS and fuel consumption reductions of up to 6.1% when compared to RBS. Increasing dynamic limitations lead to increased H2 consumption and durability by up to 200% for all tested strategies.
European Hydrogen Train the Trainer Framework for Responders: Outcomes of the Hyresponder Project
Sep 2023
Publication
Síle Brennan,
Didier Bouix,
Christian Brauner,
Dominic Davis,
Natalie DeBacker,
Alexander Dyck,
André Vagner Gaathaug,
César García Hernández,
Laurence Grand-Clement,
Etienne Havret,
Deborah Houssin-Agbomson,
Petr Kupka,
Laurent Lecomte,
Eric Maranne,
Vladimir V. Molkov,
Pippa Steele,
Adolfo Pinilla,
Paola Russo and
Gerhard Schoepf
HyResponder is a European Hydrogen Train the Trainer programme for responders. This paper describes the key outputs of the project and the steps taken to develop and implement a long-term sustainable train the trainer programme in hydrogen safety for responders across Europe and beyond. This FCH2 JU (now Clean Hydrogen Joint Undertaking) funded project has built on the successful outcomes of the previous HyResponse project. HyResponder has developed further and updated educational operational and virtual reality training for trainers of responders to reflect the state-of-the-art in hydrogen safety including liquid hydrogen and expand the programme across Europe and specifically within the 10 countries represented directly within the project consortium: Austria Belgium the Czech Republic France Germany Italy Norway Spain Switzerland and the United Kingdom. For the first time four levels of educational materials from fire fighter through to specialist have been developed. The digital training resources are available on the e-Platform (https://hyresponder.eu/e-platform/). The revised European Emergency Response Guide is now available to all stakeholders. The resources are intended to be used to support national training programs. They are available in 8 languages: Czech Dutch English French German Italian Norwegian and Spanish. Through the HyResponder activities trainers from across Europe have undertaken joint actions which are in turn being used to inform the delivery of regional and national training both within and beyond the project. The established pan-European network of trainers is shaping the future in the important for inherently safer deployment of hydrogen systems and infrastructure across Europe and enhancing the reach and impact of the programme.
Conversion of a Small-Size Passenger Car to Hydrogen Fueling: 0D/1D Simulation of EGR and Related Flow Limitations
Jan 2024
Publication
Hydrogen is seen as a prime choice for complete replacement of gasoline so as to achieve zero-emissions energy and mobility. Combining the use of this alternative fuel with a circular economy approach for giving new life to the existing fleet of passenger cars ensures further benefits in terms of cost competitiveness. Transforming spark ignition (SI) engines to H2 power requires relatively minor changes and limited added components. Within this framework the conversion of a small-size passenger car to hydrogen fueling was evaluated based on 0D/1D simulation. One of the methods to improve efficiency is to apply exhaust gas recirculation (EGR) which also lowers NOx emissions. Therefore the previous version of the quasi-dimensional model was modified to include EGR and its effects on combustion. A dedicated laminar flame speed model was implemented for the specific properties of hydrogen and a purpose-built sub-routine was implemented to correctly model the effects of residual gas at the start of combustion. Simulations were performed in several operating points representative of urban and highway driving. One of the main conclusions was that highpressure recirculation was severely limited by the minimum flow requirements of the compressor. Low-pressure EGR ensured wider applicability and significant improvement of efficiency especially during partial-load operation specific to urban use. Another benefit of recirculation was that pressure rise rates were predicted to be more contained and closer to the values expected for gasoline fueling. This was possible due to the high tolerance of H2 to the presence of residual gas.
Enhancing Waste-to-Energy and Hydrogen Production through Urban–Industrial Symbiosis: A Multi-Objective Optimisation Model Incorporating a Bayesian Best-Worst Method
Feb 2024
Publication
A surging demand for sustainable energy and the urgency to lower greenhouse gas emissions is driving industrial systems towards more eco-friendly and cost-effective models. Biogas from agricultural and municipal organic waste is gaining momentum as a renewable energy source. Concurrently the European Hydrogen Strategy focuses on green hydrogen for decarbonising the industrial and transportation sectors. This paper presents a multi-objective network design model for urban–industrial symbiosis incorporating anaerobic digestion cogeneration photovoltaic and hydrogen production technologies. Additionally a Bayesian best-worst method is used to evaluate the weights of the sustainability aspects by decision-makers integrating these into the mathematical model. The model optimises industrial plant locations considering economic environmental and social parameters including the net present value energy consumption and carbon footprint. The model’s functionalities are demonstrated through a real-world case study based in Emilia Romagna Italy. It is subject to sensitivity analysis to evaluate how changes in the inputs affect the outcomes and highlights feasible trade-offs through the exploration of the ϵ-constraint. The findings demonstrate that the model substantially boosts energy and hydrogen production. It is not only economically viable but also reduces the carbon footprint associated with fossil fuels and landfilling. Additionally it contributes to job creation. This research has significant implications with potential future studies intended to focus on system resilience plant location optimisation and sustainability assessment.
Assessing Opportunities and Weaknesses of Green Hydrogen Transport via LOHC through a Detailed Techno-economic Analysis
Aug 2023
Publication
In the transition towards a more sustainable energy system hydrogen is seen as the key low-emission energy source. However the limited H2 volumetric density hinders its transportation. To overcome this issue liquid organic hydrogen carriers (LOHCs) molecules that can be hydrogenated and upon arrival dehydrogenated for H2 release have been proposed as hydrogen transport media. Considering toluene and dibenzyltoluene as representative carriers this work offers a systematic methodology for the analysis and the comparison of LOHCs in view of identifying cost-drivers of the overall value-chain. A detailed Aspen Plus process simulation is provided for hydrogenation and dehydrogenation sections. Simulation results are used as input data for the economic assessment. The process economics reveals that dehydrogenation is the most impactful cost-item together with the carrier initial loading the latter related to the LOHC transport distance. The choice of the most suitable molecule as H2 carrier ultimately is a trade-off between its hydrogenation enthalpy and cost.
The Potential Role of Ammonia for Hydrogen Storage and Transport: A Critical Review of Challenges and Opportunities
Aug 2023
Publication
Hydrogen is being included in several decarbonization strategies as a potential contributor in some hard-to-abate applications. Among other challenges hydrogen storage represents a critical aspect to be addressed either for stationary storage or for transporting hydrogen over long distances. Ammonia is being proposed as a potential solution for hydrogen storage as it allows storing hydrogen as a liquid chemical component at mild conditions. Nevertheless the use of ammonia instead of pure hydrogen faces some challenges including the health and environmental issues of handling ammonia and the competition with other markets such as the fertilizer market. In addition the technical and economic efficiency of single steps such as ammonia production by means of the Haber–Bosch process ammonia distribution and storage and possibly the ammonia cracking process to hydrogen affects the overall supply chain. The main purpose of this review paper is to shed light on the main aspects related to the use of ammonia as a hydrogen energy carrier discussing technical economic and environmental perspectives with the aim of supporting the international debate on the potential role of ammonia in supporting the development of hydrogen pathways. The analysis also compares ammonia with alternative solutions for the long-distance transport of hydrogen including liquefied hydrogen and other liquid organic carriers such as methanol.
Modelling Methodologies to Design and Control Renewables and Hydrogen-Based Telecom Towers Power Supply Systems
Aug 2023
Publication
Proton exchange membrane fuel cell (PEMFCS) and electrolyser (PEMELS) systems together with a hydrogen storage tank (HST) are suitable to be integrated with renewable microgrids to cover intermittency and fully exploit the excess of electrical energy. Such an integration perfectly fits telecom tower power supply needs both in off-grid and grid-connected sites. In this framework a model-based tool enabling both optimal sizing and proper year-through energy management of both the above applications is proposed. Respectively the islanded optimisation is performed considering two economic indices i.e. simple payback (SPB) and levelised cost of energy (LCOE) together with two strategies of hydrogen tank management charge sustaining and depleting and also accounting for the impact of grid extension distance. On the other hand the grid connection is addressed through the dynamic programming method while downsizing PEMELS and HST sizes to improve techno-economic effectiveness thanks to grid contribution towards renewables curtailment issues mitigation. For both the above introduced HST management strategies a reduction of more than 70% of the nominal PEMELS power and 90% of the HST size which will in turn lead to SPB and LCOE being reduced by 80% and 60% in comparison to the islanded case respectively is achieved. Furthermore the charge depleting strategy relying on possible hydrogen purchase interestingly provides an SPB and LCOE of 9% and 7% lower than the charge sustaining one.
Carbon Footprint Enhancement of an Agricultural Telehandler through the Application of a Fuel Cell Powertrain
Mar 2024
Publication
The growing awareness about climate change and environmental pollution is pushing the industrial and academic world to investigate more sustainable solutions to reduce the impact of anthropic activities. As a consequence a process of electrification is involving all kind of vehicles with a view to gradually substitute traditional powertrains that emit several pollutants in the exhaust due to the combustion process. In this context fuel cell powertrains are a more promising strategy with respect to battery electric alternatives where productivity and endurance are crucial. It is important to replace internal combustion engines in those vehicles such as the those in the sector of NonRoad Mobile Machinery. In the present paper a preliminary analysis of a fuel cell powertrain for a telehandler is proposed. The analysis focused on performance fuel economy durability applicability and environmental impact of the vehicle. Numerical models were built in MATLAB/Simulink and a simple power follower strategy was developed with the aim of reducing components degradation and to guarantee a charge sustaining operation. Simulations were carried out regarding both peak power conditions and a typical real work scenario. The simulations’ results showed that the fuel cell powertrain was able to achieve almost the same performances without excessive stress on its components. Indeed a degradation analysis was conducted showing that the fuel cell system can achieve satisfactory durability. Moreover a Well-to-Wheel approach was adopted to evaluate the benefits in terms of greenhouse gases of adopting the fuel cell system. The results of the analysis demonstrated that even if considering grey hydrogen to feed the fuel cell system the proposed powertrain can reduce the equivalent CO2 emissions of 69%. This reduction can be further enhanced using hydrogen from cleaner production processes. The proposed preliminary analysis demonstrated that fuel cell powertrains can be a feasible solution to substitute traditional systems on off-road vehicles even if a higher investment cost might be required.
How Can Green Hydrogen from North Africa Support EU Decarbonization? Scenario Analyses on Competitive Pathways for Trade
Jul 2024
Publication
The carbon-neutrality target set by the European Union for 2050 drives the increasing relevance of green hydrogen as key player in the energy transition. This work uses the JRC-EU-TIMES energy system model to assess opportunities and challenges for green hydrogen trade from North Africa to Europe analysing to what extent it can support its decarbonization. An important novelty is addressing uncertainty regarding hydrogen economy development. Alternative scenarios are built considering volumes available for import production costs and transport options affecting hydrogen cost-effectiveness. Both pipelines and ships are modelled assuming favourable market conditions and pessimistic ones. From 2040 on all available North African hydrogen is imported regardless of its costs. In Europe this imported hydrogen is mainly converted into synfuels and heat. The study aims to support policymakers to implement effective strategies focusing on the crucial role of green hydrogen in the decarbonization process if new competitive cooperations are developed.
Sustainable Fuel Production Using In-situ Hydrogen Supply via Aqueous Phase Reforming: A Techno-economic and Life-cycle Greenhouse Gas Emissions Assessment
Jul 2023
Publication
Sustainable aviation fuel (SAF) production is one of the strategies to guarantee an environmental-friendly development of the aviation sector. This work evaluates the technical economic and environmental feasibility of obtaining SAFs by hydrogenation of vegetable oils thanks to in-situ hydrogen production via aqueous phase reforming (APR) of glycerol by-product. The novel implementation of APR would avoid the environmental burden of conventional fossil-derived hydrogen production as well as intermittency and storage issues related to the use of RES-based (renewable energy sources) electrolysers. The conceptual design of a conventional and advanced (APR-aided) biorefinery was performed considering a standard plant capacity equal to 180 ktonne/y of palm oil. For the advanced scenario the feed underwent hydrolysis into glycerol and fatty acids; hence the former was subjected to APR to provide hydrogen which was further used in the hydrotreatment reactor where the fatty acids were deoxygenated. The techno-economic results showed that APR implementation led to a slight increase of the fixed capital investment by 6.6% compared to the conventional one while direct manufacturing costs decreased by 22%. In order to get a 10% internal rate of return the minimum fuel selling price was found equal to 1.84 $/kg which is 17% lower than the one derived from conventional configurations (2.20 $/kg). The life-cycle GHG emission assessment showed that the carbon footprint of the advanced scenario was equal to ca. 12 g CO2/MJSAF i.e. 54% lower than the conventional one (considering an energy-based allocation). The sensitivity analysis pointed out that the cost of the feedstock SAF yield and the chosen plant size are keys parameters for the marketability of this biorefinery while the energy price has a negligible impact; moreover the source of hydrogen has significant consequences on the environmental footprint of the plant. Finally possible uncertainties for both scenarios were undertaken via Monte Carlo simulations.
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.
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