Denmark
NewGasMet - Flow Metering of Renewable Gases (Biogas, Biomethane, Hydrogen, Syngas and Mixtures with Natural Gas): Effect of Hydrogen Admixture on the Accuracy of a Rotary Flow Meter
Aug 2021
Publication
With the rise of hydrogen use in the natural gas grid a need exists for reliable measurements of the amount of energy being transported and traded for hydrogen admixtures. Using VSL’s high-pressure Gas Oil Piston Prover (GOPP) primary standard the effect of mixing hydrogen with natural gas on the performance of a high-pressure gas flow meter was investigated. The error of a rotary flow meter was determined using the best possible uncertainty by calibration with the primary standard for high-pressure natural gas flow. The rotary flow meter was calibrated using both natural gas and hydrogen enriched natural gas (nominally 15% hydrogen) at two different pressures: 9 and 16 bar. Results indicate that for the rotary flow meter and hydrogen admixtures used the differences in the meter errors between high-pressure hydrogen-enriched natural gas calibration and high-pressure natural gas calibration are smaller than the corresponding differences between atmospheric pressure air calibration and high-pressure natural gas calibration.
Feasibility of Hydrogen Storage in Depleted Hydrocarbon Chalk Reservoirs: Assessment of Biochemical and Chemical Effects
Jul 2022
Publication
Hydrogen storage is one of the energy storage methods that can help realization of an emission free future by saving surplus renewable energy for energy deficit periods. Utilization of depleted hydrocarbon reservoirs for large-scale hydrogen storage may be associated with the risk of chemical/biochemical reactions. In the specific case of chalk reservoirs the principal reactions are abiotic calcite dissolution acetogenesis methanogenesis and biological souring. Here we use PHREEQC to evaluate the dynamics and the extent of hydrogen loss by each of these reactions in hydrogen storage scenarios for various Danish North Sea chalk hydrocarbon reservoirs. We find that: (i) Abiotic calcite dissolution does not occur in the temperature range of 40-180◦ C. (ii) If methanogens and acetogens grow as slow as the slowest growing methanogens and acetogens reported in the literature methanogenesis and acetogenesis cannot cause a hydrogen loss more than 0.6% per year. However (iii) if they proceed as fast as the fastest growing methanogens and acetogens reported in the literature a complete loss of all injected hydrogen in less than five years is possible. (iv) Co-injection of CO2 can be employed to inhibit calcite dissolution and keep the produced methane due to methanogenesis carbon neutral. (v) Biological sulfate reduction does not cause significant hydrogen loss during 10 years but it can lead to high hydrogen sulfide concentrations (1015 ppm). Biological sulfate reduction is expected to impact hydrogen storage only in early stages if the only source of sulfur substrates are the dissolved species in the brine and not rock minerals. Considering these findings we suggest that depleted chalk reservoirs may not possess chemical/biochemical risks and be good candidates for large-scale underground hydrogen storage.
Overview of First Outcomes of PNR Project HYTUNNEL-CS
Sep 2021
Publication
Dmitry Makarov,
Donatella Cirrone,
Volodymyr V. Shentsov,
Sergii Kashkarov,
Vladimir V. Molkov,
Z. Xu,
Mike Kuznetsov,
Alexandros G. Venetsanos,
Stella G. Giannissi,
Ilias C. Tolias,
Knut Vaagsaether,
André Vagner Gaathaug,
Mark R. Pursell,
W. M. Rattigan,
Frank Markert,
Luisa Giuliani,
L.S. Sørensen,
A. Bernad,
Mercedes Sanz Millán,
U. Kummer,
C. Brauner,
Paola Russo,
J. van den Berg,
F. de Jong,
Tom Van Esbroeck,
M. Van De Veire,
D. Bouix,
Gilles Bernard-Michel,
Sergey Kudriakov,
Etienne Studer,
Domenico Ferrero,
Joachim Grüne and
G. Stern
The paper presents the first outcomes of the experimental numerical and theoretical studies performed in the funded by Fuel Cell and Hydrogen Joint Undertaking (FCH2 JU) project HyTunnel-CS. The project aims to conduct pre-normative research (PNR) to close relevant knowledge gaps and technological bottlenecks in the provision of safety of hydrogen vehicles in underground transportation systems. Pre normative research performed in the project will ultimately result in three main outputs: harmonised recommendations on response to hydrogen accidents recommendations for inherently safer use of hydrogen vehicles in underground traffic systems and recommendations for RCS. The overall concept behind this project is to use inter-disciplinary and inter-sectoral prenormative research by bringing together theoretical modelling and experimental studies to maximise the impact. The originality of the overall project concept is the consideration of hydrogen vehicle and underground traffic structure as a single system with integrated safety approach. The project strives to develop and offer safety strategies reducing or completely excluding hydrogen-specific risks to drivers passengers public and first responders in case of hydrogen vehicle accidents within the currently available infrastructure.
THyGA - Intermediate Report on the Test of Technologies by Segment – Impact of the Different H2 Concentrations on Safety, Efficiency, Emissions and Correct Operation
Jan 2022
Publication
This report is the very first version of the document that will present the THyGA short-term test. These tests are carried out to observe how appliances react in the short term (few minutes to few hours) on different H2NG mixtures and long-term test are observing behaviour over several weeks. The analysis is based on the test of about 20 appliances only and is not yet covering extensively all the segments of the project. However most of the aspects of the testing are included in the present version that shall be considered as a draft working document to prepare the final report. We have tried to incorporate all aspects that are important to us but there may be more aspects and more analyses that could be added and will be added in the light of the comments and corrections we will gather after the dissemination of the document.
Techno-economic Assessment of Green Ammonia Production with Different Wind and Solar Potentials
Nov 2022
Publication
This paper focuses on developing a fast-solving open-source model for dynamic power-to-X plant techno-economic analysis and analysing the method bias that occurs when using other state-of-the-art power-to-X cost calculation methods. The model is a least-cost optimisation of investments and operation-costs taking as input techno-economic data varying power profiles and hourly grid prices. The fuel analysed is ammonia synthesised from electrolytic hydrogen produced with electricity from photovoltaics wind turbines or the grid. Various weather profiles and electrolyser technologies are compared. The calculated costs are compared with those derived using methods and assumptions prevailing in most literature. Optimisation results show that a semi-islanded set-up is the cheapest option and can reduce the costs up to 23% compared to off-grid systems but leads to e-fuels GHG emissions similar to fossil fuels with today’s electricity blend. For off-grid systems estimating costs using solar or wind levelized cost of electricity and capacity factors to derive operating hours leads to costs overestimation up to 30%. The cheapest off-grid configuration reaches production costs of 842 e/t3 . For comparison the "grey" ammonia price was 250 e/t3 in January 2021 and 1500 e/t3 in April 2022 (Western Europe). The optimal power mix is found to always include photovoltaic with 1-axis tracking and sometimes different types of onshore wind turbines at the same site. For systems fully grid connected approximating a highly fluctuating electricity price by a yearly average and assuming a constant operation leads to a small cost.
Regional Uptake of Direct Reduction Iron Production Using Hydrogen Under Climate Policy
Nov 2022
Publication
The need to reduce CO2 emissions to zero by 2050 has meant an increasing focus on high emitting industrial sectors such as steel. However significant uncertainties remain as to the rate of technology diffusion across steel production pathways in different regions and how this might impact on climate ambition. Informed by empirical analysis of historical transitions this paper presents modelling on the regional deployment of Direction Reduction Iron using hydrogen (DRI-H2). We find that DRI-H2 can play a leading role in the decarbonisation of the sector leading to near-zero emissions by 2070. Regional spillovers from early to late adopting regions can speed up the rate of deployment of DRI-H2 leading to lower cumulative emissions and system costs. Without such effects cumulative emissions are 13% higher than if spillovers are assumed and approximately 15% and 20% higher in China and India respectively. Given the estimates of DRI-H2 cost-effectiveness relative to other primary production technologies we also find that costs increase in the absence of regional spillovers. However other factors can also have impacts on deployment emission reductions and costs including the composition of the early adopter group material efficiency improvements and scrap recycling rates. For the sector to achieve decarbonisation key regions will need to continue to invest in low carbon steel projects recognising their broader global benefit and look to develop and strengthen policy coordination on technologies such as DRI-H2.
Modelling and Experimental Analysis of a Polymer Electrolyte Membrane Water Electrolysis Cell at Different Operating Temperatures
Nov 2018
Publication
In this paper a simplified model of a Polymer Electrolyte Membrane (PEM) water electrolysis cell is presented and compared with experimental data at 60 ◦C and 80 ◦C. The model utilizes the same modelling approach used in previous work where the electrolyzer cell is divided in four subsections: cathode anode membrane and voltage. The model of the electrodes includes key electrochemical reactions and gas transport mechanism (i.e. H2 O2 and H2O) whereas the model of the membrane includes physical mechanisms such as water diffusion electro osmotic drag and hydraulic pressure. Voltage was modelled including main overpotentials (i.e. activation ohmic concentration). First and second law efficiencies were defined. Key empirical parameters depending on temperature were identified in the activation and ohmic overpotentials. The electrodes reference exchange current densities and change transfer coefficients were related to activation overpotentials whereas hydrogen ion diffusion to Ohmic overvoltages. These model parameters were empirically fitted so that polarization curve obtained by the model predicted well the voltage at different current found by the experimental results. Finally from the efficiency calculation it was shown that at low current densities the electrolyzer cell absorbs heat from the surroundings. The model is not able to describe the transients involved during the cell electrochemical reactions however these processes are assumed relatively fast. For this reason the model can be implemented in system dynamic modelling for hydrogen production and storage where components dynamic is generally slower compared to the cell electrochemical reactions dynamics.
Hydrogen-based Systems for Integration of Renewable Energy in Power Systems: Achievements and Perspectives
Jul 2021
Publication
This paper is a critical review of selected real-world energy storage systems based on hydrogen ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with short-term energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system.<br/>Therefore control systems and energy management strategies are important factors to achieve optimal results both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems new hybrid energy systems could be tailored to fit each situation and to reduce energy losses.
Balancing Wind-power Fluctuation Via Onsite Storage Under Uncertainty Power-to-hydrogen-to-power Versus Lithium Battery
Oct 2019
Publication
Imbalance costs caused by forecasting errors are considerable for grid-connected wind farms. In order to reduce such costs two onsite storage technologies i.e. power-to-hydrogen-to-power and lithium battery are investigated considering 14 uncertain technological and economic parameters. Probability density distributions of wind forecasting errors and power level are first considered to quantify the imbalance and excess wind power. Then robust optimal sizing of the onsite storage is performed under uncertainty to maximize wind-farm profit (the net present value). Global sensitivity analysis is further carried out for parameters prioritization to highlight the key influential parameters. The results show that the profit of power-to-hydrogen-to-power case is sensitive to the hydrogen price wind forecasting accuracy and hydrogen storage price. When hydrogen price ranges in (2 6) €/kg installing only electrolyzer can earn profits over 100 k€/MWWP in 9% scenarios with capacity below 250 kW/MWWP under high hydrogen price (over 4 €/kg); while installing only fuel cell can achieve such high profits only in 1.3% scenarios with capacity below 180 kW/MWWP. Installing both electrolyzer and fuel cell (only suggested in 22% scenarios) results in profits below 160 k€/MWWP and particularly 20% scenarios allow for a profit below 50 k€/MWWP due to the contradictory effects of wind forecasting error hydrogen and electricity price. For lithium battery investment cost is the single highly influential factor which should be reduced to 760 €/kWh. The battery capacity is limited to 88 kW h/MWWP. For profits over 100 k€/MWWP (in 3% scenarios) the battery should be with an investment cost below 510 €/kWh and a depth of discharge over 63%. The power-to-hydrogen-to-power case is more advantageous in terms of profitability reliability and utilization factor (full-load operating hours) while lithium battery is more helpful to reduce the lost wind and has less environmental impact considering current hydrogen market.
Dedicated Large-scale Floating Offshore Wind to Hydrogen: Assessing Design Variables in Proposed Typologies
Mar 2022
Publication
To achieve the Net-Zero Emissions goal by 2050 a major upscale in green hydrogen needs to be achieved; this will also facilitate use of renewable electricity as a source of decarbonised fuel in hard-to-abate sectors such as industry and transport. Nearly 80% of the world’s offshore wind resource is in waters deeper than 60 m where bottom-fixed wind turbines are not feasible. This creates a significant opportunity to couple the high capacity factor floating offshore wind and green hydrogen. In this paper we consider dedicated large-scale floating offshore wind farms for hydrogen production with three coupling typologies; (i) centralised onshore electrolysis (ii) decentralised offshore electrolysis and (iii) centralised offshore electrolysis. The typology design is based on variables including for: electrolyser technology; floating wind platform; and energy transmission vector (electrical power or offshore hydrogen pipelines). Offshore hydrogen pipelines are assessed as economical for large and distant farms. The decentralised offshore typology employing a semi-submersible platform could accommodate a proton exchange membrane electrolyser on deck; this would negate the need for an additional separate structure or hydrogen export compression and enhance dynamic operational ability. It is flexible; if one electrolyser (or turbine) fails hydrogen production can easily continue on the other turbines. It also facilities flexibility in further expansion as it is very much a modular system. Alternatively less complexity is associated with the centralised offshore typology which may employ the electrolysis facility on a separate offshore platform and be associated with a farm of spar-buoy platforms in significant water depth locations.
Complex Hydrides for Hydrogen Storage – New Perspectives
Apr 2014
Publication
Since the 1970s hydrogen has been considered as a possible energy carrier for the storage of renewable energy. The main focus has been on addressing the ultimate challenge: developing an environmentally friendly successor for gasoline. This very ambitious goal has not yet been fully reached as discussed in this review but a range of new lightweight hydrogen-containing materials has been discovered with fascinating properties. State-of-the-art and future perspectives for hydrogen-containing solids will be discussed with a focus on metal borohydrides which reveal significant structural flexibility and may have a range of new interesting properties combined with very high hydrogen densities.
At What Cost Can Renewable Hydrogen Offset Fossil Fuel Use in Ireland’s Gas Network?
Apr 2020
Publication
The results of a techno-economic model of distributed wind-hydrogen systems (WHS) located at each existing wind farm on the island of Ireland are presented in this paper. Hydrogen is produced by water electrolysis from wind energy and backed up by grid electricity compressed before temporarily stored then transported to the nearest injection location on the natural gas network. The model employs a novel correlation-based approach to select an optimum electrolyser capacity that generates a minimum levelised cost of hydrogen production (LCOH) for each WHS. Three scenarios of electrolyser operation are studied: (1) curtailed wind (2) available wind and (3) full capacity operations. Additionally two sets of input parameters are used: (1) current and (2) future techno-economic parameters. Additionally two electricity prices are considered: (1) low and (2) high prices. A closest facility algorithm in a geographic information system (GIS) package identifies the shortest routes from each WHS to its nearest injection point. By using current parameters results show that small wind farms are not suitable to run electrolysers under available wind operation. They must be run at full capacity to achieve sufficiently low LCOH. At full capacity the future average LCOH is 6–8 €/kg with total hydrogen production capacity of 49 kilotonnes per year or equivalent to nearly 3% of Irish natural gas consumption. This potential will increase significantly due to the projected expansion of installed wind capacity in Ireland from 5 GW in 2020 to 10 GW in 2030
“Bigger than Government”: Exploring the Social Construction and Contestation of Net-zero Industrial Megaprojects in England
Jan 2023
Publication
Industry is frequently framed as hard-to-decarbonize given its diversity of requirements technologies and supply chains many of which are unique to particular sectors. Net zero commitments since 2019 have begun to challenge the carbon intensity of these various industries but progress has been slow globally. Against this backdrop the United Kingdom has emerged as a leader in industrial decarbonization efforts. Their approach is based on industrial clusters which cut across engineering spatial and socio-political dimensions. Two of the largest of these clusters in England in terms of industrial emissions are the Humber and Merseyside. In this paper drawn from a rich mixed methods original dataset involving expert interviews (N = 46 respondents) site visits (N = 20) a review of project documents and the academic literature we explore ongoing efforts to decarbonize both the Humber and Merseyside through the lens of spatially expansive and technically complex megaprojects. Both have aggressive implementation plans in place for the deployment of net-zero infrastructure with Zero Carbon Humber seeking billions in investment to build the country’s first large-scale bioenergy with carbon capture and storage (BECCS) plant alongside a carbon transport network and hydrogen production infrastructure and HyNet seeking billions in investment to build green and blue hydrogen facilities along with a carbon storage network near Manchester and Liverpool. We draw from the social construction of technology (SCOT) literature to examine the relevant social groups interpretive flexibility and patterns of closure associated with Zero Carbon Humber and HyNet. We connect our findings to eight interpretive frames surrounding the collective projects and make connections to problems contestation and closure.
Optimal Scheduling of a Hydrogen-Based Energy Hub Considering a Stochastic Multi-Attribute Decision-Making Approach
Jan 2023
Publication
Nowadays the integration of multi-energy carriers is one of the most critical matters in smart energy systems with the aim of meeting sustainable energy development indicators. Hydrogen is referred to as one of the main energy carriers in the future energy industry but its integration into the energy system faces different open challenges which have not yet been comprehensively studied. In this paper a novel day-ahead scheduling is presented to reach the optimal operation of a hydrogen-based energy hub based on a stochastic multi-attribute decision-making approach. In this way the energy hub model is first developed by providing a detailed model of Power-to-Hydrogen (P2H) facilities. Then a new multi-objective problem is given by considering the prosumer’s role in the proposed energy hub model as well as the integrated demand response program (IDRP). The proposed model introduces a comprehensive approach from the analysis of the historical data to the final decision-making with the aim of minimizing the system operation cost and carbon emission. Moreover to deal with system uncertainty the scenario-based method is applied to model the renewable energy resources fluctuation. The proposed problem is defined as mixed-integer non-linear programming (MINLP) and to solve this problem a simple augmented e-constrained (SAUGMECON) method is employed. Finally the simulation of the proposed model is performed on a case study and the obtained results show the effectiveness and benefits of the proposed scheme.
Onshore, Offshore or In-turbine Electrolysis? Techno-economic Overview of Alternative Integration Designs for Green Hydrogen Production into Offshore Wind Power Hubs
Aug 2021
Publication
Massive investments in offshore wind power generate significant challenges on how this electricity will be integrated into the incumbent energy systems. In this context green hydrogen produced by offshore wind emerges as a promising solution to remove barriers towards a carbon-free economy in Europe and beyond. Motivated by the recent developments in Denmark with the decision to construct the world’s first artificial Offshore Energy Hub this paper investigates how the lowest cost for green hydrogen can be achieved. A model proposing an integrated design of the hydrogen and offshore electric power infrastructure determining the levelised costs of both hydrogen and electricity is proposed. The economic feasibility of hydrogen production from 2 Offshore Wind Power Hubs is evaluated considering the combination of different electrolyser placements technologies and modes of operations. The results show that costs down to 2.4 €/kg can be achieved for green hydrogen production offshore competitive with the hydrogen costs currently produced by natural gas. Moreover a reduction of up to 13% of the cost of wind electricity is registered when an electrolyser is installed offshore shaving the peak loads.
A Multi-objective Optimization Approach in Defining the Decarbonization Strategy of a Refinery
Mar 2022
Publication
Nowadays nearly one quarter of global carbon dioxide emissions are attributable to energy use in industry making this an important target for emission reductions. The scope of this study is hence that to define a cost-optimized decarbonization strategy for an energy and carbon intensive industry using an Italian refinery as a case study. The methodology involves the coupling of EnergyPLAN with a Multi-Objective Evolutionary Algorithm (MOEA) considering the minimization of annual cost and CO2 emissions as two potentially conflicting objectives and the energy technologies’ capacities as decision variables. For the target year 2025 EnergyPLAN+MOEA has allowed to model a range of 0-100 % decarbonization solutions characterized by optimal penetration mix of 22 technologies in the electrical thermal hydrogen feedstock and transport demand. A set of nine scenarios with different land use availabilities and implementable technologies each consisting of 100 optimal systems out of 10000 simulated ones has been evaluated. The results show on the one hand the possibility of achieving medium-high decarbonization solutions at costs close to current ones on the other how the decarbonization pathways strongly depend on the available land for solar thermal photovoltaic and wind as well as the presence of a biomass supply chain in the region.
NewGasMet - Flow Metering of Renewable Gases (Biogas, Biomethane, Hydrogen, Syngas and Mixtures with Natural Gas): Report on the Impact of Renewable Gases, and Mixtures with Natural Gas, on the Accuracy, Cost and Lifetime of Gas Meters
May 2022
Publication
For the usage of domestic gas meters with combustible gases like hydrogen natural gas or mixtures of hydrogen and natural gas in public grids the metrological behaviour of the gas meters has to fulfil the requirements described in the Measuring Instrument Directive (MID). The MID requires also that a measuring instrument shall be suitable for the application. The tightness of a meter is required in order to obtain correct results in case of accuracy tests but also for an application in the grid or for durability tests to avoid risks such as explosive gas mixtures. Due to the different properties of renewable gases leak tightness to one gas mixtures does not necessarily imply leak tightness for other gases. Hydrogen molecules are smaller than those in conventional natural gas which can more easily result in a gas leakage. The EMPIR project NEWGASMET includes beside metrological investigations also a durability test with hydrogen. In order to carry out these activities but also for further hydrogen leakage investigations for instance the investigation of proper seal materials used in the gas meter installation a reliable gas tightness test was developed.
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.
Fire Spread Scenarios Involving Hydrogen Vehicles
Sep 2021
Publication
Fire spread between vehicles provides a potential risk in parking areas with many vehicles. Several reported very large fires caused the loss of a great number of vehicles. These fires seem to be in contradiction to the European design rules for car parks assuming only a very limited number of vehicles may be on fire at the same time. The fire spread in a car park environment is dependent on many factors of both the vehicles and the structure e.g. the latter has an impact on the rate of fire spread due to reradiation of the vehicles heat release. Therefore a CFD model is established to develop a tool to assess vehicles and better understand fire scenarios in different structures. Further the model enables testing of building design to prevent and mitigate such fires scenarios involving hydrogen vehicles. In this study a real layout of a car park is modelled to investigate the effects of hydrogen emergency releases that have used different TPRD diameters. The results provide insight into the behaviour of hydrogen cars and the release pattern of the TPRD's as well as the temperature development of the concrete ceiling and concrete beams above the cars. It shows that the TPRD diameter has a little effect on the TPRD activation time of the no.1 vehicle when the amount of H2 in the tank is the same. For the surface temperature of the ceiling and beam the peak temperature for a 1mm diameter TPRD release is found highest.
Optimal Day-ahead Dispatch of an Alkaline Electrolyser System Concerning Thermal–electric Properties and State-transitional Dynamics
Oct 2021
Publication
Green hydrogen is viewed as a promising energy carrier for sustainable development goals. However it has suffered from high costs hindering its implementation. For a stakeholder who considers both renewable energy and electrolysis units it is important to exploit the flexibility of such portfolios to maximize system operational revenues. To this end an electrolyser model that can characterize its dynamic behavior is required in both electric and thermal aspects. In this paper we develop a comprehensive alkaline electrolyser model that is capable of describing its hydrogen production properties temperature variations and state transitions (among production stand-by and off states). This model is further used to study the optimal dispatch of an electrolyser based on a real-world hybrid wind/electrolyser system. The results show the model can effectively capture the coupling between thermal–electric dynamics and on–off performance of an electrolyser. The flexible operation strategy based on this model is proven to significantly increase daily revenues under different spot price conditions for electricity. Comparing the model with the ones derived from conventional modeling methods reveals this model offers more operating details and highlights several operational features such as the preference for working at partial load conditions although at the expense of more computing resources. It is suggested to use this model in studies related to energy integration operation planning and control scheme development in which the multi-domain dynamic properties of electrolysers in electricity/gas/heat need to be properly characterized. A sensitivity analysis on key parameters of such electrolyser system is also introduced to connect the daily operation with long-term planning.
Going Offshore or Not: Where to Generate Hydrogen in Future Integrated Energy Systems?
Jan 2023
Publication
Hydrogen can be key in the energy system transition. We investigate the role of offshore hydrogen generation in a future integrated energy system. By performing energy system optimisation in a model application of the Northern-central European energy system and the North Sea offshore grid towards 2050 we find that offshore hydrogen generation may likely only play a limited role and that offshore wind energy has higher value when sent to shore in the form of electricity. Forcing all hydrogen generation offshore would lead to increased energy system costs. Under the assumed scenario conditions which result in deep decarbonisation of the energy system towards 2050 hydrogen generation – both onshore and offshore – follows solar PV generation patterns. Combined with hydrogen storage this is the most cost-effective solution to satisfy future hydrogen demand. Overall we find that the role of future offshore hydrogen generation should not simply be derived from minimising costs for the offshore sub-system but by also considering the economic value that such generation would create for the whole integrated energy system. We find as a no-regret option to enable and promote the integration of offshore wind in onshore energy markets via electrical connections.
Incentive Structures for Power-to-X and E-fuel Pathways for Transport in EU and Member States
Jun 2022
Publication
Though Power-to-X pathways primarily Power-to-Liquids attract interest as solutions for decarbonising parts of the transport sector that are not suitable for electrification the regulatory framework until recently slowed down their implementation. This paper examines the updates in the main aspects of the legal framework in the European Union from 2019 to the beginning of 2022 related to Power-to-X: support schemes specific targets and potential barriers. The results show increasing interest and market entrance of electrolysis and push from the different actors and regulatory parties to establish solutions that will enable faster upscaling. However it is visible from the National Energy and Climate Plans and hydrogen strategies that the most emphasis is still on hydrogen as an end fuel for personal vehicles or power-to-gas. On the other hand few countries have implemented legal frameworks facilitating diverse PtX pathways without focusing solely on hydrogen. Nevertheless revisions of RED II have finally set up specific targets for electrofuels and Fit for 55 has introduced new actions supporting electrofuels in aviation and marine transport.
Sizing of Hybrid Supercapacitors and Lithium-Ion Batteries for Green Hydrogen Production from PV in the Australian Climate
Feb 2023
Publication
Instead of storing the energy produced by photovoltaic panels in batteries for later use to power electric loads green hydrogen can also be produced and used in transportation heating and as a natural gas alternative. Green hydrogen is produced in a process called electrolysis. Generally the electrolyser can generate hydrogen from a fluctuating power supply such as renewables. However due to the startup time of the electrolyser and electrolyser degradation accelerated by multiple shutdowns an idle mode is required. When in idle mode the electrolyser uses 10% of the rated electrolyser load. An energy management system (EMS) shall be applied where a storage technology such as a lithium-ion capacitor or lithium-ion battery is used. This paper uses a state-machine EMS of PV microgrid for green hydrogen production and energy storage to manage the hydrogen production during the morning from solar power and in the night using the stored energy in the energy storage which is sized for different scenarios using a lithium-ion capacitor and lithium-ion battery. The mission profile and life expectancy of the lithium-ion capacitor and lithium-ion battery are evaluated considering the system’s local irradiance and temperature conditions in the Australian climate. A tradeoff between storage size and cutoffs of hydrogen production as variables of the cost function is evaluated for different scenarios. The lithium-ion capacitor and lithium-ion battery are compared for each tested scenario for an optimum lifetime. It was found that a lithium-ion battery on average is 140% oversized compared to a lithium-ion capacitor but a lithium-ion capacitor has a smaller remaining capacity of 80.2% after ten years of operation due to its higher calendar aging while LiB has 86%. It was also noticed that LiB is more affected by cycling aging while LiC is affected by calendar aging. However the average internal resistance after 10 years for the lithium-ion capacitor is 264% of the initial internal resistance while for lithium-ion battery is 346% making lithium-ion capacitor a better candidate for energy storage if it is used for grid regulation as it requires maintaining a lower internal resistance over the lifetime of the storage.
NewGasMet - Flow Metering of Renewable Gases (Biogas, Biomethane, Hydrogen, Syngas and Mixtures with Natural Gas): Effect of the Renewable Gases on the Uncertainty Budgets of Gas Meters
Sep 2022
Publication
During the study of the CEN/TC 237 standards “Gas meters” in the European Metrology Programme for Innovation and Research (EMPIR) project named NEWGASMET the impact of the renewable gases (biogas biomethane hydrogen syngas and mixtures with natural gas) on the uncertainty on the gas meter was discussed and described in several recommendation reports. This report is on the activity A2.1.15 where the objective is “Using input from A2.1.2-A2.1.8 FORCE with support from Cesame CMI NEL PTB VSL and ISSI will write a report on the effects of renewable gases on the uncertainty budgets of gas meters.”
Optimized Configuration of Diesel Engine-Fuel Cell-Battery Hybrid Power Systems in a Platform Supply Vessel to Reduce CO2 Emissions
Mar 2022
Publication
The main objective of this paper is to select the optimal configuration of a ship’s power system considering the use of fuel cells and batteries that would achieve the lowest CO2 emissions also taking into consideration the number of battery cycles. The ship analyzed in this work is a Platform Supply Vessel (PSV) used to support oil and gas offshore platforms transporting goods equipment and personnel. The proposed scheme considers the ship’s retrofitting. The ship’s original main generators are maintained and the fuel cell and batteries are installed as complementary sources. Moreover a sensitivity analysis is pursued on the ship’s demand curve. The simulations used to calculate the CO2 emissions for each of the new hybrid configurations were developed using HOMER software. The proposed solutions are auxiliary generators three types of batteries and a protonexchange membrane fuel cell (PEMFC) with different sizes of hydrogen tanks. The PEMFC and batteries were sized as containerized solutions and the sizing of the auxiliary engines was based on previous works. Each configuration consists of a combination of these solutions. The selection of the best configuration is one contribution of this paper. The new configurations are classified according to the reduction of CO2 emitted in comparison to the original system. For different demand levels the results indicate that the configuration classification may vary. Another valuable contribution of this work is the sizing of the battery and hydrogen storage systems. They were installed in 20 ft containers since the installation of batteries fuel cells and hydrogen tanks in containers is widely used for ship retrofit. As a result the most significant reduction of CO2 emissions is 10.69%. This is achieved when the configuration includes main generators auxiliary generators a 3119 kW lithium nickel manganese cobalt (LNMC) battery a 250 kW PEMFC and 581 kg of stored hydrogen.
Adapting Maintenance Facilities for Hydrogen
Sep 2021
Publication
Transit planners and managers need to be armed with the best information on how to make the transition towards zero emission transit fleets. Although zero emission transit is becoming increasingly necessary many transit operators are unsure of how to make the transition and how to replace their existing infrastructure especially when it comes to on site bus maintenance facilities. Upgrading vehicle maintenance facilities to safely accommodate hydrogen can be a deciding factor in whether an operator chooses to adopt this fuel for its fleet. This paper reviews best practices in hydrogen bus maintenance facilities for transit agencies. It includes safety and infrastructure factors transit managers must consider when transitioning to servicing and maintaining fuel cell electric buses. Although local requirements and regulations vary this paper will help the reader gain insights on what needs to be considered in transitioning a workshop. As with any fuel hydrogen must be treated with respect and care. Today’s hydrogen fuel cell technologies are mature in their safety features. Fuel cell electric buses are designed and built for safety and the protocols for safe storage maintenance and refuelling are well developed and understood.
The Socio-technical Dynamics of Net-zero Industrial Megaprojects: Outside-in and Inside-out Analyses of the Humber Industrial Cluster
Feb 2023
Publication
Although energy-intensive industries are often seen as ‘hard-to-decarbonise’ net-zero megaprojects for industrial clusters promise to improve the technical and economic feasibility of hydrogen fuel switching and carbon capture and storage (CCS). Mobilising insights from the megaproject literature this paper analyses the dynamics of an ambitious first-of-kind net-zero megaproject in the Humber industrial cluster in the United Kingdom which includes CCS and hydrogen infrastructure systems industrial fuel switching CO2 capture green and blue hydrogen production and hydrogen storage. To analyse the dynamics of this emerging megaproject the article uses a socio-technical system lens to focus on developments in technology actors and institutions. Synthesising multiple megaproject literature insights the paper develops a comprehensive framework that addresses both aggregate (‘outside-in’) developments and the endogenous (‘inside-out’) experiences and activities regarding three specific challenges: technical system integration actor coordination and institutional alignment. Drawing on an original dataset involving expert interviews (N = 46) site visits (N = 7) and document analysis the ‘outside-in’ analysis finds that the Humber megaproject has progressed rapidly from outline visions to specific technical designs enacted by new coalitions and driven by strengthening policy targets and financial support schemes. The complementary ‘inside-out’ analysis however also finds 12 alignment challenges that can delay or derail materialisation of the plans. While policies are essential aggregate drivers institutional misalignments presently also prevent project-actors from finalising design and investment decisions. Our analysis also finds important tensions between the project's high-pace delivery focus (to meet government targets) and allowing sufficient time for pilot projects learning-by-doing and design iterations.
Hydrogen Deep Ocean Link: A Global Sustainable Interconnected Energy Grid<br/><br/><br/>
Mar 2022
Publication
The world is undergoing a substantial energy transition with an increasing share of intermittent sources of energy on the grid which is increasing the challenges to operate the power grid reliably. An option that has been receiving much focus after the COVID pandemic is the development of a hydrogen economy. Challenges for a hydrogen economy are the high investment costs involved in compression storage and long-distance transportation. This paper analyses an innovative proposal for the creation of hydrogen ocean links. It intends to fill existing gaps in the creation of a hydrogen economy with the increase in flexibility and viability for hydrogen production consumption compression storage and transportation. The main concept behind the proposals presented in this paper consists of using the fact that the pressure in the deep sea is very high which allows a thin and cheap HDPE tank to store and transport large amounts of pressurized hydrogen in the deep sea. This is performed by replacing seawater with pressurized hydrogen and maintaining the pressure in the pipes similar to the outside pressure. Hydrogen Deep Ocean Link has the potential of increasing the interconnectivity of different regional energy grids into a global sustainable interconnected energy system.
Economic Evaluation of a Power-to-hydrogen System Providing Frequency Regulation Reserves: A Case Study of Denmark
Mar 2023
Publication
Operating costs are dominant in the hydrogen production of a power-to-hydrogen system. An optimal operational strategy or bidding framework is effective in reducing these costs. However it is still found that the production cost of hydrogen is high. As the electrolysis unit is characterized by high flexibility providing ancillary service to the grid becomes a potential pathway for revenue stacking. Recent research has demonstrated the feasibility of providing such a service but the related economics have not been well evaluated. In this work we propose a comprehensive operation model to enable participation in the day-head balancing and reserve markets. Three types of reserves are considered by using different operational constraints. Based on the proposed operation framework we assess the economic performance of a power-to-hydrogen system in Denmark using plentiful actual market data. The results reveal that providing frequency containment reserve and automatic frequency restoration reserve efficiently raises the operational contribution margins. In parallel by investing in the cash flows net present value and break-even hydrogen prices we conclude that providing reserves makes the power-to-hydrogen project more profitable in the studied period and region.
Review on Ammonia as a Potential Fuel: From Synthesis to Economics
Feb 2021
Publication
Ammonia a molecule that is gaining more interest as a fueling vector has been considered as a candidate to power transport produce energy and support heating applications for decades. However the particular characteristics of the molecule always made it a chemical with low if any benefit once compared to conventional fossil fuels. Still the current need to decarbonize our economy makes the search of new methods crucial to use chemicals such as ammonia that can be produced and employed without incurring in the emission of carbon oxides. Therefore current efforts in this field are leading scientists industries and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector moving through all of the steps in the production distribution utilization safety legal considerations and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes legal barriers that will be faced to achieve its deployment safety and environmental considerations that impose a critical aspect for acceptance and wellbeing and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein this work sets the principles research practicalities and future views of a transition toward a future where ammonia will be a major energy player.
Assessing and Modelling Hydrogen Reactivity in Underground Hydrogen Storage: A Review and Models Simulating the Lobodice Town Gas Storage
Apr 2023
Publication
Underground Hydrogen storage (UHS) is a promising technology for safe storage of large quantities of hydrogen in daily to seasonal cycles depending on the consumption requirements. The development of UHS requires anticipating hydrogen behavior to prevent any unexpected economic or environmental impact. An open question is the hydrogen reactivity in underground porous media storages. Indeed there is no consensus on the effects or lack of geochemical reactions in UHS operations because of the strong coupling with the activity of microbes using hydrogen as electron donor during anaerobic reduction reactions. In this work we apply different geochemical models to abiotic conditions or including the catalytic effect of bacterial activity in methanogenesis acetogenesis and sulfate-reduction reactions. The models are applied to Lobodice town gas storage (Czech Republic) where a conversion of hydrogen to methane was measured during seasonal gas storage. Under abiotic conditions no reaction is simulated. When the classical thermodynamic approach for aqueous redox reactions is applied the simulated reactivity of hydrogen is too high. The proper way to simulate hydrogen reactivity must include a description of the kinetics of the aqueous redox reactions. Two models are applied to simulate the reactions of hydrogen observed at Lobodice gas storage. One modeling the microbial activity by applying energy threshold limitations and another where microbial activity follows a Monod-type rate law. After successfully calibrating the bio-geochemical models for hydrogen reactivity on existing gas storage data and constraining the conditions where microbial activity will inhibit or enhance hydrogen reactivity we now have a higher confidence in assessing the hydrogen reactivity in future UHS in aquifers or depleted reservoirs.
THyGA - Long Term Effect of H2 on Appliances Tested
May 2023
Publication
The goals of the long-term tests were to see the impact of blends of hydrogen and natural gas on the technical condition of the appliances and their performance after several hours of operation. To do so they were run through an accelerated test program amounting to more than 3000 testing hours for the boilers and more than 2500 testing hours for the cookers. The percentage of hydrogen in the test gas was 30% by volume. Three boilers and two cookers were tested by DGC and two boilers by GWI. This report describes the test protocol the results and analysis on the seven appliances tested.
On the Feasibility of Direct Hydrogen Utilisation in a Fossil-free Europe
Oct 2022
Publication
Hydrogen is often suggested as a universal fuel that can replace fossil fuels. This paper analyses the feasibility of direct hydrogen utilisation in all energy sectors in a 100% renewable energy system for Europe in 2050 using hour-by-hour energy system analysis. Our results show that using hydrogen for heating purposes has high costs and low energy efficiency. Hydrogen for electricity production is beneficial only in limited quantities to restrict biomass consumption but increases the system costs due to losses. The transport sector results show that hydrogen is an expensive alternative to liquid e-fuels and electrified transport due to high infrastructure costs and respectively low energy efficiency. The industry sector may benefit from hydrogen to reduce biomass at a lower cost than in the other energy sectors but electrification and e-methane may be more feasible. Seen from a systems perspective hydrogen will play a key role in future renewable energy systems but primarily as e-fuel feedstock rather than direct end-fuel in the hard-to-abate sectors.
Low-Carbon Optimal Scheduling Model for Peak Shaving Resources in Multi-Energy Power Systems Considering Large-Scale Access for Electric Vehicles
May 2023
Publication
Aiming at the synergy between a system’s carbon emission reduction demand and the economy of peak shaving operation in the process of optimizing the flexible resource peaking unit portfolio of a multi-energy power system containing large-scale electric vehicles this paper proposes a low-carbon optimal scheduling model for peak shaving resources in multi-energy power systems considering large-scale access for electric vehicles. Firstly the charging and discharging characteristics of electric vehicles were studied and a comprehensive cost model for electric vehicles heat storage and hydrogen storage was established. At the same time the carbon emission characteristics of multienergy power systems and their emission cost models under specific carbon trading mechanisms were established. Secondly the change characteristics of the system’s carbon emissions were studied and a carbon emission cost model of multi-energy power was established considering the carbon emission reduction demand of the system. Then taking the carbon emission of the system and the peak regulating operation costs of traditional units energy storage and new energy unit as optimization objectives the multi-energy power system peak regulation multi-objective optimization scheduling model was established and NSGA-II was used to solve the scheduling model. Finally based on a regional power grid data in Northeast China the improved IEEE 30 node multi-energy power system peak shaving simulation model was built and the simulation analysis verified the feasibility of the optimal scheduling model proposed in this paper.
THyGA - Test Report on Mitigation Solutions for Residential Natural Gas Appliances Not Designed for Hydrogen Admixture
Apr 2023
Publication
This report from the WP5 “Mitigation” provides information and test results regarding perturbations that hydrogen could cause to gas appliances when blended to natural gas especially on anatural draught for exhaust fumes or acidity for the condensates. The important topic of on-site adjustment is also studied with test results on alternative technologies and proposals of mitigation approaches.
How to Connect Energy Islands: Trade-offs Between Hydrogen and Electricity Infrastructure
Apr 2023
Publication
In light of offshore wind expansions in the North and Baltic Seas in Europe further ideas on using offshore space for renewable-based energy generation have evolved. One of the concepts is that of energy islands which entails the placement of energy conversion and storage equipment near offshore wind farms. Offshore placement of electrolysers will cause interdependence between the availability of electricity for hydrogen production and for power transmission to shore. This paper investigates the trade-offs between integrating energy islands via electricity versus hydrogen infrastructure. We set up a combined capacity expansion and electricity dispatch model to assess the role of electrolysers and electricity cables given the availability of renewable energy from the islands. We find that the electricity system benefits more from connecting close-to-shore wind farms via power cables. In turn electrolysis is more valuable for far-away energy islands as it avoids expensive long-distance cable infrastructure. We also find that capacity investment in electrolysers is sensitive to hydrogen prices but less to carbon prices. The onshore network and congestion caused by increased activity close to shore influence the sizing and siting of electrolysers.
The Role of Biomass Gasification in Low-carbon Energy and Transport Systems
Mar 2021
Publication
The design of future energy systems requires the efficient use of all available renewable resources. Biomass can complement variable renewable energy sources by ensuring energy system flexibility and providing a reliable feedstock to produce renewable fuels. We identify biomass gasification suitable to utilise the limited biomass resources efficiently. In this study we inquire about its role in a 100% renewable energy system for Denmark and a net-zero energy system for Europe in the year 2050 using hourly energy system analysis. The results indicate bio-electrofuels produced from biomass gasification and electricity to enhance the utilisation of wind and electrolysis and reduce the energy system costs and fuels costs compared to CO2-electrofuels from carbon capture and utilisation. Despite the extensive biomass use overall biomass consumption would be higher without biomass gasification. The production of electromethanol shows low biomass consumption and costs while Fischer-Tropsch electrofuels may be an alternative for aviation. Syngas from biomass gasification can supplement biogas in stationary applications as power plants district heat or industry but future energy systems must meet a balance between producing transport fuels and syngas for stationary units. CO2-electrofuels are found complementary to bio-electrofuels depending on biomass availability and remaining non-fossil CO2 emitters
Fuel Cell Solution for Marine Applications
Sep 2021
Publication
With future regulations on the horizon port authorities and ship owners/operators are looking at alternative propulsion solutions to reduce emission. Fuel cell technology provides an attractive zeroemission solution to generate electric power on board using hydrogen as a fuel. Fuel cell systems are scalable from 200kW to multi-MW providing high efficiency dispatchable clean quiet power generation. Several innovative pilot projects are on the way to demonstrate the marine application of this proven technology. Electrification of propulsion systems is advancing and fuel cell technology provides the opportunity to produce on board large quantity of power with zero-emission using hydrogen as a fuel. We will present the value proposition of having a fuel cell power generator on board of an electric vessel while discussing the safety considerations with the fuel cell module and the onboard fuel storage. We will present some of our current fuel cell marine projects and review some of the product development considerations including system architecture and safety as well as hydrogen supply and on-board fuel storage.
Correlations between Component Size Green Hydrogen Demand and Breakeven Price for Energy Islands
Jun 2023
Publication
The topic of energy islands is currently a focal point in the push for the energy transition. An ambitious project in the North Sea aims to build an offshore wind-powered electrolyser for green hydrogen production. Power-to-X (PtX) is a process of converting renewable electricity into hydrogen-based energy carriers such as natural gas liquid fuels and chemicals. PtH2 represents a subset of PtX wherein hydrogen is the resultant green energy from the conversion process. Many uncertainties surround PtH2 plants affecting the economic success of the investment and making the price of hydrogen and the levelized cost of hydrogen (LCOH) of this technology uncompetitive. Several studies have analysed PtH2 layouts to identify the hydrogen price without considering how component capacities and external inputs affect the breakeven price. Unlike previous works this paper investigates component capacity dependencies under variables such as wind and hydrogen demand shape for dedicated/non-dedicated system layouts. To this end the techno-economic analysis finds the breakeven price optimising the components to reach the lowest selling price. Results show that the hydrogen price can reach 2.2 €/kg for a non-dedicated system for certain combinations of maximum demand and electrolyser capacity. Furthermore the LCOH analysis revealed that the offshore wind electrolyser system is currently uncompetitive with hydrogen production from carbon-based technologies but is competitive with renewable technologies. The sensitivity analysis reveals the green electricity price in the non-dedicated case for which a dedicated system has a lower optimum hydrogen price. The price limit for the dedicated case is 116 €/MWh.
Day-ahead Economic Optimization Scheduling Model for Electricity–hydrogen Collaboration Market
Aug 2022
Publication
This paper presents a day-ahead economic optimization scheduling model for Regional Electricity–Hydrogen Integrated Energy System (REHIES) with high penetration of renewable energies. The electricity–hydrogen coupling devices are modelled with energy storage units and Insensitive Electrical Load (ISEL). The proposed objective function is able to capture the maximum benefits for REHIES in terms of economic benefits and can be summarized as a Quadratic Programming (QP) problem. The simulation verification is performed by MATLAB/CPLEX solver. The simulation results show that the proposed optimization model adapts the market requirement by contributing flexible collaboration between electricity and hydrogen. Also the translational properties of ISEL can implement higher economic profits and more effective utilization of renewable energy.
Anion Exchange Membrane Water Electrolyzer: Electrode Design, Lab-scaled Testing System and Performance Evaluation
Aug 2022
Publication
Green hydrogen produced by water electrolysis is one of the most promising technologies to realize the efficient utilization of intermittent renewable energy and the decarbonizing future. Among various electrolysis technologies the emerging anion-exchange membrane water electrolysis (AEMWE) shows the most potential for producing green hydrogen at a competitive price. In this review we demonstrate a comprehensive introduction to AEMWE including the advanced electrode design the lab-scaled testing system establishment and the electrochemical performance evaluation. Specifically recent progress in developing high activity transition metal-based powder electrocatalysts and self-supporting electrodes for AEMWE is summarized. To improve the synergistic transfer behaviors between electron charge water and gas inside the gas diffusion electrode (GDE) two optimizing strategies are concluded by regulating the pore structure and interfacial chemistry. Moreover we provide a detailed guideline for establishing the AEMWE testing system and selecting the electrolyzer components. The influences of the membrane electrode assembly (MEA) technologies and operation conditions on cell performance are also discussed. Besides diverse electrochemical methods to evaluate the activity and stability implement the failure analyses and realize the in-situ characterizations are elaborated. In end some perspectives about the optimization of interfacial environment and cost assessments have been proposed for the development of advanced and durable AEMWE.
Model-based Economic Analysis of Off-grid Wind/Hydrogen Systems
Sep 2023
Publication
Hydrogen has emerged in the context of large-scale renewable uptake and deep decarbonization. However the high cost of splitting water into hydrogen using renewable energy hinders the development of green hydrogen. Here we provide a cost analysis of hydrogen from off-grid wind. It is found that the current cost evaluation can be improved by examining the operational details of electrolysis. Instead of using low-resolution wind-speed data and linear electrolysis models we generate 5-min resolution wind data and utilize detailed electrolysis models that can describe the safe working range startup time and efficiency variation. Economic assessments are performed over 112 locations in seven countries to demonstrate the influence of operational models. It is shown that over-simplified models lead to less reliable results and the relative error can be 63.65% at most. Further studies have shown the global picture of producing green hydrogen. Based on the improved model we find that the levelized cost of hydrogen ranges from 1.66$/kg to 13.61$/kg. The wind-based hydrogen is cost-competitive in areas with abundant resources and lower investment cost such as China and Denmark. However it is still costly in most of the studied cases. An optimal sizing strategy or involving a battery as electricity storage can further reduce the hydrogen cost the effectiveness of which is location-specific. The sizing strategies of electrolyzers differ by country and rely on the specific wind resource. In contrast the sizing of batteries presents similar trends. Smaller batteries are preferred in almost all the investigated cases.
Data-driven Scheme for Optimal Day-ahead Operation of a Wind/hydrogen System Under Multiple Uncertainties
Nov 2022
Publication
Hydrogen is believed as a promising energy carrier that contributes to deep decarbonization especially for the sectors hard to be directly electrified. A grid-connected wind/hydrogen system is a typical configuration for hydrogen production. For such a system a critical barrier lies in the poor cost-competitiveness of the produced hydrogen. Researchers have found that flexible operation of a wind/hydrogen system is possible thanks to the excellent dynamic properties of electrolysis. This finding implies the system owner can strategically participate in day-ahead power markets to reduce the hydrogen production cost. However the uncertainties from imperfect prediction of the fluctuating market price and wind power reduce the effectiveness of the offering strategy in the market. In this paper we proposed a decision-making framework which is based on data-driven robust chance constrained programming (DRCCP). This framework also includes multi-layer perception neural network (MLPNN) for wind power and spot electricity price prediction. Such a DRCCP-based decision framework (DDF) is then applied to make the day-ahead decision for a wind/hydrogen system. It can effectively handle the uncertainties manage the risks and reduce the operation cost. The results show that for the daily operation in the selected 30 days offering strategy based on the framework reduces the overall operation cost by 24.36% compared to the strategy based on imperfect prediction. Besides we elaborate the parameter selections of the DRCCP to reveal the best parameter combination to obtain better optimization performance. The efficacy of the DRCCP method is also highlighted by the comparison with the chance-constrained programming method.
Off-grid Wind/Hydrogen Systems with Multi-electrolyzers: Optimized Operational Strategies
Sep 2023
Publication
Optimized operation of wind/hydrogen systems can increase the system efficiency and further reduce the hydrogen production cost. In this regard extensive research has been done but there is a lack of detailed electrolyzer models and effective management of multiple electrolyzers considering their physical restrictions. This work proposes electrolyzer models that integrate the efficiency variation caused by load level change start–stop cycle (including hot and cold start) thermal management and degradation caused by frequent starts. Based on the proposed models three operational strategies are considered in this paper: two traditionally utilized methods simple start–stop and cycle rotation strategies and a newly proposed rolling optimizationbased strategy. The results from daily operation show that the new strategy results in a more balanced load level among the electrolyzers and a more stable temperature. Besides from a yearly operation perspective it is found that the proposed rolling optimization method results in more hydrogen production higher system efficiency and lower LCOH. The new method leads to hydrogen production of 311297 kg compared to 289278 kg and 303758 kg for simple start–stop and cycle rotation methods. Correspondingly the system efficiencies for the new simple start–stop and cycle rotation methods are 0.613 0.572 and 0.587. The resulting LCOH from the new method is 3.89 e/kg decreasing by 0.35 e/kg and 0.21 e/kg compared to the simple start–stop and cycle rotation methods. Finally the proposed model is compared with two conventional models to show its effectiveness in revealing more operational details and reliable results.
Modeling the Long-term Evolution of the Italian Power Sector: The Role of Renewable Resources and Energy Storage Facilities
Feb 2024
Publication
The aim of this study is to investigate the long-term planning of the Italian power sector from 2021 to 2050. The key role of photovoltaic and wind technologies in combination with power-to-power systems based on hydrogen and batteries is investigated. An updated version of the OSeMOSYS tool is used which employs a clustering method for the representation of time-varying input data. First the potential of variable renewable energy sources (VRES) is assessed. A sensitivity analysis is also performed on the temporal resolution of the model to determine an adequate trade-off between the computation time and the accuracy of the results. Then a technoeconomic optimization scenario is carried out resulting in a total net present cost of about 233.7 B€. A high penetration of VRES technologies is foreseen by 2050 with a total VRES installed capacity of 272.9 GW (mainly photovoltaic and onshore wind). Batteries are found to be the preferable energy storage solution in the first part of the energy transition while the hydrogen storage starts to be convenient from about the year 2040. Indeed the role of hydrogen storage becomes fundamental as the VRES penetration increases thanks to its cost-effective long-term storage capability. By 2050 74.6 % of electricity generation will be based on VRES which will also enable a significant reduction in CO2 emissions of about 87 %.
Techno-economic Analysis and Predictive Operation of a Power-to-hydrogen for Renewable Microgrids
Oct 2023
Publication
To enhance renewable energy (RE) generation and maintain power balance energy storage systems are of utmost importance. This research introduces a cutting-edge Power-to-Hydrogen (PtH) framework that harnesses hydrogen as a clean and versatile energy storage medium. The primary focus of this study lies in optimizing power flow within a microgrid (G) equipped with RE and energy storage systems considering various factors such as RE generation power demand battery charge cycles and operational costs. To achieve the optimal balance between power generation and consumption a sophisticated mathematical solution is devised. This solution governs the charging and discharging patterns for both battery and electrolyzer ensuring a harmonious power equilibrium. The use of short-term forecasting further refines the optimization process adapting the parameters based on anticipated RE sources and load requirements. To fine-tune the power management solution for day-to-day operations an artificial neural fuzzy inference system (ANFIS)-based shortterm prediction model is employed. The predictive analysis provides confidence intervals for crucial aspects including power generation demand battery charging cycles and hydrogen generation. This facilitates precise cost estimation across various hydrogen and heat price ranges. the proposed PtH optimization framework offers an efficient approach to balance power generation and consumption in Gs driven by RE sources and energy storage. To validate the proposed approach numerical simulations are performed based on data from wind and solar farms load requirements and cost of energy. The results show that the proposed energy management strategy significantly reduces operational costs and optimizes PtH generation while maintaining power balance within the microgrid (G). The predictive approach helps fine-tune the optimization process improving efficiency and cost-effectiveness. The research convincingly demonstrate the economic advantages of adopting hydrogen as an energy storage medium paving the way for a cleaner and more sustainable energy future.
Exploring Decentralized Ammonia Synthesis for Hydrogen Storage and Transport: A Comprehensive CFD Investigation with Experimental Validation and Parametric Study
Sep 2023
Publication
Hydrogen energy plays a vital role in the transition towards a carbon-neutral society but faces challenges in storage and transport as well as in production due to fluctuations in renewable electricity generation. Ammonia (NH3 ) as a carbon-neutral hydrogen carrier offers a promising solution to the energy storage and transport problem. To realize its potential and support the development of a hydrogen economy exploring NH3 synthesis in a decentralized form that integrates with distributed hydrogen production systems is highly needed. In this study a computational fluid dynamics (CFD) model for the Ruthenium (Ru) catalysts-based Haber– Bosch reactor is developed. First a state-of-the-art kinetic model comprehensively describing the complex catalytic reaction is assessed for its sensitivity and applicability to temperature pressure and conversion. Then the kinetic model is integrated into the CFD model and its accuracy is verified through comparison with experimental data obtained from different Ru-based catalysts and operation conditions. Detailed CFD results for a given case are presented offering a visual understanding of thermal gradients and species distributions inside the reactor. Finally a CFD-based parametric study is performed to reveal the impacts of key operation parameters and optimize the NH3 synthesis reactor. The results show that the NH3 production rate is predominantly influenced by temperature with a two-fold difference observed for every 30 ◦C variation while pressure primarily affects the equilibrium. Additionally the affecting mechanism of space velocity is thoroughly discussed and the best value for efficient NH3 synthesis is found to be 180000 h−1. In conclusion the CFD model and simulation results provide valuable insights for the design and control of decentralized NH3 synthesis reactor and operation contributing to the advancement of sustainable energy technologies.
Assessing Fluctuating Wind to Hydrogen Production via Long-term Testing of Solid Oxide Electrolysis Stacks
Mar 2024
Publication
The Danish government plans two energy islands to collect offshore wind power for power distribution and green fuel production. Wind power is often criticized for lacking stability which challenges downstream fuel synthesis processes. Solid oxide electrolysis cells (SOEC) are promising for green hydrogen production on a commercial scale but the impact of fluctuating power on SOEC remains uncertain. This paper explores the feasibility of a Wind-SOEC coupled system by conducting a 2104-h durability test with the state-of-the-art Topsoe TSP-1 stack. Three periods of steady operation and two periods of dynamic operation were conducted. Wind power fluctuation was simulated during the dynamic period and two control strategies were used to handle it. The constant flow (CF) and constant conversion (CC) strategies maintain the feedstock flow rate and conversion ratio of steamto‑hydrogen respectively. Compared to steady operation the stack shows no signs of additional degradation in dynamic operation. Thus the TSP-1 stack has been proven robust and flexible enough to handle fluctuating wind power supplies under both operation strategies. Further stack performance during dynamic periods was compared and analyzed by removing degradation effects. Accordingly SOEC stacks with CC control will consume less external heat than CF to maintain a heat balance. Nevertheless SOEC systems with CF and CC control strategies may have different efficiency or hydrogen production costs. Tech-economic analyses will be needed to investigate control strategies at the system level.
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