Denmark
Discrete Event Simulation in Support to Hydrogen Supply Reliability
Sep 2009
Publication
Discrete Event Simulation (DES) environments are rapidly developing and they appear to be promising tools for developing reliability and risk analysis models of safety-critical systems. DES models are an alternative to the conventional methods such as fault and event trees Bayesian networks and cause-consequence diagrams that could be used to assess the reliability of fuel supply. DES models can rather easily account for the dynamic dimensions and other important features that can hardly be captured by the conventional models. The paper describes a novel approach to estimate gas supply security and the reliability/safety of gas installations and argues that this approach can be transferred to estimate future hydrogen supply reliability. The core of the approach is a DES model of gas or other fuel propulsion through a pipeline to the customers and failures of the components of the pipeline. We will argue in the paper that the experience gained in the modelling of gas supply reliability is very relevant to the security and safety of a future hydrogen supply and worth being employed in this area.
A Barrier Analysis of a Generic Hydrogen Refuelling Station
Sep 2009
Publication
Any technical installation need appropriate safety barriers installed to prevent or mitigate any adverse effects concerning people property and environment. In this context a safety barrier is a series of elements each consisting of a technical system or human action that implement a planned barrier function to prevent control or mitigate the propagation of a condition or event into an undesired condition or event. This is also important for new technologies as hydrogen refuelling stations being operated at very high pressures up to 900bar. In order to establish the needed barriers a hazard identification of the installation has to be carried out to identify the possible hazardous events. In this study this identification was done using the generic layout of a future large hydrogen refuelling station that has been developed by the EU NoE HySafe. This was based on experiences with smaller scale refuelling stations that has been in operation for several years e.g. being used in the former CUTE and ECTOS projects. Using this approach the object of the study is to support activities to further improve the safety performance of future larger refuelling stations. This will again help to inform the authorities and the public to achieve a proper public awareness and to support building up a realistic risk and safety perception of the safety on such future refuelling stations. In the second step the hazardous events that may take place and the barriers installed to stop hazards and their escalation are analysed also using in-house developed software to model the barriers and to quantify their performance. The paper will present an overview and discuss the state-of-the-art of the barriers established in the generic refuelling station.
Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage
Oct 2017
Publication
Hydrogen has a very diverse chemistry and reacts with most other elements to form compounds which have fascinating structures compositions and properties. Complex metal hydrides are a rapidly expanding class of materials approaching multi-functionality in particular within the energy storage field. This review illustrates that complex metal hydrides may store hydrogen in the solid state act as novel battery materials both as electrolytes and electrode materials or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore it is highlighted how complex metal hydrides may act in an integrated setup with a fuel cell. This review focuses on the unique properties of light element complex metal hydrides mainly based on boron nitrogen and aluminum e.g. metal borohydrides and metal alanates. Our hope is that this review can provide new inspiration to solve the great challenge of our time: efficient conversion and large-scale storage of renewable energy.
International Association for Hydrogen Safety ‘Research Priorities Workshop’, September 2018, Buxton, UK
Sep 2018
Publication
Hydrogen has the potential to be used by many countries as part of decarbonising the future energy system. Hydrogen can be used as a fuel ‘vector’ to store and transport energy produced in low-carbon ways. This could be particularly important in applications such as heating and transport where other solutions for low and zero carbon emission are difficult. To enable the safe uptake of hydrogen technologies it is important to develop the international scientific evidence base on the potential risks to safety and how to control them effectively. The International Association for Hydrogen Safety (known as IA HySAFE) is leading global efforts to ensure this. HSE hosted the 2018 IA HySAFE Biennial Research Priorities Workshop. A panel of international experts presented during nine key topic sessions: (1) Industrial and National Programmes; (2) Applications; (3) Storage; (4) Accident Physics – Gas Phase; (5) Accident Physics – Liquid/ Cryogenic Behaviour; (6) Materials; (7) Mitigation Sensors Hazard Prevention and Risk Reduction; (8) Integrated Tools for Hazard and Risk Assessment; (9) General Aspects of Safety.<br/>This report gives an overview of each topic made by the session chairperson. It also gives further analysis of the totality of the evidence presented. The workshop outputs are shaping international activities on hydrogen safety. They are helping key stakeholders to identify gaps in knowledge and expertise and to understand and plan for potential safety challenges associated with the global expansion of hydrogen in the energy system.
The Impact of Hydrogen Admixture into Natural Gas on Residential and Commercial Gas Appliances
Jan 2022
Publication
Hydrogen as a carbon-free fuel is commonly expected to play a major role in future energy supply e.g. as an admixture gas in natural gas grids. Which impacts on residential and commercial gas appliances can be expected due to the significantly different physical and chemical properties of hydrogen-enriched natural gas? This paper analyses and discusses blends of hydrogen and natural gas from the perspective of combustion science. The admixture of hydrogen into natural gas changes the properties of the fuel gas. Depending on the combustion system burner design and other boundary conditions these changes may cause higher combustion temperatures and laminar combustion velocities while changing flame positions and shapes are also to be expected. For appliances that are designed for natural gas these effects may cause risk of flashback reduced operational safety material deterioration higher nitrogen oxides emissions (NOx) and efficiency losses. Theoretical considerations and first measurements indicate that the effects of hydrogen admixture on combustion temperatures and the laminar combustion velocities are often largely mitigated by a shift towards higher air excess ratios in the absence of combustion control systems but also that common combustion control technologies may be unable to react properly to the presence of hydrogen in the fuel.
The Role of Lock-in Mechanisms in Transition Processes: The Case of Energy for Road Transport
Jul 2015
Publication
This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries focussing on three technology platforms: advanced biofuels e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies.<br/>The main lock-in mechanisms analysed are learning effects economies of scale economies of scope network externalities informational increasing returns technological interrelatedness collective action institutional learning effects and the differentiation of power.<br/>We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based but may also include mature niches specialised in the exploitation of renewable sources. This implies a need to distinguish between lock-in mechanisms favouring the old fossil-based regime well-established (mature) renewable energy niches or new pathways.
Hydrogen-fueled Car Fire Spread to Adjacent Vehicles in Car Parks
Sep 2019
Publication
Car park fires are known to be dangerous due to the risk of fast fire spread from one car to another. In general no fatalities are recorded in such fires but they may have a great cost in relation to damaged cars and structural repair. A very recent example is the Liverpool multi-storey car park fire from December 31 2017. It destroyed 1400 cars and parts of the building structure collapsed. This questions the validity of current design praxis of car parks. Literature studies assumes a 12 minutes period for the fire spread from one gasoline fuelled car to another. Statistical research and test from the European commission of steel structures states that in an open car park at most 3-4 vehicles are expected to be on fire at the same time.<br/>A number of investigations have been made concerning vehicles performance in car park fires but only a few are concerned with hydrogen-fuelled vehicles (HFV). It is therefore important to investigate how these new vehicles may contribute to potential fire spread scenario. The aim of the paper is to report the outcome of car park fire spread simulations involving common fuelled and hydrogen fuelled cars. The case study is based on a typical car park found in Denmark. The simulation applied numerical models implemented in the Fire Dynamic Simulator (FDS). In particular the focus of the study is on the influence of the parking distance to fire spread to adjacent vehicles in case a TPRD is activated during a car fire. The results help understanding whether different design rules should be envisaged for such structures or how a sufficient safety level can be obtained by ensuring specific parking condition for the hydrogen-fuelled cars.
Power-to-fuels Via Solid-oxide Electrolyzer: Operating Window and Techno-economics
May 2019
Publication
Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO2) into hydrogen (or syngas) which can be further converted into synthetic fuels with plant-wise thermal integration. Electrolysis stack performance and durability determine the system design performance and long-term operating strategy; thus solid-oxide electrolyzer based power-to-fuels were investigated from the stack to system levels. At the stack level the data from a 6000-h stack testing under laboratory isothermal conditions were used to calibrate a quasi-2D model which enables to predict practical isothermal stack performance with reasonable accuracy. Feasible stack operating windows meeting various design specifications (e.g. specific syngas composition) were further generated to support the selection of operating points. At the system level with the chosen similar stack operating points various power-to-fuel systems including power-to-hydrogen power-to-methane power-to-methanol (dimethyl ether) and power-to-gasoline were compared techno-economically considering system-level heat integration. Several operating strategies of the stack were compared to address the increase in stack temperature due to degradation. The modeling results show that the system efficiency for producing H2 methane methanol/dimethyl ether and gasoline decreases sequentially from 94% (power-to-H2) to 64% (power-to-gasoline) based on a higher heating value. Co-electrolysis which allows better heat integration can improve the efficiency of the systems with less exothermic fuel-synthesis processes (e.g. methanol/dimethyl ether) but offers limited advantages for power-to-methane and power-to-gasoline systems. In a likely future scenario where the growing amount of electricity from renewable sources results in increasing periods of a negative electricity price solid oxide electrolyser based power-to-fuel systems are highly suitable for levelling the price fluctuations in an economic way.
Market Segmentation of Domestic and Commercial Natural Gas Appliances
Jan 2021
Publication
The main goal of the project is to enable the wide adoption of H2NG (hydrogen in natural gas) blends by closing knowledge gaps regarding technical impacts on residential and commercial gas appliances. The project consortium will identify and recommend appropriate codes and standards that should be adapted to answer the needs and develop a strategy for addressing the challenges for new and existing appliances.<br/>This deliverable on market segmentation is part of work package 2 and provides a quantitative segmentation of the gas appliance market in terms of appliance population numbers. It therefore prepares the project partners to perform the subsequent selection of the most representative product types to be tested in the laboratories of the THyGA partners.<br/>The classification is developed to categorise appliances installed in the field based on available statistics calculation methods and estimations. As a result appliance populations are provided for each technology segment that draw a representative picture of the installed end-use appliances within the European Union in 2020.
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.
Life Cycle Assessment of Hydrogen Production and Consumption in an Isolated Territory
Apr 2018
Publication
Hydrogen produced from renewables works as an energy carrier and as energy storage medium and thus hydrogen can help to overcome the intermittency of typical renewable energy sources. However there is no comprehensive environmental performance study of hydrogen production and consumption. In this study detailed cradle to grave life cycle analyses are performed in an isolated territory. The hydrogen is produced on-site by Polymer Electrolyte Membrane (PEM) water electrolysis based on electricity from wind turbines that would otherwise have been curtailed and subsequently transported with gas cylinder by road and ferry. The hydrogen is used to provide electricity and heat through fuel cell stacks as well as hydrogen fuel for fuel cell vehicles. In order to evaluate the environmental impacts related to the hydrogen production and utilisation this work conducts an investigation of the entire life cycle of the described hydrogen production transportation and utilisation. All the processes related to the equipment manufacture operation maintenance and disposal are considered in this study.
Materials for Hydrogen-based Energy Storage - Past, Recent Progress and Future Outlook
Dec 2019
Publication
Michael Hirscher,
Volodymyr A. Yartys,
Marcello Baricco,
José Bellosta von Colbe,
Didier Blanchard,
Robert C. Bowman Jr.,
Darren P. Broom,
Craig Buckley,
Fei Chang,
Ping Chen,
Young Whan Cho,
Jean-Claude Crivello,
Fermin Cuevas,
William I. F. David,
Petra E. de Jongh,
Roman V. Denys,
Martin Dornheim,
Michael Felderhoff,
Yaroslav Filinchuk,
George E. Froudakis,
David M. Grant,
Evan MacA. Gray,
Bjørn Christian Hauback,
Teng He,
Terry D. Humphries,
Torben R. Jensen,
Sangryun Kim,
Yoshitsugu Kojima,
Michel Latroche,
Hai-wen Li,
Mykhaylo V. Lototskyy,
Joshua W. Makepeace,
Kasper T. Møller,
Lubna Naheed,
Peter Ngene,
Dag Noreus,
Magnus Moe Nygård,
Shin-ichi Orimo,
Mark Paskevicius,
Luca Pasquini,
Dorthe B. Ravnsbæk,
M. Veronica Sofianos,
Terrence J. Udovic,
Tejs Vegge,
Gavin Walker,
Colin Webb,
Claudia Weidenthaler and
Claudia Zlotea
Globally the accelerating use of renewable energy sources enabled by increased efficiencies and reduced costs and driven by the need to mitigate the effects of climate change has significantly increased research in the areas of renewable energy production storage distribution and end-use. Central to this discussion is the use of hydrogen as a clean efficient energy vector for energy storage. This review by experts of Task 32 “Hydrogen-based Energy Storage” of the International Energy Agency Hydrogen TCP reports on the development over the last 6 years of hydrogen storage materials methods and techniques including electrochemical and thermal storage systems. An overview is given on the background to the various methods the current state of development and the future prospects. The following areas are covered; porous materials liquid hydrogen carriers complex hydrides intermetallic hydrides electro-chemical storage of energy thermal energy storage hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage
Artificial Neural Network Based Optimization of a Six-step Two-bed Pressure Swing Adsorption System for Hydrogen Purification
Apr 2021
Publication
The pressure swing adsorption (PSA) system is widely applied to separate and purify hydrogen from gaseous mixtures. The extended Langmuir equation fitted from the extended Langmuir-Freundlich isotherm has been used to predict the adsorption isothermal of hydrogen and methane on the zeolite 5A adsorbent bed. A six-step two-bed PSA model for hydrogen purification is developed and validated by comparing its simulation results with other works. The effects of the adsorption pressure the P/F ratio the adsorption step time and the pressure equalization time on the performance of the hydrogen purification system are studied. A four-step two-bed PSA model is taken into consideration and the six-step PSA system shows higher about 13% hydrogen recovery than the four-step PSA system. The performance of the vacuum pressure swing adsorption (VPSA) system is compared with that of the PSA system the VPSA system shows higher hydrogen purity than the PSA system. Based on the validated PSA model a dataset has been produced to train the artificial neural network (ANN) model. The effects of the number of neurons in the hidden layer and the number of samples used for training ANN model on the predicted performance of ANN model are investigated. Then the well-trained ANN model with 6 neurons in the hidden layer is applied to predict the performance of the PSA system for hydrogen purification. Multi-objective optimization of hydrogen purification system is performed based on the trained ANN model. The artificial neural network can be considered as a very effective method for predicting and optimizing the performance of the PSA system for hydrogen purification.
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
Optimization of Geothermal- and Solar-driven Clean Electricity and Hydrogen Production Multi-generation Systems to Address the Energy Nexus
Jan 2022
Publication
Given the limited sources of fossil fuels mankind should find new ways to meet its energy demands. In this regard geothermal and solar energy are acknowledged as reliable safe promising and clean means for this purpose. In this research study a comparative analysis is applied on geothermal and solar-driven multi-generation systems for clean electricity and hydrogen production through energy and exergy assessments. The system consists of an organic Rankine cycle a proton electrolyte membrane electrolyzer and a thermoelectric generator subsystem. The Engineering Equation Solver software has been utilized in order to model the system and obtain the output contours sensitivity analysis and exergy destruction. The results were calculated considering the ambient temperature of Bandar Abbas city as a case study considering the geothermal system due to better performance in comparison to the solar system. According to the sensitivity analysis the turbine efficiency evaporator inlet temperature thermoelectric generator suitability criterion pump efficiency and evaporator inlet mass flow rate are the most influential parameters. Also the exergy analysis showed that the utmost system's exergy destruction is pertinent to the evaporator and the least is related to the pump. In addition the system produces 352816 kWh and 174.913 kg of electrical power and hydrogen during one year.
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.
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.
A Modeling Study of Lifetime and Performance Improvements of Solid Oxide Fuel Cell by Reversed Pulse Operation
Jan 2022
Publication
Chromium poisoning of the air electrode is a primary degradation mechanism for solid oxide cells (SOCs) operating under fuel cell mode. Recent experimental findings show that reversed pulse operation for SOCs operated as electrolyser cells can reverse this degradation and extend the lifetime. Here we use a multiphysics model of an SOC to investigate the effects of reversed pulse operation for alleviating chromium poisoning of the air electrode. We study the effects of time fraction of the operation under fuel cell and electrolysis modes cyclic operation starting after a certain duration and fuel cell and electrolysis current densities on the cell lifetime total power and hydrogen production. Our modeling shows that reversed pulse operation enhances cell lifetime and total power for all different cases considered in this study. Moreover results suggest that the cell lifetime total power and hydrogen production can be increased by reversed pulse operation at longer operation times under electrolysis mode cyclic operation starting from the beginning and lower electrolysis current densities. All in all this paper documents and establishes a computational framework that can serve as a platform to assess and quantify the increased profitability of SOCs operating under a co-production operation through reversed pulse operation.
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.
Life Cycle Assessment Integration into Energy System Models: An Application for Power-to-Methane in the EU
Nov 2019
Publication
As the EU energy system transitions to low carbon the technology choices should consider a broader set of criteria. The use of Life Cycle Assessment (LCA) prevents burden shift across life cycle stages or impact categories while the use of Energy System Models (ESM) allows evaluating alternative policies capacity evolution and covering all the sectors. This study does an ex-post LCA analysis of results from JRC-EU-TIMES and estimates the environmental impact indicators across 18 categories in scenarios that achieve 80–95% CO2 emission reduction by 2050. Results indicate that indirect CO2 emissions can be as large as direct ones for an 80% CO2 reduction target and up to three times as large for 95% CO2 reduction. Impact across most categories decreases by 20–40% as the CO2 emission target becomes stricter. However toxicity related impacts can become 35–100% higher. The integrated framework was also used to evaluate the Power-to-Methane (PtM) system to relate the electricity mix and various CO2 sources to the PtM environmental impact. To be more attractive than natural gas the climate change impact of the electricity used for PtM should be 123–181 gCO2eq/kWh when the CO2 comes from air or biogenic sources and 4–62 gCO2eq/kWh if the CO2 is from fossil fuels. PtM can have an impact up to 10 times larger for impact categories other than climate change. A system without PtM results in ~4% higher climate change impact and 9% higher fossil depletion while having 5–15% lower impact for most of the other categories. This is based on a scenario where 9 parameters favor PtM deployment and establishes the upper bound of the environmental impact PtM can have. Further studies should work towards integrating LCA feedback into ESM and standardizing the methodology.
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