Transmission, Distribution & Storage
Hydrogenization of Underground Storage of Natural Gas
Aug 2015
Publication
The intermittent production of the renewable energy imposes the necessity to temporarily store it. Large amounts of exceeding electricity can be stored in geological strata in the form of hydrogen. The conversion of hydrogen to electricity and vice versa can be performed in electrolyzers and fuel elements by chemical methods. The nowadays technical solution accepted by the European industry consists of injecting small concentrations of hydrogen in the existing storages of natural gas. The progressive development of this technology will finally lead to the creation of underground storages of pure hydrogen. Due to the low viscosity and low density of hydrogen it is expected that the problem of an unstable displacement including viscous fingering and gravity overriding will be more pronounced. Additionally the injection of hydrogen in geological strata could encounter chemical reactivity induced by various species of microorganisms that consume hydrogen for their metabolism. One of the products of such reactions is methane produced from Sabatier reaction between H2 and CO2. Other hydrogenotrophic reactions could be caused by acetogenic archaea sulfate-reducing bacteria and iron-reducing bacteria. In the present paper a mathematical model is presented which is capable to reflect the coupled hydrodynamic and bio-chemical processes in UHS. The model has been numerically implemented by using the open source code DuMuX developed by the University of Stuttgart. The obtained bio-chemical version of DuMuX was used to model the evolution of a hypothetical underground storage of hydrogen. We have revealed that the behavior of an underground hydrogen storage is different than that of a natural gas storage. Both the hydrodynamic and the bio-chemical effects contribute to the different characteristics.
A Review of Hydrogen/rock/brine Interaction: Implications for Hydrogen Geo-storage
Dec 2022
Publication
Hydrogen (H2) is currently considered a clean fuel to decrease anthropogenic greenhouse gas emissions and will play a vital role in climate change mitigation. Nevertheless one of the primary challenges of achieving a complete H2 economy is the large-scale storage of H2 which is unsafe on the surface because H2 is highly compressible volatile and flammable. Hydrogen storage in geological formations could be a potential solution to this problem because of the abundance of such formations and their high storage capacities. Wettability plays a critical role in the displacement of formation water and determines the containment safety storage capacity and amount of trapped H2 (or recovery factor). However no comprehensive review article has been published explaining H2 wettability in geological conditions. Therefore this review focuses on the influence of various parameters such as salinity temperature pressure surface roughness and formation type on wettability and consequently H2 storage. Significant gaps exist in the literature on understanding the effect of organic material on H2 storage capacity. Thus this review summarizes recent advances in rock/H2/brine systems containing organic material in various geological reservoirs. The paper also presents influential parameters affecting H2 storage capacity and containment safety including liquid–gas interfacial tension rock–fluid interfacial tension and adsorption. The paper aims to provide the scientific community with an expert opinion to understand the challenges of H2 storage and identify storage solutions. In addition the essential differences between underground H2 storage (UHS) natural gas storage and carbon dioxide geological storage are discussed and the direction of future research is presented. Therefore this review promotes thorough knowledge of UHS provides guidance on operating large-scale UHS projects encourages climate engineers to focus more on UHS research and provides an overview of advanced technology. This review also inspires researchers in the field of climate change to give more credit to UHS studies.
Addressing the Low-carbon Million-gigawatt-hour Energy Storage Challenge
Nov 2021
Publication
The energy system of the United States requires several million gigawatt hours of energy storage to meet variable demand for energy driven by (1) weather (heating and cooling) (2) social patterns (daily and weekday/weekend) of work play and sleep (3) weather-dependent energy production (wind and solar) and (4) industrial requirements. In a low-carbon world four storage options can meet this massive requirement at affordable costs: nuclear fuels heat storage hydrocarbon liquids made from biomass and hydrogen. Because of the different energy sector characteristics (electrical supply transportation commercial and industrial) each of these options must be developed. Capital costs associated with electricity storage at this scale using for example batteries and hydroelectric technologies are measured in hundreds of trillions of dollars for the United States alone and thus are not viable.
OIES Podcast: Global Trade of Hydrogen: What is the Best Way to Transfer Hydrogen Over Long Distances?
Aug 2022
Publication
In this podcast David Ledesma talks with Rahmat Poudineh Senior Research Fellow and Aliaksei Patonia Research Fellow on issues and options with respect to long distance transportation of the hydrogen.
Hydrogen currently is mainly a local or regional commodity. If hydrogen is to become a truly global-traded commodity it needs to be transported over long transoceanic distances in an economical way. However unlike natural gas shipping compressed or liquefied hydrogen over long distances is very inefficient and expensive. At the same time hydrogen can be converted into multiple carriers with a higher energy density and higher transport capacity such as liquid ammonia toluene/methylcyclohexane (MCH) or methanol. These chemicals have their own advantages and drawbacks and their techno-economic characteristics in terms of boil-off gas and thermodynamic and conversion losses play a key role in the efficiency of transoceanic transportation of the hydrogen.
On the other hand apart from techno-economic features there are other factors to consider for long distance transportation of the hydrogen via its careers. Here such issues as safety public acceptance as well as legal and regulatory constraints may come into play. Another factor is the availability of the industries and infrastructures already developed around any of possible hydrogen carriers as well as their potential industrial applicability beyond hydrogen. Finally technological progress in other decarbonization applications and most importantly full commercialization of CCUS solutions is likely to dramatically change the approach towards long distance hydrogen transportation.
The podcast can be found on their website.
Hydrogen currently is mainly a local or regional commodity. If hydrogen is to become a truly global-traded commodity it needs to be transported over long transoceanic distances in an economical way. However unlike natural gas shipping compressed or liquefied hydrogen over long distances is very inefficient and expensive. At the same time hydrogen can be converted into multiple carriers with a higher energy density and higher transport capacity such as liquid ammonia toluene/methylcyclohexane (MCH) or methanol. These chemicals have their own advantages and drawbacks and their techno-economic characteristics in terms of boil-off gas and thermodynamic and conversion losses play a key role in the efficiency of transoceanic transportation of the hydrogen.
On the other hand apart from techno-economic features there are other factors to consider for long distance transportation of the hydrogen via its careers. Here such issues as safety public acceptance as well as legal and regulatory constraints may come into play. Another factor is the availability of the industries and infrastructures already developed around any of possible hydrogen carriers as well as their potential industrial applicability beyond hydrogen. Finally technological progress in other decarbonization applications and most importantly full commercialization of CCUS solutions is likely to dramatically change the approach towards long distance hydrogen transportation.
The podcast can be found on their website.
Effects of Thermomechanical Processing on Hydrogen Embrittlement Properties of Ultrahigh-Strength TRIP-Aided Bainitic Ferrite Steels
Jan 2022
Publication
The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength low-alloy transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by conducting conventional tensile tests after hydrogen charging and constant load four-point bending tests with hydrogen charging. The 0.4 mass%C-TBF steel achieved refinement of the microstructure improved retained austenite characteristics and strengthening owing to thermomechanical processing. This might be attributed to dynamic and static recrystallizations during thermomechanical processing in TBF steels. Moreover the hydrogen embrittlement resistances were improved by the thermomechanical processing in TBF steels. This might be caused by the refinement of the microstructure an increase in the stability of the retained austenite and low hydrogen absorption of the thermomechanically processed TBF steels.
Risk Assessment of the Large-Scale Hydrogen Storage in Salt Caverns
May 2021
Publication
Salt caverns are accepted as an ideal solution for high-pressure hydrogen storage. As well as considering the numerous benefits of the realization of underground hydrogen storage (UHS) such as high energy densities low leakage rates and big storage volumes risk analysis of UHS is a required step for assessing the suitability of this technology. In this work a preliminary quantitative risk assessment (QRA) was performed by starting from the worst-case scenario: rupture at the ground of the riser pipe from the salt cavern to the ground. The influence of hydrogen contamination by bacterial metabolism was studied considering the composition of the gas contained in the salt caverns as time variable. A bow-tie analysis was used to highlight all the possible causes (basic events) as well as the outcomes (jet fire unconfined vapor cloud explosion (UVCE) toxic chemical release) and then consequence and risk analyses were performed. The results showed that a UVCE is the most frequent outcome but its effect zone decreases with time due to the hydrogen contamination and the higher contents of methane and hydrogen sulfide.
Large-scale Stationary Hydrogen Storage via Liquid Organic Hydrogen Carriers
Aug 2021
Publication
Large-scale stationary hydrogen storage is critical if hydrogen is to fulfill its promise as a global energy carrier. While densified storage via compressed gas and liquid hydrogen is currently the dominant approach liquid organic molecules have emerged as a favorable storage medium because of their desirable properties such as low cost and compatibility with existing fuel transport infrastructure. This perspective article analytically investigates hydrogenation systems' technical and economic prospects using liquid organic hydrogen carriers (LOHCs) to store hydrogen at a large scale compared to densified storage technologies and circular hydrogen carriers (mainly ammonia and methanol). Our analysis of major system components indicates that the capital cost for liquid hydrogen storage is more than two times that for the gaseous approach and four times that for the LOHC approach. Ammonia and methanol could be attractive options as hydrogen carriers at a large scale because of their compatibility with existing liquid fuel infrastructure. However their synthesis and decomposition are energy and capital intensive compared to LOHCs. Together with other properties such as safety these factors make LOHCs a possible option for large-scale stationary hydrogen storage. In addition hydrogen transportation via various approaches is briefly discussed. We end our discussions by identifying important directions for future research on LOHCs.
Power-to-hydrogen as Seasonal Energy Storage: An Uncertainty Analysis for Optimal Design of Low-carbon Multi-energy Systems
Jun 2020
Publication
This study analyzes the factors leading to the deployment of Power-to-Hydrogen (PtH2) within the optimal design of district-scale Multi-Energy Systems (MES). To this end we utilize an optimization framework based on a mixed integer linear program that selects sizes and operates technologies in the MES to satisfy electric and thermal demands while minimizing annual costs and CO2 emissions. We conduct a comprehensive uncertainty analysis that encompasses the entire set of technology (e.g. cost efficiency lifetime) and context (e.g. economic policy grid carbon footprint) input parameters as well as various climate-referenced districts (e.g. environmental data and energy demands) at a European-scope.
Minimum-emissions MES with large amounts of renewable energy generation and high ratios of seasonal thermal-to-electrical demand optimally achieve zero operational CO2 emissions by utilizing PtH2 seasonally to offset the long-term mismatch between renewable generation and energy demand. PtH2 is only used to abate the last 5–10% emissions and it is installed along with a large battery capacity to maximize renewable self-consumption and completely electrify thermal demand with heat pumps and fuel cells. However this incurs additional cost. Additionally we show that ‘traditional’ MES comprised of renewables and short-term energy storage are able to decrease emissions by 90% with manageable cost increases.
The impact of uncertainty on the optimal system design reveals that the most influential parameter for PtH2 implementation is (1) heat pump efficiency as it is the main competitor in providing renewable-powered heat in winter. Further battery (2) capital cost and (3) lifetime prove to be significant as the competing electrical energy storage technology. In the face of policy uncertainties a CO2 tax shows large potential to reduce emissions in district MES without cost implications. The results illustrate the importance of capturing the dynamics and uncertainties of short- and long-term energy storage technologies for assessing cost and CO2 emissions in optimal MES designs over districts with different geographical scopes.
Minimum-emissions MES with large amounts of renewable energy generation and high ratios of seasonal thermal-to-electrical demand optimally achieve zero operational CO2 emissions by utilizing PtH2 seasonally to offset the long-term mismatch between renewable generation and energy demand. PtH2 is only used to abate the last 5–10% emissions and it is installed along with a large battery capacity to maximize renewable self-consumption and completely electrify thermal demand with heat pumps and fuel cells. However this incurs additional cost. Additionally we show that ‘traditional’ MES comprised of renewables and short-term energy storage are able to decrease emissions by 90% with manageable cost increases.
The impact of uncertainty on the optimal system design reveals that the most influential parameter for PtH2 implementation is (1) heat pump efficiency as it is the main competitor in providing renewable-powered heat in winter. Further battery (2) capital cost and (3) lifetime prove to be significant as the competing electrical energy storage technology. In the face of policy uncertainties a CO2 tax shows large potential to reduce emissions in district MES without cost implications. The results illustrate the importance of capturing the dynamics and uncertainties of short- and long-term energy storage technologies for assessing cost and CO2 emissions in optimal MES designs over districts with different geographical scopes.
Thermodynamic Performance Comparison of Various Energy Storage Systems from Source-to-electricity for Renewable Energy Resources
Dec 2020
Publication
This study discusses and thermodynamically analyzes several energy storage systems namely; pumped hydro compressed air hot water storage molten salt thermal storage hydrogen ammonia lithium-ion battery Zn-air battery redox flow battery reversible fuel cells supercapacitors and superconducting magnetic storage through the first and second law of thermodynamics. By fixing an electrical output of 100 kW for all systems the energy efficiencies obtained for the considered energy storage methods vary between 10.9% and 74.6% whereas the exergy efficiencies range between 23.1% and 71.9%. The exergy destruction rates are also calculated for each system ranging from 1.640 kW to 356 kW. The highest destruction rate is obtained for the solar-driven molten salt thermal energy storage system since it includes thermal energy conversion via the heliostat field. Furthermore the roundtrip efficiencies for the electrochemical and electromagnetic storage systems are compared with the analyzed systems ranging from 58% to 94%. Renewable sources (solar wind ocean current biomass and geothermal) energy conversion efficiencies are also considered for the final round-trip performances. The molten salt and hot water systems are applicable to solar geothermal and biomass. The highest source-to-electricity efficiency is obtained for the super magnetic storage with 37.6% when using wind ocean current and biomass sources.
Impact Assessment of Hydrogen on Transmission Pipeline BPDs in IGEM/TD/1
Jul 2021
Publication
As part of the LTS Futures HyTechnical project IGEM requested that DNV GL undertake an assessment of the possible impact of hydrogen transmission on BPDs to support the development of supplements to the existing suite of natural gas standards to accommodate the possible future use of hydrogen. The current state of knowledge of the behaviour of large scale high pressure hydrogen releases is limited in comparison with the considerable body of data from research and operational experience of natural gas but is adequate to undertake an impact assessment to take account of the different gas outflow and fire characteristics of 100% hydrogen vs. natural gas.<br/>Calculations of the BPDs for 100% hydrogen pipeline fires on an equivalent basis to those in IGEM/TD/1 for natural gas have been performed with a degree of confidence in the results and demonstrated that the equivalent BPDs for 100% hydrogen are approximately 10% smaller than for natural gas. The results are presented graphically in this report.<br/>However hydrogen introduces the potential for substantially higher overpressures than natural gas due to the higher flame speed and wider flammable limits if delayed ignition is a credible event. The overpressure estimates presented in this report are intended to be scoping calculations to put the likely overpressures into context. The results suggest that significant overpressures are possible at the BPDs but there is a lack of evidence to support the estimation of the overpressures following delayed ignition of a large turbulent hydrogen release in the open (in contrast to explosions in confined or congested regions) and there is a high degree of uncertainty in the predictions presented here. It is therefore recommended that large scale pipeline rupture experiments are performed similar to those undertaken previously for hydrogen natural gas and natural gas/hydrogen mixtures but with ignition engineered to take place after a short delay in order to measure the overpressures and provide the means to validate or refine the predictions made.<br/>The analysis has highlighted limitations in the original method of calculating BPDs in IGEM/TD/1 which reflects the techniques available at the time approximately 40 years ago. Since then understanding of the hazards from pipeline failures and the ability to model the consequences and predict the associated risks to people in the surrounding area have advanced very considerably facilitated by software tools and documented in standards such as IGEM/TD/2. These methods allow the highly transient nature of a high pressure gas pipeline rupture release to be modelled more accurately and for the thermal effects of fires on people and buildings to be calculated taking account of the time-varying thermal dose.<br/>For these reasons a simple comparison of the possible overpressure effects of delayed ignition of a 100% hydrogen release at the BPDs can be misleading and implies that the overpressure hazards could be more severe than those for fires which may not be the case. Example calculations have been performed for a representative pipeline case which indicate that using current methods the predicted thermal hazard distances for 100% hydrogen pipeline fires (house burning and escape for people) are substantially greater than those estimated for overpressures following delayed ignition for similar levels of vulnerability. This report addresses buried pipelines only – the potential for more severe explosion overpressure effects for hydrogen releases may be more significant for Above Ground Installations (AGIs) especially where congestion or confinement may be present. It is recommended that similar studies are conducted to quantify the effect of hydrogen conversion on the consequences and risks associated with hydrogen releases at AGIs.<br/>Finally it is stressed that the analysis in this report does not consider the relative risks for 100% hydrogen and the equivalent natural gas pipelines. There remain uncertainties in the failure frequencies for steel pipelines transporting hydrogen and particularly the probability of immediate and delayed ignition. The likelihood of delayed ignition of a large turbulent high pressure hydrogen gas pipeline rupture release may be very low due to the wider flammability limits and lower minimum ignition energy for hydrogen compared with natural gas. Additional research is currently ongoing or planned to address the gaps in knowledge for 100% hydrogen which should allow more robust comparisons of the relative risks to be made in the future.
Cost Benefits of Optimizing Hydrogen Storage and Methanation Capacities for Power-to-Gas Plants in Dynamic Operation
Oct 2019
Publication
Power-to-Gas technologies offer a promising approach for converting renewable electricity into a molecular form (fuel) to serve the energy demands of non-electric energy applications in all end-use sectors. The technologies have been broadly developed and are at the edge of a mass roll-out. The barriers that Power-to-Gas faces are no longer technical but are foremost regulatory and economic. This study focuses on a Power-to-Gas pathway where electricity is first converted in a water electrolyzer into hydrogen which is then synthetized with carbon dioxide to produce synthetic natural gas. A key aspect of this pathway is that an intermittent electricity supply could be used which could reduce the amount of electricity curtailment from renewable energy generation. Interim storages would then be necessary to decouple the synthesized part from hydrogen production to enable (I) longer continuous operation cycles for the methanation reactor and (II) increased annual full-load hours leading to an overall reduction in gas production costs. This work optimizes a Power-to-Gas plant configuration with respect to the cost benefits using a Monte Carlo-based simulation tool. The results indicate potential cost reductions of up to 17% in synthetic natural gas production by implementing well-balanced components and interim storages. This study also evaluates three different power sources which differ greatly in their optimal system configuration. Results from time-resolved simulations and sensitivity analyses for different plant designs and electricity sources are discussed with respect to technical and economic implications so as to facilitate a plant design process for decision makers.
Operation of Metal Hydride Hydrogen Storage Systems for Hydrogen Compression Using Solar Thermal Energy
Mar 2016
Publication
By using a newly constructed bench-scale hydrogen energy system with renewable energy ‘Pure Hydrogen Energy System’ the present study demonstrates the operations of a metal hydride (MH) tank for hydrogen compression as implemented through the use solar thermal energy. Solar thermal energy is used to generate hot water as a heat source of the MH tank. Thus 70 kg of LaNi5 one of the most typical alloys used for hydrogen storage was placed in the MH tank. We present low and high hydrogen flow rate operations. Then the operations under winter conditions are discussed along with numerical simulations conducted from the thermal point of view. Results show that a large amount of heat (>100 MJ) is generated and the MH hydrogen compression is available.
Everything About Hydrogen Podcast: Storage for the Future!
Jan 2022
Publication
For our first episode of 2022 we invited Jørn Helge Dahl Global Director of Sales&Marketing at Hexagon Purus to talk about hydrogen storage with the EAH podcast and to explain the types of solutions available today Hexagon's history and plans for the future alongside some commentary on US hydrogen strategy from the gang.
The podcast can be found on their website
The podcast can be found on their website
Hydrogen Embrittlement in a 2101 Lean Duplex Stainless Steel
Sep 2019
Publication
Duplex Stainless Steels (DSSs) are an attractive class of materials characterized by a strong corrosion resistance in many aggressive environments. Thanks to the high mechanical performances DSSs are widely used for many applications in petrochemical industry chemical and nuclear plants marine environment desalination etc.<br/>Among the DSSs critical aspects concerning the embrittlement process it is possible to remember the steel sensitization and the hydrogen embrittlement.<br/>The sensitization of the DSSs is due to the peculiar chemical composition of these grades which at high temperature are susceptible to carbide nitrides and second phases precipitation processes mainly at grains boundary and in the ferritic grains. The hydrogen embrittlement process is strongly influenced by the duplex (austenitic-ferritic) microstructure and by the loading conditions.<br/>In this work a rolled lean ferritic-austenitic DSS (2101) has been investigated in order to analyze the hydrogen embrittlement mechanisms by means of slow strain rate tensile tests considering the steel after different heat treatments. The damaging micromechanisms have been investigated by means of the scanning electron microscope observations on the fracture surfaces.
Effect of Defects and Hydrogen on the Fatigue Limit of Ni-based Superalloy 718
Dec 2019
Publication
Tension-compression fatigue tests were performed on two types of Ni-based superalloy 718 with different microstructures to which small artificial defects of various shapes and sizes were introduced. Similar tests were also conducted on hydrogen-charged specimens with defects with a solute hydrogen content ranging from 26.3 to 91.0 mass ppm. In the non-charged specimens in particular the fatigue strength susceptibility to defects varied significantly according to the type of microstructural morphology i.e. a smaller grain size made the alloy more vulnerable to defects. The fatigue limit as a small-crack threshold was successfully predicted using the √area parameter model. Depending on the size of defects the fatigue limit was calculated in relation to three phases: (i) harmless-defect regime (ii) small-crack regime and (iii) large-crack regime. Such a classification enabled comprehensive fatigue limit evaluation in a wide array of defects taking into consideration (a) the defect size over a range of small crack and large crack and (b) the characteristics of the matrix represented by grain size and hardness. In addition the effect of defects and hydrogen on fatigue strength will be comprehensively discussed based on a series of experimental results.
Development of Hydrogen Storage Tank Systems Based on Complex Metal Hydrides
Sep 2015
Publication
This review describes recent research in the development of tank systems based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited especially for thermolysis-based systems where so far only demonstration projects have been performed. Hydrolysis-based systems find their way in space naval military and defense applications due to their compatibility with proton exchange membrane (PEM) fuel cells. Tank design modeling and development for thermolysis and hydrolysis systems as well as commercial applications of hydrolysis systems are described in more detail in this review. For thermolysis mostly sodium aluminum hydride containing tanks were developed and only a few examples with nitrides ammonia borane and alane. For hydrolysis sodium borohydride was the preferred material whereas ammonia borane found less popularity. Recycling of the sodium borohydride spent fuel remains an important part for their commercial viability.
Energy Transition: Measurement Needs Within the Hydrogen Industry
Dec 2017
Publication
Hydrogen in the UK is beginning to shift from hypothetical debates to practical demonstration projects. An ever-growing evidence base has showcased how the costs of hydrogen and its barriers to entry are reducing such that it now has practical potential to contribute to the decarbonisation of the UK's energy sector.
Despite this hydrogen has yet to have wide commercial uptake due in part to a number of barriers where measurement plays a critical role. To accelerate the shift towards the hydrogen economy these challenges have been identified and prioritised by NPL.
The report Energy transition: Measurement needs within the hydrogen industry outlines the challenges identified. The highest priority issues are:
This Document can be downloaded from their website
Despite this hydrogen has yet to have wide commercial uptake due in part to a number of barriers where measurement plays a critical role. To accelerate the shift towards the hydrogen economy these challenges have been identified and prioritised by NPL.
The report Energy transition: Measurement needs within the hydrogen industry outlines the challenges identified. The highest priority issues are:
- Material development for fuel cells and electrolysers to reduce costs and assess critical degradation mechanisms – extending lifetime and durability is key to the commercialisation of these technologies.
- Impact assessment of added odorant to hydrogen to aid leak detection. Measurement of its impact during pipeline transportation and on the end-use application (particularly fuel cell technology) will be important to provide assurance that it will not affect lifetime and durability.
- Determination of the blend ratio when hydrogen is mixed with natural gas in the gas grid. Accurate flow rate measurement and validated metering methods are needed to ensure accurate billing of the consumer.
- Measurement of the combustion properties of hydrogen including flame detection and propagation temperature and nitrogen oxides (NOx) emissions should it be used for heat applications to ensure existing and new appliances are suitable for hydrogen.
- Assessment of the suitability of existing gas infrastructure and materials for hydrogen transportation. Building an understanding of what adaptations might need to be made to avoid for example air permeation metal embrittlement and hydrogen leakage.
- Validated techniques for hydrogen storage which will require measurement of the efficiency and capacity of each mechanism through robust metering leakage detection and purity analysis to ensure they are optimised for the storage of hydrogen gas.
This Document can be downloaded from their website
Experimental Investigation on CO2 Methanation Process for Solar Energy Storage Compared to CO2-Based Methanol Synthesis
Jun 2017
Publication
The utilization of the captured CO2 as a carbon source for the production of energy storage media offers a technological solution for overcoming crucial issues in current energy systems. Solar energy production generally does not match with energy demand because of its intermittent and non-programmable nature entailing the adoption of storage technologies. Hydrogen constitutes a chemical storage for renewable electricity if it is produced by water electrolysis and is also the key reactant for CO2 methanation (Sabatier reaction). The utilization of CO2 as a feedstock for producing methane contributes to alleviate global climate changes and sequestration related problems. The produced methane is a carbon neutral gas that fits into existing infrastructure and allows issues related to the aforementioned intermittency and non-programmability of solar energy to be overcome. In this paper an experimental apparatus composed of an electrolyzer and a tubular fixed bed reactor is built and used to produce methane via Sabatier reaction. The objective of the experimental campaign is the evaluation of the process performance and a comparison with other CO2 valorization paths such as methanol production. The investigated pressure range was 2–20 bar obtaining a methane volume fraction in outlet gaseous mixture of 64.75% at 8 bar and 97.24% at 20 bar with conversion efficiencies of respectively 84.64% and 99.06%. The methanol and methane processes were compared on the basis of an energy parameter defined as the spent energy/stored energy. It is higher for the methanol process (0.45) with respect to the methane production process (0.41–0.43) which has a higher energy storage capability.
Sustainability Indicators for the Manufacturing and Use of a Fuel Cell Prototype and Hydrogen Storage for Portable Uses
Oct 2021
Publication
A sustainability assessment regarding the manufacturing process and the use of a new proton exchange membrane fuel cell (PEMFC) specially designed for portable hydrogen applications is presented. The initial fuel cell prototype has been configured by taking into account exclusively technical issues. However a life cycle analysis considering environmental and socioeconomic impacts is crucial to improve the model to develop a more sustainable product. From the environ‐ mental perspective the durability of the system and its efficiency are key elements required to de‐ crease the potential overall impacts. High electricity consumption for manufacturing requires a commitment to the use of renewable energies due to the high current value of the projected impact of climate change (42.5 tonnes of CO2 eq). From the socioeconomic point of view the dependence of imported components required for the synthesis of some materials displaces the effects of value added and employment in Spain potentially concentrating the largest impact on countries such as Singapore Japan and the UK whereas the cell assembly would have a greater benefit for the country of fabrication. These results provide a basis for new research strategies since they can be considered standard values for improving future upgrades of the fuel cell in terms of sustainability.
Conversion of the UK Gas System to Transport Hydrogen
May 2013
Publication
One option to decarbonise residential heat in the UK is to convert the existing natural gas networks to deliver hydrogen. We review the technical feasibility of this option using semistructured interviews underpinned by a literature review and we assess the potential economic benefits using the UK MARKAL energy systems model. We conclude that hydrogen can be transported safely in the low-pressure pipes but we identify concerns over the reduced capacity of the system and the much lower linepack storage compared to natural gas. New hydrogen meters and sensors would have to be fitted to every building in a hydrogen conversion program and appliances would have to be converted unless the government was to legislate to make them hydrogen-ready in advance. Converting the gas networks to hydrogen is a lower-cost residential decarbonisation pathway for the UK than those identified previously. The cost-optimal share of hydrogen is sensitive to the conversion cost and to variations in the capital costs of heat pumps and micro-CHP fuel cells. With such small cost differentials between technologies the decision to convert the networks will also depend on non-economic factors including the relative performance of technologies and the willingness of the government to organise a conversion program.
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