Feasibility analysis of blending hydrogen into natural gas networks

Hydrogen fuel has the potential to mitigate the negative effects of greenhouse gases and climate change by neutralizing carbon emissions. Transporting large volume of hydrogen through pipelines needs hydrogen-specific infrastructure such as hydrogen pipelines and compressors, which can become an economic barrier. Thus, the idea of blending hydrogen into existing natural gas pipelines arises as a potential alternative for transporting hydrogen economically by using existing natural gas grids. However, there are several potential issues that must be considered when blending hydrogen into natural gas pipelines. Hydrogen has different physical and chemical properties from natural gas, including a smaller size and lighter weight, which require higher operating pressures to deliver the same amount of energy as natural gas. Additionally, hydrogen's small molecular size and lower ignition energy make it more likely to permeate through pipeline materials and seals, leading to degradation, and its wider flammability limits make it a safety hazard when leaks occur. In this study, we investigate these potential issues through simulation and technical surveys. We develop a gas hydraulic model to simulate the physical characteristics of a transmission and a distribution pipeline. This model is used throughout the study to visualize the potential impacts of switching from natural gas to hydrogen, and to investigate potential problems and solutions. Furthermore, we develop a Real-Time Transient Model (RTTM) to address the compatibility of current computational pipeline monitoring (CPM) based leak detection methods with blended hydrogen. Finally, we suggest the optimal hydrogen concentration for this model, and investigate the amount of carbon reduction that could be achieved, while considering the energy needs of the system.     

A review on hydrogen production and utilization: Challenges and opportunities

Environment-friendly, safe and reliable energy supplies are indispensable to society for sustainable development and high life quality where even though social, environmental, political and economic challenges may play a vital role in their provision. Our continuously growing energy demand is driven by extensive growth in economic development and population and places an ever-increasing burden on fossil fuel utilization that represent a substantial percentage of this increasing energy demand but also creates challenges associated with increased greenhouse gas (GHG) emissions and resource depletion. Such challenges make the global transition obligatory from conventional to renewable energy sources. Hydrogen is emerging as a new energy vector outside its typical role and receiving more recognition globally as a potential fuel pathway, as it offers advantages in use cases and unlike synthetic carbon-based fuels can be truly carbon neutral or even negative on a life cycle basis. This review paper provides critical analysis of the state-of-the-art in blue and green hydrogen production methods using conventional and renewable energy sources, utilization of hydrogen, storage, transportation, distribution and key challenges and opportunities in the commercial deployment of such systems. Some of the key promising renewable energy sources to produce hydrogen, such as solar and wind, are intermittent; hydrogen appears to be the best candidate to be employed for multiple purposes blending the roles of fuel energy carrier and energy storage modality. Furthermore, this study offers a comparative assessment of different non-renewable and renewable hydrogen production systems based on system design, cost, global warming potential (GWP), infrastructure and efficiency. Finally the key challenges and opportunities associated with hydrogen production, storage, transportation and distribution and commercial-scale deployment are addressed.     

Hydrogen energy storage integrated hybrid renewable energy systems: A review analysis for future research directions

Hydrogen energy storage systems (HydESS) and their integration with renewable energy sources into the grid have the greatest potential for energy production and storage while controlling grid demand to enhance energy sustainability. This paper presents a bibliometric analysis based on a comprehensive review of the highly cited articles on HydESS to provide a detailed insight into future directions and applications. The study was carried out by using the Scopus database search engine to look for filtered keywords in the HydESS and related research. It can be demonstrated that the HydESS literature expanded rapidly from 2016 to 2021 compared to 2011 to 2015. It is found that 89.17% of published articles explained control and test systems-based methods, whereas 10.83% of publications discuss review assessments. Our analysis of highly cited articles on HydESS highlights several aspects, such as methods and systems, issues, difficulties, and challenges to establishing current constraints and research gaps. This evaluation can enhance operational performance, environmental friendliness, energy savings, uninterrupted power supply service, cost benefits, on-site generation, and adaptability. It would be beneficial for technology development and the growth of the hydESS industry. This study may act as a guideline not only for academics in determining the line of research and generating additional discoveries, but also for the government in formulating financial strategies.     

The economic and environmental impact of power to hydrogen/power to methane facilities on hybrid power-natural gas energy systems

The curtailment of renewable energy would be reduced by converting it to hydrogen or methane using power to hydrogen (P2H) facilities or power to methane (P2M) facilities. Both hydrogen and methane can be injected into the existing natural gas system which has significant potential to unlock the inherent flexibility of integrated energy systems. The coordinated operation strategy of the hybrid power-natural gas energy systems considering P2H and P2M is proposed aiming to minimize the operational cost. In addition, a method to calculate the higher heating value of hydrogen-natural gas mixture is presented along with a strategy for handling the constraints of hydrogen mixture level limits. The simulation results of three case studies demonstrate the economic and environmental benefits of P2H/P2M in terms of reductions in cost, CO₂ emissions and wind power curtailment. The differences in benefits between P2H and P2M have also been compared and analyzed.     

State-of-the-art expansion planning of integrated power,natural gas,and hydrogen systems

Renewable hydrogen is considered key in the transition towards a carbon-neutral future. This is due to its spatio-temporal storage and sector coupling potential, which has seen it referred to as energy vector. However, many unresolved issues remain regarding hydrogen's large-scale deployment, e.g. least-cost production, optimal facility siting, and overall implications on power and energy systems. Expansion planning provides an option to study these issues in the holistic context of energy systems. To this end, this article presents a comprehensive review on state-of-the-art expansion planning models that consider integrated power, natural gas, and hydrogen systems. We cluster the existing literature in terms of modelling themes and scope, study the applied systematic modelling characteristics, and conduct an in-depth analysis of the technical model features regarding hydrogen technologies and natural gas infrastructure. Finally, we identify and discuss research gaps in the existing literature.     

Models,methods and approaches for the planning and design of the future hydrogen supply chain

The infrastructure of hydrogen presents many challenges and defies that need to be overcome for a successful transition to a future hydrogen economy. These challenges are mainly due to the existence of many technological options for the production, storage, transportation and end users. Given this main reason, it is essential to understand and analyze the hydrogen supply chain (HSC) in advance, in order to detect the important factors that may play increasing role in obtaining the optimal configuration. The objective of this paper is to review the current state of the available approaches for the planning and modeling of the hydrogen infrastructure. The decision support systems for the HSC may vary from paper to paper. In this paper, a classification of models and approaches has been done, and which includes mathematical optimization methods, decision support system based on geographic information system (GIS) and assessment plans to a better transition to HSC. The paper also highlights future challenges for the introduction of hydrogen. Overcoming these challenges may solve problems related to the transition to the future hydrogen economy.     

Fostering active network management through SMEs’ practises

Managing the electricity network through ‘smart grid’ systems is a key strategy to address challenges of energy security, low carbon transitions and the replacement of ageing infrastructure networks in the UK. Small and medium enterprises (SMEs) have a significant role in shaping patterns of energy consumption. Understanding how their activities interrelate with changes in electricity systems is critical for active network management. A significant challenge for the transformation of electricity systems involves comprehending the complexity that stems from the variety of commercial activities and diversity of social and organizational practises among SMEs that interact with material infrastructures. We engage with SMEs to consider how smart grid interventions ‘fit’ into everyday operational activities. Drawing on analysis of empirical data on electricity use, smart metre data, surveys, interviews and ‘energy tours’ with SMEs to understand lighting, space heating and cooling, refrigeration and IT use, this paper argues for experimenting with the use of practise theory as a framework for bringing together technical and social aspects of energy use in SMEs. This approach reveals that material circumstances and temporal factors shape current energy demand among SMEs, with ‘connectedness’ an emergent factor.     

Effect of hydrogen blending on the energy capacity of natural gas transmission networks

In this paper the effects of hydrogen on the transport of natural gas-hydrogen mixture in a high-pressure natural gas transmission system are investigated in detail. Our research focuses on the decrease in transferable energy content under identical operating conditions as hydrogen is blended in the gas transmission network. Based on the extensive literature review the outstanding challenges and key questions of using hydrogen in the natural gas system are introduced. In our research the transmissible energy factor - TEF - is defined that quantifies the relative energy capacity of the pipeline caused by hydrogen blending. A new equation is proposed in this paper to find the value of TEF at specific pressure and temperature conditions for different hydrogen concentrations. This practical equation helps the natural gas system operators in the decision-making process when hydrogen emerges in the gas transmission system. In this paper the change of the compression power requirement, which increases significantly with hydrogen blending, is investigated in detail.     

How can the integration of renewable energy and power-to-gas benefit industrial facilities? From techno-economic,policy, and environmental assessment

This paper applies a mixed integer linear programming model developed in GAMS to simulate the integration of Power-to-Gas infrastructure into an industrial manufacturer's energy system subject to the existing thermal and electrical energy demands, as well as a third hydrogen energy profile. This work is novel in that it assesses the challenges and economic incentives available to make feasible the installation of a hydrogen-based energy storage systems within the Province of Ontario from a techno-economic, policy and environmental perspectives.The energy hub analyzed in this work uses electricity from the power grid and solar PVs to meet the manufacturer's demands, while converting the excess to hydrogen gas, which is used across an array of pathways to generate revenue. ThisThis includes a blend ofof hydrogen for fuel cell vehicles (FCVs), hydrogen for forklifts, and the direct injection of hydrogen into the facility's natural gas, adding renewable content to the heating, and manufacturing processes. Our primary objective was to implement a safe design that minimizes capital and operating costs, resulting in a favorable business case for producing hydrogen, and providing ancillary grid services. However, Power-to-Gas creates a net-emission reduction that can be used not only to sell emission allowances in the provincial carboncarbon tax program for up to $30/t-CO_2eq but to assist the Company in achieving their strategic emission reduction targets.Installation of the selected Power-to-Gas system would require a total capital investment of $2,620,448 with the electrolyzers and solar panels accounting for 41% and 17% of the capital costs, respectively. The compressors will account for most of the operating costs which total $237,653 annually. Within the energy hub, 76,073 kg-H₂ has been produced per year for end-use applications. A sensitivity analysis was performed by varying both hydrogen and carbon credit price which predicted a potentialpotential CO₂ offset of 2359.7 tonne/yr with a payback period of as little as 2.8 years.     

Solar hydrogen from North Africa to Europe through greenstream: A simulation-based analysis of blending scenarios and production plant sizing

Blending green hydrogen within the gas infrastructure is seen as the first move towards Europe's climate neutrality by 2050. Especially, Europe and North African have privileged role in energy cooperation sharing a woven and complex set of natural resources, knowledge, infrastructure, clear goals towards sustainable development. Developing common projects about hydrogen can mutually help both Europe and North Africa to achieve more sustainable, reliable and modern energy systems.This paper simulates the Greenstream gas corridor (connecting Libya to Italy) under increasing hydrogen blending scenarios using a transient and multi-component fluid-dynamic model of the gas transmission system.The additional compression energy required and the compressors’ operating hours are evaluated under the hypothesis that the energy content of the transported gas is maintained. The hydrogen profiles needed to generate the blends are obtained and used to optimally size a photovoltaic-powered electrolysis system, minimizing the compressed hydrogen storage.The results indicate that the additional energy costs of transporting hydrogen blends are up to 32.5% higher than natural gas transport, while negligibly impacting the overall efficiency of energy transport. The mismatch between solar hydrogen production and pipeline receiving potential highlights a challenge to be tackled to boost intersectoral integration.     

Hydrogen storage and delivery: Review of the state of the art technologies and risk and reliability analysis

Among all introduced green alternatives, hydrogen, due to its abundance and diverse production sources is becoming an increasingly viable clean and green option for transportation and energy storage. Governments are considerably funding relevant researches and the public is beginning to talk about hydrogen as a possible future fuel. Hydrogen production, storage, delivery, and utilization are the key parts of the Hydrogen Economy (HE). In this paper, hydrogen storage and delivery options are discussed thoroughly. Then, since safety and reliability of hydrogen infrastructure is a necessary enabling condition for public acceptance of these technologies and any major accident involving hydrogen can be difficult to neutralize, we review the main existing safety and reliability challenges in hydrogen systems. The current state of the art in safety and reliability analysis for hydrogen storage and delivery technologies is discussed, and recommendations are mentioned to help providing a foundation for future risk and reliability analysis to support safe, reliable operation.     

An alternative platform of solid-state hydrides with polymers as composite/encapsulation for hydrogen storage applications: Effects in intermetallic and complex hydrides

Hydrogen energy proved the remarkable benefits from the perspective of future energy needs and environmental concerns. However, the existing challenges in hydrogen energy technologies, mainly hydrogen storage need to be overcome. In hydrogen storage systems, metal hydrides are highly suffered by the protic species and oxygen because of their reactivity in ambient conditions, leading to surface contamination and affecting the hydrogen sorption behaviors. Moreover, the hydrogen storage in metal hydrides can be hindered by impurities such as CO and CO₂ in hydrogen gas. The new concepts of hydrides with polymers are vital for overcoming the hydrides’ contamination-related issues. This comprehensive review spotlight primarily on the alternative ways to avoid the contamination of hydrides with polymers. The researchers worldwide developed different concepts of polymer-hydrides (intermetallic and complex hydrides) systems, mainly composites and polymer encapsulation methods, to avoid contamination from the air/moisture/gas impurities and improve hydrogen sorption properties in hydrides. Interestingly, selective gas properties of polymers with hydrides show tremendous advantages because of their selective permeability of hydrogen, which influences the easier path for hydrogen diffusion to form the hydrides through the polymer matrix and prohibit the contamination of hydride materials from the other gases/protic species. Notably, this review bridges the understanding between the polymers and hydrides (intermetallic, complex and reactive hydride composite) for hydrogen storage systems.     

Generation of green hydrogen using self-sustained regenerative fuel cells: Opportunities and challenges

The ever-increasing energy demand, depleting fossil fuel reserves, and rising temperatures due to greenhouse gas emissions have necessitated the transition towards the generation of green and clean energy through renewable energy sources. Solar energy is one such renewable energy source that has received significant attention owing to its abundance and inexhaustibility. However, solar energy alone cannot replace fossil fuels in the energy portfolio. There exists a need to develop another clean energy source that can potentially act as an alternative to conventional fuels. Hydrogen proves to be an ideal candidate in this domain and can be sustainably generated by water electrolysis by powering the electrolyzer using solar energy. The hydrogen thus synthesized has net zero carbon emissions and is a suitable asset for decarbonizing the environment. This review encompasses the generation of hydrogen using PV-Electrolyzer systems and addresses the challenges associated with the same. Overcoming these drawbacks can ensure a strong position for hydrogen as an alternative fuel in the energy infrastructure. By employing electrolyzers that are fueled by renewable energy and then using that hydrogen to feed a fuel cell, this study aims to clarify the potential and constraints of producing green hydrogen. Since this area of research has not yet been fully investigated, a review article that enables and encourages academics to develop original solutions is urgently needed.     

Assessment of using hydrogen in gas distribution grids

Substantial changes in the energy system are necessary to achieve greenhouse gas neutrality. Green hydrogen is a key to defossilisation. Politicians frequently mention the use of hydrogen in the building sector to supply decentrally produced heat as a potential field of application. An advantage repeatedly mentioned is that the existing gas distribution network infrastructure is an important asset that could still be used in the future. However, there is a lack of analyses of the conversion of gas distribution networks to hydrogen focussing on the economic implications on the costs of the distribution network infrastructure. The paper provides insights using a techno-economic model network analysis (MNA) tool called gas Distribution grId modelliNg tOol (DINO). The analysis is carried out for Germany and considers hydrogen use in all counties. The results are compared to a synthetic methane and electrification scenario. In the hydrogen scenario, the total need for distribution grids is decreasing until 2050 by at least 130,000 km. The network length of the synthetic methane scenario is slightly lower and that of the electrification scenario drops to zero. The annual operation costs are lower in all scenarios as gas demand and infrastructure are reduced. Nevertheless, the total annual cost in the hydrogen scenario is potentially two times higher than in the case of the synthetic methane scenario and more than four times higher than in the electrification scenario. Based on the present results, it is questionable whether an advantage of the continued use of the existing gas distribution grid infrastructure in case of synthetic gas or hydrogen scenarios exists.     

Towards a 100% hydrogen domestic gas network: Regulatory and commercial barriers to the first demonstrator project in the United Kingdom

In the debate on the decarbonisation of heat, renewable electricity tends to play a much more dominant role than green gases, despite the potential advantages of gas in terms of utilising existing transportation networks and end-use appliances. Informed comparisons are hampered by information asymmetry; the renewable electricity has seen a huge grid level deployment whereas low-carbon hydrogen or bio-methane have been limited to some small, stand-alone trials. This paper explores the regulatory and commercial challenges of implementing the first UK neighbourhood level 100% low-carbon hydrogen demonstration project. We draw on existing literature and action research to identify the key practical barriers currently hindering the ability of strategically important actors to accelerate the substitution of natural gas with low carbon hydrogen in local gas networks. This paper adds much needed contextual depth to existing generic and theoretical understandings of low-carbon hydrogen for heat transition feasibility. The learnings from pilot projects, about the exclusion of hydrogen calorific value from the Local Distribution Zone calorific value calculation, Special Purpose Vehicle companies, holding of liability and future costs to consumers, need to be quickly transferred into resilient operational practice, or gas repurposing projects will continue to be less desirable than electrification using existing regulations, and with more rapid delivery.     

Optimum hydrogen generation capacity and current density of the PEM-type water electrolyzer operated only during the off-peak period of electricity demand

A requirement for widespread adoption of fuel cell vehicles in the transportation sector will be ready availability of pure hydrogen at prices that result in operating costs comparable to, or less than, that of gasoline internal combustion engine vehicles. The existing electrical power grid could be used as the backbone of the hydrogen infrastructure system in combination with water electrolyzers. A water electrolyzer can contribute to the load leveling by changing operational current density in accordance with the change of electricity demand. The optimum hydrogen generation capacity and current density of the polymer electrolyte membrane (PEM)-type water electrolyzer operated only during the off-peak period of electricity demand in respect of both the shortest time required for start and the higher efficiency of water electrolysis are obtained as 500 Nm³ h⁻¹ and 30 kA m⁻², respectively. This PEM-type water electrolyzer could be used in the hydrogen refueling stations and energy storage systems constructed around hydrogen.     

氢储能调峰站发展路径探索研究

氢储能是解决可再生能源消纳和缓解峰谷电差的有效方式之一,通过电转氢技术可以实现规模化、长期、广域的储能。借助我国电网基建优势,谷电时段将可再生能源丰富地区电能输送到高纯氢需求中心,在用户端电解制氢,提高输电通道利用率,解决氢气远距离运输成本、安全等关键问题。本文介绍了氢储能现状,给出了氢储能调峰站典型设计方案,分析了在高纯氢需求中心建设氢储能调峰站的技术和经济可行性。同时提出氢储能调峰站潜在的风险与挑战,并给出发展建议。     

A linear diversity constraint - Application to scheduling in microgrids

Microgrids usually operate in disparate locations and may not be connected to the national grid. The potential sources of electricity in microgrids are wind farms, solar energy, biomass, tidal energy, among others. However, microgrids that are connected to the national grid are gaining importance, because they can supply electricity to the national grid when they have an excess and buy from it when they are in shortage. Such a symbiotic relationship with the national grid helps reduce investment in storage capacity and minimizes other operational costs. In this work, we develop a mathematical model MILP - (mixed integer linear programming) for scheduling operations in microgrids connected to the national grid. We allow several realistic features such as time constraints for the purchase/sale of power from/to the national grid; round trip efficiency of batteries; hydrogen generation, and limits on storage and retrieval rates from batteries/hydrogen tanks/natural gas tanks. Furthermore, to maintain diversity in the generation of electricity from multiple resources, we develop and impose a novel linear diversity constraint on the production schedule without sacrificing the ease of schedule implementation.     

Evaluation of the safe separation distances of hydrogen-blended natural gas pipelines in a jet fire scenario

The desire for sustainable development in various countries has increased the use of hydrogen energy. Considering cost and time savings, the introduction of hydrogen into existing natural gas pipelines is an excellent option, and the failure consequences of hydrogen blending in natural gas pipelines should be considered. In this study, a solid flame model is used to calculate the thermal radiation intensity of a hydrogen-blended natural gas jet fire. A method is proposed to modify the calculation of the view factor in the near field, and parameters such as the specific heat capacity and calorific value of pure gas are replaced by the parameters of the mixed gas. The data of the Thornton and modified models are compared with the experimental results, and the modified model result is found to be more accurate. Using the modified model, the variations in different hydrogen blending ratios, internal pressures, and pipe diameters with the safe separation distance of the thermal radiation intensity in a pipeline accident are investigated, and the relationships between them are analyzed.     

Wind hydrogen energy system and the gradual replacement of natural gas in the State of Ceará – Brazil

The original model for the solar hydrogen energy system created by Veziroglu and Basar in the 70’s was adapted to the State of Ceará – Brazil. The State of Ceará has one of the greatest wind potentials in Brazil and it is estimated to be around 35 GW. At the present year, there are 494 MW wind farms in operation. The aforementioned State also has a natural gas grid of pipelines serving a great number of consumers. There are studies in literature considering the injection of hydrogen into the natural gas pipeline up to 20% in volume without substantial modifications in the natural gas infrastructure. The main objective of this article is to use that model in order to evaluate long term scenarios in which the off peak wind generated hydrogen gradually replaces natural gas in such important State of Brazil. The system is supposed to start in the year 2015 and the economical revenue when it is fully implemented can reach respectively US$ 730 million or US$ 1 billion in the slow or fast scenario of hydrogen introduction into the energy matrix of that important State of Brazil.