A Constraint Disaggregation Method for Structure-Preserving Aggregations in LP Problems: Application to Renewable Energy Grids with Hydrogen Storage

<p indent=0mm>As a kind of important clean and renewable energy, hydrogen energy has received increasing attention. In the past, the majority of researchers from colleges and universities, Chinese Academy of Sciences and other institutions carrying out hydrogen energy related research were supported by the National Natural Science Foundation of China, Ministry of Science and Technology. Nowadays many enterprises are also involved, including both private enterprises and state owned enterprises. This is a significant shift in this research field that will further promote the development of hydrogen energy industry. Hydrogen industry includes hydrogen production, separation, storage and transportation, application and other links. Great strides have been made in these fields in recent years. Some of these fields are developing rapidly, while others are still facing many challenges. This paper makes a systematic analysis and induction of the status, issues and future development potential of the hydrogen industry chain. The paper is divided into seven parts, including hydrogen preparation, hydrogen storage, hydrogen transportation, hydrogen pipeline transportation, liquid hydrogen manufacturing, storage and transportation, hydrogen refueling station, conclusions and suggestions. In the part of hydrogen preparation, we introduce the methods of hydrogen preparation, separation and purification, the annual changes of world pure hydrogen and mixed hydrogen production, the relationship between hydrogen price of different hydrogen production methods and main raw material price, and the comparison of hydrogen production technologies and characteristics of different electrolytic water. In the part of hydrogen storage, four main methods: High-pressure gas hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage and organic liquid hydrogen storage are introduced, and the performances of these four methods are compared. In the part of hydrogen transportation, we introduce several common hydrogen transportation methods, the performance comparison of several common hydrogen transportation methods, and the price variance by distance of the three main hydrogen transportation methods. In the part of hydrogen pipeline transportation, the construction of two domestic hydrogen pipelines and the comparison of relevant parameters, as well as the situation of hydrogen transportation pipelines around the world are introduced. In the part of liquid hydrogen production, storage and transportation, the production methods of liquid hydrogen, the difference in calorific value between hydrogen fuel and other fuels, the preparation level of liquid hydrogen all over the world and the development direction in the future are introduced. In the part of hydrogenation stations, the construction, operation, cost and problems of hydrogenation refueling stations around the world are introduced. Finally, based on the contents above, we draw some conclusions and suggestions as follows: (1) In terms of hydrogen production, it is necessary to reduce the cost, develop hydrogen production from fossil raw materials to clean energy electrolytic water, focus on the development of proton exchange membrane green hydrogen preparation technology and enlarge its scale. (2) In terms of hydrogen storage, it is necessary to select appropriate hydrogen storage methods and improve their performance according to different applications. In the field of transportation, it is necessary to develop a hydrogen storage system with a weight density greater than 5wt% and a volume density greater than <sc>40 g/L,</sc> which is cost-effective and easy to control hydrogen absorption and desorption. In the non-transportation field, it is necessary to develop large-scale, low energy consumption and high safety hydrogen storage technology. (3) In terms of hydrogen transportation, it is necessary to strengthen the development of pipeline hydrogen transportation and liquid hydrogen transportation technology. (4) In terms of hydrogen refueling station, it is necessary to realize the localization of key equipment such as compressors and hydrogen injectors, improve the operation efficiency of hydrogen refueling stations and reduce the operational cost; Hydrogen production stations and liquid hydrogen refueling stations need to be developed.

With the rapid increase in the photovoltaic (PV) installations, the intermittency and the variability of the solar energy sources will lead to the frequent and steep ramping operation of conventional fossil generation. Consequently, energy storage is required for efficient use of the renewable energy source. Hydrogen production via electrolysis can provide both short and long duration capacity as a controllable load to reduce grid fluctuations and improve the resilience of the energy system. Once the hydrogen is produced, it must be stored before it is consumed. High pressure gaseous hydrogen storage is the most popular and mature hydrogen storage technology due to the technical simplicity, reliability, energy efficiency as well as affordability [1]. Compressed hydrogen storage with a fast filling-emptying rate can be used as a hydrogen multiple-purpose station for both stationary fuel cell and fuel cell electric vehicle (FCEV) applications. Although hydrogen electrolyzers, stationary fuel cells, and FCEV refueling stations have been extensively studied, little work has been done integrating these hydrogen technologies with a utility PV field to ensure electric grid stability, maximize PV utilization and efficiently produce and consume hydrogen. A model for a complete system of hydrogen production via electrolysis and high-pressure hydrogen storage was developed. The dynamic performance of different hydrogen storage filling and emptying operations with electrolyzer, stationary fuel cell and FCEV shows the feasibility and flexibility of the integrated hydrogen system.A high-fidelity dynamic model of a Proton Exchange Membrane (PEM) electrolyzer was developed for hydrogen production from PV electricity. A parallel multi-stage hydrogen compression system with cascade tanks for filling/emptying was designed and modeled. A non-adiabatic lumped dynamic model was developed for the storage tank with heat transfer from the tank to ambient air. The Soave-Redlich-Kwong equation of state was adopted to account for the non-ideal gas response of high-pressure gaseous hydrogen [2]. The 1 MW electrolyzer under full load produces hydrogen at 200 Nm3/hr (17.7 kg/hr) and the hydrogen can be compressed up to the maximum pressure of 45 MPa suitable for heavy-duty fuel cell vehicles.The storage tanks can be filled with constant/varied hydrogen flow from the electrolyzer depending on the PV power. The compressor and heat exchanger duties as well as the storage tank pressure and temperature are monitored and controlled. The tanks can be discharged to the stationary fuel cell and/or FCEVs. The dynamic performance of integrated hydrogen system for PV smoothing (filling with varied hydrogen flow in short time-scale), peak shaving (filling and emptying with constant hydrogen flow in long time-scale) and FCEV refueling (cascade filling and emptying) will be presented. The feasibility and flexibility of integrated hydrogen production and storage system for grid operation will be shown.[1] Li, Mengxiao, Yunfeng Bai, Caizhi Zhang, Yuxi Song, Shangfeng Jiang, Didier Grouset, and Mingjun Zhang. "Review on the research of hydrogen storage system fast refueling in fuel cell vehicle." International Journal of Hydrogen Energy 44, no. 21 (2019): 10677-10693.[2] Xiao, Lei, Jianye Chen, Yimei Wu, Wei Zhang, Jianjun Ye, Shuangquan Shao, and Junlong Xie. "Effects of pressure levels in three-cascade storage system on the overall energy consumption in the hydrogen refueling station." International Journal of Hydrogen Energy 46, no. 61 (2021): 31334-31345.

&amp;lt;p&amp;gt;To meet global commitments to reach net-zero carbon emissions by 2050, the energy mix must reduce emissions from fossil fuels and transition to low carbon energy sources.&amp;amp;#160; Hydrogen can support this transition by replacing natural gas for heat and power generation, decarbonising transport, and facilitating increased renewable energy by acting as an energy store to balance supply and demand. For the deployment at scale of green hydrogen (produced from renewables) and blue hydrogen (produced from steam reformation of methane) storage at different scales will be required, depending on the supply and demand scenarios. Production of blue hydrogen generates CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; as a by-product and requires carbon capture and storage (CCS) for carbon emission mitigation. &amp;amp;#160;Near-future blue hydrogen production projects, such as the Acorn project located in Scotland, could require hydrogen storage alongside large-scale CO&amp;lt;sub&amp;gt;2 &amp;lt;/sub&amp;gt;storage. Green hydrogen storage projects, such as renewable energy storage in rural areas e.g. Orkney in Scotland, will require smaller and more flexible low investment hydrogen storage sites. Our research shows that the required capacity can exist as engineered geological storage reservoirs onshore and offshore UK. We will give an overview of the hydrogen capacity required for the energy transition and assess the associated scales of storage required, where geological storage in porous media will compete with salt cavern storage as well as surface storage such as line packing or tanks.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We will discuss the key aspects and results of subsurface hydrogen storage in porous rocks including the potential reactivity of the brine / hydrogen / rock system along with the efficiency of multiple cycles of hydrogen injection and withdrawal through cushion gasses in porous rocks. We will also discuss societal views on hydrogen storage, exploring how geological hydrogen storage is positioned within the wider context of how hydrogen is produced, and what the place of hydrogen is in a low-carbon society. Based on what some of the key opinion-shapers are saying already, the key considerations for public and stakeholder opinion are less likely to be around risk perception and safety of hydrogen, but focussed on questions like &amp;amp;#8216;who benefits?&amp;amp;#8217; &amp;amp;#8216;why do we need hydrogen in a low-carbon society?&amp;amp;#8217; and &amp;amp;#8216;how can we do this in the public interest and not for the profits of private companies?&amp;amp;#8217;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We conclude that underground hydrogen storage in porous rocks can be an essential contributor to the low carbon energy transition.&amp;lt;/p&amp;gt;

Hydrogen energy is considered to be one of the most environmentally friendly and potential green energy options due to its characteristics of producing only water and no carbon emissions after combustion. Low‐carbon and zero‐carbon can be achieved using hydrogen energy. Therefore, in the future, it will be the mainstream because it can achieve the goal of net‐zero carbon emissions. Hydrogen can be obtained using hydrogen purification technologies, which are mainly divided into pressure swing adsorption technology, condensation separation technology, metal palladium membrane separation technology, and metal hydride separation technology. Hydrogen storage technologies are mainly divided into compressed hydrogen storage, liquefied hydrogen storage, cryo‐compressed hydrogen storage, metal hydrides hydrogen storage, liquid organic hydrogen carriers, and underground hydrogen storage. Additionally, with the increasing focus on renewable energy, solid‐state hydrogen storage holds great promise for future applications in various sectors.

Assessing the potential of large-scale geological hydrogen storage in North Dakota's Bakken Formation: A case study integrating wind-powered hydrogen production

To meet the Paris Agreement targets, the world needs to transition to a deeply decarbonized energy system. In addition to energy efficiency gains, this will require greater renewable power generation and electrification, and the scaling of technologies to reduce the carbon footprint. Hydrogen is recognized to play a key role ensuring renewable power exploitation without overloading the grid and acting as energy storage medium to harmonize continuous power requirements with the intermittency of the renewables. From a global solutions provider perspective, there is the need to reassess the technological and intellectual portfolio to overcome the new challenges posed by these new scenarios. In this context, Saipem spent an important effort on designing a safe and efficient offshore green hydrogen production and storage module placed onto offshore facilties. Looking at the offshore hydrogen value chain, the focus has been dedicated to the sea water treatment, hydrogen production and hydrogen storage building blocks. A summary of the state of art technologies for hydrogen production and storage is provided. In particular, the rationale behind the technologies choice is explained: reverse osmosis for the sea water treatment, Proton Exchange Membrane (PEM) for the water electrolysis and Liquid Organic Hydrogen Carrier (LOHC) for hydrogen storage. In addition, the design basis and main technical and economic outcomes are reported. A very important topic addressed by the paper is safety: the offshore green hydrogen production and storage module was designed in compliance with international codes and standards, in particular the provisions and designs of safety and loss prevention systems. Some highlights from the safety regulatory framework investigation are provided. This work adds an important brick in the picture of the new plants required by the energy transition, demonstrating the technical feasibility and constructability of an offshore hydrogen production and storage system.

Hydrogen storage in porous geological formations – onshore play opportunities in the midland valley (Scotland, UK)

With the rapid industrialization, increasing of fossil fuel consumption and the environmental impact, it is an inevitable trend to develop clean energy and renewable energy. Hydrogen, for its renewable and pollution-free characteristics, has become an important potential energy carrier. Hydrogen is regarded as a promising alternative fuel for fossil fuels in the future. Therefore, it is very necessary to summarize the technological progress in the development of hydrogen energy and research the status and future challenges. Hydrogen production and storage technology are the key problems for hydrogen application. This study applied bibliometric analysis to review the research features and trends of hydrogen production and storage study. Results showed that in the 2004-2018 period, China, USA and Japan leading in these research fields, the research and development in the world have grown rapidly. However, the development of hydrogen energy still faces the challenge of high production cost and high storage requirements. Photocatalytic decomposition of water to hydrogen has attracted more and more research in hydrogen production research, and the development of new hydrogen storage materials has become a key theme in hydrogen storage research. This study provides a comprehensive review of hydrogen production and storage and identifies research progress on future research trend in these fields. It would be helpful for policy-making and technology development and provide suggestions on the development of a hydrogen economy.

The research, development, and practical application of renewable energies are becoming a major trend with environmental problems such as increasingly serious global warming and the depletion of oil resources. Hydrogen is an ideal alternative energy source due to its cleanness and high combustion ratio. It is recognized as the most likely replacement for the existing coal and oil systems as the future energy base of the global economy. But as things stand, the hydrogen reserve technology and hydrogen storage technology at the current stage all have certain advantages and disadvantages. Based on this background, the study summarizes the current state of the art of hydrogen energy production technologies such as direct hydrogen production from fossil fuel, hydrogen production from electrolysis of water, hydrogen production from biomass, as well as four types of hydrogen storage methods, namely, high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage, and organic liquid hydrogen storage, and analyzes the advantages and disadvantages of each technology. Among them, hydrogen production from electrolyzed water and bio-hydrogen production are the technologies with higher potential but still need to improve economic competitiveness. The high-pressure gaseous hydrogen storage technology can also be brought to market on a wide scale after cost reduction.

Techno-economic analysis of a nuclear-wind hybrid system with hydrogen storage

Geographical and seasonal differences in the supply and demand of renewable energy is a great challenge for building a sustainable future energy system. One approach is to store renewable energy in the form of hydrogen in existing depleted underground gas reservoirs and retrieve this energy on demand. However, it is unknown if the storage of hydrogen is technologically feasible, specifically if hydrogen can be stored in the same way as natural gas in porous reservoirs and if there are negative impacts on integrity and safety of the surface and subsurface storage facility. To answer these questions, RAG Austria AG has conducted field and laboratory experiments in the past decade. We have injected gas mixtures containing up to 20 volume percent of hydrogen into a depleted porous gas reservoir as part of the field test. First, we evaluated the gas composition, downhole pressure and temperature measurements as well as microbial data from the field test. Our findings suggest changes in the composition of produced gas, however no negative effects on reservoir integrity and no apparent geochemical effects. Next, we investigated the tightness of the caprock against hydrogen intrusion. The experimental results show that the behavior of hydrogen in the sealing materials is similar to that of natural gas. Furthermore, laboratory experiments with pure hydrogen revealed that diffusion effects in reservoir rocks can be neglected for the timeframe of seasonal gas storage. Taken together, these first results indicate that storage of hydrogen in depleted porous gas reservoirs could be a way forward to have hydrogen as a more reliable and versatile energy carrier. Still, we need to gain more insights regarding safety and technical feasibility for the underground storage of pure hydrogen. To address this, RAG Austria AG will start an unprecedented field test with pure hydrogen in a porous depleted gas reservoir in 2023.

Since hydrogen usually exists on Earth as part of a compound, it has to be synthesized in specific processes in order to be used as a product or energy source. This can be achieved by different technical methods, and various primary energy sources, – both fossil and renewable fuels, in solid, liquid or gaseous form, – can be used in these technical production processes. Hydrogen has only a very low volumetric energy density, which means that it has to be compressed for storage and transportation purposes. The most important commercial storage method, – especially for end users, – is the storage of hydrogen as a compressed gas. A higher storage density can be achieved by hydrogen liquefaction. Novel materials-based storage media (metal hydrides, liquids or sorbents) are still at the research and development stage. The storage of hydrogen (for example, to compression or liquefaction) requires energy; work is, in present, on more efficient storage methods. Unlike electricity, hydrogen can be successfully stored in large amounts for extended periods of time. For example, in long-term underground storage facilities hydrogen can play an important role as a buffer store for electricity from surplus provided by renewable energies. At present, pure hydrogen is generally transported by lorry in pressurize gas containers, and in some cases also in cryogenic liquid tanks. Moreover, local/regional hydrogen pipeline networks are available in some locations. Another solution for storage and transportation are Liquid Organic Hydrogen Carriers (LOHC) that can use long pipe networks and ships. In the near future, the natural gas supply infrastructure or oil (transportation pipelines and underground storage facilities) could also be used, in specific conditions, for the storage and transportation of pure or blended hydrogen with methane. This could be essential for transition because most important primary energy source for hydrogen production currently is natural gas, at 71%, followed by oil, coal and electricity (as a secondary energy resource). Steam reforming (from natural gas) is the most commonly used method for hydrogen production. In this new light, the article explores the trend and prospects for hydrogen, presented in the literature, as a source of energy competing with gas and oil resources in the global energy system of the future.

Optimization of a solar hydrogen storage system: Exergetic considerations

Provides a brief analysis of the current state of research in the field of hydrogen production and storage for hydrogen energy applications. The conducted analysis shows that the primary industrial method for hydrogen production at the current stage of hydrogen technology development is the classical method of water electrolysis. In this regard, the study examines various types of electrolyzers, comparing them based on operating temperature, stack voltage efficiency, as well as their advantages and disadvantages. It is shown that the reduction in the cost of renewable electricity increases interest in water electrolysis, as this method allows for hydrogen production without emitting carbon dioxide (CO₂). Hydrogen storage mainly relies on traditional technologies such as compressed gas and cryogenic liquid, while for large-scale applications, underground storage is the preferred method. In recent years, there has been rapid development in solid-phase hydrogen storage, which is considered the safest storage method. To store larger amounts of hydrogen in a smaller volume, one solution is to compress it to high pressure. The most common method of hydrogen storage is compression in steel gas cylinders at pressures of up to 700 bar. When hydrogen gas is compressed to 700 bar, its volumetric density reaches 36 kg/m³. This can be achieved using modern lightweight composite steel high-pressure cylinders.

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids