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Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Industrial and public interest in hydrogen technologies has risen strongly recently, as hydrogen is the ideal means for medium to long term energy storage, transport and usage in combination with renewable and green energy supply. In a future energy system, the production, storage and usage of green hydrogen is a key technology. Hydrogen is and will in future be even more used for industrial production processes as a reduction agent or for the production of synthetic hydrocarbons, especially in the chemical industry and in refineries. Under certain conditions material based systems for hydrogen storage and compression offer advantages over the classical systems based on gaseous or liquid hydrogen. This includes in particular lower maintenance costs, higher reliability and safety. Hydrogen storage is possible at pressures and temperatures much closer to ambient conditions. Hydrogen compression is possible without any moving parts and only by using waste heat. In this paper, we summarize the newest developments of hydrogen carriers for storage and compression and in addition, give an overview of the different research activities in this field

Large-scale energy storage plants based on power-to-gas-to-power (PtG–GtP) technologies incorporating high temperature electrolysis, catalytic methanation for the provision of synthetic natural gas (SNG) and novel, highly efficient SNG-fired Allam reconversion cycles allow for a confined and circular use of CO2/CH4 and thus an emission-free storage of intermittent renewable energy. This study features a thorough technology assessment for large-scale PtG–GtP storage plants based on highly efficient sCO2 power cycles combined with subsurface CO2 storage. The Allam cycle employs supercritical CO2 as working fluid as well as an oxy-combustion process to reach high efficiencies of up to 66%. The entire PtG–GtP process chain assessed in this study is expected to reach maximum roundtrip efficiencies of 54.2% (with dedicated and sufficient O2 storage) or 49.0% (with a dedicated air separation unit). The implementation of said energy storage systems into existing national energy grids will pose a major challenge, since they will require far-reaching infrastructural changes to the respective systems, such as extensive installations of renewable generation and electrolysis capacities as well as sufficient subsurface storage capacities for both CO2 and CH4. Therefore, this study incorporates an assessment of the present subsurface storage potential for CO2 and CH4 in Germany. Furthermore, a basic forecast study for the German energy system with an assumed mass deployment of the proposed SNG-based PtG–GtP energy storage system for the year 2050 is conducted. In case of a fully circular use of CO2/CH4, when electricity is solely generated by renewable energy sources, 736 GW of renewables, 234 GW of electrolysis and 62 GW of gas-to-power capacities are required in the best case scenario in 2050. The total storage volume on the national scale of Germany for both CO2 and CH4 was determined to be 7.8 billion N m3, respectively, leading to a CH4 storage capacity of 54.5 TW h. The presented investigations illustrate the feasibility of large-scale energy storage systems for renewable electricity based on high temperature electrolysis, catalytic methanation and Allam power cycles paired with large subsurface storages for CO2 and CH4.

A newly developed composite material has been explored based on metal hydrides in combination with polymers enriched with highly porous carbon. As metal hydride, a RHC (reactive hydride composite) was chosen (e.g., MgH2 + 2 LiBH4). The hydride is infiltrated into the pores of the porous carbon suppressing the long-range phase separation of the two different hydrides by nano-confinement. The aim is to maintain fast kinetics and achieve cycle stability of the RHC (reactive hydride composite). The combination of RHC and porous carbon is then integrated into a polymer film to allow an easy and safe handling of the material. To produce a storage system out of such a film, the thin material is rolled in the same style like a rolled membrane module; i.e., it is rolled together with a thin spacer (e.g., steel mesh) allowing an easy hydrogen access to all parts of the membrane. The last step is the implementation of the rolled storage module into the tank shell. To analyze different design concepts and the behavior of this newly developed composite storage material, extensive FEM-simulations have been realized for different cooling structures. The latter is necessary to fulfil the thermodynamic requirements and to maximize the speed of hydrogen storage. Therefore, the temperature development within the storage during hydrogen feeding are investigated. Beside this, the hydrogen flow as well as the kinetics of the chemical reaction are analyzed. Based on such extensive simulations of different design concepts, the most promising overall storage systems are developed and systematically optimized. Finally, the total hydrogen content of the overall storage system is calculated and compared between different design concepts. Based on this, conclusions are drawn about robust criteria how to construct a cooling and heating device for this new storage material. Bundesministerium für Bildung und Forschung

In post fossil energy systems, hydrogen may gain significant importance as a secondary energy carrier, especially for transportation purposes. This widely published statement is justified by the fact that hydrogen can be produced from fluctuating electricity provided, for example, by wind turbines or photovoltaic systems. The hydrogen provision depends on the availability of electrical energy and is then stored to be used depending on the given demand. However, the efficient storage of hydrogen as an energy carrier is challenging from a techno-economic point of view, for example, due to the low volumetric energy density of hydrogen under standard conditions as well as other challenging properties. Especially for mobile applications (e.g., cars, trucks, ships, trains) it is very important to have hydrogen storage options with high volumetric and gravimetric energy densities to allow highly efficient use and to be fully competitive compared to other options possible within the transportation sector. Thus, in recent years, various storage technologies and concepts have been developed to achieve this challenging goal. The three most widely developed options are high-pressure storage tanks, storage as liquid hydrogen, and storage of the hydrogen gas in metal hydride. But there are also other possibilities and ideas to allow hydrogen storage for mobile applications, such as liquid organic hydrogen carriers (LOHC), activated carbon, Metal–Organic-Frameworks (MOFs), and others. Against this background, the overall goal of this chapter is to describe the various possibilities to store hydrogen for mobile applications. This is realized based on physical and chemical principles as well as the current state of the technology. Additionally, ongoing developments and possible technological breakthroughs are outlined. Besides this, each option is characterized by comparable key figures (e.g., storage density, storage efficiency) for the current state of technology to allow an easy and transparent comparison. Additionally, the hydrogen storage systems discussed are compared to the target values of the DOE (US Department of Energy), which defines internationally accepted goals for the energy density and the costs of hydrogen storage. Finally, the various options are compared to each other. Based on this, statements are made defining which storage option under which frame condition can play which role at which point in time.