Hydrogen generation by electrolysis and storage in salt caverns: Potentials,economics and systems aspects with regard to the German energy transition

The Plan-DelyKaD project focused on an in-depth comparison of relevant electrolysis technologies, identified criteria for and selected most relevant salt cavern sites in Germany, studied business case potentials for applying hydrogen taken from storage to different end-users and engaged in identifying the future role of hydrogen from large scale storage in the German energy system. The focus of this paper is on the latter three topics above. The bottom-up investigation of most suitable salt cavern sites was used as input for a model-based analysis of microeconomic and macroeconomic aspects. The results identify dimensions and locations of possible hydrogen storages mostly in Northern Germany with ample potential to support the integration of fluctuating renewable electricity into the German power system. The microeconomic analysis demonstrates that the most promising early business case for hydrogen energy from large scale storage is its application as a fuel for the mobility sector. From a system perspective the analysis reveals that an optimized implementation of hydrogen generation via electrolysis and storage in salt caverns will have a positive impact on the power system in terms of reduced curtailments of wind power plants and lower residual peak loads.     

A hybrid method for hydrogen storage and generation from water

This communication describes a new hybrid method for storing hydrogen in solid inorganic hydride materials as well as producing it from water based on the reaction between LiOH/LiOH·H₂O and LiH. As a hydrogen storage method, the release and uptake of hydrogen in this method are accomplished via a series of simple reactions with good kinetics within a practically reasonable temperature range. The reversible hydrogen storage capacity of the material system is 6–8.8 wt.% at <350 °C. This capacity is one of the highest among all other metal hydrides known to date in the same temperature range. As a hydrogen production method, 100% of hydrogen generated by this method comes from water by its reaction with alkali metal oxides. This method is also an environmentally friendly alternative to the current commercial processes for hydrogen production. The preliminary thermodynamic calculation on energy required for complete regeneration shows that the current system is energetically favorable.     

Hydrogen storage in binary and ternary Mg-based alloys: A comprehensive experimental study

This study focused on hydrogen sorption properties of 1.5 μm thick Mg-based films with Al, Fe and Ti as alloying elements. The binary alloys are used to establish as baseline case for the ternary Mg–Al–Ti, Mg–Fe–Ti and Mg–Al–Fe compositions. We show that the ternary alloys in particular display remarkable sorption behavior: at 200 °C the films are capable of absorbing 4–6 wt% hydrogen in seconds, and desorbing in minutes. Furthermore, this sorption behavior is stable over cycling for the Mg–Al–Ti and Mg–Fe–Ti alloys. Even after 100 absorption/desorption cycles, no degradation in capacity or kinetics is observed. For Mg–Al–Fe, the properties are clearly worse compared to the other ternary combinations. These differences are explained by considering the properties of all the different phases present during cycling in terms of their hydrogen affinity and catalytic activity. Based on these considerations, some general design principles for Mg-based hydrogen storage alloys are suggested.     

Air compressor efficiency in a Vietnamese enterprise

Compressed air systems in a Vietnamese footwear manufacturing enterprise consume about 10% of enterprise's total electric power supply. Energy efficiency of these air compressor systems, either equipped with new and efficient compressors or old and inefficient ones, can only reach between 5% and 10%. In other words, regardless whatever air compressors were installed, energy loss from the compressor systems was over 80%. This study discovered that energy loss was due to non-optimized operations of the air compressor systems and air leakages. The objectives of the paper are to uncover energy saving potential in Vietnamese air compressor systems, demonstrate methodologies used in the auditing and assessment, share auditing and assessment results, and serve a guide on how to analyze energy efficiency in a compressed air system. This paper concludes that energy efficiency investment in air compressor systems in the Vietnamese enterprise could be extremely cost-effective. If the enterprise invests USD 84,000 in the air compressors to improve efficiency performance, the investment capital will be recovered in about six months. The net present value of the investment will be about USD 864,000 at a discount rate of 12%.     

Mechanochemical modification of LiAlH4 with Fe2O3 - A combined DFT and experimental study

LiAlH₄ is a promising material for hydrogen storage, having the theoretical gravimetric density of 10.6 wt% H₂. In order to decrease the temperature where hydrogen is released, we investigated the catalytic influence of Fe₂O₃ on LiAlH₄ dehydrogenation, as a model case for understanding the effects transition oxide additives have in the catalysis process. Quick mechanochemical synthesis of LiAlH₄ + 5 wt% Fe₂O₃ led to the significant decrease of the hydrogen desorption temperature, and desorption of over 7 wt%H₂ in the temperature range 143–154 °C. Density functional theory (DFT)-based calculations with Tran-Blaha modified Becke-Johnson functional (TBmBJ) address the electronic structure of LiAlH₄ and Li₃AlH₆. ⁵⁷Fe Mössbauer study shows the change in the oxidational state of iron during hydrogen desorption, while the ¹H NMR study reveals the presence of paramagnetic species that affect relaxation. The electron transfer from hydrides is discussed as the proposed mechanism of destabilization of LiAlH₄ + 5 wt% Fe₂O₃.     

High temperature electrolysis using Molten Carbonate Electrolyzer

Molten Carbonate Fuel Cells (MCFC) are a well-developed and commercial technology that can operate also as an electrolyzer producing hydrogen from steam. In this study, a system for the production of hydrogen based on Molten Carbonate Electrolyzer (MCE) is presented. The system receives, as an external input, water and recovers internally the additional gas streams required as input to the electrolyzer. The system products are, separately, pure oxygen and hydrogen. A calculation sheet was implemented to analyze the energy equilibrium and gas mix compositions. The system can produce 0.074 Nl h^?1 cm^?2 of hydrogen with an inlet power density of 0.213 W cm^?2 for an energy consumption of 3.40 kWh Nm_H2^?3. Sensitivity studies on current density, utilization factors of both steam and CO₂ were analyzed considering energy equilibrium of the stack unit and the post processing processes. Results show how current density has higher impact on system equilibrium compared to the other parameters.     

Beyond Haber-Bosch: The renaissance of the Claude process

Ammonia may be one of the energy carriers in the hydrogen economy. Although research has mostly focused on electrochemical ammonia synthesis, this however remains a scientific challenge. In the current article, we discuss the feasibility of single-pass thermochemical ammonia synthesis as an alternative to the high-temperature, high-pressure Haber-Bosch synthesis loop. We provide an overview of recently developed low temperature ammonia synthesis catalysts, as well as an overview of solid ammonia sorbents. We show that the low temperature, low pressure single-pass ammonia synthesis process can produce ammonia at a lower cost than the Haber-Bosch synthesis loop for small-scale ammonia synthesis (<40 t-NH₃ d^?1).     

Towards a hydrogen economy in Poland

The global changes in energy policy, including the increasing contribution of renewable sources of energy to the total output of produced energy and various attempts to introduce advanced energy technologies, and the increasingly efficient use of the energy that had already been emitted are sufficient reasons to discuss Poland's energy policy. The present work features an analysis of the current state of Poland's energy economy and the economic factors that affect the power industry. The tenets of Poland's current energy policy are also presented in the context of hydrogen energy. The possibilities and limitations concerning the transition to hydrogen power in Poland are discussed taking into account a number of aspects, some of which include the degree of development of the electric power infrastructure, the current and future demand for electric energy with regard to the current geopolitical and economic situation of Poland, and Poland's membership in the European Union.     

螺杆式空压机变频节能技术的应用

文章论述高压变频调速装置的原理,通过压缩机变频恒压控制节能分析和计算,阐述变频调速技术在空压机供气领域的应用。节省电能的同时改善空压机性能,提高供气品质。     

并联冰蓄冷空调在汽车上的应用

本文分析了汽车空调采用冰蓄冷技术的优点：降低油耗并且可以满足制冷负荷增大时的舒适性，并对其与汽车运行工况的匹配控制作了探讨。     

Thermodynamic analysis and experimental investigation of a unique photoelectrochemical hydrogen production system

In this study, we thermodynamically analyze and experimentally investigate a continuous type hybrid photoelectrochemical H₂ generation reactor. This system enhances solar spectrum use by employing photocatalysis and PV/T. Additionally, by replacing electron donors with electrodes to drive the photocatalysis, the potential of pollutant emissions are minimized. In this study, the present reactor is tested under electrolysis operation during which the present reactor is investigated under three different inlet mass flow rates (0.25, 0.50, and 0.75 g/s) and four different operating temperatures (20, 40, 60, and 80 °C). Some parametric studies are run by varying the environmental temperature between 0 and 40 °C. In addition, the impact of coating the membrane electrode assembly of the reactor with Cu₂O is investigated. The present results show that the highest energy and exergy efficiencies occur at the environmental temperature of 20 °C which is about 60% and 50%, respectively. The Cu₂O coated membrane gives a lot higher current readings, meaning that the coating makes the membrane more conductive and increases H₂ production by permitting ions at a higher rate.     

From wave to jet and from jet to hydrogen: A promising hybrid system

One of the main challenges that our society must overcome in this century is that of finding alternative energy sources to fossil fuels. These, ideally, must be inexpensive, less polluting than current fuels and available for a substantial time. One promising alternative is hydrogen, which has the great advantage that it can be produced by coupling renewable energy devices with water electrolysis. Several projects devoted to connecting photovoltaic and wind systems with electrolysis devices have been successful; however, little research has been done into the coupling of ocean wave energy converters with water electrolysis. The work here proposes a basic system that stores the energy from waves in the form of hydrogen. The WEC considered is a novel design known as a Blow-Jet, which captures waves and converts them into a water jet. The performance of the Blow-Jet is found to depend more on wavelength than on wave height. The electrolyser results show, at 0.200 A and 1.88 V, that the electrolysis of water produces 0.082 Nl h⁻¹ of hydrogen and a current efficiency (η_I) of 90.58%.     

Large-vscale hydrogen production and storage technologies: Current status and future directions

Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen.     

浦东大酒店的中央空调冷凝热回收

介绍了上海浦东大酒店的冷凝热回收技术，讨论了经济效益及社会效益，指出了该项技术的推广领域。     

Metal hydride hydrogen storage and compression systems for energy storage technologies

Along with a brief overview of literature data on energy storage technologies utilising hydrogen and metal hydrides, this article presents results of the related R&D activities carried out by the authors. The focus is put on proper selection of metal hydride materials on the basis of AB₅- and AB₂-type intermetallic compounds for hydrogen storage and compression applications, based on the analysis of PCT properties of the materials in systems with H₂ gas. The article also presents features of integrated energy storage systems utilising metal hydride hydrogen storage and compression, as well as their metal hydride based components developed at IPCP and HySA Systems.