Storage Concept Research Articles

Adsorption and Separation by Flexible MOFs.

Flexible metal-organic frameworks(MOFs) offer unique opportunities due to their dynamic structural adaptability. This review explores the impact of flexibility on gas adsorption, highlighting key concepts for gas storage and separation. Specific examples demonstrate the principal effectiveness of flexible frameworks in enhancing gas uptake and working capacity. Additionally, mixed gas adsorption and separation of mixtures are reviewed, showcasing their potential in selective gas separation. The review also discusses the critical role of the single gas isotherms analysis and adsorption conditions in designing separation experiments. Advanced combined characterization techniques are crucial for understanding the behavior of flexible MOFs, including monitoring of phase transitions, framework-guest and guest-guest interactions. Key challenges in the practical application of flexible adsorbents are addressed, such as the kinetics of switching, volume change, and potential crystal damage during phase transitions. Furthermore, the effects of additives and shaping on flexibility and the "slipping off effect" are discussed. Finally, the benefits of phase transitions beyond improved working capacity and selectivity are outlined, with a particular focus on the advantages of intrinsic thermal management. This review highlights the potential and challenges of using flexible MOFs in gas storage and separation technologies, offering insights for future research and application.

A Scenario-Based Simulation Study for Economic Viability and Widespread Impact Analysis of Consumption-Side Energy Storage Systems

This study investigates energy storage within the contexts of production-side and consumption-side energy storage concepts. The theoretical advantages of consumption-side energy storage over production-side systems are initially explored. The analysis is supported by a scenario-based simulation, with results presented to assess the feasibility and applicability of consumption-side energy storage under varying conditions. The simulation examines multiple scenarios, incorporating economic assessments to evaluate the viability of such systems. Additionally, the study explores the broader impact of consumption-side energy storage when adopted by 5 million, 10 million, 20 million, and 40 million residential consumers across separate scenarios. The analysis emphasizes the potential for shifting peak-period energy consumption to nighttime usage and assesses the corresponding reduction in energy generation requirements and transmission line loads, alongside the economic benefits derived from postponing energy infrastructure investments. The study focuses exclusively on residential consumers, with the energy storage systems referred to as residential energy storage systems (RESS). These systems are assumed to be organized and managed by energy provider companies rather than individual consumers. The research also considers the potential costs associated with implementing RESS. The simulation-based findings reveal significant benefits, including reduced reliance on new power plants, decreased risk of transmission line overload, increased utilization of renewable energy resources, financial advantages for both energy providers and consumers, and positive environmental impacts. These results provide valuable insights with implications for shaping future energy policies, particularly in the United States.

Physics-based numerical evaluation of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) in the Upper Jurassic reservoir of the German Molasse Basin

Abstract. Concepts of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) (> 50 °C) are investigated in this study for system application in the Upper Jurassic reservoir (Malm aquifer) of the German Molasse Basin (North Alpine Foreland Basin). The karstified and fractured carbonate rocks exhibit favourable conditions for conventional geothermal exploitation of the hydrothermal resource. Here, we perform a physics-based numerical analysis to further assess the sustainability of HT-ATES development in the Upper Jurassic reservoir. With an estimated heating capacity of approx. 19.5 MW over half a year, our approach aims at determining numerically the efficiency of heat storage under the in situ Upper Jurassic reservoir conditions and projected operation parameters. In addition, the hydraulic performance of the HT-ATES system is further evaluated in terms of productivity and injectivity index. The numerical models build upon datasets from three operating geothermal sites at depths of approx. 2000–3000 m TVD, located in a subset of the reservoir dominated by karst-controlled fluid fluxes. Commonly considered as a single homogeneous unit, the 500 m thick reservoir is subdivided into three discrete layers based on field tests and borehole logs from the three considered sites. The introduced vertical heterogeneity with associated layer-specific enhanced permeabilities allows to examine potentially arising favourable heat transfer, and in combination with the facilitated high operation flow rates (100 kg s−1) to evaluate thermal recoveries in the multilayered reservoir. All simulations account for fluid density and viscosity variation based on thermodynamically consistent equations of state (EOS). Computation results reveal that the reservoir layering induces preferential fluid and heat migration primarily into the high-permeability zone, while thermal front propagation into the lower permeable rock matrix is inhibited. The simulations further display a gradual temperature increase in the warm wellbore and its surrounding host rock, and a consequent progressive improvement in the heat recovery efficiency. Despite the elevated permeability that may trigger advective heat losses, heat recovery factor values range from approx. 0.7 over the first year of operation to over 0.85 after 10 years of operation. An additional scenario is examined with fluid injection solely in the high permeable zone, in order to quantify potential enhancement in the recovery efficiency by omitting fluid injection in the lower-permeability layers where heat propagation is diminished. This is due to the geometrical shape of the thermally perturbed rock volume as heat losses occur during thermal equilibration between injected fluid and reservoir rock, as well as at the contact-surface area between propagating thermal front and adjacent rock matrix. Results suggest that under the stratified reservoir configuration, additionally constrained by the selected spatial distribution of rock properties, heat storage performed only into the upper high-permeability zone corresponds to an improved thermal performance. Simulation results further indicate that density-induced buoyant fluxes, which would considerably decrease thermal efficiencies are inhibited in the system, and the prevailing heat transport mechanism is forced convection.

Numerical experiments on hydrogen storage characterization in porous media using elastic full-waveform inversion

In recent years, underground hydrogen storage (UHS) has garnered significant attention as a concept for large-scale energy storage. Developing hydrogen characterization and monitoring methods specific to each target geologic formation (e.g., salt caverns, reservoirs in depleted oil/gas fields, and saline aquifers in porous media) is crucial for the safe operation of hydrogen storage. However, due to the limited number of actual operations and laboratory experiments (e.g., rock physics for hydrogen) related to UHS in porous media, the specifications required for seismic monitoring (e.g., P-/S-wave velocity and density changes generated by hydrogen injection) are not yet fully understood. A recent study showed the results of laboratory experiments on cyclic UHS in porous media. The experiments demonstrated that P-wave velocity decreases nonlinearly with increasing hydrogen saturation in sandstone specimens, with a reduction of up to 3.5% observed at 36% hydrogen saturation. This study presents hydrogen characterization in porous media with conditions similar to the experiment using elastic full-waveform inversion (FWI) for time-lapse surface seismic data. The shot data are generated by seismic forward modeling for several synthetic subsurface models that incorporate a hydrogen plume. The hydrogen plume assumes four velocity-density scenarios, partially based on the laboratory study results. Numerical experiments are conducted to explore the validity and challenges of hydrogen characterization using elastic FWI.

Comparing the Pressure Containment Requirements of Three Subsea Hydro-Pneumatic Energy Storage Concepts

Abstract Hydro-pneumatic energy storage has significant potential for being deployed subsea and co-located with offshore wind farms. The pressure containment storing the compressed air is the bulkiest and most expensive component of such a storage technology. This paper evaluates three different subsea hydro-pneumatic energy storage concepts, comparing their volumetric storage densities, the steel and concrete anchoring requirements and cost of the pressure containment. The pressure variation experienced by the pressure containment across the storage cycle for the three variants, which would impact the efficiency of energy conversion machinery, is also compared. It is shown that having separate accumulators, each designed for a different operating pressure, offers the potential of reducing the cost of the pressure containment by up to 40% as compared to that for the simple concept having a single accumulator. A novel approach is presented to achieve such cost reduction without constraining the energy conversion machinery to operate over a wider operating pressure range.

(Invited) Active Learning Strategies for Teaching Electrochemical Energy Conversion and Storage: Insights from Science Clubs

Electrochemistry is rapidly growing, yet its crucial role in emerging industries and research is not sufficiently mirrored in the curriculum of US and Mexican universities. While undergraduate students are briefly exposed to basic electrochemistry concepts within general and physical chemistry courses, dedicated electrochemistry education is often reserved for graduate programs. Furthermore, teaching electrochemistry is challenging as it is a multifaceted subject encompassing concepts from various disciplines. Despite this complexity, electrochemistry equips students with invaluable skills in analytical chemistry, experimental design, instrumental analysis, and device engineering. Recognizing the need for a skilled workforce to meet the demands of emerging industries, it is imperative to reinvigorate electrochemistry education and introduce it at the early undergraduate level to foster interest and deeper engagement.To bridge this educational gap, we have developed a science workshop focusing on teaching electrochemical energy conversion and storage concepts to high school and early undergraduate students. As part of Clubes de Ciencia MX, a Mexican initiative promoting science and engineering summer workshops, this unique experience has utilized active learning strategies to teach and encourage electrochemistry for two consecutive years. The workshop covers five fundamental areas (Figure 1): electrochemistry basics, water electrolysis, electrocatalysis, fuel cells, and battery technology. By integrating short lectures, group discussions, and interactive learning through experiments, games, and project-based activities, we strive to ignite students' passion for electrochemistry. We have also conducted assessments to examine the workshop's effectiveness and influence on students' understanding of the role of electrochemistry in climate empowerment and sustainability. This unique experience aims to captivate and inspire early-career students, nurturing the next generation of scientists and engineers who will revolutionize our world. Figure 1

(Invited) A Non-Stabilized Supersaturated High-Energy-Density Storage Concept for the Redox Flow Battery and Its Demonstration in an H2-V System

Redox flow battery (RFB)-based storage systems have the unique feature of separating power generation from energy storage, allowing individually sized systems uncoupling power from capacity. RFBs can be used for days-long energy storage, but because of the low solubility of most ions and molecules in both aqueous and non-aqueous solvents,[1,2] scaling these RFB systems for days-long applications requires significant storage tanks and floor area.Our team has been working on a new storage method for Vanadium electrolytes that significantly increases the energy storage density while still maintaining the traditional flow battery design.[3] This method involves storing the reactants as both soluble ions and as undissolved solids, only allowing liquid-containing soluble ions to circulate through the battery. To achieve this, a solid form of Vanadium salt must be precipitated within the storage tanks, with an applied temperature swing to dissolve this solid and keep the electrolyte below saturation level for transport to the flow battery. To run this system without any form of external heating or cooling, we propose to allow saturated electrolyte to enter the flow battery during operation. This presentation will discuss the operation of a V-H2 redox flow battery system operating at 2.5 M total vanadium concentration (above the 1.8M solubility limit of VOSO4)[4] and its comparison to a more traditional sub-saturated system at 2.5M and 1.5M total vanadium ion concentrations respectively.

Developing an Ontology on Battery Production and Characterization with the Help of Key Use Cases from Battery Research

Materials science research faces challenges due to diverse and evolving measurements, materials, and methods. Managing research data in a way that is understandable, comparable, and reproducible is essential for high data quality, particularly for data science and machine learning applications. In Li‐ion batteries research data storage concepts and structures vary widely between institutions and researchers, leading to difficulties in data comparison and understanding. To address the issue of data structuring, battery production and characterization ontology (BPCO) is developed. The ontology builds on existing ontologies like the Platform MaterialDigital core ontology and quantities, units, dimensions, and types ontology to model standard battery production processes, characterization methods, and materials. The BPCO is based on a workflow structure to be accessible to nonexperts and, unlike highly specialized existing ontologies, models the whole production process removing the need for separate data structures and enabling the identification of dependencies between parameters. This work builds upon a previously published paper in which the taxonomy and fundamental strategies for ontology development are established. The article presents the developed ontology and its use for structuring research data in three key use cases, that is, different experiments performed to validate the ontology's capabilities, provide feedback, and ensure its applicability.

Disintegration of Thin Liquid Metal Films Engendered by Aluminum Corrosion.

Liquid metals (LMs) illustrate a fantastic future. Thus, great endeavors are made to earn a comprehensive understanding of this fluid and carve it into a niche. Herein, by revisiting the combination of Ga-based LMs and aluminum (Al), a new phenomenon, namely the disintegration of LM films on encountering water, is identified. Deviating from previous investigations where the LM generally took the form of bulk puddles, the LM-Al slurry is spread as thin films here. In this case, Al debris embedded in the LM matrix hydrolyzes and therefore can exert disjoining pressure strong enough to split the thin film into countless tiny LM droplets. Based on this mechanism, transient circuits independent of substrate decomposition are realized. Furthermore, taking advantage of the portfolio strategy of pure LM and the LM-Al slurry, novel concepts of flood warning and information storage and encryption are demonstrated. Integrating these functions all in one demonstrates the versatility of the disintegration of thin LM films engendered by Al corrosion, which provides a scientific insight into ephemeral art and makes the Ga─Al combination more illuminating.

Thermophysical Properties of the Hydrogen Carrier System Based on Aqueous Solutions of Isopropanol or Acetone

One concept for the safe storage and transport of molecular hydrogen (H2) is the use of hydrogen carrier systems which can bind and release hydrogen in repeating cycles. In this context, the liquid system based on isopropanol and its dehydrogenated counterpart acetone is particularly interesting for applications in direct isopropanol fuel cells that are operated with an excess of water. For a comprehensive characterization of diluted aqueous solutions of isopropanol or acetone with technically relevant solute amount fractions between 0.02 and 0.08, their liquid density, liquid viscosity, and interfacial tension were investigated using various light scattering and conventional techniques as well as equilibrium molecular dynamics (EMD) simulations between (283 and 403) K. Polarization-difference Raman spectroscopy (PDRS) was used to monitor the liquid-phase composition during surface light scattering (SLS) experiments on viscosity and interfacial tension. For comparison purposes and to expand the database, capillary viscometry and dynamic light scattering (DLS) from bulk fluids with dispersed particles were also applied to determine the viscosity while the pendant-drop (PD) method allowed access to the interfacial tension. By adding isopropanol or acetone to water, density and, in particular, interfacial tension decrease significantly, while viscosity shows a pronounced increase. The behavior of viscosity and interfacial tension is closely related to the strong hydrogen bonding between the unlike mixture components and the pronounced enrichment of both solutes at the vapor–liquid interface, as revealed by EMD simulations. For an aqueous solution with an isopropanol amount fraction of 0.04, minor variations in interfacial tension and viscosity were found in the presence of pressurized H2 up to 7.5 MPa. Overall, the results from this study contribute to an extended database for diluted aqueous solutions of isopropanol or acetone, especially at temperatures above 323 K.

Unification of insertion and supercapacitive storage concepts: Storage profiles in titania

Insertion storage in battery electrodes and supercapacitive storage are typically considered to be independent phenomena and thus are dealt with in separate scientific communities. Using tailored experiments on titanium oxide thin films of various thicknesses, we demonstrate the simultaneous occurrence of both processes. For the interpretation of the entire storage profile encompassing both contributions, the (free) energies of the charge carriers in the mixed conductor and the neighboring phase are the only materials parameters required. The experimental results enable no less than a unification of insertion and supercapacitive storage, the first being dominant for thick films, the latter for thin films or negligible electronic conductivity. Therefore, the size of the storage medium and the nature of the current collecting phases can be used to tune power density versus energy density.

Porous Monolithic Perovskite Structures for High-Temperature Thermochemical Heat Storage in Concentrated Solar Power (CSP) Plants and Renewable Electrification of Industrial Processes

A novel approach towards thermal energy storage of surplus renewable energy (RE) is introduced via a hybrid thermochemical/sensible heat storage concept implemented with the aid of porous structures made of redox metal oxides, capable of reversible reduction/oxidation upon heating/cooling in direct contact with air, accompanied, respectively, by endothermic/ exothermic heat effects and demonstrating fully reversible dimensional changes under cyclic operation. The proposed modular storage units can be heated during the day to a level exceeding the metal oxide’s reduction onset temperature either by hot air streams from air-operated Concentrated Solar Power (CSP) tower plants or via surplus/cheap RE-electricity from photovoltaics, wind, or other renewable sources (“charging”/energy storage step). When this RE sources become non-available or upon demand, the fully charged system can transfer its energy to a controlled airflow that passes through the porous oxide block and initiates the exothermic oxidation of the reduced metal oxide. Thus, a hot air stream is produced which can be used to provide electricity or exploitable heat for industrial processes. The present work elaborates on the operating principles and the potential application of this concept and reports progress in the preparation and shaping of reticulated porous ceramics (RPCs also known as “ceramic foams”) from CaMnO3-based perovskite compositions and their preliminary testing with respect to cyclic reduction-oxidation.

USE OF GEOSYNTHETICS FOR DEWATERING, CONTAINEMENT AND DISPOSAL OF MINING SLUDGE

Whether it is sludge produced by the technological process of flotation, sludge tailings or sludge produced in another process, which contains pollutants such as heavy metals, it is necessary to dispose it in a controlled manner to reduce the risk for contamination of environment. Mining sludge has been disposed in open basins for decades, recently with measures taken to reduce the possibility of leakage or spillage of toxic contents into the environment. Reduction of the space for permanent disposal of sludge and significant reduction of the risk of spreading contamination is achieved using geosynthetics. In this paper, we will present the concept of dewatering and permanent storage of mining sludge in woven geotextile tubes, as well as the concept of using geosynthetic materials for the safe closure of mining sludge lagoons. Both concepts presented in the paper are accompanied by one case study.

System friendliness of distributed resources in sustainable energy systems

The increasing share of volatile renewable energy generation in current and future energy systems which does not follow the demand, makes it necessary to shift the synchronization tasks to the system and demand level. The intended demand side consumption management is usually incentivized via financial mechanisms. However, the optimum design of related incentives is still unclear. It is usually discussed under the term “system friendliness” which in turn still lacks a broadly accepted definition. In this article we introduce a new technical definition of “system friendliness” and develop comprehensive and holistic related indicators. For that, we introduce the burden concept for energy systems which represents the amount of technical infrastructure required for stable operation. We use the concept of a hypothetical system energy storage to derive indicators that are capable of quantifying the system friendliness of a given point-of-interest. The developed indicators are independent of regulations or market environments which enables comparability of results between studies and different systems. In a case study we demonstrate our newly developed methodology and exemplary examine decentral district energy storages. Our findings demonstrate that today’s regulatory environments that usually support residential self-consumption maximization are counterproductive. Instead, we show that dynamic end-user prices coupled with dynamic feed in tariffs are able to incentivize an almost 100% system friendly behavior of distributed prosumers.

Multi-objective optimization of distributed green infrastructure for effective stormwater management in space-constrained highly urbanized areas

Green infrastructure (GI) is essential for stormwater management, but its implementation in highly urbanized areas is challenging due to the limited space available for GI retrofitting. There is a lack of comprehensive evaluations that assess the spatial adaptability, functionality, and cost-benefit of various GI measures, and optimize their placement to achieve the maximum reduction rate of total runoff (RTR) and reduction rate of pollution load (RPL) while minimizing life cycle cost (LCC) in space-constrained highly urbanized areas (SCHUA). To address this issue, a novel concept of infiltration, retention, and storage integrated GI (IRS-GI) for SCHUA was proposed, and a framework coupling the Storm Water Management Model (SWMM) with multi-objective optimization algorithms was developed to determine the optimal IRS-GI layout, focusing on the objectives of RTR, RPL, and LCC. The impacts of different GI type, size, and location, rainfall return periods, and algorithms (NSGA-II and NSGA-III) were then examined. The results showed that IRS-GI could achieve satisfactory RTR and RPL results while single-type GI may struggle to meet requirements. Optimization outcomes were significantly influenced by rainfall return periods, with cost-benefit decreasing as return periods increasing. Besides, the optimization results of NSGA-II and NSGA-III showed differences, and the comprehensive Pareto frontier obtained by reapplying non-dominated sorting could achieve more comprehensive results for determining the optimal IRS-GI configuration. Under the urban drainage design standard, the optimal IRS-GI layout, covering 32.97 % of the green spaces, 38.57 % of the rooftop, and 60.98 % of the ordinary roads and squares, respectively, could achieve a RTR of 50.09 %, RPL of 57.00 %, and LCC of 0.79 × 108 CNY/yr. Additionally, the optimal configuration suggested that a higher proportion of GI downstream of drainage system may contribute to better cost-benefit, emphasizing the need for location-specific GI solutions. This research offers valuable insights for optimizing GI in SCHUA, advancing sustainable urban stormwater management.

Model-based evaluation of ammonia energy storage concepts at high technological readiness level

Ammonia is a promising carbon-free energy carrier since it can be stored as a liquid at mild conditions and its production process from hydrogen and nitrogen is established and efficient. Several Ammonia-to-Power concepts have been proposed in the literature, many of which employ not-yet-mature electrochemical technologies. We model the charging and discharging phases of three ammonia energy storage concepts in Aspen Plus seeking a compromise between efficient concepts and mature technologies. In the charging phase, ammonia is produced via the Haber–Bosch process using hydrogen from low-temperature water electrolysis for all the considered concepts. For the discharging phase, three ammonia conversion processes are modeled: (i) ammonia is thermally decomposed into nitrogen and hydrogen by using thermal energy from storage, and hydrogen is converted into electricity in a fuel cell; (ii) ammonia is thermally decomposed by using heat generated through the combustion of a fraction of the ammonia stream, and the produced hydrogen is supplied to a fuel cell; (iii) ammonia is used as a fuel in a combined power cycle. We compare these concepts with respect to roundtrip efficiency and levelized cost of electricity. The roundtrip efficiency and the levelized cost of electricity of the modeled concepts are ca. 30–34 % and 0.28–0.31 €kWh−1 (for an electricity purchase price of 0.03 €kWh−1). Concept (i) has both the highest roundtrip efficiency and the lowest levelized cost of electricity. We identify the process bottlenecks via an exergy analysis.

Feasibility Study on Production of Slush Hydrogen Based on Liquid and Solid Phase for Long Term Storage

To achieve net-zero objectives, the expansion of renewable energy sources is anticipated to be accompanied by an increased use of carbon-free fuels, such as hydrogen. Internationally, there are proposals for transporting hydrogen by synthesizing it into carriers like ammonia or Liquid Organic Hydrogen Carriers (LOHCs). However, considering the energy consumption required for hydrogenation and dehydrogenation processes and the need for high-purity hydrogen production, the development of liquid hydrogen transportation technologies is becoming increasingly important. Liquid hydrogen, with a density approximately one-sixth that of liquid natural gas and a boiling point roughly 90 K lower, poses significant challenges in suppressing and managing boil-off gas during transportation. Slush hydrogen, a mixture of liquid and solid phases, offers potential benefits. with an approximate 15% increase in density and an 18% increase in thermal capacity compared to liquid hydrogen. The latent heat of fusion of solid hydrogen effectively suppresses boil-off gas (BOG), and the increased density can reduce transportation costs. This study experimentally validated the long-duration storage and transportation concept of slush hydrogen by adapting NASA’s (National Aeronautics and Space Administration) proposed IRAS (Integrated Refrigeration and Storage) technology for compact and mobile tanks. Slush hydrogen was successfully produced by reaching the triple point of hydrogen, resulting in a composition of 47% solid and 53% liquid, with a density of approximately 80.9 kg/m3. Most importantly, methodologies were presented to observe and measure whether the hydrogen was indeed in the slush state and to determine its density. Additionally, CFD (Computational Fluid Dynamics) analysis was performed using solid hydrogen properties, and the results were compared with experimental values. Notably, this analytical technique can be utilized in designing large-capacity tanks for storing slush hydrogen.

Lunar Electrochemistry Enabling Microgrid Energy Storage on the Moon

This talk will cover an atypical paradigm of large scale energy storage technology - the need for scalable energy storage using resources available at the point of use for sustained human presence in space exploration. For Lunar surface power reliability, large scale energy storage enables increased safety factor for power generation downtime, but the launch mass of energy storage makes scalable storage to the level of microgrids or grids unappealing. This is compounded by a central paradox of safe energy storage, that achieving high energy density intrinsically carries greater safety risk in storing greater energy in a smaller mass or volume. In situ resource utilization aims to solve both these problems, enabling safe and scalable energy storage to be deployed for Lunar surface power reliability. However, a long road remains between the nascent field of ISRU energy storage as it exists today and its needed destination to enable future sustained human presence on the Moon and Mars.This talk will survey applications of electrochemical energy storage technologies and concepts with a focus on how Lunar resources can principally drive the electrochemistry. Brief mention will be given to non-electrochemical technologies such as thermal or mechanical methods, but the emphasis will be on electrochemistry owing to rapid advances in electrochemical state-of-the-art on Earth. Examples will include beyond Li-ion intercalation chemistry, metal-air cells, redox flow batteries, and regenerative fuel cells, using Lunar regolith and water as primary resources. For each technology, the talk will highlight where the study of “Lunar electrochemistry” must deviate from current terrestrial research to enable energy storage optimized for ISRU, rather than a simple transplant of Earth technology to Lunar application.

The Electrochemical Acetone/Isopropanol Hydrogenation Cycle: Full-Cell Performance of the Electrochemical Dehydrogenation of Isopropanol

Molecular hydrogen has exceptionally high gravimetric energy density but low volumetric energy density at ambient conditions. This discrepancy requires technical measures to increase its volumetric energy density for widespread hydrogen applications. Compressed hydrogen and liquified hydrogen are the most established hydrogen storage technologies. In addition, thermocatalytic liquid organic hydrogen carriers (LOHC) have drawn significant attention in the last decade.[1] LOHC couples consist of a hydrogen-lean and a hydrogen-rich form that can be reversibly converted into each other on demand. So far, only a few approaches adapted this hydrogen storage concept to electrochemistry. However, there is strong interest in electrochemical liquid organic hydrogen carriers (EC-LOHC) as electrochemical processes offer significant advantages like flexible operation, device size, scalability, and system simplicity.[2] This contribution demonstrates the concept of acetone/isopropanol as an electrochemical liquid organic hydrogen carrier focusing on the electrochemical dehydrogenation of isopropanol in a polymer electrolyte membrane electrode assembly (PEM-MEA) setup. The isopropanol oxidation at a PtRu electrode shows two distinct oxidation peaks at 0.18 V vs. RHE and 0.75 V vs. RHE, whereby the first oxidation peak is associated with a selective oxidation of isopropanol to acetone, electrons and protons.[3] The produced protons travel from the PtRu anode through the PEM and recombine with the electrons at the Pt cathode to form hydrogen. Therewith, this configuration is an electrolysis cell that produces hydrogen out of isopropanol upon polarization above the reversible cell potential.The study investigates the influence of acetone/isopropanol concentrations, temperature, and flow rates on the I-V characteristics of the electrochemical dehydrogenation of isopropanol at voltages below 0.35 V, revealing its possible potential as EC-LOHC.

Presentation of a distributed testing infrastructure for joint experiments across multiple remote laboratories for robust development of new district heating concepts

4th-generation district heating networks confront numerous challenges such as integrating decentralized renewable energy sources, bidirectional heat transfer, new storage concepts, low-temperature operation, custom heat supply, data management, and advanced control strategies. Laboratory and hardware-in-the-loop testing offer a safe, cost-effective environment for testing and validating these innovations. This paper presents a framework for joint experiments in multiple remote laboratories, enhancing the testing of district heating system components. This distributed testbed enhances the efficiency of testing by utilizing existing equipment and expertise from various laboratories, thereby reducing costs and time and allowing for more scenarios to test. It targets manufacturers, grid operators, and research institutions, facilitating collaborative lab work for technology testing before field deployment. This approach allows for diverse test scenarios, considering component interactions across different locations without identical hardware or software. The framework's efficacy is shown in a proof-of-concept with a low-temperature district heating network integrated across four Fraunhofer Institutes. An initial experiment connects a test building and a ground-source heat pump physically existing in different labs with emulated models of a district heating network and a geothermal source. Results from a three-week operation validate the framework's performance.