Energy Storage Concept Research Articles

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.

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.

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.

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.

Addressing Individual Layers and Their Optical Properties in Artificial MoS2 Bilayers via Sulfur Isotope Labeling.

The physicochemical properties of van der Waals (vdW) heterostructures are driven by the delicate interactions between the individual layers in a multilayer stack. While addressing the monolayers of different compositions in the multilayer is feasible, exploring the intrinsic properties of the monolayers of the same composition within a multilayer is extremely challenging. This becomes of utmost importance in energy conversion and storage concepts based on layered vdW materials. For example, the charge distribution on the individual layers can be determined, and the behavior can be disentangled. We introduce sulfur isotope labeling as a powerful tool for separately addressing monolayers in vdW heterostructures composed of transition metal disulfides. Using chemical vapor deposition (CVD), we prepared monolayers of MoS2 using natural sulfur (NatS) and 34sulfur (34S) as precursors. Artificial bilayers were then prepared by transferring Mo34S2 onto MoNatS2. Thanks to the different masses of NatS and 34S, we were able to disentangle the spectral fingerprints of phonons and excitons in the two layers using Raman and photoluminescence microspectroscopy. Also, the charge distribution on the individual layers was revealed through Raman spectra analysis. Our work thus provides a different perspective for understanding the functionalities and optical properties of smart architecture based on transition metal chalcogenides.

Heat transfer and fluid flow analysis of PCM-based thermal energy storage concept for double pass solar air heater

Solar air heaters (SAHs) are flat plate collectors used for drying applications without causing any negative impact to the environment. However, SAH suffers from two drawbacks: first is the low convective heat transfer due to formation of boundary layer along the absorber plate, and second is the low thermal efficiency resulting from the lack of solar energy available after sunshine hours. The present study aims to examine the heat transfer and friction factor characteristics of double-pass SAH using two composite roughness geometries: perforated baffles and semicylindrical PCM tubes. The study is conducted at design parameters: blockage ratio (eb/Hd) of 0.4 to 0.8 and tube radius ratios (rt/Hd) of 0.2 to 0.5 under different Reynolds numbers (Re) from 3000 to 13,000. The maximum Nusselt number (Nu) and friction factor (f) are determined to be 200 at Re of 13,000 and 0.629 at Re of 3000, respectively, for the constant value of rt/Hd as 0.3 and eb/Hd as 0.8. In the range of parameters analyzed, maximum increase in Nu and f is determined to be 5.08 times and 65.80 times, respectively, over the smooth duct. Furthermore, correlations are derived for Nu and f with mean absolute error of 4.7% and 3.8%, respectively.

Organics-based aqueous batteries: Concept for stationary energy storage with resource feasibility

The integration of large-scale energy storage batteries and sustainable power generation is a promising way to reduce the consumption of fossil fuels and lower CO2 emissions. The significant materials demand for large-scale energy storage will address the limitation of resource availability. Organics-based aqueous batteries employing organic materials emerge as a promising settlement to face this challenge. Such types of batteries satisfy requirements related to elemental availability, inherent safety, cost affordability, technical reliability, and environmental sustainability meeting the demands of large-scale, long-duration energy storage.

The Heat Flux Method for hybrid iron–methane–air flames

Recently, a cyclic energy storage concept was proposed involving the use of metal powder as CO2-free energy carrier, known as the metal fuel cycle. In this cycle, the burning of iron powder is considered as the discharge agent of the energy carrier. However, for this cycle to be an efficient one, a better understanding of the laminar burning velocity of iron powder is required. This study presents a newly developed burner based on the Heat Flux Method (HFM), which can measure the burning velocities of flat hybrid iron–methane–air flames. Since laminar iron flames are difficult to stabilize and have – even for micron-sized particles – burning velocities in close proximity to their terminal velocity, methane is used as a stabilizing agent. In this paper, the design of the new burner system is presented with results for burning velocities of iron–methane–air flames. The results show a steady decrease in burning velocity when iron is added to a stoichiometric methane–air flame down to 16 cm/s. It is hypothesized that in the case of relatively low iron concentrations, the iron acts as a heat sink within these flames, consequently reducing the flame temperature and laminar burning velocity. For these low concentrations, methane is the governing fuel. At concentrations above 250 g/m3, the reduction of the burning velocity comes to a halt, and the iron becomes the governing fuel in the flame. A comprehensive error analysis reveals that the primary sources of uncertainty stem from fluctuations in the iron content and parabolic fitting of the thermocouple measurements in the HFM.Novelty and Significance statementThe novelty of this study is a newly developed burner based on the well-known Heat Flux Method (HFM). In accordance with the HFM, a new burner was designed to facilitate stable flat adiabatic hybrid iron–methane–air flames for the first time and measure its key parameter, the adiabatic burning velocity. Further, a metered iron powder dispersion system was developed for accurate iron mass flow measurements. The results show a steady decrease in burning velocity when iron is added to a stoichiometric methane–air flame in relatively low concentrations and show a very weak dependence of the burning velocity on the iron content at iron concentrations above 250 g/m3. These findings enable the validation of 1D simulations for iron-laden flames. A detailed assessment of the measurement uncertainties reveals that the largest source of uncertainty can be derived back to the stability of iron mass flow, leading to small flame propagation fluctuations on relatively short intervals.

Molecular Photoelectrochemical Energy Storage Materials for Coupled Solar Batteries.

ConspectusSolar-to-electrochemical energy storage is one of the essential solar energy utilization pathways alongside solar-to-electricity and solar-to-chemical conversion. A coupled solar battery enables direct solar-to-electrochemical energy storage via photocoupled ion transfer using photoelectrochemical materials with light absorption/charge transfer and redox capabilities. Common photoelectrochemical materials face challenges due to insufficient solar spectrum utilization, which restricts their redox potential window and constrains energy conversion efficiency. In contrast, molecular photoelectrochemical energy storage materials are promising for their mechanism of exciton-involved redox reaction that allows for extra energy utilization from hot excitons generated by superbandgap excitation and localized heat after absorption of sub-bandgap photons. This enables more efficient redox reactions with a less restricted redox potentials window and, thus, better utilization of the full solar spectrum. Despite these advantages, practical application remains elusive due to the mismatch between the short lifetime of the charge separation state (<ns) and the slower redox reaction rate (>μs). This mismatch results in a significant portion of the photogenerated charges recombining before participating in desired electrochemical energy storage reactions, leading to diminished overall efficiency. It is therefore highly important to develop molecular materials with intrinsic prolonged charge separation state and extrinsic effective mass-electron transfer to enable efficient coupled solar batteries for practical applications.In this Account, we begin with an introduction of the general solar-to-electrochemical energy storage concept based on molecular photoelectrochemical energy storage materials, highlighting the advantages of periodic oxidative donor-reductive acceptor porous aggregate structures that have synergistic implications on charge separation state lifetime extension and mass-electron transfer. We then present our earliest trial on the design and application of molecular photoelectrochemical energy storage materials, which stimulated our subsequent studies on tuning electron donor and acceptor structures for enhanced charge separation and diverse photoelectrochemical redox reactions. Moreover, we introduce the best practices in the design and assembly of various coupled solar battery devices, along with our literature contributions and progresses in solar-to-electrochemical energy storage efficiency (ηSES) over nearly the past decade. Finally, we conclude by highlighting the universality of our strategies as essential design principles, spanning from regulating long-lived charge separation states and photocoupled ion transfer processes in molecular materials to the construction of efficient coupled solar batteries. We offer perspectives on the synergy between photovoltage and redox potentials and the practical significance of 3D printing, providing key evaluation indicators for large-scale application. This Account provides molecular level insights for the construction of high-efficiency photoelectrochemical energy storage materials and guidance for practical solar-to-electrochemical energy storage applications.

Working Fluid Selection and Thermodynamic Optimization of the Novel Renewable Energy-Based RESTORE Seasonal Storage Technology

Abstract Seasonal-based energy storage is expected to be one of the main options for the decarbonization of the space heating sector by increasing the renewables dispatchability. Technologies available today are mainly based on hot water and can only partially fulfill the efficiency, energy density and affordability requirements. This work analyzes a novel system based on pumped thermal energy storage (PTES) concept to maximize renewables and waste heat exploitation during summer and make them available during winter. Organic fluid-based cycles are adopted for the heat upgrade during hot season (heat pump (HP)) and to produce electricity and hot water during cold season (power unit (PU)). Upgraded thermal energy drives an endothermic reaction producing dehydrated solid salts, which can be stored for months using inexpensive and high energy density solutions. This paper focuses on thermodynamic cycles design, comparing the performance attainable with several working fluids. Two different configurations are investigated: coupled systems, sharing the fluid and heat exchangers in both operating modes, and decoupled systems. A preliminary economic assessment completes the study, including a sensitivity analysis on electricity and heat prices. Cyclopentane is identified as a promising working fluid for coupled systems, reaching competitive round trip efficiencies (RTEs), maximizing the ratio between performance and HX surfaces, without excessive turbomachinery volume ratios and volumetric flows. Economic analysis shows that solutions with lower efficiency, but also lower capital cost, can achieve competitive payback times (PBT). On the contrary, decoupled systems are less attractive, as they reach slightly higher thermodynamic performance, but require higher capital costs, possibly being of interest only in specific applications.

Rigid structural battery: Progress and outlook

The advancement of high-energy-density batteries is vital for the development of lightweight, durable, and intelligent fully electric mobility systems. Reducing battery weight not only increases energy density but also confers load-bearing properties to the energy storage setup. These integrated batteries, known as rigid structural batteries, effectively encapsulate the concept of structural energy storage. The design of rigid structural batteries follows principles of mechanical/electrochemical decoupling at the microscale, and coupling at the macroscale. Based on achieving mechanical/electrochemical decoupling at different scales, we categorize rigid structural batteries into component-level, unit-level, and material-level rigid structural batteries. This review aims to summarize the progress in this field concerning mechanical/electrochemical decoupling at various scales and discuss fundamental design principles and core issues to address in rigid structural batteries. It also proposes strategies for the expeditious implementation of rigid structural batteries, aiming for long-term breakthroughs to surpass performance bottlenecks.

Ceramic-Based Dielectric Materials for Energy Storage Capacitor Applications.

Materials offering high energy density are currently desired to meet the increasing demand for energy storage applications, such as pulsed power devices, electric vehicles, high-frequency inverters, and so on. Particularly, ceramic-based dielectric materials have received significant attention for energy storage capacitor applications due to their outstanding properties of high power density, fast charge-discharge capabilities, and excellent temperature stability relative to batteries, electrochemical capacitors, and dielectric polymers. In this paper, we present fundamental concepts for energy storage in dielectrics, key parameters, and influence factors to enhance the energy storage performance, and we also summarize the recent progress of dielectrics, such as bulk ceramics (linear dielectrics, ferroelectrics, relaxor ferroelectrics, and anti-ferroelectrics), ceramic films, and multilayer ceramic capacitors. In addition, various strategies, such as chemical modification, grain refinement/microstructure, defect engineering, phase, local structure, domain evolution, layer thickness, stability, and electrical homogeneity, are focused on the structure-property relationship on the multiscale, which has been thoroughly addressed. Moreover, this review addresses the challenges and opportunities for future dielectric materials in energy storage capacitor applications. Overall, this review provides readers with a deeper understanding of the chemical composition, physical properties, and energy storage performance in this field of energy storage ceramic materials.

Potential of Aluminum as a Metal Fuel for Supporting EU Long‐Term Energy Storage Needs

AbstractThe EU's energy transition necessitates availability of green energy carriers with high volumetric energy densities for long‐term energy storage (ES) needs. A fully decarbonized scenario considering renewable energy availability is analyzed underpinning the need for such carriers. Considering the shortcomings of Power‐to‐X technologies in terms of efficiency and low volumetric density, Aluminum (Al) is identified as a potential alternative showing significantly high volumetric energy densities (23.5 kWh L−1). In this paper, an Al‐based long‐term ES concept is investigated, taking advantage of the inherent recycling of the active species (i.e., Al2O3 to Al) coupling decarbonized Hall–Héroult process with an Al‐steam oxidation for simultaneous hydrogen (H2) and heat generation. This work demonstrates an innovative lab‐scale fine Al powder‐steam oxidation process at ≈900 °C without use of catalysts or additives, exploiting alumina as inert material. Conducted SEM‐EDX analysis on oxidized Al provides supporting evidence in favor of employed oxidation pathway, hindering tendency of aluminum oxide (Al2O3) clumping and enabling direct use of oxides in the smelting process for fully recyclability. Moreover, outcomes of XRD analyses are presented to validate the measured total H2 yields.

A Review on Energy Storage Technologies: Current Trends and Future Opportunities

Despite the fact that numerous energy storage technologies have already been reviewed in the scientific literature, these innovations are right now at various stages of technological development, with only a few having been demonstrated for use on a large scale. The majority of research articles on energy storage give detailed descriptions of these technologies, but there is little data on how these technologies compared when used for energy storage. This paper provides a comprehensive review on energy storage concepts and also compares the different energy storage technologies in terms of research trends and future opportunities. Among the reviewed energy storage technologies, the thermochemical energy storage (TCES) method stands as an attractive and potential alternative to the conventional heat storage methods like sensible and latent thermal energy storage (STES and LTES) for several reasons that include: high energy storage density, minimal heat losses between the system and surroundings, and long term heat storage.

Electric truck gravity energy storage: An alternative to seasonal energy storage

AbstractThe global shift toward a sustainable and eco‐friendly energy landscape necessitates the adoption of long‐term, high‐capacity energy storage solutions. This research introduces an inventive energy storage concept involving the movement of granular materials from a lower elevation to a higher point within natural terrains such as mountains or excavated mining sites. Electrical energy is employed to charge electric batteries that elevate the granular material, thereby storing potential energy. Subsequently, this material is transported down during the electricity generation phase, and the regenerative braking mechanism converts the gravitational energy to replenish the vehicle's battery. The stored energy within these vehicles is then dispatched during peak demand periods or utilized by the vehicles for other freight transportation purposes. Our findings demonstrate a power cost of 1200 USD/kW, an energy storage expense spanning from 1 to 10 USD/kWh, a levelized cost of storage ranging from 35 to 200 USD/MWh, and a global annual potential of approximately 5.4 PWh. Electric vehicle gravity energy storage showcases its capability to bolster sustainable development by offering seasonal and multi‐year energy storage services.

Multi-Purpose Structure-Integrated Zinc-Polyiodide Hybrid Flow Battery As Sustainable Energy Storage System for Extraterrestrial Environments

For the energy supply of spacecrafts, such as space stations, satellites or orbiters, primarily solar power is used, which conversion, however, is subject to constant fluctuations due to rotational and orbital movements. In order to secure energy security for technical operations, the maintenance of scientific test series as well as life-support measures even during dark phases, various types of batteries such as nickel-hydrogen or nickel-cadmium batteries have been used as buffer storage over the years. However, due to the isolated locations in which they are used, energy storage systems for space applications must have a particularly long service life and operational reliability in order to be able to reduce resource-intensive replacement missions as well as hazards to people and technology.Since the battery systems used in space applications have in some cases shown significant deficits in these areas, a novel storage concept was developed in the "SpaceFlow" project, which was awarded third place in the europewide idea competition INNOspace Masters DLR Challenge, using the particularly safe and durable flow battery technology. The energy storage concept is based on the space-efficient integration of pressure-stable yet flexible flow battery cells into the supporting structure of spacecraft. In this way, in addition to energy storage as the primary task, other functions such as mechanical stiffening of the modules, support of thermal management or absorption of radiation can be realized.The "SpaceFlow"battery is realized as a zinc-polyiodide hybrid flow battery, which achieved incomparably high energy densities in laboratory tests. An energy density of 167 Wh/l was demonstrated and the potential to increase the energy density even up to 350 Wh/l was shown. The currently most widely used all-vanadium flow battery achieves energy densities of about 30 Wh/l. To optimize the cell chemistry zinc-polyiodide, various additives will be tested in the project. For a controlled formation of dendrites, for example, polyethylene glycol, methanesulfonic acid, chromium ions and, in general, alcohols, especially ethanol, could be added to the electrolytes as additives. In organic compounds, the presence of hydroxyl groups is an important factor in stabilizing the Zn ions. The deposition is also influenced by these. The search for additional alcohol and ether compounds offers the potential to find new additives. Chromium ions provide electrostatic shielding during zinc deposition, inhibiting dendrite growth.The iodine side (cathode) can be optimized mainly by improving the solubility of I2 in water. Stabilization of I2 without the binding of I- provides more free I-, which can react and help increase the capacity of the battery. Bromine ions or polyvinylpyrrolidone can be used to stabilize I2. Other additives such as KI and NH4Cl can be used for improved conductivity. Another approach is to improve diffusion at the cathode. For this purpose, a molybdenum sulfide coating can be applied, which improves the reaction rate with only a slight overpotential.The talk will present the novel storage concept and achievable functionalities as well as the latest project results of the flow cell design development and the design of a zinc polyiodide electrolyte, which must not be hazardous to humans and and at the same time must have a high energy density, to meet the requirements of space applications.

Optimizing scenarios of a deep geothermal aquifer storage in the southern Upper Rhine Graben

Based on a newly developed geological 3D reservoir model for the demonstration site of the ‘Freiburger Bucht’ in the Upper Rhine Graben (SW Germany), geothermal development and realization concepts of an aquifer thermal energy storage (ATES) in the Buntsandstein aquifer were elaborated and energetically evaluated by numerical modeling. The thermal–hydraulic coupled modeling was performed with the FE-software OpenGeoSys and COMSOL. For this purpose, the geological model was converted into a numerical model and calibrated by local and regional, hydrogeological and geothermal measured values. A detailed study based on two-phase storage-heating cycles per year with constant injection temperature on the ‘hot side’ of the ATES, different volumetric flow rates, and temperature spreads was performed to quantify possible storage capacities, energies, and efficiencies. The calculated efficiency of the cyclic storage operation in this study, averaged over 10 storage heating cycles, are between 50 and 85%, depending on flow rate and temperature spread. The efficiency of the individual storage heating cycles increases from year to year in all scenarios considered, as the ‘hot side’ of the storage heats up in the long term. To increase ATES’ efficiency, also horizontal wells were integrated into the numerical model and the results were compared with those of inclined wells.

Optimized scheduling study of user side energy storage in cloud energy storage model.

With the new round of power system reform, energy storage, as a part of power system frequency regulation and peaking, is an indispensable part of the reform. Among them, user-side small energy storage devices have the advantages of small size, flexible use and convenient application, but present decentralized characteristics in space. Therefore, the optimal allocation of small energy storage resources and the reduction of operating costs are urgent problems to be solved. In this study, the author introduced the concept of cloud energy storage and proposed a system architecture and operational model based on the deployment characteristics of user-side energy storage devices. Additionally, a cluster scheduling matching strategy was designed for small energy storage devices in cloud energy storage mode, utilizing dynamic information of power demand, real-time quotations, and supply at the load side. Subsequently, numerical analysis was conducted to verify that the proposed operational mode and optimal scheduling scheme ensured the maximum absorption of renewable energy, improved the utilization rate of energy storage resources at the user side, and contributed to peak shaving and load leveling in the power grid. The model put forward in this study represents a valuable exploration for new scenarios in energy storage application.