Search Results (20)

This study presents a comprehensive exergy-based thermodynamic analysis of a standalone liquid air energy storage (LAES) system integrated with internal thermal storage and an Organic Rankine Cycle (ORC) for sustainable large-scale energy storage applications. Unlike conventional studies, this work focuses on providing a scalable design framework by quantifying storage fluid requirements on a per-unit-mass-flow and per-MWh-capacity basis, enabling the results to be generalized for various power outputs and storage capacities. The proposed system configurations with two- and three-stage compression were compared in terms of liquid yield, round-trip efficiency (RTE), exergy efficiency, and storage fluid requirements. Results indicate that the optimal operating pressures are 190 bar for charging and 130 bar for discharging. At 200 bar charging pressure, the liquid yield increases from 0.51 (at 60 bar) to 0.86, while the maximum RTE reaches 62% in the base case and 68% with ORC integration. Incorporating ORC enhances the RTE by approximately 6–7% compared with conventional configurations through improved low-grade waste heat recovery and energy utilization. The two-stage compression configuration with ORC demonstrates the best thermodynamic performance, providing higher exergy efficiency, greater net power output, and lower thermal storage requirements. Furthermore, the reduction in thermal storage fluid demand contributes to improved resource utilization and lower infrastructure requirements for large-scale deployment. Additional sensitivity analyses indicate that thermal losses significantly reduce system performance, whereas ambient temperature fluctuations within ±15 K have only a minor influence on round-trip efficiency and liquid yield due to compensating effects between charging and discharging processes. The findings of this study provide scalable design insights for LAES systems and demonstrate the potential of ORC-assisted LAES technology to support renewable energy integration, sustainable grid flexibility, and low-carbon energy infrastructure development. Full article

The development of lithium-ion batteries (LIBs) capable of extreme fast charging (XFC) while preserving safety, durability, and practical energy density remains a central challenge for next-generation electric transportation and grid-scale storage. Conventional graphite anodes are fundamentally limited at high current densities by sluggish intercalation kinetics, which cause lithium plating, motivating the exploration of alternative insertion materials. This review provides a comprehensive and internally consistent assessment of titanium-based oxide anodes, encompassing TiO₂ polymorphs, lithium titanate (Li₄Ti₅O₁₂), and Wadsley–Roth titanium niobium oxides, through the combined lenses of crystal topology, diffusion pathways, redox chemistry, interfacial behavior, and resource scalability. By systematically comparing structural frameworks and electrochemical mechanisms across these material classes, we demonstrate that fast-charging performance is governed not by nano-structuring alone, but by the intrinsic coupling between operating potential, framework rigidity, and multi-electron redox activity. While Li₄Ti₅O₁₂ establishes the benchmark for safety and cyclability, and TiO₂ polymorphs provide structural versatility, titanium niobium oxides uniquely reconcile high theoretical capacity with minimal lithiation strain and open diffusion channels, positioning them as highly promising candidates for sub-10 min charging without catastrophic degradation. This review highlights the persistent obstacles these materials suffer, such as limited round-trip energy efficiency (RTE), interfacial gas evolution, poor dopant stability, and unsustainable extraction, while simultaneously exploring targeted design strategies to overcome them. Finally, this review provides a materials design and comparison framework for the development of safe, high-power, and commercially viable ultrafast-charging LIBs. Full article

This study presents a comprehensive dynamic system analysis of air-based Brayton batteries for the coupled generation of electricity, heat, and cooling. Building upon a previously published structural concept study, the most promising system architectures were modeled and evaluated using quasi-stationary simulations with dynamically designed thermal energy storage (TES) in Ebsilon Professional^®. The results show round-trip efficiencies (RTEs) of up to 50% for pure electricity generation and round-trip utilizations (RTUs) exceeding 85% for combined heat and power. Integration of waste heat further increases RTU to more than 100%, albeit at the expense of electrical efficiency. Dynamic simulations demonstrate stable operation with load gradients up to 2 MW min⁻¹, highlighting suitability for flexible industrial and grid applications. Regenerator-based TES exhibits the most favorable trade-off between efficiency and cost, while hybrid configurations of solid and liquid media offer additional optimization potential. The estimated investment costs range between 200 and 800 EUR/kWh_el, comparable to other large-scale Carnot battery systems. The findings provide a validated framework for the techno-economic design and control of next-generation Brayton battery systems and lay the foundation for experimental validation and pilot-scale implementation. Full article

To assess multi-energy complementarity and commercial development status in thermodynamic energy storage systems, this review systematically examines compressed air energy storage (CAES), compressed CO₂ energy storage (CCES), and Carnot battery (CB), focusing on principles, engineering demonstrations, and thermal integration. Their ability to integrate external heat, conduct combined cooling, heating and power (CCHP), or achieve high round-trip efficiency (RTE) through different pathway positions them as critical enablers for achieving net-zero emissions. Over 240 research articles retrieved from Web of Science and other databases, supplemented by publicly available reports published between 2020 and 2025, were systematically analyzed and synthesized. Current technologies demonstrate evolution from single-function storage to multi-energy hubs, with RTEs reaching 75% (CAES/CCES) and 64% (CB). Thermal integration significantly enhances RTEs. The CCES features a 100 MW/1000 MWh demonstration facility, concurrently necessitating accelerated distributed applications with high efficiency (>70%) and energy density (>50 kWh/m³). All three enable grid flexibility (China’s CAES network), industrial decarbonization (CCES carbon–energy depositories), and thermal integration (CB-based CCHP). These systems require >600 °C compressors and AI-optimized thermal management (CAES), high-pressure turbines and carbon–energy coupling (CCES), as well as scenario-specific selection and equipment reliability validation (CB) to achieve the targets of the Paris Agreement. Full article

With the large-scale grid connection of renewable energy and the surge of peak power system demand, liquid carbon dioxide energy storage technology has become a research hotspot due to its high energy density and environmental friendliness. However, most of the existing research focuses on the steady-state performance of the system, and the parameter coupling and transient response characteristics under dynamic operating conditions are not yet clear. To this end, this paper constructs a dynamic simulation model of a 10 MW-class liquid carbon dioxide energy storage (LCES) based on the Simulink platform, focuses on the coupling effects of the compressor inlet temperature, pressure, and mass flow rate and the expander inlet mass flow rate on the system parameters, and reveals the dynamic correlation between the system work and the state of charge value of the tank under the variable power working condition. The results show that the system’s round-trip efficiency (RTE) is 65.3% under design conditions, and the energy density reaches 34.79 kW·h·m⁻³. Perturbation analysis shows that when the compressor inlet temperature rises from 283.15 K to 303.15 K, the power consumption fluctuates in the range of 96.84% to 102.99% under design conditions. The inlet pressure perturbation (0.5~1.5 bar) will cause the power consumption of the compressor to change by 80.2%. In variable power operation, the state of charge value of the high-pressure liquid tank level in the energy storage stage rises from 0 to 84.89%, and the state of charge value of the high-pressure liquid tank level in the energy release stage decreases from 84.89% to 31.48%. The dynamic model proposed in this paper can accurately capture the transient response characteristics of the system and provide theoretical support for the optimization design and engineering application of LCES. Full article

This paper presents a zero-dimensional dynamic model of redox flow batteries (RFBs) for the system-level analysis of energy loss. The model is used to simulate multi-cell systems considering the effect of design and operational parameters on energy loss and overall performance. The effect and contribution of stack losses (e.g., overpotential and crossover losses) and system losses (e.g., shunt currents and pumps) to total energy loss are examined. The model is tested by using literature data from a vanadium RFB energy storage. The results show that four parameters mainly affect RFB system performance: manifold diameter, stack current, cell standard potential, and internal resistance. A reduction in manifold diameter from 60 mm to 20 mm reduced shunt current loss by a factor of four without significantly increasing pumping loss, thus boosting round-trip efficiency (RTE) by 10%. The increase in stack current at a low flow rate increases power, while the cell standard potential and internal resistance play a crucial role in influencing both power and energy output. In summary, the modeling activities enabled the understanding of critical aspects of RFB systems, thereby serving as tools for system design and operation awareness. Full article

Liquid air energy storage (LAES) is one of the most promising technologies for power generation and storage, enabling power generation during peak hours. This article presents the results of a study of a new type of LAES, taking into account thermal and electrical loads. The following three variants of the scheme are being considered: with single-stage air compression and the use of compression heat for regasification (Case 1); with single-stage compression and the organic Rankine cycle (Case 2); and with three-stage air compression/expansion and the organic Rankine cycle (Case 3). To analyze the proposed schemes, the Aspen HYSYS v.12 software package was used to compile models of the studied cycles. The analysis shows that round-trip efficiency (RTE) can be as high as 54%. The cost of 1 kg of liquid air is USD 7–8. Moreover, it is shown that the generation of electrical energy largely depends on the operation of the expander plant, followed by the organic Rankine cycle (ORC). Full article

The Battery Energy Storage System (BESS) is one of the possible solutions to overcoming the non-programmability associated with these energy sources. The capabilities of BESSs to store a consistent amount of energy and to behave as a load by releasing it ensures an essential source of flexibility to the power system. Nevertheless, BESSs have some drawbacks that pose limitations to their utilization. Indeed, effectively managing the stored and released energy is crucial, considering the degradation of performance associated with these systems over time. The substantial capital expenditure (CAPEX) required to install these systems represents a current constraint, impeding their broader adoption. This work evaluates a techno-economic analysis of a 2MW/2MWh BESS providing multiple services, namely participating in capacity and balance markets. The analysis is based on a BESS model implemented in SIMULINK, adopting online data gathered from a Lithium Iron Phosphate (LFP) battery facility. The model evaluates the auxiliary power consumption, state-of-charge (SoC), state of health (SoH), and the round-trip efficiency (RTE) of the overall system. The analysis is based on three price profiles: 2019 (Business-As-Usual), 2020 (COVID-19), and 2022 (Gas Crisis). Furthermore, this work conducts a case study to analyze the behavior of the BESS. It entails a sensitivity analysis, specifically evaluating the influence of CAPEX and upward bid price on the economic viability of the project. The results show a strong relation between the CAPEX variation and the Internal Rate of Return (IRR) of the project. Full article

A liquid carbon dioxide energy storage (LCES) system has the characteristic of compact structure and easy liquefaction. As a component of heat recovery in the LCES system, the recuperator plays a crucial role in influencing the round trip efficiency (RTE) of the energy storage system, but very little attention has been paid to it even though its operation conditions are quite different from other thermal systems. In this case, the thermal and hydraulic design of the recuperator in the LCES system was completed. The flow characteristics and thermal performance of the recuperator under design conditions were analyzed, and the effects of operating at various loads on the flow characteristics and thermal performance of the recuperator were investigated. It was found that from the inlet to the outlet, the resistance coefficient of CO₂ on the cold side increased gradually while decreasing gradually on the hot side. Down the flow direction, the average temperature of CO₂ on the cold side increased sharply, while decreasing slowly in the hot side. When the systems discharged with varying loads, the pressure drop increased along both channels, but the resistance coefficient decreased gradually on both channels. The heat transfer coefficient (HTC) increased gradually on both sides too. The Nusselt number (Nu) in the first half of the cold side did not change much, while increasing gradually in the second half, but it continued to increase on the hot side. Full article

The recent increase in the use of carbonless energy systems have resulted in the need for reliable energy storage due to the intermittent nature of renewables. Among the existing energy storage technologies, compressed-air energy storage (CAES) has significant potential to meet techno-economic requirements in different storage domains due to its long lifespan, reasonable cost, and near-zero self-decay. When viewed as a battery system, the key performance metrics of CAES, like energy density (ED), round trip efficiency (RTE), and the depth of discharge (DoD), have poor values when compared with other battery technologies in similar domains. This prevents CAES from transitioning to a state-of-the-art form of energy storage. This paper reviews the transition of CAES concepts from carbonized to carbonless types of CAES, along with different single-objective optimization strategies and their effects on the overall system’s performance. It was discovered that competing performance metrics attributes cause single-objective optimization to have trade-offs that worsen at least one other preferred metric. The topology limitations of the generic CAES design were noted to prevent its use in different domains. To ensure that the optimal convergence of subsystem parameters is retained during charging and discharging periods, a suitable topology and subunit combinations for different domains are necessary. Possible options for solving these problems are identified so that the effects of the trade-offs imposed by optimization are either suppressed or eliminated. Full article

Pumped thermal energy storage (PTES) is a promising long-duration energy storage technology. Nevertheless, PTES shows intermediate round-trip efficiency (RTE—0.5 ÷ 0.7) and significant CAPEX. sCO₂ heat pumps and power cycles could reduce PTES CAPEX, particularly via reversible and flexible machines. Furthermore, the possibility to exploit freely available heat sources (such as waste heat and/or CSP inputs) could increase RTE, making the system capable of an apparent RTE > 100% as well as reducing CAPEX, avoiding the need for two TES systems. This paper analyses the potential valorization of industrial waste heat (WH) to enhance PTES thermodynamic performance as well as increase industrial energy efficiency, valorizing different levels of WH sources in the 100–400 °C temperature range. In fact, the use of additional heat, otherwise dumped into ambient surroundings, may contribute to avoiding the need for a second TES, thus enhancing plant competitiveness. Starting from an assessment of the most relevant industrial sectors to apply the proposed solution (looking at available WH and electric flexibility needed), this paper analyses the feasibility of a specific sCO₂-based PTES case study, where the cycle is integrated into a cement production plant with a WH temperature of around 350 °C. It is demonstrated that the CAPEX of the proposed systems are still relevant and only a robust exploitation of the PTES in the ancillary service market could attract industrial customers’ interest in sCO₂ PTES. Full article

In this study, noble metal-free Co(OH)F and CoP nanorod electrocatalysts were prepared and explored as bifunctional oxygen electrodes (BOE) in anion exchange membrane-unitized regenerative fuel cells (AEM-URFCs). A CoP nanorod was synthesized from Co(OH)F via the hydrothermal treatment of cobalt nitrate, ammonium fluoride, and urea, followed by phosphorization. The crystal structures, surface morphologies, pore distributions, and elemental statuses of the obtained catalysts were analyzed to identify the changes caused by the incorporation of fluorine and phosphorus. The presence of F and P was confirmed through EDS and XPS analyses, respectively. Using these catalysts, the AEM-based URFCs were operated with hydrogen and oxygen in the fuel cell mode and pure water in the electrolysis mode. In addition, the electrocatalytic activities of the catalysts were evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. In the AEM-URFC test, the CoP catalyst in the BOE delivered the best performance in the fuel cell mode (105 mA cm⁻² at 0.3 V), and Co(OH)F was suitable for the water electrolyzer mode (30 mA cm⁻² at 2.0 V). CoP and Co(OH)F exhibited higher round trip efficiency (RTE) and power densities than the conventional Co₃O₄ catalyst. Full article

Adiabatic Compressed Air Energy Storage (ACAES) is regarded as a promising, grid scale, medium-to-long duration energy storage technology. In ACAES, the air storage may be isochoric (constant volume) or isobaric (constant pressure). Isochoric storage, wherein the internal pressure cycles between an upper and lower limit as the system charges and discharges is mechanically simpler, however, it leads to undesirable thermodynamic consequences which are detrimental to the ACAES overall performance. Isobaric storage can be a valuable alternative: the storage volume varies to offset the pressure and temperature changes that would otherwise occur as air mass enters or leaves the high-pressure storage. In this paper we develop a thermodynamic model based on expected ACAES and existing CAES system features to compare the effects of isochoric and isobaric storage. Importantly, off-design compressor performance due to the sliding storage pressure is included by using a second degree polynomial fit for the isentropic compressor efficiency. For our modelled systems, the isobaric system round-trip efficiency (RTE) reaches 61.5%. The isochoric system achieves 57.8% even when no compressor off-design performance decrease is taken into account. This fact is associated to inherent losses due to throttling and mixing of heat stored at different temperatures. In our base-case scenario where the isentropic compressor efficiency varies between $55\%$ and $85\%$, the isochoric system RTE is approximately 10% lower than the isobaric. These results indicate that isobaric storage for CAES is worth further development. We suggest that subsequent work investigate the exergy flows as well as the scalability challenges with isobaric storage mechanisms. Full article

As renewable energy production is intermittent, its application creates uncertainty in the level of supply. As a result, integrating an energy storage system (ESS) into renewable energy systems could be an effective strategy to provide energy systems with economic, technical, and environmental benefits. Compressed Air Energy Storage (CAES) has been realized in a variety of ways over the past decades. As a mechanical energy storage system, CAES has demonstrated its clear potential amongst all energy storage systems in terms of clean storage medium, high lifetime scalability, low self-discharge, long discharge times, relatively low capital costs, and high durability. However, its main drawbacks are its long response time, low depth of discharge, and low roundtrip efficiency (RTE). This paper provides a comprehensive review of CAES concepts and compressed air storage (CAS) options, indicating their individual strengths and weaknesses. In addition, the paper provides a comprehensive reference for planning and integrating different types of CAES into energy systems. Finally, the limitations and future perspectives of CAES are discussed. Full article

Grid-scale electrical energy storage (EES) is a key component in cost-effective transition scenarios to renewable energy sources. The requirement of scalability favors EES approaches such as pumped-storage hydroelectricity (PSH) or compressed-air energy storage (CAES), which utilize the cheap and abundant storage materials water and air, respectively. To overcome the site restriction and low volumetric energy densities attributed to PSH and CAES, liquid-air energy storage (LAES) has been devised; however, it suffers from a rather small round-trip efficiency (RTE) and challenging storage conditions. Aiming to overcome these drawbacks, a novel system for EES is developed using solidified air (i.e., clathrate hydrate of air) as the storable phase of air. A reference plant for solidified-air energy storage (SAES) is conceptualized and modeled thermodynamically using the software CoolProp for water and air as well as empirical data and first-order approximations for the solidified air (SA). The reference plant exhibits a RTE of 52% and a volumetric storage density of 47 kWh per m³ of SA. While this energy density relates to only one half of that in LAES plants, the modeled RTE of SAES is comparable already. Since improved thermal management and the use of thermodynamic promoters can further increase the RTEs in SAES, the technical potential of SAES is in place already. Yet, for a successful implementation of the concept—in addition to economic aspects—questions regarding the stability of SA must be first clarified and challenges related to the processing of SA resolved. Full article