Short-term Energy Storage Research Articles

Economic evaluation of kinetic energy storage systems as key technology of reliable power grids.

In recent years, energy-storage systems have become increasingly important, particularly in the context of increasing efforts to mitigate the impacts of climate change associated with the use of conventional energy sources. Renewable energy sources are an environmentally friendly source of energy, but by their very nature, they are not able to supply the required amount of energy in a uniform distribution. This study evaluated the economic efficiency of short-term electrical energy storage technology based on the principle of high-speed flywheel mechanism using vacuum with the help of an innovative approach based on life cycle cost analysis (LCC). The innovative potential of high-speed flywheel energy storage systems (FESS) can be seen in increasing the reliability of the electricity transmission system with the possibility of providing control power to compensate for residual loads caused by volatile renewable power sources and power sinks. Based on the research conducted, the LCC method was selected in this study as the most appropriate method to evaluate the economic efficiency of a high-speed FESS used to compensate for short-term fluctuations in an upgraded electric transmission system. As a result, the adjusted LCC per MWh values were compared with the average intra-hour margin realisable in the Intra-Day OTE Market, while the margin calculation also considered the efficiency of the inertial storage. Under the modelled technical and economic conditions, it was found that a high-speed FESS project that can compensate for short-term fluctuations in the electricity transmission system can be economically efficient in the Czech Republic.

Unlocking self-discharge: Unveiling the mysteries of electrode-free Zn-MnO2 batteries with advanced in situ techniques in mild acid aqueous electrolytes

We introduce a novel approach to Zinc-MnO2 battery architecture utilizing a 3D network of carbon nanofibers as both current collector and electrode material, promising enhanced performance and longevity for large-scale energy storage. Employing mild aqueous electrolytes, we address the challenge of managing self-discharge, crucial for short-term energy storage. Advanced coupled characterization techniques, including in-situ EQCM (Electrochemical Quartz Crystal Microbalance) and high-resolution optical microscopy, elucidate self-discharge mechanisms across over multiple length scales. Findings reveal that the self-discharge is mainly at the zinc electrode due to concomitant dissolution of Zinc (corrosion) and HER (Hydrogen Evolution Reaction) phenomena. Interestingly, the corrosion current was estimated irrespective of charging protocol and remains consistent, indicating the independence of zinc corrosion kinetics from the length scale. Finally, the morphology of the zinc layer appears to be critical, suggesting that self-discharge is primarily a chemical process. This innovative design strategy offers the potential for high-performance Zinc-MnO2 batteries with extended cycle life to meet the requirements of large-scale energy storage applications.

Simulation of a Tidal Current-Powered Freshwater and Energy Supply System for Sustainable Island Development

Sustainable development of islands cannot be achieved without the use of renewable energy to address energy and freshwater supply issues. Utilizing the widely distributed tidal current energy in island regions can enhance local energy and water supply security. To achieve economic and operational efficiency, it is crucial to fully account for the unique periodicity and intermittency of tidal current energy. In this study, a tidal current-powered freshwater and energy supply system is proposed. The marine current turbine adopts a direct-drive configuration and will be able to directly transfer the power of the turbine rotation to the seawater pump to improve the energy efficiency. Additionally, the system incorporates batteries for short-term energy storage, aimed at increasing the capacity factor of the electrolyzer. A simulation is conducted using measured inflow velocity data from a full 12 h tidal cycle. The results show that the turbine’s average power coefficient reaches 0.434, the electrolyzer’s average energy efficiency is 60.9%, the capacity factor is 70.1%, and the desalination system’s average specific energy consumption is 6.175 kWh/m3. The feasibility of the system design has been validated.

Thermodynamic and economic analysis of a novel compressed air energy storage system coupled with solar energy and liquid piston energy storage and release

Compressed air energy storage (CAES) is one of the important means to solve the instability of power generation in renewable energy systems. To further improve the output power of the CAES system and the stability of the double-chamber liquid piston expansion module (LPEM) a new CAES coupled with liquid piston energy storage and release (LPSR-CAES) is proposed. The coupled LPEM conducts suction stage B at the end of the expansion stage, ensuring stable exhaust pressure and temperature for the module. By establishing the thermodynamic and economic models of LPSR-CAES, the effect laws of key node parameters on the system performance are investigated. The results show that the heat transfer between liquid droplets and air dominates the heat transfer in LPEM. The proposed LPEM exhibits excellent isothermal performance and stability, with a maximum temperature difference of about 20 K during the cycle, and stable exhaust temperature changes within 10 K. Under the design conditions, the converted electrical efficiency, round-trip efficiency, exergy efficiency and net present value of the system are 68.31 %, 58.86 %, 66.99 % and 12.25 M$ respectively. The higher the solar supplement temperature, the more outstanding the thermal and economic performance of the system. The short-term energy storage system performance of the proposed system is more prominent. Based on the actual light data, the system can achieve 72.09 % and 69.41 % of converted electrical efficiency and exergy efficiency, respectively, at the 219th day. The results of this study provide theoretical support for the engineering application of the proposed system.

Thermally driven MnCl2[sbnd]NH4Cl resorption cycle for seasonal thermal management of urban buildings

The frequency of extreme weather conditions caused by global greenhouse gas emissions has led to a significant increase in energy consumption for refrigeration and heating supply in urban buildings. However, conventional sensible and latent heat storage technologies hold low thermal energy storage density and short-term energy storage capabilities. Additionally, electrically driven compression refrigeration with non-negligible global warming potential (GWP) is unsuited to high ambient temperatures in summer. We propose an advanced strategy, adopting the MnCl2NH4Cl resorption cycle to achieve efficient desorption refrigeration of NH4Cl and resorption heating supply of MnCl2 under seasonal conditions. Experimental results have demonstrated that our proof-of-concept system can output 70 °C heat with a thermal energy storage density of 166.2 kJ·kg−1, providing continuous heating for 30.5 min under the winter ambient temperature of 10 °C. Moreover, COPref remained at 0.589 for continuous indoor refrigeration lasting 58.5 min under summer ambient and refrigeration temperatures of around 30 °C and 2 °C, respectively. This exceptional adaptability to ambient temperatures enables efficient adjustment of urban building comfort. Our work presents a promising zero-carbon pathway for replacing conventional fossil fuels employed in the thermal management of urban buildings with solar energy.

One-dimensional lepidocrocite titania mesoparticles integrated with activated carbon for high-performance supercapacitor applications

Herein, we mix titania-based, TiO2, porous mesostructured, comprised of one-dimensional lepidocrocite nanofilaments, 1DLs, ≈ 5 × 7 Å2 in cross-section, with activated carbon, AC, to create unique composite structures with exceptional electrochemical properties. The synthesis method is facile, cost-effective, and scalable. While the porous mesoparticles, PMs, possess excellent protonic conductivity and exhibit enhanced faradic behavior in acidic aqueous media, their low electronic conductivity restricts their power output. The problem is solved by mixing the PMs with AC powders with various loadings. Electrolytes used were sulfuric acid, H2SO4, potassium hydroxide, KOH, lithium and Na-sulphates. The best PM loading was found to be 25 wt%. The resulting composite exhibits a specific capacitance (capacity) of 1024 Fg−1 (554 mAhg−1) at a 2 mVs−1 scan rate, with 97 % cyclic stability over 10,000 cycles when the electrolyte was 1 M H2SO4. Upon integration into a symmetrical device, the composite exhibited a specific energy of 135 Whkg−1 at 0.5 Ag−1. Further, it demonstrated a peak specific power of 18 kWkg−1, while retaining a specific energy of 54 Whkg−1 at 5 Ag−1. Notably, following 100,000 cycles at 1 Ag−1, the symmetrical cell sustained approximately 50 % of its initial specific capacitance. Subsequently, a 24 h self-discharge test revealed a decrease in cell voltage from 1.95 V to 0.48 V, thereby highlighting the potential suitability of these supercapacitors for short-term energy storage applications.

Flexible energy utilization potential of demand response oriented photovoltaic direct-driven air-conditioning system with energy storage

The surge in air conditioning electricity consumption exacerbates grid peak load. To counteract grid peaking pressures and accommodate a high penetration rate of renewable energy, a photovoltaic direct-driven air-conditioning system (PVACS) integrated with energy storage was suggested. The power response characteristics of the air conditioner based on indoor temperature set-point regulation were clarified with an on-site test. The test results indicated a significant flexible energy utilization potential through intelligent temperature management. Whereas, its flexibility is limited by high ambient temperature or inadequate air conditioner capacity. Then, the effects of demand response were simulated, aiming to achieve the synchronization between air conditioner power and photovoltaic (PV) power. Simulation results showed that the demand response strategies effectively reduced peak power by 45.2% and increased self sufficiency ratio and self consumption ratio to 0.83 and 0.91, respectively. Moreover, the role of short-term electricity energy storage was considered for further promoting solar energy accommodation and grid peak shaving. Optimized energy storage further reduced peak power by more than 23.4%, while mitigating the temporal supple-demand mismatch.

Modeling energy storage in long-term capacity expansion energy planning: an analysis of the Italian system

This paper presents a framework to represent short-term operational phenomena associated with renewables capacity factors and final service demand distributions in a capacity-expansion and integrated energy system optimization model. The aim is to study the potential role of energy storage technologies coupled with renewable energy sources aiding the decarbonization of the overall energy system. The proposed methodology is implemented in an energy system optimization model named Tools for Energy Model Optimization and Analysis (TEMOA) and then tested in a case study focused on the Italian energy system. We examine a collection of scenarios that includes reference time scale scenarios, time scale sensitivity scenarios, and technology alternative scenarios. This paper's findings indicate that energy storage is crucial for fully decarbonizing the Italian power sector by 2050 in the absence of a low-carbon baseload. Additionally, it suggests that approximately 10 % of Italy's electricity generation in 2050 should be routed through short-term energy storage devices.

Optimization and Control of Electric Ship Microgrids With Short-Term Energy Storage Systems

Optimization and Control of Electric Ship Microgrids With Short-Term Energy Storage Systems

Optimizing Mid-Temperature Sodium Iodine Batteries for Sustainable Large-Scale Energy Storage: A Comprehensive Modeling Approach and Experimental Validation

The need for safe, eco-friendly, low-cost batteries for large scale implementation rises in the presence of the expansions of renewable energy sources. High-temperature liquid sodium batteries (e.g. sodium-sulfur) are a well-established technology for large-scale grid storage. Combining the molten sodium anode with an aqueous iodine cathode overcomes the problems of thermal loses and sealing by reducing the operating temperature to about 100°C. This leads to higher cost efficiency, energy density and a simplified cell design.Here we present a novel modelling approach for complex carbon-based cathode structures and its limits and abilities on enhancing the utilizable capacity. Due to their sustainability and high efficiency, which is comparable to Li-Ion –batteries, mid-temperature sodium-iodine batteries are a promising candidate for stationary energy storage applications. With a high specific energy of around 200 Wh kg-1, sodium-iodine batteries have the ability to meet the growing demand of short-term energy storage caused by the integration of renewable energy sources into the power grid. Up to this day, the detailed processes inside the battery are not well-understood. Quantities like initial species concentrations, C-rate, cell design and cathode geometry have large impacts on the overall battery performance. A deeper understanding of these processes is inevitable for enhancing the battery performance by choosing the optimal abovementioned quantities. We set up a fully resolved 3D Simulation model to gain insight into microstructural processes inside the battery, as experimental studies are limited to macroscopic quantities like electronic current and potential. The methodology is based on continuum hypothesis by using an open-source CFD software, which is rewritten accordingly. The proposed spatially resolved three-dimensional simulation model takes charge and mass transport, heterogeneous and homogeneous reactions as well as the electrochemical processes into account. Results show that transport limitations confine the utilizable capacity of the battery [1].This contribution focuses on enhancing the battery energy density and efficiency by including open-pored glassy carbon foam structures in the cathode half-cell [2, 3]. We state simulation predicted, optimal morphology properties of such a structure. Furthermore, we describe the evaluation of improved thermodynamic data of the aqueous iodine solution by refitting simulation results to polarization curves. We utilize a novel impedance spectroscopy simulation method for sodium iodine batteries to improve parameterization of the underlying electrochemical model by comparing the results with experimental data. References Gerbig, F., Cernak, S., Nirschl, H. (2021). 3D Simulation of Cell Design Influences on Sodium–Iodine Battery Performance. Energy Technology, vol. 9, no. 6, p. 2000857Gerbig, F., Cernak, S. and Nirschl H. (2021), Towards a Novel Sodium-Iodine Battery with an Aqueous Catholyte: Numerical Investigations of Complex Cathode Structures, ECS Trans., vol. 104, no. 1, pp. 123–130Gerbig, M. Holzapfel, and H. Nirschl, Simulating the Impact of Glassy Carbon Foam Electrodes on the Performance of Sodium Iodine Batteries, J. Electrochem. Soc., vol. 170, no. 4, p. 40517, 2023, doi: 10.1149/1945-7111/accab7. Figure 1

Hybrid energy storage sizing in energy hubs: A continuous spectrum splitting approach

Renewable powered energy hub is a promising way to realize efficient use of renewable resources through multi-energy integration. To cope with the fluctuation of renewable power at different timescales, long-term and short-term energy storage devices are essential. This paper proposes a frequency-domain approach to determine the appropriate capacities of hydrogen and battery energy storage units in an electricity–hydrogen–heat integrated energy hub. The net demand is mapped to the frequency domain via discrete Fourier transformation (DFT). A continuous spectrum splitting method is developed to allocate the frequency components among generator, hydrogen storage and battery storage. Compared with the time-domain method, it makes better use of the spectral characteristics of the year-round data, leading to robust sizing results without complex modeling of uncertainty. In contrast to the existing cut-off frequency method which assigns high-frequency components to battery storage and low-frequency components to generators according to a cut-off frequency, the proposed framework allows a single spectrum component to be allocated to multiple system devices, which not only makes the optimization model convex but also improves optimality. In addition, the spectrum clustering process further reduces the number of core variables and the computational efficiency is high. The rationality of the sizing results is verified through online operation, where the proposed method achieves an average of 1.93% total load shedding rate compared with 4.42% of the time-domain method, verifying the operation reliability under uncertainty. While fully utilizing the spectrum characteristics, the investment cost is about 22% less than the cut-off frequency result.

Planning of wind-photovoltaic-storage-hydrogen-water for a zero-carbon microgrid on an independent island

Due to low daily demand and the remote location from the shoreline, diesel generators dominate the energy supply on these islands, resulting in significant emissions of harmful gases. In this paper, a collaborative planning approach is proposed for a zero-carbon microgrid incorporating wind turbines (WTs), photovoltaic modules (PVs), electrochemical energy storages(EESs), hydrogen energy storages(HESs), and sea water desalination on an independent island. Long-term and short-term energy storage mechanisms, represented by HESs and EESs, respectively, are coordinated to harness the abundant wind and solar energy resources. Additionally, consideration is given to the requirement for sea water desalination to achieve a self-sustained equilibrium of zero-carbon water and electricity for the island’s inhabitants. Illustrative analysis demonstrates that the proposed planning method accounts for the stability and environmental preservation in terms of the planning and operation. This has profound implications for advancing the transformation of the island’s microgrid energy infrastructure, enhancing the utilization of renewable energy, and bolstering the self-sustaining capacity of hydropower resources.

Control strategy design and performance analysis of a low carbon and high ratio green energy CCHP (LCHRG-CCHP) system

In order to solve the compatibility of combined cooling, heating and power (CCHP) system with green energy and the coupling problem with energy storage equipment, the system structure (LCHRG-CCHP system) proposed in this paper for the low-carbon and high-green energy compatible optimization research of the integrated energy system integrating green energy and flexible hybrid energy storage. Aiming at the high compatibility and low carbon emission of CCHP system to green energy, the traditional CCHP system, the combination of CCHP system and green energy, the combination of CCHP system and green energy and short-term energy storage, and the combination of CCHP system and green energy and long-term and short-term energy storage are compared. The intelligent optimization algorithm combining improved sine dung beetle optimizer and linear support vector machine algorithm (MDBO-LSVM) is used to solve the problem. The results show that in the CCHP system, the coupling of short-term energy storage and long-term energy storage can effectively improve the compatibility of the system with green energy. The proportion of green energy in the system proposed in this paper is increased by 13.32 %, which can reach an average of 23.91 %, while the carbon emissions are reduced by 37.34 %, which effectively improves the energy utilization rate.

A compressible degree of freedom as a means for improving the performance of heaving wave energy converters

A compressible degree of freedom (CDOF) can provide a means of improving wave power capture by adjusting the system stiffness and providing short-term energy storage, reducing or even eliminating the requirement for two-way electrical power flow as is typical in wave energy control systems. With the overarching goal of investigating and facilitating the application of a CDOF within wave energy converter (WEC) design, this paper focuses primarily on the case of heaving buoys, and on using air volumes to provide the compressible spring effect. Analytical formulae for the natural frequencies are used to gain fundamental insights into the main design considerations. Numerical methods are used to augment this understanding, helping to elucidate the effect of geometric parameters and scale on the required compressible volumes and the efficacy of the CDOF. Beginning with the WaveBot WEC, case studies are then used to demonstrate the design drivers in a more applied context, as well as highlighting the benefit of a self-reacting power take-off (PTO) system. The assimilation of these results with the findings of a detailed literature review culminates in a set of recommendations (or guiding principles) for designing a compressible degree of freedom to improve the performance of a heaving wave energy converter. These recommendations apply both to full-scale WECs, and to the design of scale physical modelling studies for validating the analytical and numerical models.

Analysis of Supercapacitors in Renewable Energy Systems for Managing Power Fluctuations

Environmental decarbonization drives the world to find better ways to generate and store energy. Sustainable energy in the form of solar and wind is explored with the use of conventional energy storage systems (batteries) to close the gap. Green energy generation is weather-dependent, leading to power output fluctuations, and the short-term variability in irradiance adversely affects the system’s energy output and reliability. Standalone operation of a generating system necessitates a storage energy unit that manages transient loading and effectively shares power between the load and energy storage. This article presents an approach to managing energy fluctuations when renewable energy sources fluctuate, this occurs when short-term variability in irradiance, and transient loading occurs. The approach uses supercapacitors as a short-term energy storage solution. The proposed configuration has the following key advantages: effective power sharing, rapid charge, and discharge cycles in supercapacitors result in voltage restoration under transient conditions. The performance of the system is confirmed in MATLAB/Simulink. The proposed study confirms that integrating supercapacitors with PV systems does provide significant power oscillation management when sudden variations occur in renewable sources. A practical test was performed using smaller components following the same concept, and the results supported the hypothesis. The results show that the output voltage is managed when oscillation in irradiance occurs. This is seen in the simulation without supercapacitors when the output voltage fluctuates between 100 and 450 V within the first second of the simulation; however, with the introduction of SC, the voltage becomes stable and maintains an output of 620 V within 0.02 seconds. This is further supported by the experimental outcomes where almost 50% of the solar panel is covered and the output voltage is maintained.

Equalizing multi-temporal scale adequacy for low carbon power systems by co-planning short-term and seasonal energy storage

Power supply faces seasonal security risks due to the large seasonal volatility of renewable energy sources (RES) generation. Power systems with high shares of RES generation are more difficult to keep seasonal and daily/hourly supply adequacy at the same level. Therefore, this paper first addresses multi-temporal adequacy detail accounting for differences in RES output and timing of production, and demand. Then a planning approach is proposed for sizing short-term and seasonal energy storage accompanying with RES to achieve multi-temporal adequacy equilibrium. Unlike existing methods based on linking typical days or 8760-h simulations, the seasonal electricity adequacy constraints are captured by orderly clustering yearly net power curves, then the energy balance constraints are decoupled into long-term (i.e., seasonal) and short-term (i.e., hourly) energy balances. At the short-term scale, the robust optimization is used to address the uncertainty and randomness of wind and solar generation, in the same time realizing the coordination of short-term and seasonal energy storage. A modified column and constraint generation algorithm is used to solve the min-max-min model with binary variables. Finally, case studies are carried out on the Garver-6 system and the Northwest China Power Grid. The results demonstrate that the proposed planning method ensures multi-temporal scale adequacy equilibrium for high-RES power systems, and improving the planned system's economic performance.

Strengths, weaknesses, opportunities and threats of demand response in district heating and cooling systems. From passive customers to valuable assets

Buildings can deliver short-term thermal energy storage by utilising the thermal capacity of the building construction and/or by activating the water tanks included in the heating/cooling installation. The flexibility potential of demand management using decentralized thermal energy storage has been quantified in many theoretical modelling studies, and it is considered an essential technology for an affordable energy transition. We have investigated the drivers and barriers to the adoption of demand management in buildings in district heating and cooling systems via a Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis and presented 17 elements that shape the current and future application of this concept. The results indicate that the application of the DR concept has left the theoretical studies and moved towards real-life applications. Yet, there is a lack of feasible business models and regulatory frameworks supporting the large-scale application of the concept. Utilities and their customers do not fully understand the benefits of the DR concept; therefore they are reluctant to adopt it outside of the research projects where the test environment is fully controlled and with limited impact and timeline. Therefore, the regulatory framework must be adjusted to allow DHC operators to develop new business models and DR tariffs that will incentivise the customers to deliver flexibility to the system without compromising their comfort and everyday practices and increasing energy poverty.

Steam Storage Rankine Cycle for Unutilized Applications in Distributed High-Temperature Waste Heat Recovery

In the light of increasingly valuable resources and a trend towards more efficient processes pushed by climate change, distributed Waste Heat Recovery (WHR) is an important element in the transformation of the energy supply. In recent years, however, WHR systems have often been optimized and implemented for steady-state applications. In this paper, dynamic system modeling and a Steam Rankine Cycle (SRC) pilot plant with 40 kWel are used to investigate applications unutilized thus far for the conversion of high-temperature waste heat into electricity using a shell boiler with 1.27 m3 of liquid water for short-term energy storage. In addition to experimental investigations of the storage system as an Uninterruptible Power Supply (UPS) and the input and output of +/−100% electrical power peaks for grid-assistive operation, a control concept for the use of volatile waste heat is developed from a model-based controller design up to a Model Predictive Control (MPC) with the help of a dynamic system simulation. Based on the validated model and experimental measurement data, outlooks for concrete applications with higher storage capacity and power are provided.

Experimental Verification of Novel Bi-Directional qZSI Based DC/DC Converter for Short Term Energy Storage Systems

This paper presents a new bi-directional isolated DC/DC converter for supercapacitor (SC) interfacing. During the SC charging mode, the converter operates as a VSI-based step-down DC/DC converter and during the energy recovery mode, as a qZSI-based step-up DC/DC converter. For galvanic isolation and voltage matching a medium frequency transformer was implemented. To achieve higher SC voltage boost the qZSI with the two-stage quasi-Z-source (qZS) network was introduced. The paper discusses the PSIM simulation and experimental results of proposed converter operating with a 14.4 V 142 F supercapacitor

Simulation of a Hybrid System Wind Turbine-Battery-Ultracapacitor.

In order to improve the predictability of power generation from wind, short term energy storage in batteries combined with ultra capacitors (UCaps) is proposed. The system is simulated with SIMULINK and contains detailed models of a lead acid battery pack and a simple model of the UCap bank. The wind energy conversion system (WECS) is simulated by measured time series with a time resolution of one second. The objective of the simulation is to determinate the system configuration that is able to guarantee a predictable energy output to the grid during a given time interval. Within this time, the storage system should be able to compensate all type of rapid changes originated by wind speed fluctuations. Another important issue is the integration of an ultra capacitor bank. It is investigated its influence on the charge and discharge stress of the battery. It is demonstrated that quick changes in wind power generation can be covered by a reasonable size of battery capacity for a prediction time interval of 10 min. Very short transients in energy flow (1-10 s) are absorbed by the UCap bank which minimizes the deterioration of the battery because important current peaks do not reach the battery. The final system design is based on measurements at a 600 kW constant speed WECS. Its typical, very sharp changes in power output (more than 200 kW/s possible) are smoothed by a 500 Ah lead acid battery with 300 cells in series (voltage range: 480 – 720 V). In parallel to the battery a 10 F UCap bank is connected. To hold 720 V, the bank consists of 240 UCaps connected in series (3 V / 2400 F each).