Renewable Energy Storage Systems Research Articles

Enhancing Islanded Power Systems: Microgrid Modeling and Evaluating System Benefits of Ocean Renewable Energy Integration

The energy transition hinges on the effective integration of renewable energy sources into the power grid. Islands can provide invaluable insights into the challenges and opportunities of integrating variable renewable energy into the grid due to their relatively small power systems, isolated grids, and diverse availability of renewable energy resources. This paper presents a study on the system benefits and challenges of marine energy integration in insular power systems, focusing on the Orkney Islands as a case study. A microgrid modeling approach that optimizes the mix of renewable sources and energy storage systems for future scenarios considering strategic time horizons (2030, 2040, and 2050) was employed. Results suggest that integrating ocean energies, namely, wave and tidal energy, yields notable benefits compared to traditional renewable energy sources exclusively. These benefits encompass reduced installed capacity, minimized energy storage requirements, lower excess generation, and overall cost-saving.

An economic and environmental optimization model for sizing a hybrid renewable energy and battery storage system in off-grid farms

This paper presents a model for optimizing the life cycle economic and environmental impacts of a hybrid renewable energy and battery storage system – as energy supply technologies (EST) for off-grid farms. Micro-hydropower and photovoltaics represent the primary renewable energy (RE) sources, with batteries and a diesel generator considered as possible back-up systems. A modified Non-dominated Sorting Genetic Algorithm II (NSGA-II) was developed and applied to a case study farm in Southern Spain and provided different EST solutions to optimize a design based on economic (life cycle costing or LCC) and environmental (life cycle assessment or LCA) constraints. The results highlighted that cases with a strong dependence on batteries could achieve minimum costs and lower impacts for climate change and energy resources (non-renewable fuels). In contrast, the optimal system for minimizing the consumption of material resources (metals/minerals) resulted in higher fuel use, which was up to 25% more expensive. The optimal EST solutions used up to 37% of the total energy generated; however, the results were sensitive to energy production-demand distributions. This methodology can help identify the most cost-effective solutions with the lower environmental impacts for decarbonizing the agricultural sector.

A predictive tool for power system operators to ensure frequency stability for power grids with renewable energy integration

The increased penetration levels of renewable energy resources (RESs) transform the power generation schema into one that is more susceptible to changes due to weather conditions, complicated load profiles, and reduced inertia levels. One of the main challenges that power grids can encounter under varying and low system inertia (SI) is poor frequency response (FR). Therefore, this paper proposes a novel online tool for assessing, predicting, and enhancing the frequency stability (FS) of power systems with renewable power generation and energy storage systems (ESS). Firstly, the tool provides accurate tracking of the SI in real-time settings using recursive least square identification and Kalman filtering to provide accurate and computationally efficient results. Secondly, the tool estimates the FR of the whole system in a virtual environment for different contingencies and inertia levels. The accuracy of the FR is improved by classifying the frequency response models (FRMs) based on the SI levels. Lastly, the proposed tool computes the optimal additional estimated reserve power (ERP) required from PV and battery energy storage systems (BESS) to provide inertial and primary frequency support to the power grid at the onset of a contingency. In addition, a reserve power allocation and load-shedding strategies are proposed and implemented to dynamically adjust the reserve power of PV power plants. This dynamic control of the PV power plant reserve capacity guarantees the availability of adequate reserves for addressing unforeseen systems contingencies. Moreover, dedicated FR controllers for PV and BESS are employed to emulate the synchronous machine’s inertial response (IR) and primary frequency control (PFC). The performance of the proposed tool and the FR controllers are tested and validated on a generic power grid and the IEEE 39 bus system using MATLAB Simulink and the OPAL-RT real-time simulation software.

Hydrothermal synthesis of ZnO@MoTe2 nanocomposite as excellent electrocatalyst for hydrogen evolution reaction (HER)

The comprehension of novel fundamental inquiries about the design of electrocatalysts is of paramount importance in enhancing the availability of renewable energy resources and advancing the progress of exceptionally durable and effective nonprecious electrocatalysts for the process of water splitting. Enhancing the capacity of renewable energy storage systems through the usage of nonprecious nanocomposites for efficient H2O splitting holds the potential to foster a more sustainable and environmentally conscious society, hence mitigating the impact of global warming. The nanocomposite exhibits proficient catalytic kinetics for the HER process owing to the enhanced accessibility of MoTe2′s most active zones. The physical property of the nanocomposite was established through in-process characterization using different analytical techniques. In a basic environment, the ZnO@MoTe2 combination exhibited a significant value for the generation of hydrogen using electrocatalysts based on ZnO@MoTe2, which was a 34 mV dec-1 Tafel slope. The nanocomposite exhibited a higher turn-over frequency rate (TOF) of 2.4 s−1 than pure materials. The ZnO@MoTe2 nanocomposite displays a higher surface area of 1125 cm2 and a low Rct value of 93 Ω. The electrocatalyst exhibits exceptional stability and durability. During 50 h in an alkaline environment, the application of chronopotentiometry reveals no substantial decrease in potential. The utilization of nanocomposite based electrocatalysts has been shown to provide efficient quick charge kinetics, a noteworthy observation. The results of this study offer a novel, reliable and effective electrocatalyst that has potential applications in the advancement of electrocatalytic devices for hydrogen gas (H2) production. These devices can be developed employing cost-effective technologies and naturally occurring materials widely available worldwide.

Real-time pricing based on convex hull method for smart grid with multiple generating units

With the growing demand and complex supply structure for electricity, higher requirements are proposed for generating units to regulate the peak load, resulting in significant increases in the startup cost. These issues bring urgent need to develop new pricing mechanisms. The real-time pricing (RTP) is an ideal pricing mechanism for clipping peak load and balancing supply and demand. This paper designs an RTP mechanism for the smart grid which integrates multiple generating units on the supply side and distributed renewable energy generation devices and energy storage systems on the demand side. Focusing on the interests of both supply and demand sides, a social welfare maximization model that incorporates startup costs of generating units is formulated. To tackle the discontinuity in the proposed model, the convex hull method is utilized to transform the primal model and derive the convex hull price which is widely regarded as an optimal price that can reflect the aggregate cost of generating units but has rarely extended to RTP. The related dual theory indicates that the convex hull price can be obtained by the Lagrange multiplier of the proposed social welfare maximization problem associated with the supply–demand balance constraint. Moreover, a distributed iterative algorithm based on the subgradient projection method is employed to solve the dual problem. Simulation results validate rationality and effectiveness of the proposed pricing mechanism.

Discharging process within a renewable energy storage system via numerical simulation in existence of water based nanomaterial

Discharging process within a renewable energy storage system via numerical simulation in existence of water based nanomaterial

Flexible asymmetric supercapacitor based on Hyphaene fruit shell-derived multi-heteroatom doped carbon and NiMoO4@NiCo2O4 hybrid structure electrodes

In accordance with ecological strategies for the production of renewable energy storage systems, herein, starting from the Hyphaene fruit shell (HFS) as a new carbon precursor, multi-heteroatom (O, N, S, P, and Si) self-doped porous carbon was successfully synthesized through carbonization and chemical activation (KOH) processes. The obtained honeycomb-like carbon structure (HFSC2) as negative electrode exhibited excellent electrochemical performance with high cycling stability and high specific capacitance of 337 F g−1 in 3 M KOH electrolyte solution. Meanwhile, the NiMoO4@NiCo2O4 hybrid nanostructure as a positive electrode was prepared through a simple two-step hydrothermal method followed by the annealing process. The NiMoO4/NiCo2O4 on Ni foam exhibits a very high specific capacitance of 1582 F g−1 at a current density of 0.5 A g−1 and excellent cycling stability of 82% after 3000 cycles. Further, for the practical application, the synthesized asymmetric all-solid-state supercapacitor offered high specific capacitance of 63.38 F g−1 (360.26 mF cm−2), a high energy density of 28.5 Wh kg−1 and a high-power density of 3800 W kg−1 at 14.8 Wh kg−1 within a voltage window of 0–1.8 V. These prominent electrochemical performances suggest that Hyphaene fruit shell-derived multi-heteroatom carbon and NiMoO4@NiCo2O4 hybrid electrodes have considerable applications in the field of energy storage technologies.

Profitability of Hydrogen-Based Microgrids: A Novel Economic Analysis in Terms of Electricity Price and Equipment Costs

The current need to reduce carbon emissions makes hydrogen use essential for self-consumption in microgrids. To make a profitability analysis of a microgrid, the influence of equipment costs and the electricity price must be known. This paper studies the cost-effective electricity price (EUR/kWh) for a microgrid located at ‘’La Rábida Campus’’ (University of Huelva, south of Spain), for two different energy-management systems (EMSs): hydrogen-priority strategy and battery-priority strategy. The profitability analysis is based, on one hand, on the hydrogen-systems’ cost reduction (%) and, on the other hand, considering renewable energy sources (RESs) and energy storage systems (ESSs), on cost reduction (%). Due to technological advances, microgrid-element costs are expected to decrease over time; therefore, future profitable electricity prices will be even lower. Results show a cost-effective electricity price ranging from 0.61 EUR/kWh to 0.16 EUR/kWh for hydrogen-priority EMSs and from 0.4 EUR/kWh to 0.17 EUR/kWh for battery-priority EMSs (0 and 100% hydrogen-system cost reduction, respectively). These figures still decrease sharply if RES and ESS cost reductions are considered. In the current scenario of uncertainty in electricity prices, the microgrid studied may become economically competitive in the near future.

Multi-objective scheduling of a steelmaking plant integrated with renewable energy sources and energy storage systems: Balancing costs, emissions and make-span

As an energy-intensive industry, the steel industry grapples with increasing energy costs and decarbonisation pressures. Therefore, multi-objective optimisation is widely applied in the production scheduling of the steelmaking plant. However, the optimal solution prioritising energy savings and emission reductions may lead to impractical or less economically efficient solutions, since the processing time requirement (PTR) of steel production orders in real-world production is neglected. This study fills the research gap by discussing the impact of PTR on the make-span of the steelmaking process and incorporating it into the optimisation model. Considering the variability of PTR, the solving of the multi-objective scheduling problem is transformed into the selection from Pareto solutions with different make-spans. To better leverage the temporal flexibility of the steelmaking process, a what-if-analysis-based strategy coupled with the Normal Boundary Intersection method is proposed to generate a series of evenly distributed Pareto solutions. The energy storage system is integrated to improve the time granularity of the steelmaking plant's flexibility. Our case studies demonstrate that the electricity and emission costs are reduced by 68.5%, indirect emissions are reduced by 83.5%, and the on-site renewable energy self-consumption rate increases by 12.1%. The effectiveness of the proposed method implies that it is of great relevance to the development of a cleaner steel industry in the future.

An aging- and load-insensitive method for quantitatively detecting the battery internal-short-circuit resistance

Early-stage detection of the battery internal short circuit (ISC) can effectively prevent batteries from fire-related accidents. However, it is technically challenging because the current leakage signals at the beginning stage of the ISC could be submerged by the joint effect of battery aging, battery balancing, measurement noise, and highly dynamic charging/discharging behaviors. Aiming at these issues, we here propose an equalization-based method to quantitatively calculate short circuit resistance for pack applications. The relationship between the balanced capacity and short circuit resistance is mathematically derived and unified for both passive and active equalization systems. Battery-in-the-loop experiments show that when the short-circuit resistance changes from 55 to 330 Ω, the error of our prediction can be well-bounded within ±2%, outperforming most existing algorithms. Further, the computational burden of the proposed method is similar to that of the Ah-counting method, requiring no additional information on the batteries’ aging status. Since our method supports arbitrary load profiles, it can be used in a wide range of applications such as electrified vehicles and renewable energy storage systems.

Research on multi-market strategies for virtual power plants with hydrogen energy storage

As the main body of resource aggregation, Virtual Power Plant (VPP) not only needs to participate in the external energy market but also needs to optimize the management of internal resources. Different from other energy storage, hydrogen energy storage systems can participate in the hydrogen market in addition to assuming the backup supplementary function of electric energy. For the Virtual Power Plant Operator (VPPO), it needs to optimize the scheduling of internal resources and formulate bidding strategies for the electric-hydrogen market based on external market information. In this study, a two-stage model is constructed considering the internal and external interaction mechanism. The first stage model optimizes the operation of renewable energy, flexible load, extraction storage, and hydrogen energy storage system based on the complementary characteristics of internal resources; the second stage model optimizes the bidding strategy to maximize the total revenue of the electricity energy market, auxiliary service market and hydrogen market. Finally, a typical scenario is constructed and the rationality and effectiveness of the strategy are verified. The results show that the hybrid VPP with hydrogen storage has better economic benefits, resource benefits and reliability.

Trimetallic Oxide Electrocatalyst for Enhanced Redox Activity in Zinc-Air Batteries Evaluated by In Situ Analysis.

Researchers are investigating innovative composite materials for renewable energy and energy storage systems. The major goals of this studies are i) to develop a low-cost and stable trimetallic oxide catalyst and ii) to change the electrical environment of the active sites through site-selective Mo substitution. The effect of Mo on NiCoMoO4 is elucidated using both in situ X-ray absorption spectroscopy and X-ray diffraction analysis. Also, density functional theory strategies show that NiCoMoO4 has extraordinary catalytic redox activity because of the high adsorption energy of the Mo atom on the active crystal plane. Further, it is demonstrated that hierarchical nanoflower structures of NiCoMoO4 on reduced graphene oxide can be employed as a powerful bifunctional electrocatalyst for oxygen reduction/evolution reactions in alkaline solutions, providing a small overpotential difference of 0.75V. Also, Zn-air batteries based on the developed bifunctional electrocatalyst exhibit outstanding cycling stability and a high-power density of 125.1mW cm-2 . This work encourages the use of Zn-air batteries in practical applications and provides an interesting concept for designing a bifunctional electrocatalyst.

A Symmetric Bipolar Quadratic Buck–Boost Converter With Synchronous Triple Switches

A novel non-isolated bipolar DC-DC converter is described in this study. The proposed converter provides negative and positive outputs with the same voltage level and common ground. It exploits three power switches with the synchronous operation, resulting in a simple controller and driver implementation. Compared with the conventional counterpart DC-DC converters, the proposed converter offers buck-boost ability with a wide control range of the switching duty cycle. Additionally, the proposed converter draws a continuous and smooth current from the DC input source, making it an excellent choice for renewable energy sources (RES) and energy storage systems (ESS). Likewise, the proposed quadratic converter can provide a higher voltage boost ability with the same switching duty cycle compared to the existing transformerless bipolar converters. Hence, it offers lower conduction losses and higher efficiency for the same demanded output voltages. Theoretical analysis and experimental results based on a sample prototype are presented to prove the proposed converter's performance in CCM mode.

Techno-economic assessment of a hybrid renewable energy storage system for rural community towards achieving sustainable development goals

Urbanization and population growth are driving carbon emissions, along with the imperative for renewable energy transition, necessitating researching the impact of hybrid renewable energy storage systems towards achieving sustainable development goals. The article presents a techno-economic assessment of a stand-alone hybrid system in a grid-deficient rural community in a developing country, Bangladesh. The optimal system sizing includes an 8.67 kW of photovoltaic, 7 kWh lithium-ion battery, 6 kW of electrolyzer, 1.8 kW fuel cell, 5 kg of hydrogen tank and 1.67 kW converter, which can achieve a net present cost of $25,099 and levelized cost of energy of $0.34$/kWh. Results show hybrid system supports sustainable development goals by offering clean energy, emphasizing the need for government support, investment, and scaling in rural developing areas.

Decision‐dependent distributionally robust integrated generation, transmission, and storage expansion planning: An enhanced Benders decomposition approach

AbstractIntegrated generation, transmission, and storage expansion planning (IGT&SP) is the cornerstone to realize low‐carbon transition considering security constraints in the long run. A novel IGT&SP planning scheme is proposed to balance the planning cost, i.e. renewable energy sources (RESs) and energy storage systems, based on the distributionally ambiguity sets. A novel decision‐dependent ambiguity set is proposed to capture the relation between the uncertainties of RES output and long‐term planning. A two‐stage risk‐averse distributionally robust optimization is formulated, where the RESs, energy storage systems, and transmission line expansion are optimized in the first stage and a unit commitment problem is proposed in the second‐stage optimization to assess the performance of the expanded system. This problem is reformulated into a two‐stage optimization problem with complete mixed‐integer recourse, where the state variable is binary. A novel enhanced Benders decomposition algorithm is proposed to solve the IGT&SEP efficiently, where the cutting planes are generated by a primal‐dual relaxation of the recourse problem. Simulations are conducted on the modified IEEE‐30 test system and modified IEEE‐118 test system. Compared with adjustable robust optimization and L1‐norm Wasserstein distance‐based distributionally robust optimization, numerical results verify the effectiveness of the proposed IGT&SP, together with the solution algorithm.

Stress redistribution in a multilayer chamber for compressed air energy storage in abandoned coalmine: Elastic analytical insights and material choice

AbstractCompressed air energy storage (CAES) is attracting attention as one of large‐scale renewable energy storage systems. Its gas storage chamber is one of key components for its success. A successful utilization of an abandoned coalmine roadway depends on the stability of the gas storage chamber. The chamber is a multilayer structure and the redistribution of the stress and displacement in each layer is critical to the chamber stability. So far, this redistribution mechanism under any lateral pressure coefficient and internal air pressure has been unclear and thus a quick and easy evaluation on the CAES chamber stability becomes difficult. In this study, the redistributions of stress and displacement in each layer are analytically solved based on complex variable function theory. First, the stress and displacement in three CAES multilayer structures are obtained under any lateral pressure coefficient and internal air pressure. Then, a comprehensive parameter b1 is obtained to describe the redistribution of stress and displacement in rock mass, lining layer, and grout layer. Its linkage with lateral pressure coefficient, internal air pressure, and material properties is analytically expressed. Thirdly, an analytical expression is obtained for the influence range of internal air pressure on chamber stress. Finally, the role and selection of lining and grouting layers are explored at different lateral pressure coefficient and internal air pressure. It is found that the CAES chamber stability can be effectively and quickly evaluated by these analytical solutions and comprehensive parameters and enhanced by a material with low bulk modulus but high shear modulus.

IrOx-MoO3 nano-heterostructure electrocatalysts for efficient acidic water oxidation

Rational design of Ir-based electrocatalyst with high performance and low cost remains as an urgent requirement to speed up the sluggish acidic water oxidation to produce hydrogen in renewable energy conversion and storage systems. In this work, the highly dispersed IrOx nanoparticles are fabricated on MoO3 sheets coated Ti meshes (c-IrOx-MoO3/Ti) as efficient electrocatalytic electrodes for acidic water oxidation. The heterogeneous c-IrOx-MoO3/Ti catalysts show much higher acidic oxygen evolution reaction activity (∼200 mV overpotentials at 10 mA cm−2) and long-term stability (longer than 130 h at 100 mA cm−2) with extremely low Ir content (∼28.35 μgIr cm−2) as compared to the IrOx/Ti and commercial IrO2 catalysts. The special intertwined formation of MoO3 sheets through electrodeposition effectively promotes the uniform dispersion of IrOx nanoparticles and the electrocatalytic performance. Theoretical calculations reveal that the electronic modulation on the MoO3-IrOx heterogeneous interface optimized the adsorbed energies for oxygen intermediates on the active Ir sites of the catalysts. The self-assembled proton exchange membrane single-cell electrolyzer test further verifies that the fabricated c-IrOx-MoO3/Ti catalysts demonstrate a greatly lower voltage and higher stability for water electrolysis than the commercial IrO2 catalysts. This work provides a new pathway to designing highly active and acid-resistant Ti-supported water oxidation catalysts with ultra-low Ir content.

The role of energy communities in electricity grid balancing: A flexible tool for smart grid power distribution optimization

The unpredictability of renewable energy systems can affect the stability of the electricity grid, causing voltage and frequency imbalances. In this work, a suitable methodology based on the peer-to-peer scheme applied to energy communities is developed and implemented in a simulation tool useful for investigating energy management strategies for decision-making aims. The developed model discretizes the energy community and its users into multiple control volumes, taking into account various technologies. It incorporates energy balances for individual users as well as the entire energy community, considering prosumers, consumers, energy storage systems, and electric vehicles. Moreover, the model enables the exploration of different solutions for grid frequency regulation and optimization of distributed energy resources. Additionally, the tool can predict electricity demand one day ahead, facilitating the organization of renewable energy availability and storage systems to minimize grid interactions and flatten electricity demand. The model incorporates different objective functions, including self-consumption, self-sufficiency, and grid-balancing factors, to evaluate the performance of energy communities. To show the capability of the developed model, it will be adopted to optimize the performance of an investigated community. As a result, an increase in renewable energy self-consumption from 59.4 to 83.9 MW h/year is achieved. Furthermore, the objective of grid balancing was achieved by guaranteeing a non-fluctuating load and providing 1.46 and 7.71 MW h/year for upward and downward grid frequency regulation. These findings illustrate the positive impact of energy dispatching management on the integration of renewable energy sources and the importance of further studying this topic to ensure grid stability.

A three-phase reactor assessment for the deployment of Liquid Organic Hydrogen Carriers (LOHCs): dybenzyltoluene and indoles mixture systems as case studies

As a result of the large increase in the production of renewable energies, energy storage and energy carrier systems are required to meet the most ambitious objectives. In this area, hydrogen stands out as one of the most powerful tools. However, its low volumetric energy density and its challenging storage conditions lead to the search for new forms of storage. Liquid organic hydrogen carriers (LOHCs) are positioned as a promising option to store hydrogen using a catalytic reversible reaction at moderate temperature. Notwithstanding, although reactor technology is the core section of the LOHC process, it has not been assessed yet. Therefore, in this work, a three-phase reactor analysis is performed including mass, heat, and momentum phenomena along with kinetics. In particular, the two most important reactors for three-phase reactions are evaluated, trickle bed and slurry. And two of the most attractive LOHCs systems, dybenzyltoluene and a mixture composed of 1,2-dimethylindole and 7-ethylindole, are considered. The influence of the operating and design variables was studied. The results show that, for hydrogenation slurry reactors, a first region may be formed where gas–liquid is the main resistance (60%–95%). It eventually ends up with a second one where kinetics becomes the controlling step. At this point, a better catalyst use is expected for the first region. Alternatively, trickle bed hydrogenation reactors are largely controlled by mass transfer over almost the whole reactor length. If the dehydrogenation process is assessed, kinetics resistance is predominant. Surrogate models are developed to optimize the reactor performance and to include the full reactor operation in futures process design analysis allowing for an effective deployment of LOHCs systems.

Active disturbance rejection control of an islanded PV/wind/battery microgrid with power quality enhancement by SAPF

<p><span lang="EN-US">The focus in this study is on an islanded microgrid based on hybrid renewable energy sources and storage systems. This latter is considered as an essential element for all off-grid autonomous systems to offer a reliable and stable operation. The proposed system is composed of a photovoltaic system, a wind power system based on a synchronous generator and a storage system. The proposed control strategy is intended to control, through the load side converter (LSC), the AC bus voltage in terms of amplitude and frequency under different operating conditions, and to obtain, through the bi-directional battery side converter (BSC), a better regulation between the available production and the global load demand. The proposed strategy also contributes to the power quality improvement in the AC bus by controlling the PV inverter to work as a shunt active power filter to provide the required harmonic current component to non-linear loads. A new robust control strategy for internal current and voltage control loops is proposed in this research paper, it’s the active disturbance rejection control (ADRC) and it is based on the extended state observer which allows to estimate all disturbances affecting the control, such as modeling errors and parameter variations.</span></p>