Intermittent Renewable Sources Research Articles

Energy, economic and environmental benefits of Demand Response for improving building energy flexibility

The increasing penetration of intermittent renewable sources in power generation at local and building-level poses growing issues in balancing generation and demand. To avoid imbalances, it is therefore necessary to ensure adequate levels of flexibility in the building energy system. This can be done both on the generation side, through the coupling of different energy carriers (cogeneration, power-to-heat solutions) and/or the integration of storage systems, and on the demand side, through smart “demand response” programs. This paper considers a tourist facility located in central Germany as a case study to evaluate the energy, economic and environmental benefits that can be obtained from the application of appropriate demand response strategies. The electrical demand data of the facility are monitored at both aggregate and individual load levels and made available by means of a cloud platform. The facility includes two stationary combined heat and power internal combustion engines powered by natural gas and a photovoltaic system. The results show how, thanks to appropriate load management, it is possible, on the one hand, to increase the self-consumption of PV-generated energy and, on the other hand, to keep more constant the load of the engines, which can therefore operate with better efficiencies. This results in both a reduction in energy expenses and a decrease in carbon dioxide emissions attributable to the building.

Hydrogen production, storage, and transportation: recent advances.

One such technology is hydrogen-based which utilizes hydrogen to generate energy without emission of greenhouse gases. The advantage of such technology is the fact that the only by-product is water. Efficient storage is crucial for the practical application of hydrogen. There are several techniques to store hydrogen, each with certain advantages and disadvantages. In gaseous hydrogen storage, hydrogen gas is compressed and stored at high pressures, requiring robust and expensive pressure vessels. In liquid hydrogen storage, hydrogen is cooled to extremely low temperatures and stored as a liquid, which is energy-intensive. Researchers are exploring advanced materials for hydrogen storage, including metal hydrides, carbon-based materials, metal-organic frameworks (MOFs), and nanomaterials. These materials aim to enhance storage capacity, kinetics, and safety. The hydrogen economy envisions hydrogen as a clean energy carrier, utilized in various sectors like transportation, industry, and power generation. It can contribute to decarbonizing sectors that are challenging to electrify directly. Hydrogen can play a role in a circular economy by facilitating energy storage, supporting intermittent renewable sources, and enabling the production of synthetic fuels and chemicals. The circular economy concept promotes the recycling and reuse of materials, aligning with sustainable development goals. Hydrogen availability depends on the method of production. While it is abundant in nature, obtaining it in a clean and sustainable manner is crucial. The efficiency of hydrogen production and utilization varies among methods, with electrolysis being a cleaner but less efficient process compared to other conventional methods. Chemisorption and physisorption methods aim to enhance storage capacity and control the release of hydrogen. There are various viable options that are being explored to solve these challenges, with one option being the use of a multilayer film of advanced metals. This work provides an overview of hydrogen economy as a green and sustainable energy system for the foreseeable future, hydrogen production methods, hydrogen storage systems and mechanisms including their advantages and disadvantages, and the promising storage system for the future. In summary, hydrogen holds great promise as a clean energy carrier, and ongoing research and technological advancements are addressing challenges related to production, storage, and utilization, bringing us closer to a sustainable hydrogen economy.

An in-Depth Exploration of the Electrocatalytic Stability of Sn-Based Electrocatalysts for the Electrochemical CO2 Reduction Towards Formate

Over the past decades, the electrochemical CO2 reduction (eCO2R) into industrially valuable products has become one of the most promising technologies to valorize anthropogenic CO2 emission, while also providing a means of energy storage for intermittent renewable sources. A wide variety of products, such as formic acid/formate (HCOOH/HCOO-), carbon monoxide (CO), methane (CH4), methanol (CH3OH), ethylene (C2H4) etc., can be obtained. The eCO2R towards formic acid/formate (FA), a 2-electron transfer process, has the potential to generate the highest revenue per mole of consumed electrons, which originates from the fact that FA can be produced with high Faradaic efficiencies on cheap and earth abundant metals, such as Sn, Bi, Pb, Hg, In and Cd. State-of-the-art Sn-based electrocatalysts have been reported to reach selectivities approaching 100% at industrially relevant current densities. Looking at the long-term performance of these state-of-the-art Sn-based electrocatalysts, only seven have a minimum reported stability of 72 hours, with the maximum being 100 days (2400 h) of stable operation. Even though Bi-based catalysts currently outperform Sn-based electrocatalysts in terms of stability, Sn-based catalysts are still believed to be viable alternatives if an extended stability of over 80 000 hours can be achieved. Sn-based electrocatalyst stability thus remains inadequate and appears to be a crucial piece to the puzzle. 1 In this research, we elucidate the major degradation pathways that impair long-term electrocatalytic performance, by determining the chemical and physical phenomena that occur during the electrochemical reduction reaction on the surface and in the bulk of Sn-based catalysts. Simultaneously, the possibilities of a variety of mitigation strategies are explored, and insight into stability issues related to Sn-based electrocatalysts and CO2 electrolysers is gathered.Firstly, Sn was incorporated into a more open, carbon based supporting material (N-doped ordered mesoporous carbon) in an attempt to significantly increase the stability by inhibiting agglomeration and nanoparticle detachment. An N-doped carbon supporting material was chosen for its high surface area and in order to enhance the initial adsorption of CO2, which is commonly referred to as the rate-limiting step, for the eCO2R towards formate, in literature. These novel electrocatalysts provide us with valuable insights into the influence of the supporting material on their electrochemical performance and highlighted the potential of the particle confinement strategy to increase the morphological electrocatalyst stability during electrolysis.In a next step, we demonstrated the successful application of the recently developed pomegranate-structured SnO2 (Pom. SnO2) and SnO2@C (Pom. SnO2@C) nanocomposite electrocatalysts for the efficient electrochemical conversion of CO2 to formate. With an initial selectivity of 83 and 86% towards formate and an operating potential of -0.72 V and -0.64 V vs. RHE, respectively, these pomegranate SnO2 electrocatalysts are able to compete with most of the current state-of-the-art Sn-based electrocatalysts in terms of activity and selectivity. Given the importance of electrocatalyst stability, long-term experiments (24 h) were performed and a temporary loss in selectivity was noticed for the Pom. SnO2@C electrocatalyst. Ex situ XRD and XPS were used to link this temporary selectivity loss of the Pom. SnO2@C electrocatalyst to the in situ SnO2 reduction to metallic Sn. While this electrochemical degradation occurs in both electrocatalysts, it is more pronounced in the Pom. SnO2@C electrocatalyst since it isn’t offset by the morphological electrocatalyst degradation revealing new and selective SnOx active sites, as suspected for the Pom. SnO2. Furthermore, we were able to largely restore its selectivity upon drying and exposure to air. Of all the used (24 h) electrocatalysts, the pomegranate SnO2@C had the highest selectivity over a time period of one hour, reaching an average recovered FE of 85%, while the commercial SnO2 and bare pomegranate SnO2 electrocatalysts reached an average of 79 and 80% FE towards formate, respectively. Finally, the pomegranate structure of Pom. SnO2@C was largely preserved due to the presence of the heterogeneous carbon shell, which acts as a protective layer, physically inhibiting particle segregation/pulverisation and agglomeration.Utilizing the particle confinement strategy, we increased the morphological stability of pomegranate structured SnO2 electrocatalysts and demonstrated the reversible nature of the in situ SnO2 reduction. Van Daele, K. et al. Sn-Based Electrocatalyst Stability: A Crucial Piece to the Puzzle for the Electrochemical CO2Reduction toward Formic Acid. ACS Energy Lett. 6, 4317–4327 (2021). Figure 1

(Invited) Understanding Capacity Fade Behavior in Aqueous Organic Redox Flow Batteries Via Zero-Dimensional Models and High-Throughput Cell Cycling

Aqueous Organic Redox Flow Batteries (AORFBs) have emerged as promising and potentially disruptive technologies for the storage of electrical energy from intermittent renewable sources for use over long discharge durations when the sun isn’t shining and the wind isn’t blowing. AORFBs could become preferred over Li-ion batteries for grid-scale stationary storage due to their potentially low-cost active materials made of Earth-abundant elements, their inherent non-flammability, and the intrinsic decoupling of energy and power capacities in the flow battery design. Our group has demonstrated that calendar life, rather than cycle life, limits molecular lifetimes in AORFBs due to various molecular instabilities that lead to side reactions, thus inhibiting performance [1]. To accurately determine molecular fade rates, we utilize potentiostatic cycling to avoid artifacts caused by drifts in internal resistance and employ volumetrically unbalanced compositionally symmetric cell configurations to distinguish molecular fade from membrane crossover or the two sides drifting out of balance.We have developed a high-throughput setup for AORFBs, capable of cycling cells at elevated temperatures, providing a new dimension in the flow battery characterization space to explore multiple cell parameters simultaneously. The recent incorporation of the decay of active material into zero-dimensional cell-cycling models for AORFBs [2,3] allows for exploration of the causes of various trends seen in flow cell temporal capacity behavior. Complemented by zero-dimensional modelling, we explore temporal capacity evolution in symmetric cells driven by different capacity fade mechanisms such as active species degradation [4], self-discharge [5], and membrane crossover. Collectively, these results highlight the relevance of electrochemical techniques to understand molecular degradation in AORFBs and expedite the screening process of candidate molecules for long lifetime AORFBs, which may enable massive grid penetration of intermittent renewable energy.[1] M.-A. Goulet and M. J. Aziz, “Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods,” Journal of The Electrochemical Society, 165, A1466 (2018).[2] S. Modak and D. G. Kwabi, “A Zero-Dimensional Model for Electrochemical Behavior and Capacity Retention in Organic Flow Cells,” Journal of the Electrochemical Society, 168, 080528 (2021).[3] B. J. Neyhouse, J. Lee, F. R. Brushett, “Connecting Material Properties and Redox Flow Cell Cycling Performance through Zero-Dimensional Models” Journal of The Electrochemical Society, 169, 090503 (2022).[4] D. G. Kwabi, Y. Ji, M. J. Aziz, “Electrolyte Lifetime in Aqueous Organic Redox Flow Batteries: A Critical Review,” Chemical Reviews, 120, 6467 (2020).[5] E. M. Fell, D. De Porcellinis, Y. Jing, V. Gutierrez-Venegas, R. G. Gordon, S. Granados-Focil, M. J. Aziz, “Long-term stability of ferri-/ferrocyanide as an electroactive component for redox flow battery applications: On the origin of apparent capacity fade,” ChemRxiv (2022). https://chemrxiv.org/engage/chemrxiv/article-details/62913087f89e5d4e6ee8828d

Electrification and hydrogenation on a PV-battery-hydrogen energy flexible community for carbon–neutral transformation with transient aging and collaboration operation

Considering the distinct differences in intrinsic characteristics (e.g., energy efficiency, power density, and response time), the synergy operation of combined hydrogen (H2) and battery systems within the source-grid-load-storage framework offers a promising solution to stabilize intermittent renewable energy supply, mitigate grid power fluctuations, and enhance system independence. However, the idling power of the H2 system (fuel cell and electrolyzer) poses significant limitations on H2 charging/discharging from intermittent renewable power sources, thereby affecting overall system performance. However, the current literature provides little progress on how to effectively self-consume onsite renewable energy and supply the electricity demand with high energy/power density in a fast response. To address these challenges, this study proposes and applies the H2-battery compensation operation in the hybrid H2-battery energy storage system to mitigate the adverse effects of idling power during low-carbon transformations. Additionally, transient degradation models for the battery and fuel cell (FC) are integrated into the system to dynamically quantify real-time aging, thereby avoiding performance overestimation. Moreover, the study also includes a comparative analysis of the pre-estimation on the H2 tank pressure level, and a parametrical analysis of the HV number and battery capacity. Results show that, compared to the isolated H2 energy storage system, the H2-battery synergy operation reduces the grid demand shortage coverage ratio from 91.01% to 57.8%. Furthermore, the proposed H2-battery compensation operation effectively overcomes the limitations of idling power during power charging/discharging of the H2 system, resulting in an increase of H2 demand shortage coverage ratio from 8.9% to 17.29%, and the decrease in battery degradation ratio from 1.73% to 1.65%. Afterward, a novel indicator, degradation cost per kWh energy, is proposed to quantify the techno-economic performance of the combined battery and H2 system. According to the results, the techno-economic feasibility is dependent on the proportion of battery and H2 capacities, with the FC ranging from 0.49 to 1.15 CNY/kWh and the battery ranging from 0.82 to 0.91 CNY/kWh. The research results provide valuable frontier guidelines for the design and operation of multi-energy systems, as well as innovative energy-sharing strategies, to achieve sustainable and carbon–neutral transformation.

Experimental analysis of boost limits in a hydrogen fueled PFI internal combustion engine

In recent years we have witnessed a renewed interest in the use of hydrogen as a fuel for the land transportation sector, not only for the decarbonisation of the propulsion system but also, above all, as an energy vector for accumulating excess energy deriving from the use of intermittent renewable sources such as wind and photovoltaics.The present study shows the results of an ongoing research aimed at fine-tuning ready-to-market strategies for the use of hydrogen in ICEs. Starting from a turbocharged engine fueled by natural gas and utilized on light commercial vehicles, a low-cost indirect hydrogen injection system (PFI) was implemented, combined with appropriate injection strategies and boost pressure analysis, this last assuming a fundamental aspect in recovering engine performance that inevitably deteriorates with the use of diluted mixtures.It is found that the adoption of an air/hydrogen lambda value (λ) ≈ 2.5 allows the utilization of high boost ratios without knocking and backfire and with the possibility of reaching performance similar to the original natural gas fueled engine, with a higher efficiency (> 39 %) and with low NOx emissions (< 200 ppm).

How to minimise the cost of green hydrogen with hybrid supply: A regional case study in China

Hydrogen produced from renewables-fuelled electrolysis has the potential to provide deep decarbonisation for sectors that are the most difficult to decarbonise, but the intermittency of renewable sources may result in low electrolyser utilisation and, consequently, high costs. This study determines the greenhouse gas (GHG) emissions and levelised cost of hydrogen (LCOH) associated with blending wind electricity with the grid to increase electrolyser utilisation. A novel cost model was developed to determine the production performance, costs and embodied CO2 emissions of an electrolyser with hybrid fuel supply (wind and grid) considering dynamic load constraints of alkaline (ALK) and Proton exchange membrane (PEM) electrolysers and using high-resolution historical weather data to determine wind production profiles in two case study regions: northern (Bayannur) and southern (Pingtan) China. The results show that using 52% of grid electricity in an ALK electrolyser in Bayannur reduces LCOH by 11%, increasing hydrogen production by 74% but with 17.4 kg CO2/ kg H2 generated in CO2 emissions. When a carbon price is accounted for, the optimal electrolyser utilisation is reduced to 40%, with the LCE 44% reduced. Emissions of 9.8 kg CO2/kg H2 are lower than for stream methane reforming with carbon capture. In Southern China (Pingtan), LCOH is higher than Bayanur because of the high electricity cost. The economic benefits of increasing grid power depend primarily on the total CAPEX cost, grid power cost, and carbon tax. By altering the carbon tax, the optimal blend of wind/ grid differs. The grid contribution to the optimal blend diminishes as a carbon tax approaches 35 USD/ t CO2.

Improved Control Strategy for Water Pumping System Fed by Intermittent Renewable Source

This paper focuses on a water pumping system fed by a hybrid (PV–Wind) generator. The water pumping system uses centrifugal pumps driven by variable speed Induction Motors (IM) controlled by a Field Oriented Control (FOC). The absence of battery storage to decouple sources and power demand is the main originality of the contribution, together with the typical adaptation of the FOC strategy. Furthermore, the absence of battery storage will consequently lead to fixing the system operating point at a steady state which is imposed both by the intermittent renewable energy sources and by the hydraulic load characteristics. The basic idea is then to adapt the system impedance by using the two degrees of freedom offered by the power source inverter in order to control, firstly, the DC bus voltage and, secondly, the rotor flux of the induction machine; the adaptation of the FOC strategy is based on this idea. Simulation results clearly confirmed by experimental investigations show the satisfying performance of the system even with variable powers of the intermittent renewable source.

Composite reliability assessment of systems with grid‐edge renewable resources via quasi‐sequential Monte Carlo and cross‐entropy techniques

AbstractThe still growing share of intermittent renewable sources in the electric energy matrix is a factor that greatly increases the complexity of modelling electrical power systems. Although its exploitation is conditioned to the geographic location where the natural resource emerges itself, when this location coincides with the grid‐edge of the system, close to the consumer, the composite reliability assessment is exposed to the combination of two problems: (i) representation of the intermittent energy availability of generators; and (ii) failure event rarity. To address the first problem, a fast Monte Carlo tool capable of representing chronological aspects can be used. For the second problem, an efficient variance reduction technique that adapts well to the composite problem of generation and transmission must be established. Therefore, a quasi‐sequential Monte Carlo simulation tool aided by importance sampling via the cross‐entropy method is proposed as an efficient and robust procedure for evaluating the composite reliability of systems with renewable participation at grid‐edge. The method is evaluated through a modified version of the IEEE Reliability Test System ‐ 1996, which presents renewable generation in consumer load buses and rarity in the composite failure.

Grid-Forming Services From Hydrogen Electrolyzers

Hydrogen electrloyzers are power-to-gas storage devices that can facilitate large-scale integration of intermittent renewable sources into the future power systems. Due to their fast response and capability to operate in different loading conditions, they can be used as responsive loads providing support to AC grid during transients. This paper suggests taking one step further and using hydrogen electrolyzers to provide grid-forming services to the grid. As a result, the electrolyzer's role is elevated from supporting the grid (responsive load) to actively participating in forming voltage and frequency of the grid. The grid-forming capability of electrolyzer is linked to its hydrogen production constraints, which can potentially pose limitations on the grid-forming services. Besides the grid-forming mode, two additional operating modes, i.e., DC voltage mode and constant power mode, are proposed to ensure a safe operation of the electrolyzer in case of adversary interaction between grid-forming operation and hydrogen production constraints. This paper also studies the impacts of grid-forming services on the electrolyzer's physical features such as hydrogen stack temperature and efficiency. Comprehensive simulations are conducted on a low-inertia test network whose topology is inspired by a portion of the transmission grid in South Australia to confirm the effectiveness of the proposed concept under various operational conditions of the electrolyzer and upstream AC grid. Moreover, the practical feasibility of the proposed control system is experimentally validated by conducting hardware-in-the-loop tests.

Material Challenges and Hydrogen Embrittlement Assessment for Hydrogen Utilisation in Industrial Scale

Hydrogen has been studied extensively as a potential enabler of the energy transition from fossil fuels to renewable sources. It promises a feasible decarbonisation route because it can act as an energy carrier, a heat source, or a chemical reactant in industrial processes. Hydrogen can be produced via renewable energy sources, such as solar, hydro, or geothermic routes, and is a more stable energy carrier than intermittent renewable sources. If hydrogen can be stored efficiently, it could play a crucial role in decarbonising industries. For hydrogen to be successfully implemented in industrial systems, its impact on infrastructure needs to be understood, quantified, and controlled. If hydrogen technology is to be economically feasible, we need to investigate and understand the retrofitting of current industrial infrastructure. Currently, there is a lack of comprehensive knowledge regarding alloys and components performance in long-term hydrogen-containing environments at industrial conditions associated with high-temperature hydrogen processing/production. This review summarises insights into the gaps in hydrogen embrittlement (HE) research that apply to high-temperature, high-pressure systems in industrial processes and applications. It illustrates why it is still important to develop characterisation techniques and methods for hydrogen interaction with metals and surfaces under these conditions. The review also describes the implications of using hydrogen in large-scale industrial processes.

Influence of Hydrogen Electrode Active Layer Thickness on Electrochemical Performance of Solid Oxide Cell Operating in Electrolysis Mode

Reversible solid oxide cell technology (RSOC) is a key technology in future hydrogen energy concept and may play a significant role in stabilizing intermittent renewable electric power sources. This work handles an attempt to optimize the thickness of the hydrogen electrode active layer (HEAL) for solid oxide cells designed and developed initially for fuel cell application (SOFC). Five cells with HEAL thickness of 0, 7, 12, 16 and 20 μm, prepared using industrial manufacturing methods, are analyzed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods under a wide range of operating conditions. Optimal thickness of an active layer studied depends on operating conditions. Depending on the temperature and feed gas water content applied highest performances were achieved for cells with HEAL thicknesses between 7 and 16 μm. At 800 °C and 90% feed gas water content, the best cell had an active layer of 7 μm, drawing −3.5 A cm−2 current at −1.4 V.

(Best Student Presentation) Extending the NaCl-AlCl3 Phase Diagram to Enable Low-Cost, Long-Duration Na-Al Batteries for the Grid

Achieving deep grid decarbonization via intermittent renewable power sources requires extensive grid-scale energy storage technologies to deliver stable power during periods of low generation. Doing so at scale and at low cost further adds to this challenge, as current solutions generally rely on geographically limited solutions such as pumped hydro storage, or costly battery chemistries focusing primarily on Li-ion technologies. As an alternative, battery systems based on lower cost materials such as sodium offer an attractive alternative for low-cost, scalable, and non-geographically limited electrochemical energy storage.This work combines an abundant and inexpensive molten sodium metal anode with a cost-effective aluminum cathode to provide a proof-of-concept alternative for grid-scale energy storage. Building on prior work utilizing the high reversibility of the neutral sodium chloroaluminate (NaAlCl4) molten salt electrolyte commonly used for classic molten sodium batteries, this work demonstrates greater capacity utilization of the NaCl-AlCl3 binary system by ‘overcharging’ this Na-Al battery to form an acidic chloroaluminate catholyte, NaAl2Cl7. Leveraging the reaction between NaAlCl4 and NaAl2Cl7 in conjunction with that between Al/NaCl and NaAlCl4 advantageously utilizes the majority of Na available in the cathode for capacity, in addition to providing a higher discharge voltage (~ 2 V compared to ~ 1.6 V for the NaAlCl4 reaction), thereby adding ~ 119 Wh kg-1 additional specific energy, on top of the 493 Wh kg-1 theoretical specific energy of the neutral Na-Al battery reaction between Al/NaCl and NaAlCl4.Fundamental aspects of the acidic chloroaluminate reaction are investigated, showing that cells using only the acidic reaction are able to cycle for hundreds of cycles. The acidic reaction between NaAlCl4 and NaAl2Cl7 occurs via a solution-phase reaction, unlike the two-phase neutral reaction between NaCl/Al and NaAlCl4, and we confirm via Raman and NMR spectroscopies that complete conversion to NaAl2Cl7 occurs at end of charge. Na-Al batteries utilizing both reactions demonstrate high areal capacity (~ 46 mAh cm-2) and excellent reversibility. Enabled by the rapid mass transfer and solid-liquid reaction mechanism of the chloroaluminate catholyte, a higher areal capacity cell with ~ 132 mAh cm-2 is demonstrated, allowing a discharge duration of 28.2 h, implying that this Na-Al battery chemistry may be suitable for long-duration energy storage for grid applications. Finally, the raw active materials cost of this battery is estimated to be only ~ $7 kWh-1, which is promising for enabling low-cost renewable power utilization for the grid. Figure 1

Leveraging Temperature-Dependent (Electro)Chemical Kinetics to Accelerate Redox Flow Battery Active Material Characterization

Aqueous Organic Redox Flow Batteries (AORFBs) have emerged as promising and potentially disruptive technologies for the storage of electrical energy from intermittent renewable sources for use over long discharge durations when the sun isn’t shining and the wind isn’t blowing. AORFBs could become preferred over Li-ion batteries for grid-scale stationary storage due to their potentially low-cost active materials made of earth-abundant elements, their inherent non-flammability, and the intrinsic decoupling of energy and power capacities in the flow battery design. Our group has demonstrated that calendar life, rather than cycle life, limits molecular lifetimes in AORFBs due to various molecular instabilities that lead to side reactions, thus inhibiting performance [1]. To accurately determine molecular fade rates, we utilize potentiostatic cycling to avoid artifacts caused by drifts in internal resistance and employ volumetrically unbalanced, compositionally symmetric cell configurations to distinguish molecular fade from membrane crossover or cell unbalancing. Redox-active organic molecule stability has improved to the point that the most stable chemistries degrade at less than 1% per year [2]. With further lifetime increases, the measurement of lower capacity fade rates necessitates higher precision coulometry methods [3] and thermally accelerated degradation protocols [4] to determine which stabilizing approaches are most effective without waiting for multi-month cycling tests to quantify capacity fade.We have developed a high-throughput setup for cycling AORFBs at elevated temperatures, providing a new dimension in the flow battery characterization space to explore. Capacity fade rates of previously published redox-active organic molecules, as functions of temperature, are evaluated in the high-throughput setup providing the ability to extrapolate fade rates to lower operating temperatures. The effect of temperature on electrochemical regeneration [5,6] of decomposed organic molecules is also explored. Collectively, these results highlight the importance of accelerated decomposition protocols to expedite the screening process of candidate molecules for long lifetime AORFBs, which may enable massive grid penetration of intermittent renewable energy.[1] M.-A. Goulet and M. J. Aziz, “Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods,” Journal of The Electrochemical Society , 165, A1466 (2018).[2] M. Wu, Y. Jing, A. A. Wong, E. M. Fell, S. Jin, Z. Tang, R. G. Gordon, M. J. Aziz, “Extremely Stable Anthraquinone Negolytes Synthesized from Common Precursors,” Chem, 6, 1432 (2020).[3] T. M. Bond, J. C. Burns, D. A. Stevens, H. M. Dahn, J. R. Dahn, "Improving Precision and Accuracy in Coulombic Efficiency Measurements of Li-Ion Batteries", Journal of The Electrochemical Society, 160, A521 (2013).[4] D. A. Stevens, R. Y. Ying, R. Fathi, J. N. Reimers, J. E. Harlow, J. R. Dahn, "Using High Precision Coulometry Measurements to Compare the Degradation Mechanisms of NMC/LMO and NMC-Only Automotive Scale Pouch Cells", Journal of The Electrochemical Society, 161, A1364 (2014).[5] M. Wu, M. Bahari, E. M. Fell, R. G. Gordon, M. J. Aziz, “High-performance anthraquinone with potentially low cost for aqueous redox flow batteries”, Journal of Materials Chemistry A, 9, 26709 (2021).[6] Y. Jing, E. W. Zhao, M.-A. Goulet, M. Bahari, E. M. Fell, S. Jin, A. Davoodi, E. Jónsson, M. Wu, C. P. Grey, R. G. Gordon, M. J. Aziz, “In situ electrochemical recomposition of decomposed redox-active species in aqueous organic flow batteries,” Nature Chemistry, 14, 1103, (2022).Figure caption: Capacity fade rates of an anthraquinone derivative, measured in symmetric cells, as a function of temperature. Figure 1

Grid integration of a 500 kW alkaline electrolyzer system for harmonic analysis and robust control

In the past decades, wind and solar energy installation has rapidly increased. The electric grid has been ever increasingly penetrated with such intermittent renewable sources, which inevitably increase the schedule difficulty and cause stability issues. To solve such problems and efficiently utilize the renewable energy, electrolyzer plants are integrated into the grid. This work provides a simulation result of a 500 kW alkaline electrolyzer system including converter topology and electrolyzer performance modeling. Two case studies are carried out in MATLAB®/Simulink® and PLECS to investigate the harmonic distortion and system response during voltage deviation in the distribution grid. The simulation result indicates that different short circuit ratio values affect the total harmonic distortion and the harmonic sidebands are mainly affected by controller bandwidth and switching frequency. The designed system maintains 95% DC link voltage even when subjected to a 20% voltage dip in the point of connection.

Enhancing the performance of consolidated voltage–frequency control of multi‐area hybrid interconnected power systems using electric vehicles

AbstractElectricity consumers desire a reliable and uninterrupted power supply for their equipment. Frequency and voltage are fluctuated due to the increase in intermittent renewable sources in the power systems. To mitigate these problems, a novel multi‐term fractional‐order PID (MFOPID) controller is proposed for improving the combined voltage‐frequency control of a three‐area hydrothermal system (THS) that incorporates a realistic dish‐Stirling solar thermal system (RDSTS). Suitable nonlinearity constraints are considered in both thermal‐hydro units. The proposed controller parameters are optimized using the artificial flora algorithm. Electric vehicle (EV) fleets have been introduced for the first time into the system under consideration. The MFOPID controller outperforms the PID with filter coefficient (PIDN) controller, according to a comparative assessment of the system dynamic responses under various investigations. Investigations exhibit that the system dynamic performance marginally degrades after the incorporation of the RDSTS into all control area of the three‐area THS. The analysis reveals that the assimilation of EVs into the considered system provides better system damping and reduces oscillations and peak deviations. The efficiency of electric vehicles is influenced by battery state‐of‐charge (SOC). The system performance deteriorates when the SOC of the EVs is more than 80% charging and less than 50% discharging at the time of disturbance. Moreover, the MFOPID controller provides a faster injection of EV power into the system during perturbation compared to the PIDN controller. Sensitivity analysis validated the MFOPID controller's sturdiness against numerous physical system conditions.

Optimizing Load Frequency Control in Standalone Marine Microgrids Using Meta-Heuristic Techniques

Integrating renewable resources into the electrical systems of marine vessels achieves the dual goal of diversifying energy resources and reducing greenhouse gas emissions. The presence of intermittent renewable sources and sudden nonlinear load changes can cause frequency deviations in isolated hybrid marine microgrids. To address this issue, the paper proposes a conventional PID (proportional–integral–derivative)-controller-based LFC (load frequency controller) which is optimized by meta-heuristic optimization algorithms, namely, PSO (particle swarm optimization), GWO (grey wolf optimization) and hybrid PSO-GWO. The proposed LFC was designed using transfer functions of various microgrid components, with ITAE (integral time absolute error) and ITSE (integral time square error) serving as performance indices. The proposed LFC’s validation was performed through HIL (hardware-in-loop) real-time simulation using a DS 1104 R&amp;D controller board, with simulation results showing the better performance of the optimized frequency response compared to the nonoptimized LFC controller in terms of rise time, fall time, slew rate and overshoot. The hybrid PSO-GWO algorithm performs better than the other optimization algorithms. The simulation results demonstrate the stability and robustness of the proposed controller. In summary, the proposed PID-controller-based LFC can regulate frequency deviation in standalone hybrid marine microgrids effectively.

Start–Stop Cyclic Durability Analysis of Membrane–Electrode Assemblies Using Polyflourene-Based Electrolytes for an Anion-Exchange Membrane Water Electrolyzer

Highly durable anion-exchange membranes and ionomers are essential for developing cost-effective green hydrogen generation. The anion-exchange membrane and ionomer must withstand chemical attacks by OH– ions as well as nonlinear mechanical stress caused by irregular bubble formation when the electrolyzer is coupled with intermittent power sources. Herein, we examined the durability of a trimethylammonium-modified poly(fluorene-alt-tetrafluorophenylene) (PFT-C10-TMA)-based membrane and ionomer under dynamic operation to evaluate its competency to couple with intermittent power sources. The durability of membrane–electrode assembly (MEA) prepared using these polymer membrane and ionomer was evaluated by performing 1000 start–stop voltage cycles in 1 M KOH solution at 80 °C while varying the applied cell voltage. The electrochemical performances of the MEA and electrodes were simultaneously evaluated using an electrolyzer with reference electrodes, and the chemical structure of the polymer was examined before and after the durability test using NMR techniques. The MEA based on a commercial Sustainion XB-7 ionomer and X37-50 RT anion-exchange membranes showed the catalyst leaching during start–stop cycles, resulting in reduced cell performance. On the other hand, the MEAs with the PFT-C10-TMA membrane and ionomer demonstrated promising high chemical and mechanical durability under dynamic start–stop operation, encouraging the development of electrolyzers that can function with intermittent renewable power sources.

Systematic Determination of Optimal Design-Points of Fully Integrated Power-to-SNG Process Chains Via Detailed Simulation of SOEC Stacks

The denomination Power-to-SNG covers technologies for the production of synthetic natural gas (SNG) through methanation of electrolytic hydrogen and captured carbon, enabling long-term storage of electrical energy from intermittent renewable sources. A methodology leveraging the pinch method for the optimization of the operating conditions of power-to-SNG plants is presented and applied to a system layout comprising a series of fixed-bed methanation reactors, a biomass gasification process and solid oxide electrolysis cell (SOEC) stacks, which recover the heat produced by the exothermic methanation process. For the system optimization, a rapid SOEC stack model is built from an underlying detailed multi-physics 3D model whilst maintaining its accuracy. Simulations reveal a maximum system HHV efficiency of 85.2% while identifying optimal operating conditions for all plant components. Moreover, the necessity of integrated system optimization strategies is showcased, as the predicted ideal conditions in the system strongly differ from the optimal conditions of the isolated components.

3D Printing of MXenes-Based Electrodes for Energy Storage Applications

Energy storage devices (ESD) including batteries, and supercapacitors are becoming progressively imperative in the transition to a renewable energy future, as they enable the integration of intermittent renewable sources into the grid and provide backup power during outages. There are already reviews available on various energy storage materials and systems. However, the challenges in the choice of suitable materials and fabrication technology are yet to establish for the commercialization of affordable and efficient ESDs in every aspect of practical needs. Therefore, we realize that the review on the newly developed two-dimensional (2D) MXenes-based energy storage electrodes and devices fabricated through suitably advanced 3D printing technology is the need of the hour, and will be able to attract broad audiences of the related field. MXenes are a class of 2D materials having lamella structures that have shown great promise for energy storage applications due to their versatile redox behavior, high surface area, high electrical conductivity, and ability to accommodate intercalated ions. However, the processing of 2D MXenes suffers from serious agglomeration due to weak Van der Waals attraction and reduces its actual energy storage performances. In a few recent studies, it is observed that advanced 3D printing has enabled the fabrication of MXenes with complex and customized geometries, opening up new possibilities for developing high-performance energy storage devices. Therefore, this review is important for a comprehensive discussion on this topic. So, in this review, we discuss the recent breakthroughs in 3D printed MXene-based batteries and supercapacitors, the advantages of using 3D printing for the fabrication of tailor-designed MXenes-based ESDs, existing challenges, and the opportunities available for further exploration towards the successful commercialization of ESDs. Overall, this review is an insightful articulation for the future seeking to stay at the forefront of this exciting and rapidly-expanding field.