Intermittent Renewable Sources Research Articles

Heat absorption/release efficiency betterment of phase change material inside a shell-and-tube latent heat storage system under six different conditions of tube and fins

Researchers are exploring innovative solutions for thermal energy storage to address the challenges posed by intermittent renewable sources, enhance energy efficiency, and contribute to the global shift towards cleaner and more sustainable energy practices. In the pursuit of an optimal system to improve the heat release/absorption efficiency of phase change materials (PCMs), a unique shell and tube latent heat storage system with four rectangular fins was designed. The melting and solidification behaviors of the material in this device were examined by manipulating the tube's position within the shell and fins around the tube. Six different cases were considered such as case A (tube in the center of the shell), case B (tube at the top of the shell), case C (tube at the bottom of the shell), case D (tube in the center of the shell with fins on its sides), case E (tube at the top of the shell with fins located in its bottom section), and case F (tube at the bottom of the shell with fins located in its top section). Cases D and E were the best options for absorbing and releasing heat in the shortest time. However, it should be noted that case F was faster during the melting process and dropped behind in the final stages. The authors proposed that if achieving a balanced result without incurring additional costs is essential, case D is a suitable option since it offers reasonable performance in melting and solidification processes. However, suppose researchers and developers of energy storage systems are seeking higher performances where heat absorption and release occur much more rapidly. In that case, it is suggested to construct one of the cases, E or F, and implement a rotational mechanism to enable access to the other case. Based on the outcomes, cases D and F needed 6235 s and 7552 s, respectively, to fully melt. While all cases even required more than 3 h to solidify 80 % of the PCM. The complete melting speed of Case F is 21.12 % faster than that of Case D. Additionally, the time required for 50 % solidification is 14.79 % faster for Case E compared to Case D. During 3 h, this system could absorb 1172 kJ of energy (cases D and F) and release 893 kJ of energy (cases D and E).

Renewable hydrogen production through electrolysis: An analysis of the cost gap for its economic competitiveness in Italy

With global policies targeting greenhouse gas emission reduction, renewable hydrogen produced by water electrolysis powered with renewable electricity appears a promising alternative to fossil fuels. However, still high capital costs, reliance on intermittent renewable electricity sources, and high electricity cost hinder the economic viability of electrolyzers. This work develops a comprehensive analysis for assessing the need of an incentive to make renewable hydrogen economically viable, identifying different archetypes of electrolysis plant representative of a wide range of applications. A techno-economic optimization model is set up that minimize the average hydrogen production cost and compute the cost gap that makes hydrogen economically competitive with the fossil alternative, defining the optimal size and operation of the plant components while satisfying the hydrogen demand. The model is applied to the Italian case study. Sensitivity analyses investigate the impact of economy of scales, renewable electricity availability and introduction of the emission trading system. Cost gaps ranging between 8.1 €/kg and 29.9 €/kg highlights the need of an incentive to allow the deployment of this technology, thus meeting the hydrogen penetration targets.

Modified Tilt-integral active disturbance rejection controller with inertia emulated direct current link for frequency control of marine microgrid

The increasing integration of intermittent renewable sources (RSs) poses a dynamic frequency stability challenge for modern marine vessel microgrids. To address this issue, this paper proposes a novel control approach, specifically targeting frequency and tie-line power stabilization in a diverse source marine microgrid (MμG) with two intertied areas featuring renewable (wind-wave) sources. The suggested approach introduces a modified tilt-integral active disturbance rejection (TI-ADRC) controller designed to ensure effective damping of power frequency oscillations. As the control scheme depends on the optimal setting of the proposed controller, a recently developed marine predator technique (MPT) has been adopted. The performance of the proposed controller is compared with other recent controllers viz. PID, tilt-integral derivative (TID), two-degree-of-freedom (2DOF)-PID, fuzzy-PI, and ADRC to validate its superiority. To further enhance the system dynamics, a precise modeling of inertia emulated direct current (IEPDC) tie link is incorporated in microgrid system. The impact assessments, considering time delays with pre/post IEPDC link, demonstrate a substantial 57.79% and 81.53% reduction in peak frequency overshoot compared to DC link (conventional model) and AC link, respectively. The analysis of the eigen plot confirms the stability of the control system. Sensitivity assessments of the controller against ± 30% parametric variations and load fluctuations are conducted, affirming its robustness. Finally, the result from OPAL-RT confirm the practicality of the proposed method. It is asserted that the suggested controller is reliable and functions well in n the presence of diverse disruptions and parametric variations.

Magnetic field based finite element method for magneto-static problems with discontinuous electric potential distributions

We introduce two finite element formulations to approximate magneto-static problems with discontinuous electric potential based respectively on the electrical scalar potential and the magnetic field. This work is motivated by our interest in Liquid Metal Batteries (LMBs), a promising technology for storing intermittent renewable sources of energy in large scale energy storage devices. LMBs consist of three liquid layers stably stratified and immiscible, with a light liquid metal on top (negative electrode), a molten salt in the middle (electrolyte) and a heavier liquid metal on bottom (positive electrode). Energy is stored in electrical potential differences that can be modeled as jumps at each electrode-electrolyte interface. This paper focuses on introducing new finite element methods for computing current and potential distributions, which account for internal voltage jumps in liquid metal batteries. Two different formulations that use as primary unknowns the electrical potential and magnetic field, respectively, are presented. We validate them using various manufactured test cases, and discuss their applications for simulating the current distribution during the discharge phase in a liquid metal battery.

Development of the Squaramide Scaffold for High Potential and Multielectron Catholytes for Use in Redox Flow Batteries.

Nonaqueous organic redox flow batteries (N-ORFBs) are a promising technology for grid-scale storage of energy generated from intermittent renewable sources. Their primary benefit over traditional aqueous RFBs is the wide electrochemical stability window of organic solvents, but the design of catholyte materials, which can exploit the upper range of this window, has proven challenging. We report herein a new class of N-ORFB catholytes in the form of squaric acid quinoxaline (SQX) and squaric acid amide (SQA) materials. Mechanistic investigation of decomposition in battery-relevant conditions via NMR, HRMS, and electrochemical methods enabled a rational design approach to optimizing these scaffolds. Three lead compounds were developed: a highly stable one-electron SQX material with an oxidation potential of 0.51 V vs Fc/Fc+ that maintained 99% of peak capacity after 102 cycles (51 h) when incorporated into a 1.58 V flow battery; a high-potential one-electron SQA material with an oxidation potential of 0.81 V vs Fc/Fc+ that demonstrated negligible loss of redox active material as measured by pre- and postcycling CV peak currents when incorporated in a 1.63 V flow battery for 110 cycles over 29 h; and a proof-of-concept two-electron SQA catholyte material with oxidation potentials of 0.48 and 0.85 V vs Fc/Fc+ that demonstrated a capacity fade of just 0.56% per hour during static H-cell cycling. These findings expand the previously reported space of high-potential catholyte materials and showcase the power of mechanistically informed synthetic design for N-ORFB materials development.

Development of an Energy Planning Model Using Temporal Production Simulation and Enhanced NSGA-III

This paper presents an innovative model of Energy Planning Model which allows navigating the complexities of modern energy systems. Our model utilizes a combination of Temporal Production Simulation and an Enhanced Non-Dominated Sorting Genetic Algorithm III to address the challenge associated with fluctuating energy demands and renewable sources integration. The model represents a significant advancement in energy planning due to its capacity to simulate energy production and consumption dynamics over time. The unique feature of the model is based on Temporal Production Simulation, meaning that the model is capable of accounting for hourly, daily, and seasonal fluctuations in energy supply and demand. Such temporal sensitivity is crucial for optimization in systems with high percentages of intermittent renewable sources, as existing planning solutions largely ignore such fluctuations. Another component of the model is the Enhanced NSGA-III algorithm that is uniquely tailored for the nature of multi-objective energy planning where one must balance their cost, environmental performance, and reliability. We have developed improvements to NSGAIII to enhance its efficiency when navigating the complex decision space associated with energy planning to reach faster convergence and to explore more optimal solutions. Methodologically, we use a combination of in-depth problem definition approach, advanced simulation, and algorithmic adjustments. We have validated our model against existing models and testing it in various scenarios to illustrate its superior ability to reach optimal energy plans based on efficiency, sustainability, and reliability under various conditions. Overall, through its unique incorporation of the Temporal Production Simulation and an improved optimization algorithm, the Energy Planning Model provides novel insights and practical decision support for policymakers and energy planners developed to reach the optimal sustainable solutions required for the high penetration of renewables.

The effects of reducing renewable power intermittency through portfolio diversification

Intermittency of renewable power sources is a growing concern for grid reliability in the United States and it has not been properly addressed by public policy for very long. One simple way to mitigate this problem is to diversify the renewable energy portfolio. This work studies the case of Texas, a state that not only is the largest wind power producer in the US, but that also has faced considerable diversification in its renewable energy portfolio in the past ten years. A dispatch model is proposed to simulate how thermal generators respond to changes in the intermittency of renewable sources. Additionally, since higher renewable output usually means higher intermittency and vice-versa, a mean–variance analysis is used to study this trade-off. Results indicate that although intermittency decreases the reliability of the grid, reducing it can have adverse effects as increasing the dispatch of polluting power sources and decreasing the revenues of thermal generators, what can decrease important investment in dispatchable power sources in the long-term. Also, results show that the subsidy design adopted by the federal government is an obstacle to portfolio diversification.

Neural network predictive control in renewable systems (HKT-PV) for delivered power smoothing

The reduction of power fluctuations from intermittent renewable sources is one of the most pressing challenges today. Recent research has shown that prediction and control mechanisms, when combined with energy storage systems, significantly contribute to improving these techniques. However, substantial research gaps still exist regarding the optimization of energy storage system operability. This article introduces an innovative power smoothing method based on neural network predictive control, in conjunction with the exponential moving average method. The proposed approach encompasses the ability to substantially reduce energy fluctuations, optimize battery state of charge, and mitigate ramp rates, thereby preventing deep discharges that shorten battery lifespan. Furthermore, the control system's primary objective is to optimize energy exchange with the grid, surpassing the performance offered by other conventional power smoothing methods. The control system excels in optimizing energy exchange within the network, surpassing conventional methods. Extensive testing on the University of Cuenca microgrid reveals a consistently more stable and higher battery charge compared to conventional methods. Numerical results for underscore the method's effectiveness with a fluctuation suppression rate of 30.78 % compared to 34.85 % (low pass filter) and 36.22 % (ramp rate) methods respectively. The enhanced voltage profiles at the common coupling point ensure the delivery of high-quality and stable power.

On Green Hydrogen Generation Technologies: A Bibliometric Review

Green hydrogen, produced by water electrolysis with renewable energy, plays a crucial role in the revolution towards energy sustainability, and it is considered a key source of clean energy and efficient storage. Its ability to address the intermittency of renewable sources and its potential to decarbonize sectors that are difficult to electrify make it a strategic component in climate change mitigation. By using a method based on a bibliometric review of scientific publications, this paper represents a significant contribution to the emerging field of research on green hydrogen and provides a detailed review of electrolyzer technologies, identifying key areas for future research and technology development. The results reflect the immaturity of a technology which advances with different technical advancements, waiting to find the optimal technical solution that allows for its massive implementation as a source of green hydrogen generation. According to the results found in this article, alkaline (ALK) and proton exchange membrane (PEM) electrolyzers seem to be the ones that interest the scientific community the most. Similarly, in terms of regional analysis, Europe is clearly committed to green hydrogen, in view of the analysis of its scientific results on materials and electrolyzer capacity forecasts for 2030.

Evaluation and deployment of a unified MPPT controller for hybrid Luo converter in combined PV and wind energy systems

AbstractThis work emphasizes the development and examination of a Hybrid Luo Converter integrated with a unified Maximum Power Point Tracking (MPPT) for both grid and independent hybrid systems. The primary objectives of this hybrid system are to efficiently harness power from intermittent and variable renewable sources while elevating low-voltage energy inputs to utility-grade levels. Unlike previous studies employing specific MPPT algorithms for solar and wind sources, this work aims to simplify the control system by utilizing a unified MPPT controller. This research also introduces a novel approach involving dual-lift hybrid Luo converters to create hybrid systems, operating exclusively or concurrently based on the availability of renewable resources. To maximize power generation from all renewable sources, a unified MPPT algorithm is developed. The hybrid system, incorporates 500 W wind and 560 W PV systems, the innovative Luo converter, and the unified MPPT controller. A comprehensive comparative analysis is presented, comparing the hybrid system's performance with that of traditional control algorithms, such as the Perturb & Observe, and Radial Basis Function Network controllers. The successful prototype of the converter validates the practicality of the proposed approach.

Climate policy with electricity trade

Trade reduces the effectiveness of climate policies such as carbon pricing when domestic products are replaced by more carbon-intensive imports. We investigate the impact of unilateral carbon pricing on electricity generation in a country open to trade through interconnection lines. We characterize the energy mix with intermittent renewable sources of energy (wind or solar power). Electricity trade limits the penetration of renewables due to trade-induced competition. A carbon border adjustment mechanism (CBAM) removes this limit by increasing the cost of imported power, or by deterring imports. The CBAM must be complemented by a subsidy on renewables to increase renewable generation above domestic consumption. The interconnection line is then used to export power rather than importing it when renewables are producing. We also examine network pricing and investment into interconnection capacity. A higher carbon price increases interconnection investment which further reduces the effectiveness of carbon pricing. In contrast, when renewable electricity is exported, a higher subsidy on renewables reduces further carbon emissions by expanding interconnection capacity.

Implementation of Fluidized Bed Concept to Improve Heat Transfer in Ecological Adsorption Cooling and Desalination Systems

Sustainable development policy focuses on reducing the carbon footprint generated by the global industry and energy sector. Replacing conventional energy sources with environmentally friendly ones requires advanced research to increase energy efficiency and reduce the instability and intermittence of renewable sources. Moreover, adsorption chillers are an opportunity to introduce net-zero emission technologies to the refrigeration, air-conditioning, and desalination industries. Adsorption devices could be popularized if a method of effective heat transfer in the volume of the adsorption bed is developed. The innovative concept of introducing fluidized beds into the adsorption system can achieve the most promising results in improving energy efficiency. To confirm the adopted assumption, heat transfer coefficient calculations for the packed and fluidized bed were carried out in this paper based on experimental tests and literature data. The empirical research aims to extend the fundamental knowledge in the implementation of fluidization under low-pressure conditions, characteristic of the adsorption systems’ working cycle. Experiments were conducted on a unique test stand equipped with the Intensified Heat Transfer Adsorption Bed (IHTAB) reactor prototype. Five adsorption bed samples were analyzed. The reference sample consisted only of silica gel, and the subsequent ones contained aluminum or carbon nanotubes with 5 and 10% additions. In the case of samples with admixtures, the fluidized state increased the heat transfer coefficient on average from approx. 36.9 W/m2 K to approx. 245.4 W/m2 K.

Optimal Tuning of PID Controllers for LFC in Renewable Energy Source Integrated Power Systems Using an Improved PSO

The constant rise in energy demand and concerns about climate change have led to increased penetration of renewable energy sources (RES). Maintaining active power balance between generation and demand in power systems with significant penetration of these highly variable and intermittent renewable sources requires an efficient load frequency control (LFC) strategy. One such strategy that has gained the attention of researchers is optimal tuning of PID controllers of LFC using metaheuristic method. This paper presents a PSO variant for optimal tuning of PID controllers for load frequency control of power system integrated with renewable energy resources. The proposed PID tuning technique is tested on a two-area power system commonly used in the literature. Seven scenarios have been used to validate the effectiveness of the proposed Load Frequency Control. For more realistic evaluation, governor dead band and communication time delays have been incorporated in the test system in one of the scenarios. Simulation results obtained when compared with those of three well-known PID-tuning metaheuristic algorithms produced shorter settling time and smaller frequency and tie line power deviations.

Balancing Energy and Material Efficiency in Green Hydrogen Production via Water Electrolysis

Green hydrogen is increasingly regarded as a pivotal solution in achieving “net zero by 2050” in carbon neutrality across various sectors and industries. Ambitious decarbonisation roadmaps largely depend on the successful deployment of electrolysis technologies. Among these, Proton Exchange Membrane Electrolysis (PEMEL) stands out for its efficiency, compact design, and adaptability to intermittent renewable power sources. PEMEL is gradually being commercialised, and considerable uncertainty remains regarding its future environmental performance at a plant level. Therefore, future PEMEL cells should be life cycle engineered with a focus on improving materials efficiency by investigating enhanced electrochemical catalysts, membranes, and electrodes for an improved membrane electrode assembly (MEA). In this study, we simulate a 10MW PEMEL plant, identify key operational parameters and evaluate future MEA development scenarios to assess their impact on energy consumption, material utilisation, and system durability. Our findings shed light on the potential trade-offs between energy and material efficiency, providing valuable insights to mitigate environmental hotspots. By focusing on these trade-offs, this work contributes significantly to the ongoing efforts to improve the environmental and operational performance of PEMEL plants.

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).