Renewable Energy Conversion Research Articles

First-principles study of the relationship between the formation of single atom catalysts and lattice thermal conductivity

Single atom catalysts (SACs) have been in the forefront of catalysts research because of their high efficiency and low cost and provide new ideas for development of renewable energy conversion and storage technologies. However, the relationship between the intrinsic properties of materials such as lattice thermal conductivity and catalysis remains to be explored. In this work, the lattice thermal conductivity of BN and graphene was calculated by ShengBTE. In addition, the adsorption properties of 3d-TM (TM = V, Cr, Mn, Fe, Co, Ni) on BN and graphene were investigated using first-principles methods, and it was found that Ni atom can form relatively stable SACs compared to other TMs. The molecular dynamics (MD) simulation and migration barrier of Ni loaded on BN and graphene were calculated. Our study found that graphene has higher thermal conductivity and is easier to form SACs than BN, but the SACs formed on BN surface have higher thermodynamic stability.

Precision tuning of highly efficient Pt-based ternary alloys on nitrogen-doped multi-wall carbon nanotubes for methanol oxidation reaction

The electrochemical methanol oxidation is a crucial reaction in the conversion of renewable energy. To enable the widespread adoption of direct methanol fuel cells (DMFCs), it is essential to create and engineer catalysts that are both highly effective and robust for conducting the methanol oxidation reaction (MOR). In this work, trimetallic PtCoRu electrocatalysts on nitrogen-doped carbon and multi-wall carbon nanotubes (PtCoRu@NC/MWCNTs) were prepared through a two-pot synthetic strategy. The acceleration of CO oxidation to CO2 and the blocking of CO reduction on adjacent Pt active sites were attributed to the crucial role played by cobalt atoms in the as-prepared electrocatalysts. The precise control of Co atoms loading was achieved through precursor stoichiometry. Various physicochemical techniques were employed to analyze the morphology, element composition, and electronic state of the catalyst. Electrochemical investigations and theoretical calculations confirmed that the Pt1Co3Ru1@NC/MWCNTs exhibit excellent electrocatalytic performance and durability for the process of MOR. The enhanced MOR activity can be attributed to the synergistic effect between the multiple elements resulting from precisely controlled Co loading content on surface of the electrocatalyst, which facilitates efficient charge transfer. This interaction between the multiple components also modifies the electronic structures of active sites, thereby promoting the conversion of intermediates and accelerating the MOR process. Thus, achieving precise control over Co loading in PtCoRu@NC/MWCNTs would enable the development of high-performance catalysts for DMFCs.

Combining Renewable Electricity and Renewable Carbon: Understanding Reaction Mechanisms of Biomass-Derived Furanic Compounds for Design of Catalytic Nanomaterials.

ConspectusDespite the growing deployment of renewable energy conversion technologies, a number of large industrial sectors remain challenging to decarbonize. Aviation, heavy transport, and the production of steel, cement, and chemicals are heavily dependent on carbon-containing fuels and feedstocks. A hopeful avenue toward carbon neutrality is the implementation of renewable carbon for the synthesis of critical fuels, chemicals, and materials. Biomass provides an opportune source of renewable carbon, naturally capturing atmospheric CO2 and forming multicarbon linkages and useful chemical functional groups. The constituent molecules nonetheless require various chemical transformations, often best facilitated by catalytic nanomaterials, in order to access usable final products.Catalyzed transformations of renewable biomass compounds may intersect with renewable energy production by offering a means to utilize excess intermittent electricity and store it within chemical bonds. Electrochemical catalytic processes can often offer advantages in energy efficiency, product selectivity, and modular scalability compared to thermal-driven reactions. Electrocatalytic reactions with renewable carbon feedstocks can further enable related processes such as water splitting, where value-adding organic oxidation reactions may replace the evolution of oxygen. Organic electroreduction reactions may also allow desirable hydrogenations of bonds without intermediate formation of H2 and need for additional reactors.This Account highlights recent work aimed at gaining a fundamental understanding of transformations involving biomass-derived molecules in electrocatalytic nanomaterials. Particular emphasis is placed on the oxidation of biomass derived furanic compounds such as furfural and 5-hydroxymethylfurfural (HMF), which can yield value-added chemicals, including furoic acid (FA), maleic acid (MA), and 2,5-furandicarboxylic acid (FDCA) for renewable materials and other commodities. We highlight advanced implementations of online electrochemical mass spectrometry (OLEMS) and vibrational spectroscopies such as attenuated total reflectance surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS), combined with microkinetic models (MKMs) and quantum chemical calculations, to shed light on the elementary mechanistic pathways involved in electrochemical biomass conversion and how these paths are influenced by catalytic nanomaterials. Perspectives are given on the potential opportunities for materials development toward more efficient and selective carbon-mitigating reaction pathways.

Energy security challenges and opportunities in the carbon neutrality context: A hierarchical model through systematic data-driven analysis

This study contributes to fundamental knowledge about energy security strategy for carbon neutrality by identifying important tendencies in terms of future challenges and opportunities from the state-of-the-art literature and by evaluating regional position gaps and global energy strategy for carbon neutrality. Addressing carbon emissions plays an undeniable role in energy security improvement since most countries have advanced to responding to climate change. However, whether these responses achieve actual good outcomes remains questionable. Since there are plenty of related studies and indicators, this study conducts data-driven analysis to generate an energy security and carbon neutrality model and indicates the challenges and opportunities for future assessments. A hybrid method incorporating content analysis, the fuzzy Delphi method, interpretive structural modeling, the fuzzy decision-making trial and evaluation laboratory, and the entropy weight method is implemented to understand the complex system of energy security and carbon neutrality and its inner interrelationships as well as regional perspectives. There are 19 valid indicators clustered into 5 aspects that form a strategic hierarchical model. Overall, sustainable energy strategies, renewable energy conversion, and carbon mitigation approaches are found to be causal aspects. The top critical indicators are cobenefits, the energy transition, a low-carbon society, renewable energy policy, renewable energy sources, energy resilience, and low-carbon technology. Regional assessment is taken as an approach; despite the imbalance in the information provided by regions, the outputs still leave much room for development.

Enhancing the Photoelectrochemical Performance of a Nanoporous Silicon Photocathode through Electroless Nickel Deposition.

Renewable energy sources, particularly solar energy, are key to our efforts to decarbonize. This study investigates the photoelectrochemical (PEC) behavior of nanoporous silicon (NPSi) and its Ni-coated hybrid system. The methods involve the application of a Ni coating to NPSi, a process aimed at augmenting catalytic activity, light absorption, and carrier transport. Scanning electron microscopy was used to analyze the morphological changes on NPSi surfaces due to the Ni coating. Results demonstrate that the Ni coating creates unique structures on NPSi surfaces, with peak PEC performance observed at 15 min of coating time and 60 °C. These conditions were found to promote electron-hole pair separation and uniform Ni coverage. A continuous 50-min white light illumination experiment confirmed stable PEC fluctuations, showing the interplay of NPSi's characteristics and Ni's catalytic effect. This study provides practical guidance for the design of efficient water-splitting catalysts, contributing to the broader field of renewable energy conversion.

Nonlinear control strategies with maximum power point tracking for hybrid renewable energy conversion systems

AbstractThis paper addresses the problem of controlling and optimizing a hybrid renewable energy system, specifically consisting of a photovoltaic (PV) generator and a wind energy conversion system comprising a wind turbine and a permanent magnet synchronous machine. The primary control objectives involve maximizing power extraction from both the PV and wind turbine while ensuring efficient injection of the extracted energy into the electrical network and maintaining a suitable power factor. This study presents two key innovations that distinguish it from existing research. Firstly, it introduces a new hybrid PV/aerogenerator energy source that eliminates the need for a DC/DC converter in the PV structure. Secondly, unlike previous works that rely on various measurements such as wind speed, temperature, and irradiance, our approach only requires measurements of electrical variables. This advancement significantly reduces the number of sensors required and enhances the overall reliability of the system.

Strategies to Enhance Interfacial Spatial Charge Separation for High‐Efficiency Photocatalytic Overall Water‐Splitting: A Review

Developing efficient photocatalysts for overall water‐splitting (OWS) has garnered considerable attention due to their potential in renewable energy conversion and storage. Enhancing the efficiency of interfacial spatial charge separation poses a key challenge in this field, as it plays a momentous role in the photocatalytic process. In this review article, a range of strategies aimed at improving interfacial spatial charge separation in photocatalysts for realizing high‐efficiency OWS are explored. To provide a comprehensive understanding, first the fundamentals of photocatalytic water‐splitting are introduced and the main bottlenecks in the reaction process, along with various charge separation and transfer mechanisms are identified. Subsequently, recent advancements and efforts in designing spatial charge separation at the interfaces of 0D, 1D, 2D, and 3D nanostructured photocatalysts are discussed. Finally, a summary is presented and a long‐term outlook for spatial charge separation in the field of OWS is offered. By consolidating the current state‐of‐the‐art research, this review highlights the key challenges and favorable circumstances for future advancements in the pursuit of efficient OWS.

Establishing theoretical landscapes for identifying basal plane active sites in MBene toward multifunctional HER, OER, and ORR catalysts

Exploring multifunctional electrocatalysts to realize efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is urgently desired for developing novel renewable energy storage and conversion technologies. However, integrating these three merits in one single catalyst remains a big challenge due to the difficulty in balancing the adsorption strengths of multiple reaction intermediates. Herein, through first-principles calculations, we systematically investigated the electrocatalytic activity of M2B2, M3B4, and M4B6 type MBenes (M = Cr, Mn, Fe, Co, and Ni) for multifunctional HER, OER, and ORR. The results indicate that most of the investigated MBenes show outstanding catalytic activity for HER with hydrogen adsorption Gibbs free energy close to the optimal value (0 eV). Thereinto, Ni2B2 and Co3B4 MBenes can be promising multifunctional HER/OER/ORR electrocatalysts, and Fe3B4 MBene is expected to be a promising bifunctional electrocatalyst for HER/ORR. Especially, Ni2B2 MBene is even better than the benchmark RuO2 catalyst with ultralow low overpotentials of 0.26 and 0.30 V for OER and ORR, respectively. Then, we proposed that the overpotentials of OER/ORR can be well described by the varied ΔGOH* on MBene, which has been further illuminated through the d-band center and charge transfer analysis. Importantly, new scaling relations between the adsorption energies of OOH* and O* on MBenes have been established, where ΔGOOH* and ΔGO* possess different slopes versus ΔGOH*, allowing the significantly lower overpotentials of OER and ORR to be achieved. This work provides not only promising multifunctional HER/OER/ORR electrocatalysts but also new scaling relations to achieve the rational design of MBene-based electrocatalysts.

Optimization Strategies and Nonlinear Control for Hybrid Renewable Energy Conversion System

Optimization Strategies and Nonlinear Control for Hybrid Renewable Energy Conversion System

Advancing sustainable development goals with machine learning and optimization for wet waste biomass to renewable energy conversion

With the rapid surge in global population, urbanization, and improved living standards, there has been a significant increase in untreated wet waste. This escalation poses a critical challenge for waste management and raises considerable environmental concerns. One pivotal solution is the conversion of this wet waste into valuable energy resources and carbon-neutral mediums, a strategy aligning with the United Nations Sustainable Development Goal 7 (SDG7) - Affordable and Clean Energy, and Sustainable Development Goal 15 (SDG15) - Life on Land. Hydrothermal carbonization (HTC) and pyrolysis have emerged as effective technologies due to their ability to process large volumes of wet waste and convert it into energy-rich and carbon-stable products with high energy efficiency. This study introduces a novel framework incorporating advanced machine learning techniques (including deep neural networks, random forest, and eXtreme gradient boosting) with dual-objective optimization. This approach enables a comparative analysis of the solid products from HTC and pyrolysis, focusing on their Carbon Stability Index (CSI) and Return on Energy Investment (REI) index. This assessment enables the tailoring of char production towards specific applications, yielding optimal conditions for high energy efficiency and stable carbon sequestration. In a case study involving wet food waste, the analysis indicated a significant enhancement from 4.83 to 14.43 in REI and an increase from 47.4 to 57.98 in CSI compared to conventional HTC solutions. Moreover, the uncertainty analysis demonstrated that our machine learning-based model provides robust and reliable predictions, with most of the R-squared (R2) values exceeding 0.90, meeting or exceeding the R2 values reported in similar ML models of biomass conversion in the literature, reinforcing its potential for practical applications. Our study also plots the solid products in a Van Krevelen diagram, showing composition changes during conversion. These findings exemplify the potential of these processes in bolstering the primary objectives of SDG7 and SDG15, thereby contributing to a more sustainable future.

Oxygen-atom-bridged Ru–Sn–Ce heterojunction for enhanced oxygen evolution reaction in acidic media

Developing for highly active and stable electrocatalysts for oxygen evolution reaction (OER) is of significant importance for some renewable energy conversion and storage systems. While, the prerequisite for further optimizing the activity of electrocatalysts is whether their original composition has potential for development. Herein, we firstly managed to combine theoretical and experimental efforts to establish Ru0.4Sn0.3Ce0.3O2 (RSCO) as a promising electrocatalyst for acidic OER. The X-ray absorption and density functional theory studies reveal that the local coordination environment and electronic structure of Ru sites in RSCO is optimized by the oxygen atom bridged Sn and Ce at heterogeneous interfaces, thereby resulting in a low energy barrier. In addition, the electrochemical results indicate that the activity and stability of RSCO obviously surpasses that of the RuO2 prepared by same method as RSCO. Most encouragingly, the OER activity of RSCO can be substantially enhanced only by optimizing the calcination temperature, meaning the possibility of further improvement the intrinsic activity of such oxygen atom bridged Ru based complex by proper surface or interfacial engineering.

Technical and economic appraisal for harnessing a proposed hybrid energy system nexus for power generation and CO2 mitigation in Cross River State, Nigeria

By creating hybrid energy systems and obtaining a framework that equally satisfies a continuous operation for renewable energy technology, this study presents renewable and sustainable energy options as an integral method to energy transitioning from non-renewable to renewable energy utilization in Cross River State, Nigeria. For a needed load of 2424.25 kWh/day in Cross River State, this study focused on proposing a designed hybrid energy system (HES) nexus, mitigating CO2, and appraisal of the technical and economic viability. To accomplish this, HOMER software was utilized in simulating the ideal components that suggested a HES nexus. The software enabled the selection of the optimal HES using various renewable energy sources since it predicts future electrical demand, wind speed, solar irradiation, and temperature. Economic results obtained showed that the proposed HES's Levelized cost of energy (LCOE), net present cost (NPC), and operating cost (OC) were $0.89/kWh, $10,138,702 and $134,084.37 respectively. Further technical appraisal showed that the renewable energy conversion systems (RECs) make up 78.74% of the proposed HES. The photovoltaic (PV) arrays were primarily responsible for the hybrid energy system's electricity output. The annual electrical energy output was 1,984,111kWh (89.4%), produced by the PV arrays. The generic fuel cell produced the least, at 29,957kWh/year, accounting for just 1.35% of the total electricity produced. However, the wind power plant produced 205,365kWh/year annually. Furthermore, comparing the HES with diesel-powered generators, the system achieves a net-zero carbon emission status. Therefore, it has proven to be the most reliable energy as it will solve the problem of energy demand and reduces carbon emissions in Cross River State, Nigeria

An Optimized Switching Strategy Based on Gate Drivers with Variable Voltage to Improve the Switching Performance of SiC MOSFET Modules

This paper proposes an optimized switching strategy (OSS) based on a silicon carbide (SiC) MOSFET gate driver with variable voltage, which allows simultaneous variations in several different parameters to optimize the switching performance of semiconductor devices. As a relatively new device, the SiC MOSFET shines in the field of high power density and high-frequency switching; it has become a popular solution for electric vehicles and renewable energy conversion systems. However, the increase in voltage and current slope caused by high switching speeds inevitably increases the overshoot and oscillation in a circuit and can even generate additional losses. The principle of this new control strategy is to change the voltage and current in the turn-on and turn-off stages by changing the gate driver’s voltage. That is, we reduced the drive’s voltage after a certain time delay and maintained it for a period of time, thus directly controlling the slopes of di/dt and dv/dt. This study focused on the optimization of the SiC MOSFET by changing the time delay preceding the decrease in the voltage of the gate driver, analyzing and calculating the optimal time delay before the decrease in the voltage of the gate driver, and verifying the findings using LTspice simulation software. The simulated results were compared and analyzed with hard-switching strategies. The results showed that the proposed OSS can improve the switching performance of SiC MOSFETs.

Coordination Engineering of Dual Co, Ni Active Sites in N-Doped Carbon Fostering Reversible Oxygen Electrocatalysis.

The development of affordable and non-noble-metal-based reversible oxygen electrocatalysts is required for renewable energy conversion and storage systems like metal-air batteries (MABs). However, the nonbifunctionality of most of the catalysts impedes their use in rechargeable MAB applications. Moreover, the loss of active sites also affects the long-term performance of the electrocatalyst toward oxygen electrocatalysis. In this work, we report a simplistic yet controllable chemical approach for the synthesis of dual transitional metals such as cobalt, nickel, and nitrogen-doped carbon (CoNi-NC) as bifunctional electrode materials for rechargeable zinc-air batteries (ZABs). The spatially isolated Ni-N4 and Co-N4 active units were rendered for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. The individual efficacy of both reversible reactions enables an ΔE value of ∼0.72 V, which outperforms several bifunctional electrocatalysts reported in the literature. The half-wave potential (E1/2) and overpotential were achieved at 0.83 V and 330 mV (vs RHE) for ORR and OER, respectively. The peak power density of ZAB equipped with the CoNi-NC catalyst was calculated to be 194 mW cm-2. The present strategy for the synthesis of bifunctional electrocatalysts with dual active sites offers prospects for developing electrochemical energy storage and conversion systems.

Performance and fatigue analysis of an integrated floating wind-current energy system considering the aero-hydro-servo-elastic coupling effects

Integration of multiple offshore renewable energy converters holds immense promise for achieving cost-effective utilization of marine energy. Integrated Floating Wind-Current Energy Systems (IFESs) have garnered considerable attention as a means to harness the abundant wind and marine resources in deep-sea areas using a single device. However, the dynamic responses of IFESs are significantly influenced by the coupling of aerodynamic and hydrodynamic loads. To assess the performance of a 10 MW + Spar-type IFES under wind-wave-current loadings, this study develops an aero-servo-elastic model within the hydrodynamic analysis tool AQWA. By utilizing the fully coupled model, this study investigates the platform motions, tower loads, and power production of the IFES under various environmental conditions. A comparative analysis is conducted by comparing the results with those obtained for a floating offshore wind turbine (FOWT). Furthermore, fatigue damage at the tower base of both the IFES and FOWT is evaluated. It is found that the presence of current turbines leads to improved platform stability, significant increases in total power production, and reduced fatigue damage at the tower base. These novel findings corroborate the potential and advantages of IFES concepts in enhancing the stability and energy harvest efficiency of floating marine energy converters.

Heterogeneous ultra-thin FeCo-LDH@Co(OH)2 nanosheets facilitated electrons transfer for oxygen evolution reaction

Developing cost efficient, robust, non-precious metal electrocatalysts for oxygen evolution reaction (OER) is a significant challenge in water splitting for renewable energy conversion. A novel electrocatalyst of heterogeneous ultra-thin FeCo-LDH@Co(OH)2 nanosheets derived from 2D Zeolitic imidazolate framework facilitated electrons transfer for OER. DFT calculation revealed that heterogeneous interfaces reduced adsorption energy barriers of intermediates in rate-determining step of OER. The CoOOH with higher CoIII valence state derived from surface reconstruction, which was detected via in-situ Raman spectroscopy, activated O ions to provide higher intrinsic activity. XPS results confirmed that electrons transfer from Co(OH)2 to FeCo-LDH accelerated alkaline OER kinetics. The FeCo-LDH@Co(OH)2–0.5 exhibited low overpotentials of 230 mV at 10 mA cm−2 and maintained long durability for 300 h. This study opened up a new method for design and synthesis of ultrathin LDHs electrocatalysts.

COA-CNN-LSTM: Coati optimization algorithm-based hybrid deep learning model for PV/wind power forecasting in smart grid applications

Power prediction is now a crucial part of contemporary energy management systems, which is important for the organization and administration of renewable resources. Solar and wind powers are highly dependent upon environmental factors, such as wind speed, temperature, and humidity, making the forecasting problem extremely difficult. The suggested composite model incorporates Long Short-Term Memory (LSTM) and Swarm Intelligence (SI) optimization algorithms to produce a framework that can precisely estimate offshore wind output in the short term, addressing the discrepancies and limits of conventional estimation methods. The Coati optimization algorithm enhances the hyper parameters CNN-LSTM. Optimum hyper parameters improvise learning rate and performance. The day-ahead and hour-ahead short-term predictions RMSE can be decreased by 0.5% and 5.8%, respectively. Compared to GWO-CNN-LSTM, LSTM, CNN, and PSO-CNN-LSTM models, the proposed technique achieves an nMAE of 4.6%, RE 27% and nRMSE of 6.2%. COA-CNN-LSTM outperforms existing techniques in terms of the Granger causality test and Nash-Sutcliffe metric analysis for time series forecasting performance, scores are 0.0992 and 0.98, respectively. Experimental results show precise and definitive wind power-making predictions for the management of renewable energy conversion networks. The presented model contributes positively to the body of knowledge and development of clean energy.

Multi‐objective design optimization of microreactor arrays for distributed renewable energy conversion: A case study

AbstractRenewable energy accommodation entails extensive use of modular devices, whose performance degrades remarkably from the lab scale to the industrial scale. This work presents a multi‐objective design optimization approach for modular devices scale‐up as exemplified by hierarchical numbering‐up of reverse water‐gas shift microreactors. The optimization objectives cover a wide span of competing system performance metrics, including the reaction performance, energy efficiency, space occupation, environmental impact, and costs. The decision variables involve the hierarchical geometry, branching, and inter‐stack connection schemes of the microreactor stacks. The obtained Pareto‐optimal designs suggest that multiple short stacks with small intra‐stack distribution channels and large inter‐stack connection tubes can well balance cost and performance. Meanwhile, single‐stack structures with large distribution channels are more suitable for portable applications. The methodology not only can be extended to the numbering‐up of various types of microreactors but also has essential guidance for the integration design of other modular devices.

Stochastic electrical, thermal, cooling, water, and hydrogen management of integrated energy systems considering energy storage systems and demand response programs

Energy hub (EH) is a multi-energy system that combines several energy sources to increase energy supply efficiency, flexibility, and reliability. In this paper, a stochastic two-step multi-objective optimization method is proposed for multi-EH planning that focuses on economic, environmental, and security concerns. In order to meet the demands for electricity, heating, cooling, hydrogen, natural gas, and water, the proposed model includes several components, such as nonrenewable and renewable energy sources, cogeneration units, converters, and storage systems. Also, price-based demand response programs are implemented to provide demand-side flexibility for EHs. The proposed multi-objective framework investigates the total cost of the system, average reserve index (ARI), emissions of the system, and energy not supplied (ENS), simultaneously. EHs categorize their objectives into main and secondary based on priority. Since the total cost is so important, it has been recognized as the primary objective that is minimized in the first step. Also, the emissions, ENS, and ARI are the secondary objectives that are optimized in the second step simultaneously. The proposed model's efficiency is evaluated using an 18-bus test network in both summer and winter seasons. The simulation results present that the proposed model improves the emission, ARI, and ENS by 47.78 %, 53.4 %, and 23.38 % in summer seasons, respectively. And also, the multi-objective framework improves the emission, ARI, and ENS by 45.66 %, 65.84 %, and 52.56 % in winter seasons, respectively.

Combination of Mn-Mo Oxide Nanoparticles on Carbon Nanotubes through Nitrogen Doping to Catalyze Oxygen Reduction.

An efficient and low-cost oxygen catalyst for the oxygen reduction reaction (ORR) was developed by in situ growth of Mn-Mo oxide nanoparticles on nitrogen-doped carbon nanotubes (NCNTs). Doped nitrogen effectively increases the electron conductivity of the MnMoO4@NCNT complex and the binding energy between the Mn-Mo oxide nanoparticles and carbon nanotubes (CNTs), leading to fast charge transfer and more catalytically active sites. Combining Mn and Mo with NCNTs improves the catalytic activity and promotes both electron and mass transfers, greatly enhancing the catalytic ability for ORR. As a result, MnMoO4@NCNT exhibited a comparable half-wave potential to commercial Pt/C and superior durability, demonstrating great potential for application in renewable energy conversion systems.