Unit Energy Research Articles

System frequency response model and droop coefficient setting considering renewable energy participation in frequency regulation

The highly uncertain and uncontrollable power output of renewable energy sources (RES), when integrated into power systems at high penetration levels, reduces system inertia and introduces uncertain changes in system structure, parameters, and frequency response characteristics. This renders traditional frequency regulation analysis methods and frequency response models inapplicable, lacking a generalized model to describe renewable energy’s participation in frequency regulation. Thus, this paper proposes a method where RES utilize suitable means to reduce load, thereby contributing to frequency regulation. Furthermore, employing Virtual Synchronous Machine (VSM) technology, these renewable energy units emulate the inertia and droop characteristics of Synchronous Generators (SG), enabling their equivalent modeling alongside traditional generators within a single-machine aggregate model. An SFR (System Frequency Response) model integrating renewable energy’s frequency regulation has been established. This model enables the analysis of the relationships between the system’s equivalent droop coefficient and the frequency nadir, nadir time, and quasi-steady-state point. Furthermore, the required equivalent droop coefficients are proposed for various sending-end system capacities and operating conditions. Finally, the model’s validity and accuracy are confirmed through a modified WSCC 4-machine 10-bus system, offering theoretical underpinnings for stable system operation and optimized operational planning.

Modeling Thermal Runaway Mechanisms and Pressure Dynamics in Prismatic Lithium-Ion Batteries

Lithium-ion batteries play a vital role in modern energy storage systems, being widely utilized in devices such as mobile phones, electric vehicles, and stationary energy units. One of the critical challenges with their use is the thermal runaway (TR), typically characterized by a sharp increase in internal pressure. A thorough understanding and accurate prediction of this behavior are crucial for improving the safety and reliability of these batteries. To achieve this, two new combined models were developed: one to simulate the thermal runaway and another to simulate the internal cell pressure. The thermal model tracks a chain of decomposition reactions that eventually lead to TR. At the same time, the pressure model simulates the proportional increase in pressure due to the evaporation of the electrolyte and the gases produced from the decomposition reactions. What sets this work apart is the validation of the pressure model through experimental data, specifically for prismatic lithium-ion cells using NMC chemistries with varying stoichiometries—NMC111 and NMC811. While the majority of the literature focuses on the simulation of temperature and pressure for cylindrical cells, studies addressing these aspects in prismatic cells are much less common. This article addresses this gap by conducting pressure validation experiments, which are hardly documented in the existing studies. Furthermore, the model’s accuracy and flexibility are tested through two experiments, conducted under diverse conditions to ensure robust and adaptive predictions of cell behavior during failure scenarios.

A novel late-stage oscillating discharge current for plasma regulation and its effect in material removal in electrical discharge machining

Abstract Improving the material removal rate (MRR) has recently become one of the most important issues in electrical discharge machining. During the discharge process, a large portion of molten material cannot be sufficiently expelled from the molten pool but re-solidifies, ultimately resulting in low energy utilization and machining efficiency. Unlike existing methods that primarily focus on optimizing general discharge parameters, this study aims to enhance molten material expulsion and MRR through discharge plasma regulation by employing a redesigned late-stage oscillating discharge current. During a single-pulse discharge process, this kind of discharge current firstly remains constant to ensure stable heat transfer from the plasma to the workpiece, then transitions to periodic oscillations to enhance plasma movement and facilitate molten material expulsion. High-speed plasma observations and heat-flow coupling simulations are conducted to analyze the effects of the discharge currents on material removal, and the optimal oscillation start time is obtained. Experimental results in machining stainless steel demonstrate that the use of the late-stage oscillating discharge current, in comparison to the conventional rectangular discharge current, results in a 74% increase in material removal volume per unit of energy and a 56% in average recast layer thickness.

Research on carbon emission accounting and low carbon operation methods for urban water supply systems

Under the environment of global warming, how to promote the innovative and efficient development of water supply system is the key to sustainable urban development. There is still room for improvement in the study of carbon emissions in urban water supply systems and there is a lack of appropriate rationale for low-carbon operation and management of waterworks. A water-energy-carbon (WEC) framework is established in Fuzhou to account for the carbon emissions from 2013 to 2022 and the level of coupling and coordination development is evaluated in this study. A multi-objective optimization model and a system dynamics (SD) model were developed to optimize the low-carbon operation of the water supply system and predict future climate impacts. We also provide a quantitative and qualitative evaluation method for low-carbon operation. The results show that carbon emissions generated by electricity consumption and chemical use in the water supply system contribute greatly, and the coupling coordination level is high. Under different scenarios, the optimal solutions of carbon emissions, carcinogenic risk factors and unit energy economy range from 1.63 to 3.82 kt CO2-eq, 4.4 × 10−5 to 2.7 × 10−4, and 0.26 to 0.73 RMB/MJ. In the SD model, the water supply system can achieve 17 % and 20 % carbon reduction in 2025 and 2030. Its carbon reduction direction is mainly reflected in public service water use. This study provides a reference for optimizing the operation of water supply systems.

Modeling root effects on soil detachment capacity using critical flow depth and unit energy of cross section in soils under Fraxinus excelsior L. species

The flow depth is an important hydraulic parameter for calculating other hydraulic parameters of overland flow. There is notable changes in hydraulic parameter when the roots of a plant develop in the topsoil. A power regression equation between soil detachment capacity (Dc) and unit energy of cross section (UEC) was established in soils under Fraxinus excelsior L. species based on the Froude number. For measuring Dc, samples collected from soils under the studied species and subjected to five slopes (from 13.9 to 33.9%) and five water discharges (from 0.39 to 0.77 l m−1 s−1) by a hydraulic flume. Compared with the soil with absence of root, the soil with presence of root had lower Dc. The results showed a strong power relationship between the unit energy of cross section and Dc, suggesting that soil detachment rate in rill erosion can be estimated using this hydraulic parameter (R2 = 0.84). This finding is particularly relevant for hillslopes with slopes from 12% to 31%, where the proposed mathematical model could be applied to predict Dc. Overall, this investigation supports a broader use of native species (such as the european ash Fraxinus excelsior L.), as a useful eco-engineering conservation practice and an alternative technique instead of utilizing artificial and expensive conservation practices.

Numerical simulation and energy consumption analysis of ventilation patterns in grain silo

Mechanical ventilation is an effective method to ensure the security of grain storage, which directly impacts the storage duration and storage quality. In this work, considering the coupling effect of grain physical parameters and gas-solid phase interaction on ventilation, the porous media, non-thermal equilibrium and turbulence models were employed to investigate the variation of velocity field and temperature field under four ventilation patterns: vertical ventilation duct (VD), transverse ventilation duct (HD), combined roof inhalation duct (CRD), and combined bottom inhalation duct (CBD). The relative standard deviation (RSD) and unit energy consumption were used to evaluate the performance of different ventilation patterns quantitatively. The results show a relative deviation of 5.12 % between simulation and experiments. Compared with VD and HD, CRD and CBD exhibit higher velocity values and gradient in the center of grain silo. The physical parameters of grain have obvious impacts on velocity field, and paddy has the highest velocity values due to its higher porosity. CRD has a significant advantage in cooling speed and effect, with the grain surface temperature at 12 m and 25 m lower than other patterns by 1.2 °C and 1.8 °C, respectively. The large porosity of paddy can advance cooling time by up to 5–10 h, while the lower specific heat capacity and higher thermal conductivity of peanut result in cooling temperatures 1.5 °C–2.4 °C lower than other grain. The temperature RSD of VD is lower than other ventilation patterns, and the unit energy consumption of CRD and CBD is better.

An ejector-enhanced dual-temperature R290 mechanical dehumidification cycle: Energy consumption, exergy, economic, and carbon footprint evaluation

Currently, the mechanical dehumidification based on the vapor compression is the commonly applied for air dehumidification. However, with the increasingly concerns about refrigerant alternative, using eco-friendly refrigerant such as R290 in the mechanical dehumidification cycle is become more important. Additionally, conventional mechanical dehumidification cycle (CMDC) have large irreversible throttling loss generated by expansion valve. Therefore, a modified ejector-enhanced dual-temperature condensation R290 mechanical dehumidification cycle (EDMDC) is proposed in this study to reduce the throttling loss by employing the ejector. Then, the energy and exergy utilization efficiency, investment cost and carbon footprint of the conventional and modified are analyzed and compared. The results demonstrated that the modified cycle performs better than the conventional cycle. Specifically, the coefficient of performance and volume cooling capacity of the modified cycle are improved by 14.0% and 13.9%, respectively, compared to the conventional cycle. Moreover, because of the applying of ejector, the throttling loss in the modified cycle is significantly reduced, which achieves a 13.6% improvement in exergy efficiency. On the other hand, although using ejector improves the initial investment of modified cycle, it could still achieve a 11.84% improvement in unit energy output cost. The assessment of carbon emissions shows that the modified system using R290 could reduce carbon emissions by 15.6% and 19.7%, respectively, compared to system using R32 and R134a. This proves the outstanding eco-friendly advantages of R290 in replacing high global warming potential refrigerants. Therefore, it is worthwhile to promote the application of R290 refrigerant in the mechanical dehumidification field.

Using process modeling and simulation to determine the sustainability of a novel lactic acid biorefinery in Europe: Influence of process improvements, scale, energy source, and market conditions

The biorefinery concept aims to produce multiple high-value products from bio-based feedstocks. One such product is lactic acid, which is used across several industries such as food, pharmaceuticals, cosmetics, and chemicals. Lactic acid yield is influenced by several factors, and improvements in performance are often first demonstrated at lab-scale, requiring prospective models which make assumptions about how the system will be optimized to understand the potential of a commercial-scale plant. This study assesses the economic and environmental sustainability of a proposed lactic acid biorefinery through the combination of process modelling, techno-economic assessment, and life cycle assessment. The case study proposes producing high purity lactic acid from industrial candy waste and liquid digestate in Denmark through lactic acid fermentation and downstream membrane separations. A base case is first modelled to determine the economic and environmental hotspots of the system; scenarios are then modelled where improvement methods are implemented reducing consumption of energy, chemicals, water, and the production of waste, upscaling the system, and integrating bioenergy. Finally, a cost sensitivity analysis is run varying bioenergy, water, chemical, and labor costs based on the European market. By optimizing unit processes, scale, energy sources and market conditions, the lactic acid unit production cost and global warming potential can be lowered by 94% and 80% compared to the base case, respectively. However, these are optimized in different scenarios, indicating a trade-off in optimizing economic and environmental criteria. As even best-case lactic acid unit production cost is found to be 141–232% higher than market price, this production pathway will require further improvement or market changes before it can be commercially viable.

Death of California Solar? The Impact of Net Metering Policy on Californian Solar Installations

Since 1995, net metering policy has provided a constant incentive for customers of California’s Investor-Owned Utilities (IOUs) to install solar panels. Under the IOUs’ net metering programs, customers with solar systems receive a full retail rate credit for each unit of excess energy they generate and export back to the grid. This has allowed customers with an appropriately sized solar system to zero out their electricity bills, applying credits from hours when they generate excess solar energy towards the cost of non-solar energy use. However, in December 2021, the California Public Utilities Commission (CPUC) announced plans to significantly alter net metering policy beginning April 15, 2023. Under their new policy, colloquially referred to as “NEM3,” export credits are aligned with utilities’ avoided costs rather than customers’ retail rates, resulting in a roughly 80% reduction in excess generation compensation. However, NEM3 only applies to new solar customers; customers who interconnected their system before April 15 were grandfathered into a full retail rate net metering program for 20 years, providing a major incentive to install solar before this date. This paper uses a difference-in-differences model approach to estimate the impact of the CPUC’s announced plans to alter net metering programs on solar installation levels. The results suggest that the CPUC’s plans spurred a statistically significant 0.396% point, or 31%, increase in month-over-month installation growth in the IOUs. This increase implies customers are responsive to changes in net metering policy and suggests decreases in Californian residential solar installations post-implementation of NEM3 are likely.

Mixing-controlled compression ignition of ethanol using exhaust rebreathe at a low-load operating condition—Single cylinder experiments in a heavy-duty diesel engine

As pollutant emissions regulations in the heavy-duty sector become further stringent, the energy requirements in this sector continue to increase. Due to the high-power density and operating period requirements within this sector, full electrification is challenging. A viable solution to meet the stringent requirements for criteria pollutant and greenhouse gas (GHG) emissions is the use of low carbon renewable fuels. Low carbon renewable fuels are desirable due to their lower carbon content per unit energy compared to conventional fossil diesel fuel. However, implementing some low carbon renewable fuels in the heavy-duty sector poses challenges due to their low reactivity and the prevalent mixing-controlled compression ignition (MCCI) combustion strategy. Because of this, ignition assistance is needed to ignite low reactive renewable fuels in MCCI. This work investigates the use of a variable valve actuation (VVA) strategy, exhaust rebreathe, as an ignition assistance method to ignite pure fuel grade ethanol (E98) in MCCI. Exhaust rebreathe utilizes the hot combustion products from the previous cycle by reinducing the exhaust back into the cylinder during the intake stroke from a secondary exhaust valve event. The reinduction of exhaust into the cylinder increases the in-cylinder bulk gas temperature aiding in the ignitability of the low reactive fuel. The exhaust rebreathe strategy as an ignition assistance method is investigated in this work by conducting single cylinder engine experiments on a heavy-duty diesel engine fueled with E98. Exhaust pressure is varied for the exhaust rebreathe strategy to achieve combustion characteristics with E98 similar to diesel at a low-load, high engine speed operating condition. Additionally, an elevated intake air temperature strategy is implemented to compare to the exhaust rebreathe strategy as another form of ignition assistance with the objective to induce heat in-cylinder prior to combustion without the presence of diluent. Furthermore, zero-dimensional (0D) constant pressure chemical kinetic simulations are conducted to evaluate the most reactive conditions for ethanol to achieve ignition delay times similar to n-heptane. The experimental results demonstrate that at a high speed, low load condition—the elevated intake air temperature strategy with ethanol requires 120°C intake temperature to yield an ignition delay similar to diesel. When accounting for the energy required to heat the intake air, the brake thermal efficiency is 40% lower than the diesel baseline. On the contrary, the exhaust rebreathe strategy with an exhaust pressure of 1.5 bar-a, is able to achieve the same ignition delay with an MCCI combustion process but maintain a brake thermal efficiency within 5% of the baseline diesel engine.

Optimal Design of Water Distribution System Using Improved Life Cycle Energy Analysis: Development of Optimal Improvement Period and Unit Energy Formula

Water distribution systems (WDSs) are crucial for providing clean drinking water, requiring an efficient design to minimize costs and energy usage. This study introduces an enhanced life cycle energy analysis (LCEA) model for an optimal WDS design, incorporating novel criteria for pipe maintenance and a new resilience index based on nodal pressure. The improved LCEA model features a revised unit energy formula and sets standards for pipe rehabilitation and replacement based on regional regulations. Applied to South Korea’s Goyang network, the model reduces energy expenditure by approximately 35% compared to the cost-based design. Unlike the cost-based design, the energy-based design achieves results that can relatively reduce energy when designing water distribution networks by considering recovered energy. This allows designers to propose designs that consume relatively less energy. Analysis using the new resilience index shows that the energy-based design outperforms the cost-based design in terms of pressure and service under most pipe failure scenarios. The implementation of the improved LCEA in real-world pipe networks, including Goyang, promises a practical life cycle-based optimal design.

Generation of heat and electricity load profiles with high temporal resolution for Urban Energy Units using open geodata

Urban areas account for up to 87% of global energy consumption, with around a third of CO2 emissions from the building sector. Germany recently enacted a law targeting carbon neutrality in heating by 2045, requiring all municipalities to submit transformation plans for their heating infrastructure. Many are in early stages and need innovative methods to achieve these goals. This study proposes an automated GIS-based approach to generate heat and electricity load profiles for geographically referenced residential buildings and districts in Germany, using only open data. The methodology offers hourly temporal resolution and spatial detail from individual buildings to Urban Energy Units (UEUs), a concept introduced in prior studies. Nine distinct heating load profiles and nine electricity load profiles were identified. These profiles can adapt to different weather datasets and to three building refurbishment scenarios. The methodology and energy analysis were applied to a district in Oldenburg, Germany, demonstrating the model’s flexibility under varying boundary conditions. For this district, the analysis revealed a total heat demand of 9.9±7 GWh/a and an electricity demand of 2.3±0.126 GWh/a, with respective errors of 45% and 39% when compared to other local data, this demand is presented in both yearly and hourly resolutions. This methodology intends to support German municipalities by accelerating the initial phases of the municipal heating plans and deliver high-quality data on building heat and electricity demand.

Quantum chemical investigations into the structural and spectroscopic properties of choline chloride-based deep eutectic solvents

The chemical process industries are progressively embracing green technologies and sustainable waste management techniques due to growing environmental concerns and the impact of climate change. Deep eutectic solvents (DESs), formed by combining neutral molecules (e.g., choline chloride, ChCl) with hydrogen bond donors, have emerged as promising eco-friendly solvents with diverse applications in chemical, pharmaceutical, and separation processes. In this context, modern quantum-based research is focused on eutectic mixtures, particularly those formed by ChCl as a hydrogen bond acceptor with various hydrogen bond donors at specific mole ratios. The properties and validity of these DESs are investigated through density functional theory (DFT) analysis of their molecular dynamics simulations. This quantum computational approach offers valuable insights for designing the desired conductive liquids. Furthermore, the density of states analysis allows for studying the electronic structure and quantifying the number of states occupied per unit of energy. The quantum and vibrational properties of experimentally synthesized DESs are simulated using DFT B3LYP/6–31G(d,p). Current research aims to design and understand the properties of eutectic solvents to develop novel, environmentally benign alternatives for the chemical industry.

A fully enclosed wave energy converter and effects of cable-based PTO on power absorption

Abstract Existing wave energy converters (WECs) are limited by high unit energy costs, narrow bandwidths and vulnerability to seawater corrosion, making it difficult for wave energy to compete with solar and wind energy. This paper presents a fully enclosed WEC based on cable-driven parallel mechanisms, which absorbs energy from multiple directions to enhance the total energy absorption efficiency and bandwidth. The configuration of the inner cable-parallel mechanism (CDPM) is the key to this improved absorption efficiency. A configuration synthesis method of cable-driven parallel mechanisms is proposed to generate more configurations for the fully enclosed WEC. The motion equation of the fully enclosed WEC is derived to evaluate the power absorption performance. Moreover, a configuration synthesis method for realizing n-DOF configurations in the fully constrained CDPMs is proposed, and the configurations of these n-DOF fully-constrained CDPMs with (n + 1) cables are acquired. Then, the power absorption performance under different PTO parameters and wave frequencies is calculated, and the effects of the CDPM configuration are investigated. The results indicate that the proposed WECs exhibit excellent performance in mean absorbed power and bandwidth. Several principles for configuration selection are provided to further improve the performance of the CDPM-based fully enclosed WEC.

Low-carbon economic optimization strategy for industrial loads in parks considering source-load-price multivariate uncertainty

A low-carbon economic optimization method is proposed for industrial loads in parks considering multivariate uncertainty. Model of dynamic load node carbon intensity is proposed considering the uncertainty of clean energy and dynamic conventional units carbon intensity based on system currents. The robustness is improved based on multi-interval uncertainty set. The gap is filled by hybrid copula model with Generalized Autoregressive Conditional Heteroskedasticity (GARCH) prices in the uncertainty model. The GARCH is used to built the marginal distribution function of prices, and a hybrid copula model is proposed to obtain the joint probability density function based on the weights calculated by Euclidean distance. The LNCI probability distributions of the regulation potential of loads are proposed with the virtual energy storage and the virtual power model to improve the descriptive ability of uncertainty based on the expansion and contraction functions. Finally, the typical scenarios are extracted based on Monte Carlo and Wasserstein measures. The Column sum Constraint Generation algorithm and strong duality theory are used to get the robust-stochastic optimization. The method proposed in the paper has a positive effect on enterprises to rationalize their production schedules, reduce electricity and carbon emissions costs and increase the revenue from participating in grid regulation.

State primary standard for units of absorbed dose and absorbed dose rate of photon, electron, proton radiation and in carbon ion beams, quantity, fuence, fux density and energy of particles in proton beams and heavy charged particles GET 38-2024

The problem of ensuring the accuracy and traceability of the measurement results of the absorbed dose in carbon ion beams, as well as the measurement results of the amount, fluence, flux density and energy of particles in proton and heavy charged particles beams is considered. Until now, in practice, these values have been measured only by indirect methods. The lack of approved measuring instruments for the quantities under consideration and the metrological traceability of measurement results of these quantities to standards did not allow achieving consistency of measurement methods used in practice and confirming the reliability of the results obtained. To solve this problem, three measuring complexes have been developed and created, which are included in the State Primary Standard of units of absorbed dose and absorbed dose rate of photon, electron, proton radiation and in carbon ion beams, quantity, fluence, flux density and energy of particles in proton and heavy charged particles beams GET 38-2024. The measuring complex for reproducing the unit of absorbed dose in carbon ion beams consists of an adiabatic calorimeter, a thermostating system, a data collection and processing system and a vacuum pumping station. To reproduce the unit of energy of protons and heavy charged particles, a complex has been implemented, which includes a total absorption calorimeter, a data collection and processing system, a vacuum pumping station and a particle count determination system based on the use of a Faraday cup. To reproduce the units of fluence and particle flux density in proton and heavy charged particles beams, a measuring complex has been created containing a Faraday cup, a set of collimators and a low current meter. The schemes, the principles and the results of studies of the metrological characteristics of the developed measuring complexes are described. The results are relevant for the field of radiation therapy and radiation resistance tests of the electronic component base used in the space industry.

Design and optimization for a longitudinal-flow corn ear threshing device of low loss and low energy consumption

The traditional corn grain harvester threshing device has the problems of high grain breakage rate, high unthreshed grain rate and high energy consumption when harvesting high water content corn ears. A longitudinal-flow corn ear threshing device and its measurement and control system were proposed to overcome these problems. The working performance and energy consumption of the threshing device were optimized by conducting three factors and five levels corn ear threshing experiments. The experiments took the threshing cylinder speed (X1), threshing gap (X2), and guide vane angle (X3) as the experimental factors, and the grain breakage rate (Y1), unthreshed grain rate (Y2), unit energy consumption (Y3), and threshing concave pressure (Y4) as the experimental indicators. According to the experimental results, the quadratic polynomial regression models between experimental indicators and experimental factors were established. Through models optimization, the optimal working parameters for the threshing device were obtained as X1 at 392.40 r/min, X2 at 40.70 mm, and X3 at 33.16°. Through conducting verification experiment, it was found that under the optimal parameters, the experimental indicators were Y1 at 2.32 ± 0.06 %, Y2 at 0.48 ± 0.04 %, Y3 at 2.14 ± 0.10 kJ/kg, and Y4 at 46.28 ± 3.23N. The errors between the experimental results and the quadratic polynomial regression models were less than 5 %, which indicated that the models had high prediction accuracy. Compared with the unoptimized experimental indicators, the optimized experimental indicators Y1, Y2, Y3 and Y4 decreased by 36.26 %, 39.24 %, 14.74 % and 16.27 %, respectively. The working performance of the threshing device was significantly improved, and the energy consumption was significantly reduced. The relevant research could provide reference for the optimization of the mechanical structure and working parameters of the corn ear threshing device.

The study of active support for energy storage system in system frequency regulation

Abstract As the penetration of new energy sources increases, the proportion of traditional energy units continues to decline, reducing the inertia and primary frequency regulation capability of the power system. Therefore, exploring the frequency support capabilities of energy storage systems with low inertia is crucial. Based on this, this paper first proposes an active frequency support method for energy storage system based on a Voltage Source Virtual Synchronous Generator (VSG), aiming to enhance system inertia and reduce response delay. Based on this issue, a parameter tuning optimization selection model based on the Transient Search Optimization (TSO) algorithm is proposed to determine the optimal power output and best frequency regulation parameters for the energy storage system. Finally, the model proposed in this paper is applied to the IEEE 14-bus system to verify its effectiveness.

Activation of peroxymonosulfate by MnOOH/g-C3N5: Study on highly selective removal of phenolic pollutants and its non-radical pathway

In this research, the MnOOH/g-C3N5 material was successfully synthesized, demonstrating its efficacy in selectively removing phenolic organic pollutants. This material outperformed traditional free radical pathways, exhibiting higher selectivity, enhanced persulfate utilization efficiency, and strong resistance to background anions and complex organic matter. Using phenol as the target pollutant, the MnOOH/g-C3N5/PMS system achieved 81 % mineralization, a PMS utilization efficiency of 88 %, and a 75 % process unit energy consumption value in degrading phenol. This efficient degradation is attributed to the synergistic effects of high-valence metal oxides (MnV(O)/MnIV(O)), singlet oxygen (1O2), and electron transfer complexes, as confirmed by electrochemical analysis and In-situ EPR. Additionally, Transmission Electron Microscopy observations disclosed the development of an amorphous shell on the MnOOH/g-C3N5 surface post-reaction. Electrochemical Impedance Spectroscopy analysis suggested an enhanced charge transfer resistance, further affirming the role of MnOOH/g-C3N5 as an "electron transfer station" in the electron transfer process, accompanied by the formation of electron transfer complexes. This study provides crucial scientific insights and theoretical guidance for applying MnOOH/g-C3N5 materials in environmental engineering.

A two-stage bi-level electricity-carbon coordinated optimization model for China's coal-fired power system considering variable renewable energy bidding

With China's grid-connected large-scale variable renewable energy, coal-fired power system is progressively changing from being the main supplier of electric energy to providing flexibility services. The coal-fired power system must increase operating efficiency during this transition process by considering the technical characteristics of various coal-fired power units. Additionally, the trading strategies of coal-fired power units in the electricity-carbon market are impacted differently depending on the extent of VRE penetration. This paper innovatively considers these two factors and proposes a two-stage bi-level clearing model in electricity-carbon joint market to coordinate the synergistic development of variable renewable energy and coal-fired power. The upper level of the model aims to maximize the total profits of the coal-fired power system and variable renewable energy units, while the lower level of the model minimizes the total purchasing costs. Coal-fired power units and variable renewable energy units compete to sell electric energy, with the latter buying peaking regulation from the former. The research results indicate that the proposed model can significantly reduce 66.79 % carbon emissions, increase 33.96 % non-fossil variable renewable energy integration and optimize the generation structure of coal-fired power system.