Renewal Rate Research Articles

Optimization method for capacity of BESS considering charge‐discharge cycle and renewable energy penetration rate

AbstractIn order to achieve the “carbon peaking and carbon neutrality” goals, we must vigorously develop renewable energy power generation. As the penetration of renewables progressively escalates, the corresponding demand for battery energy storage systems (BESS) within the power grid rises concomitantly. This paper presents an innovative optimization approach for configuring BESS, taking into account the incremental variations in renewable energy penetration levels and BESS charge‐discharge cycles. Employing incremental analytical techniques and pivotal metrics such as capacity elasticity, the proposed method determines the optimal penetration rate and corresponding BESS capacity outcomes for deploying energy storage systems. An example analysis of a rural power distribution benchmark is carried out by using the method in this paper, which proves the effectiveness of the method in this paper. This methodology was substantiated through its application to a case study of a rural power distribution benchmark, thereby validating its efficacy. Furthermore, it was compared with the particle swarm optimization, providing a comparative assessment of their relative performance.

Global Optimization and Quantitative Assessment of Large-Scale Renewables-Based Hydrogen System Considering Various Transportation Modes and Multi-Field Hydrogen Loads

In the past, hydrogen was mostly produced from fossil fuels, causing a certain degree of energy and environmental problems. With the development of low-carbon energy systems, renewable energy hydrogen production technology has developed rapidly and become one of the focuses of research in recent years. However, the existing work is still limited by small-scale hydrogen production systems, and there is a lack of comprehensive research on the whole production-storage-transportation-utilization hydrogen system (PSTUH2S), especially on the modeling of different hydrogen transportation modes and various hydrogen loads in different fields. To make up for these deficiencies, the specific physical and mathematical models of the PSTUH2S are firstly described in this paper, with a full account of large-scale water-electrolytic hydrogen production from renewable power curtailment and grid power, various hydrogen storage and transportation modes, and multi-field hydrogen consumption paths. Furthermore, to achieve the maximum economic, energy, and environmental benefits from the PSTUH2S, a multi-objective nonlinear optimization model is also presented herein and then solved by the hybrid method combining the nonlinear processing method, the CPLEX solver and the piecewise time series production simulation method. Lastly, case studies are conducted against the background of a region in northwest China, where hydrogen consumption capacity in various years is accurately assessed and the potential advantages of the PSTUH2S are demonstrated. As the simulation results show, the power curtailment of renewable energy generation can be reduced by 3.61/11.87/14.72 billion kW·h in 2025/2030/2035, respectively, thus contributing to a 4.98%~10.09% increase in the renewable energy consumption rate and millions of tons of carbon emission reduction in these years. In terms of the total equivalent economic benefits, the proposed method is able to bring about a cost saving of USD 190.44 million, USD 634.66 million, and USD 865.87 million for 2025, 2030, and 2035, respectively.

Optimizing government strategy for deep decarbonization in towns: A game theory approach incorporating energy storage services

Renewable district energy systems present a promising solution for decarbonizing the energy sector. However, optimal strategies to mitigate the financial challenges of deep decarbonization are still underexplored. This study aims to optimize government subsidy strategies and users' system designs to facilitate cost-effective deep decarbonization using game theory. Two indicators, the renewable generation rate (RGR) and the self-sufficiency rate (SSR), are formulated to understand the principles of achieving deep decarbonization. Additionally, the study introduces a new strategy called subsidy plus energy storage service (SUB + ESS), contrasting it with the traditional subsidy-only strategy. Key findings indicate that merely increasing the RGR requirements does not achieve deep decarbonization due to energy mismatches. Restricting the SSR requirements proves effective in achieving deep decarbonization but imposes a significant economic burden on the government. When the SSR requirement is set at 100%, carbon emissions are reduced by 93%, but the government's subsidy expenditure increases nearly fivefold. In contrast to the subsidy-only strategy, the novel SUB + ESS strategy, with a 100% SSR requirement, reduces government expenditure by approximately 52% and lowers total expenditure by 19.7%. A two-stage decarbonization strategy is proposed: initially, offering subsidies is sufficient, but as deeper decarbonization is pursued, establishing energy storage service becomes essential.

Differential metal and metalloid contents in fresh and cooked Charu mussels (Mytella charruana) from a southeastern Brazilian estuary and associated human health risks

Sepetiba Bay, a key estuarine ecosystem in southeastern Brazil, faces significant metal inputs, with a differential pollution gradient from the bay's entrance to inner areas, raising environmental and public health concerns. This study assessed metal levels in fresh and cooked samples of highly consumed Charu mussels (Mytella charruana) from three bay areas, one near the bay entrance (P1), with higher water renewal rates, one in the northern bay area (P2) and one the eastern bay (P3), presenting lower water renewal rates. Variations in metal and metalloid concentrations across sites were observed, with P3 exhibiting higher levels in fresh mussels for most elements, except for As, which was higher at P2 (0.35 ± 0.45 mg kg−1). Cooked samples demonstrated similar trends for Cu (1.30 ± 0.39 mg kg−1), Ni (0.28 ± 0.20 mg kg−1), and V (0.75 ± 0.28 mg/kg−1), indicating that cooking in contaminanted estuary water does not significantly reduce contamination. Significant differences were detected for Ni, Cd (0.014 ± 0.008 mg kg−1), Zn (14.28 ± 2.50 mg kg−1), and V at P1, which were significantly higher than at P3. Significant Fe (246 ± 68 mg kg−1), Al (109 ± 33 mg kg−1), and Mn increases were observed from P1 to P3. Mussels sampled from P3, near an abandoned military area and urban center, exhibited high Fe and Al levels, attributed to both natural processes and industrial activities. Metal concentrations in Charu mussels often exceeded regulatory limits set by Brazilian, North American, and European agencies. Calculated Se molar ratios indicate that while Se can mitigate Hg toxicity, high Hg levels in Sepetiba Bay's Charu mussels still pose significant health risks. Similarly, high levels of Ag, Cd, and Pb suggest ineffective Se protection. However, Se appears effective against As toxicity. The Health Benefit Value of Selenium (HBVSe) indicate Se's overall protective benefits against Hg toxicity. Higher HBVSe values in cooked mussels at P1 and P2 suggest that cooking increases Se bioavailability. However, raw mussels at P3 had higher HBVSe values than cooked ones, highlighting the need for site-specific assessments. Calculated Hazard Indices indicate general high health risks from mussel consumption, and As levels in Charu mussels indicate high carcinogenic risks. These findings emphasize the need for comprehensive Charu mussel monitoring and environmental management efforts at Sepetiba Bay.

An advanced kernel search optimization for dynamic economic emission dispatch with new energy sources

Integrating renewable energy sources, such as wind and photovoltaic power generation, into the power grid is crucial for sustainable power system development and mitigating pollutant emissions. However, these sources’ inherent uncertainty and randomness pose significant challenges to grid operations. Metaheuristic algorithms offer efficient solutions to optimization problems in this context and are widely employed in practice. Kernel Search Optimization (KSO) has emerged as a prominent metaheuristic algorithm due to its parameter-free nature and applicability to power dispatch problems. Nevertheless, KSO’s limited local search capabilities necessitate enhancements for improved performance. This paper introduces an enhanced variant of KSO, termed Upgraded Kernel Search Optimization (UKSO), which incorporates differential evolution techniques, including mutation, crossover, and selection mechanisms, to bolster KSO’s search capabilities and overall performance. The efficacy and feasibility of UKSO are evaluated through comprehensive testing using the CEC2017 benchmark. Comparative analysis demonstrates that UKSO outperforms other algorithms by achieving more optimal solutions. To address power dispatch challenges in the context of renewable energy sources, a Two-Time Energy Dispatch (TTED) model is proposed, leveraging a weighted summation approach to minimize total fuel costs and pollution emissions simultaneously. The application of the Prophet model, based on Bayesian fitting, facilitates accurate prediction of wind and photovoltaic power outputs. Through experimentation across small (8 and 14 units) and large (58 units) systems, the feasibility of UKSO and TTED is validated. In complex scenarios, UKSO demonstrates a 0.69% to 3.64% reduction in pollution emissions and a 0.99% to 1.23% decrease in economic costs compared to KSO under varying weight configurations. Furthermore, UKSO achieves a renewable energy generation utilization rate exceeding 90%, emphasizing its ability to iterate efficiently through complex problems and its efficacy in addressing renewable power dispatch challenges. These results highlight the practical significance of UKSO in optimizing power systems and provide valuable insights for future research and applications in this domain.

Multi-objective optimization method for medium and long-term power supply and demand balance considering the spatiotemporal correlation of source and load

The medium and long-term supply-demand imbalance of the power system in the context of the new power system is becoming more and more prominent due to the fluctuation and intermittency brought about by the high proportion of new energy sources connected to the grid. In this regard, a multi-objective power supply-demand balance optimization method considering the spatiotemporal correlation of source and load is proposed in this work. First, the autocorrelation and inter-correlation characteristics of source and load are analyzed. On this basis, a multi-dimensional scenario set construction method considering the spatiotemporal correlation of source and load is proposed. Then, the planning capacity of each regional power source and the system operation under each scenario are taken as the optimization variables. Renewable energy electricity curtailment, equivalent annual total cost, and inter-region transmission electricity are taken as the optimization objectives. Various constraints such as power source planning and operation, power balance, inter-region power transmission, and renewable energy power curtailment rate are considered comprehensively. The optimization method for the medium and long-term power supply and demand balance is proposed. Finally, the method is applied to Hunan Province, China to guide power planning. The results show that compared with traditional multi-dimensional correlation scene construction methods, the average probability density functions error of wind turbine output, photovoltaic output, and load constructed in this work decrease by 44.08 %, 73.64 %, and 57.54 %, respectively. It takes into account the regional, temporal, temporal autocorrelation, and inter-correlation of the source and load, and has similar characteristics to historical data. Compared with traditional planning that only considers economy, the optimization plan for power supply and demand balance in this work reduces electricity curtailment and inter-region transmission by 97.04 % and 72.71 %, respectively, balancing renewable energy consumption, economy, and regional independent balancing indicators.

Effect of L-Glycine on Carcass Parameters, Blood Biochemicals, and Jejunal Histomorphometry of Commercial Broiler Chicken

A study was conducted for duration of six weeks on 240, day-old Cobb-430Y broiler strain chicks and randomly distributed to four groups each containing three replicates and 20 chicks per replicate. Group A was Negative Control (NC) contained 3% Low Protein (LP) diet containing 19.50, 18.00 and 16.50% crude protein (CP) for broiler pre-starter, starter and finisher phases, respectively. Positive Control (PC) group B contained standard protein 22.50, 21.00, and 19.50% CP as per breeder recommendation. No L-Glycine was added to NC and PC diets. Group C (NC+Gly1) was formulated by adding 0.640, 0.810, and 0.630% L-Glycine in NC diet to arrive 2.30, 2.30, and 2.00% digestible (Dig.) Gly + Ser levels while group D (NC+Gly2) was formulated by supplementation of 0.755, 0.985, and 0.740% L-Glycine in NC diet to arrive 2.40, 2.40, and 2.10% digestible Gly + Ser levels in broiler pre starter, starter and finisher diets respectively. Digestible Gly + Ser levels of NC group were 1.71, 1.56 and 1.43%; and of PC group were 2.02, 1.91 and 1.76%, respectively for broiler pre starter, starter and finisher diets. Ratio of dig. Met, Thr, Trp, Arg, and Val. ratioed to Lys. were balanced in all diets. All diets were isocaloric (3010, 3100, and 3200 kcal ME /kg) for broiler pre starter, starter and finishaer phases, respectively. Results showed that the L-Glycine supplementation in AA-balanced 3% LP diet did not affect per cent eviscerated yield, giblet yield, ready-to-cook yield, and breast meat yield but helped to reduce abdominal fat without altering serum biochemical parameters. Dig. Gly + Ser levels of 2.30, 2.30, and 2.00% (L-Glycine levels of 0.640, 0.810, and 0.630%) in 3% low protein (19.50, 18.00, and 16.50% CP) for broiler pre starter, starter and finisher diets helps to improve jejunal crypt depth leads to increasing cell renewal rate and maturation in the gut. Incorporation of L-Glycine is recommedded to maintain Dig. Gly + Ser levels of 2.30, 2.30, and 2.00% in broiler pre starter, starter and finisher phases with reduction of 3% CP in breeder recommended commercial broiler diet. Reducing dietary crude protein using L-Glysine without harming broiler performance could be economical.

Industrial Park low-carbon energy system planning framework: Heat pump based energy conjugation between industry and buildings

The accelerating urbanization, rapid industrial development, and excessive consumption of fossil fuels pose survival challenges such as energy depletion and environmental degradation for humanity. In the context of industrial park development, constructing a low-carbon energy system, increasing the proportion of renewable energy, enhancing energy-level matching, and utilizing heat pumps for deep waste heat recovery are effective approaches to reduce fossil energy consumption and alleviate environmental pressures. Addressing issues such as diverse thermal flows in industrial sites, complex electricity-heat-cooling energy demands, and unclear industrial-building energy coupling mechanisms, this paper proposes a two-stage planning framework, comprising the following five steps: (1) constructing a waste heat utilization system centered around heat pumps, (2) establishing a mechanism for matching heat sources, equipment, and thermal sinks, (3) establishing an energy conversion model and energy quality quantification system, (4) optimizing waste heat utilization path allocation, and (5) conducting a system energy flow analysis. Case studies demonstrate that the proposed system achieves optimized matching of multiple heat sources and sinks in industrial and building scenarios through thermal integration, meeting diverse energy demands in the park, including electricity, cooling, and multi-grade heat. After coupling with traditional steam pipeline networks, the annual total cost and annual steam power consumption decrease by 33% and 39% respectively, with a waste heat contribution rate of up to 26% and a renewable energy penetration rate of up to 25%, and a waste heat recovery system payback period of 6 years. By establishing an energy quality quantification system and conducting multi-objective optimization considering losses and economic costs, this paper provides Pareto frontier solutions, offering references for engineering proposals. The proposed networked waste heat recovery system is characterized by low energy consumption and high economic efficiency, effectively integrating the energy characteristics of industrial parks and demonstrating engineering applicability.

A two-layer and three-stage dynamic demand response game model considering the out of sync response for gases generators

Traditional integrated demand response model lacks evaluation mechanism during the response process, posing a risk of over-response and excessive changes in the original power consumption order. To address this issue, a two-layer and three-stage dynamic demand response game model is proposed on the load side, which considers the internal game of response loads, and the absolute loads time nodes of “peak-flat-valley”are set as the response signals. And the demand response strategy of this phase will be formulated based on the response evaluation results of the previous phase. On the power generation side,an analysis is conducted focusing on the out-of-sync response of gases generators caused by time delay in gas networks. Ensuring a stable energy supply since it serves as a prerequisite for effective demand response actions. Finally, four possible game schemes are proposed considering the priority of demand response loads. The case study demonstrates this proposed demand response strategy can increase original power consumption maintenance order rate to 95.82% and power supply reliability to 98.33%. Besides, the renewable energy curtailment rate and demand response cost are reduced by 4.64% and 51.43%, respectively.

Spatial Analysis on Resource Utilization, Environmental Consequences and Sustainability of Rice–Crayfish Rotation System in Jianghan Plain, China

The rice–crayfish rotation system (RCR), originating in the Jianghan Plain, is developing rapidly in various regions of China and has been characterized by unbalanced regional development, which has also led to widespread concerns and discussion on its environmental impacts and sustainability. This study selects representative RCR production areas in the Jianghan Plain, including Jianli, Qianjiang, Shishou, Shayang, Gong’an and Honghu, to analyze resource inputs, resource utilization efficiency, environmental impacts and sustainability by employing the emergy analysis method. Our analysis of Jianli, Honghu, Qianjiang, Gong’an, Shishou and Shayang reports total emergy inputs ranging from 6.46 × 1016 to 8.25 × 1016, with renewable rates between 78.38% and 84.34%. Shishou leads in the unit emergy value (5.58 × 10−1) and the emergy yield ratio (5.30). The sustainability evaluation finds that the environmental loading ratio is from 0.19 to 0.28 and the emergy index for sustainable development varies between 1.27 and 3.00. This analysis indicates that the southern regions have higher inputs and efficiency, with southeastern areas showing lower environmental impact and higher sustainability. We also underscore the impact of non-renewable resources on environmental outcomes and sustainability, suggesting tailored development strategies for the rice–crayfish rotation system’s optimization and sustainable growth.

Optimal dispatch of integrated electricity and heating systems considering the quality-quantity regulation of heating systems to promote renewable energy consumption

The integrated electricity and heating system (IEHS) can improve energy efficiency and promote renewable energy consumption. When quality-quantity regulation (QQR) is adopted, namely adjusting hydraulic and thermal conditions of heating system, the increase in operation flexibility is more remarkable. However, present IEHS dispatch models considering QQR overlook hydraulic characteristics of valves and variable frequency pumps resulting in inexecutable dispatch results easily and hindering IEHS's flexibility potential. Furthermore, loop networks and the access of multiple heat sources in heating systems may lead to flow reversal, but current research adopts a fixed flow direction which suppresses the potential of flow reversal to improve flexibility. In this paper, we propose an IEHS dispatch model considering QQR to promote renewable energy consumption, which considers hydraulic characteristics of valves and variable frequency pumps, and flow reversal. Specifically, we introduce two binary flow direction labels for every branch in heating system model and then the IEHS dispatch model which can deal with flow reversal is established. A sequential solution process combining linear and nonlinear optimization is formulated to overcome the non-convex feature of IEHS dispatch model. Specifically, piecewise linearization and piecewise McCormick relaxation are combined to handle complex nonlinear terms in the dispatch model. Therefore, a mixed integer linear programming model is obtained and solved, of which results are used as initial values for nonlinear optimization. Results in the case study show that operation cost is decreased by 0.97 % and renewable power consumption rate is increased from 83.31 % to 84.42 % after considering valve adjustment. Operation cost is further decreased by 6.06 % and renewable power consumption rate is increased to 94.04 % after considering flow reversal.

Selection of an economics-energy-environment scheduling strategy for a community virtual power plant considering decision-makers’ risk attitudes based on improved information gap decision theory

To address the impact of decision-makers' risk attitudes (DMRA) and uncertainties on dispatch strategy in community integrated energy systems, a multi-objective dispatch model of a community virtual power plant (CVPP) is proposed. Firstly, a novel CVPP model that considers DMRA and a multi-objective satisfaction model of economics-energy-environment are built. Secondly, the information gap decision theory (IGDT) model is improved by considering uncertainties of renewable energy, loads, and DMRA. Thirdly, the VIKOR method is improved by using the weights from multiple objective functions derived by combining the entropy weight and full consistency method. And the conservative and risky strategy selection methods in the VIKOR method are used to select the optimal strategy from the obtained multi-objective Pareto solution set that satisfies decision-makers with risk preferences. Thus, the impact of DMRA on optimal strategy selection is fully described. Finally, the proposed model's effectiveness is validated using a multi-scenario example of a residential area. The results indicate that: 1) The novel CVPP provides realistic scheduling strategies based on the DMRA. 2) After implementing demand response, the resident cost and net carbon emissions are reduced by 9 % and 91 %, respectively. Energy supplier profit and renewable energy utilization rate are increased. The constructed IGDT model also improves multiple objectives. 3) The improved IGDT model's uncertainty and deviation factors allow for diverse scheduling strategies. Simultaneously, the improved VIKOR method provides a new method for decision-makers to select strategies. The model is a guide for selecting scheduling strategies and a way of encouraging the usage of renewable energy.

Features of the microstructural organization of the small intestine in weaning piglets

The material for the study was fragments of the wall of the duodenum, jejunum and ileum obtained from five piglets at the age of 41 days. The selected tissue samples were fixed during the day in a 10.0% solution of neutral formalin. Their further processing in order to obtain histological sections was carried out according to a generally accepted method. The obtained histological sections were stained with hematoxylin and eosin and according to Van Gieson. All morphometric data obtained were subjected to statistical processing.It was found that in the studied animals, the small intestine is arranged in accordance with the general plan of structure peculiar to mammals. Its wall is formed by the mucous membrane, submucosal base, as well as muscle and serous mem-branes. The epithelial layer of the mucous membrane of the small intestine is represented by a single-layer prismatic epithelium, which is a highly dynamic structure that quickly reacts to changing loads due to the high rate of cell renewal. The bulk of the epithelial layer is represented by edged enterocytes (about 90.0% of the entire cell population). In addition to them, goblet-shaped, endocrine, Panethovian, proliferating and stem cells take part in the formation of the epithelial lining of the small intestine.

Two-stage stochastic programming for multi-objective optimization of sustainable utility systems integrating with combined heat and power units

Utility systems provide thermal energy and power for industrial processes while emitting significant amounts of carbon dioxide. This study investigates the integration of Combined Heat and Power (CHP) units and renewable energy sources into utility systems in the context of diverse energy demands and low-carbon operations. A two-stage stochastic programming model (TSSP) is proposed for sustainable utility systems. The main objective of the model is to minimize the annual total cost and the other two objectives are to maximize renewable energy penetration rate and minimize grid net interaction level. The model tackles renewable energy sources’ uncertainty and evaluates environmental metrics by computing carbon emission costs. In TSSP, the first stage involves new equipment capacity planning. The second stage involves considering uncertainties related to wind speed and solar radiation. Monte Carlo simulations and probability density functions were used to generate a variety of scenarios for the optimization of operational scheduling decisions. Finally, a case study was conducted to validate the effectiveness of the proposed model. Compared to traditional deterministic optimization in utility systems, the two-stage stochastic programming of sustainable utility systems can reduce carbon emissions by 5.6 percent annually and overall costs by 8,907,733 CNY. It provides decision-makers with a range of reference options by balancing multiple objectives, including economic factors, renewable energy penetration rate, and grid interaction level.

EXPERIENCE OF USING STEM CELLS IN PATIENTS WITH ATOPIC DERMATITIS

Recent research in this area has shown that in many tissues, including skin, stem cells become dormant as they mature, slowing down their rate of division and not responding as effectively to stimulation [1]. A decrease in the activity of stem cells leads to the fact that the rate of skin renewal slows down and defects begin to accumulate in it; the skin ages [2]. Recently, the attention of scientists has been attracted by plant stem cells, which produce a complex of molecular regulators that are universal. These regulators are capable of changing the functioning of human skin stem cells, partially returning them the energy of youth [3]. One of the most popular ingredients today is Swiss apple stem cells. Each adult apple stem cell can independently generate new cells and, in a concentration of just 0.1%, stimulate the division of human stem cells by 80% [4]. Phytostem (plant) cells were discovered relatively recently - only in the second half of the 20th century [5]. And the most effective in influencing human cells are considered to be plant stem cells, green apple phytostem cells. Scientists have proven that they are active biostimulators of human cells [6]. Plant cell preparations are absolutely hypoallergenic, unlike those obtained from animal or human tissues.

The counting principle makes number words unique

Abstract Following Ariel (2021. Why it’s hard to construct ad hoc number concepts. In Caterina Mauri, Ilaria Fiorentini, & Eugenio Goria (eds.), Building categories in interaction: Linguistic resources at work, 439–462. Amsterdam: John Benjamins), we argue that number words manifest distinct distributional patterns from open-class lexical items. When modified, open-class words typically take selectors (as in kinda table), which select a subset of their potential denotations (e.g., “nonprototypical table”). They are typically not modified by loosening operators (e.g., approximately), since even if bare, typical lexemes can broaden their interpretation (e.g., table referring to a rock used as a table). Number words, on the other hand, have a single, precise meaning and denotation and cannot take a selector, which would need to select a subset of their (single) denotation (??kinda seven). However, they are often overtly broadened (approximately seven), creating a range of values around N. First, we extend Ariel’s empirical examination to the larger COCA and to Hebrew (HeTenTen). Second, we propose that open-class and number words belong to sparse versus dense lexical domains, respectively, because the former exhibit prototypicality effects, but the latter do not. Third, we further support the contrast between sparse and dense domains by reference to: synchronic word2vec models of sparse and dense lexemes, which testify to their differential distributions, numeral use in noncounting communities, and different renewal rates for the two lexical types.

Research on the shear thickening polishing CaF2 with textured hollow polishing tool

Due to its excellent precision and surface quality, ultra-precision polishing has become a necessary machining technology for obtaining ultra-smooth surface. Shear thickening polishing (STP) uses the non-Newtonian shear thickening mechanisms to achieve high-precision and low-cost polishing. A kind of textured hollow polishing tool for shear thickening polishing was proposed in our work to improve the renewal rate and utilization rate of STP slurry, and the high-performance polishing to achieve the STP of Calcium fluoride (CaF2). Firstly, the preparation process of STP slurry was explored, and the influence of abrasive concentration on its rheological properties was analyzed, resulting in the determination of the optimal concentration. And on this basis, combined the computational fluid dynamics (CFD) simulation analysis, the design of textured hollow polishing tool was analyzed to study the influence of different texture structures on the flow velocity field and pressure field of the STP slurry. Secondly, the experimental platform was set up and its kinematics and material removal mechanism were analyzed. The material removal mathematical model was constructed based on Preston equation, which was then experimentally validated. The relative error between the experimental and theoretical values was 8.36 %. Finally, the interactive experiment was designed and the optimal process parameters were obtained based on response surface method (RSM) analysis. The experimental results indicated that the surface roughness of CaF2 converged to 5.9 nm, which proved the potential of the proposed textured hollow polishing tool as a promising polishing method for STP.

Optimal allocation of multiple energy storage in the integrated energy system of a coastal nearly zero energy community considering energy storage priorities

Energy storage technologies play a vital role in the low-carbon transition of the building energy sector. However, integrating multiple energy storage (MES) into integrated energy system (IES) in high-demand coastal communities remains a challenging task. This study proposes a novel regional IES that incorporates batteries, compressed air energy storage, and thermal energy storage for the simulated coastal community in Hong Kong; then developed the multi-objective optimization considering matching, economic, and environmental performance on MES capacity allocation with specially consideration of three energy management strategies under different energy storage priorities. The results show that all three storage priorities perform favorable outcomes across all objectives; compared to a reference scenario without storage, they achieve a relative net present value (NPVr) over 40 million HKD, a 0.29 improvement in matching performance, and over 2600 tCO2 in carbon emission reduction. Moreover, the renewable energy consumption rate exceeds 90 %, and the annual electricity import demand reduction rate exceeds 50 %. Sensitivity analysis highlights that larger energy storage capacities do not necessarily yield better outcomes, emphasizing the importance of synergistic interactions among multiple storage technologies. The presented energy system with MES and the optimal allocation approach herein may provide valuable insights for future energy planning in nearly-zero energy communities.

Uncertainties in physical and tracer methods in actual groundwater recharge estimation in the thick loess deposits of China

Groundwater recharge (GR) can be estimated with physical, tracer techniques and numerical modelling; however, the uncertainties in these methods have not been fully interpreted. This study selected six methods for actual GR estimation in the saturated zones with different data requirements and method assumptions, including two physical methods (i.e., water table fluctuation WTF and Darcy's law DL) and four tracer techniques (i.e., chloride mass balance CMB, tritium renewal rate TRR, chlorofluorocarbons CFC and 14C dating method CBD). Taking the loess tablelands of China as an example study area, we first analyzed the uncertainties in these methods and then recommended the appropriate methods for GR estimation in regions with thick vadose zones. Overall, the recharge rates from WTF, CMB and CFC (88 ± 24, 98 ± 33 and 53 ± 9 mm/year) were much greater than those from DL, TRR and CBD (10 ± 3, 14 ± 3 and 7 ± 5 mm/year). The differences in estimated GR are closely related to the method parameters, assumptions and temporal scales. Specifically, the model parameters (e.g., specific yield, hydraulic conductivity) exhibit large ranges due to spatiotemporal heterogeneity, and the physical methods are more sensitive to hydrogeological parameters compared with the tracer techniques. The uncertainties related to model assumptions originate from the simplified water/solute movement processes. The lag effect of the thick vadose zone largely limits WTF and TRR, but contributes to CMB. Ignoring the mixing and dispersion effect may overestimate recharge by 36–48 % for CFC, and the heterogeneity of the aquifer reduces the potential of CBD for recharge estimation. Overall, CMB is considered as the most optimal method for estimating GR in the thick loess deposits. This study deepens the understanding of the uncertainties in GR assessment methods in regions with thick vadose zones.

Influence of the DC frequency limit controller on the frequency characteristics of the multi-area asynchronous interconnected power grid with renewable energy integration

To systematically analyze the impact of the DC frequency limit controller (FLC) configuration scheme on the frequency characteristics of asynchronous interconnected power grids with renewable energy integration, a comprehensive frequency analysis model for three-area asynchronous interconnected power grids including the FLC is proposed. The model is based on the SFR model considering renewable energy integration and includes a simplified model of the DC FLC. A rigorous validation of the rationality and stability of the model is achieved through detailed mathematical calculations and pole-zero analysis. Taking the local power grids as an example, the established model is used to study the difference between single- and double-sided configuration of the DC FLC, the relationship between the increase in the renewable energy penetration rate and the frequency characteristics of each regional power grid, and the influence of DC FLC configuration on the maximum acceptance ratio of renewable energy. Through data comparison and theoretical analysis, the influence of FLC configuration on the frequency characteristics of each region of the asynchronous power grid under renewable energy integration is obtained. The results show that the configuration of a bilateral FLC on the DC line has more advantages in alleviating the complementary power disturbance at both ends and obvious limitations on the non-complementary power disturbance at both ends. Compared with the configuration of the bilateral FLC, the configuration of a unilateral FLC on the weak grid has a larger proportion of renewable energy acceptance. When the DC FLC power transmission capacity is sufficient, the weak grid and the adjacent two asynchronous grid DC tie lines are configured with a single-sided FLC, and the weak grid is theoretically connected to the renewable energy penetration rate of up to 100%.