Energy Perspective Research Articles

Energy and environmental performance from field operation of commercial-scale SOFC systems

Solid Oxide Fuel Cells (SOFCs) are capable of generating electrical and thermal power with very high conversion efficiency and almost no pollutant emissions into the atmosphere. Despite extensive literature on SOFC-based energy system models and experimental testing at the cell and short-stack level, there is currently a lack of performance data for SOFC modules under actual field conditions. To fill this gap, the present work investigates the energy and environmental performance of six SOFC modules, ranging in size from 10 to 60 kW, over thousands of hours of operation. These systems, supplied by the three leading SOFC manufacturers in Europe, have been installed and operated in different non-residential buildings worldwide, as part of the European Comsos project. The aim of this study is to establish a comprehensive set of field operation data to characterise commercial-scale SOFC systems. Specifically, raw data are processed to derived electrical and thermal efficiency maps, degradation rates and pollutant emissions, including particulate matter (PM), nitrogen oxides (NOx) and carbon monoxide (CO). A comparison with competing technologies is also provided to better highlight the potential benefits of adopting SOFC-based cogeneration systems. Values in the range of 51–61% were found for the system-level electrical efficiency under rated conditions. The electrical efficiency also remained consistently high across a wide modulation range (between 50% and 100% of rated power), with peak values reaching 65%. In addition, promising results were obtained for the average percentage loss in electrical efficiency, with a minimum value of 0.7%/1000 h. Regarding the environmental analysis, NOx and CO emissions were analysed at both constant and variable power output, proving to be impressively low across the entire modulation range. The same applies to PM concentrations, which were below ambient level. Overall, SOFCs demonstrated to be one of the best cogeneration solutions for commercial-scale systems (tens to hundreds of kW in size), from both an energy and environmental perspective. However, further reductions in costs and dedicated financial schemes are necessary for a widespread market penetration.

Does energy policy uncertainty matter for renewable energy and energy efficiency technologies? An affordable and clean energy perspective

Uncertainty can affect both macroeconomic indicators and the environment. Countries are implementing various energy policies to combat global warming, but these policies contain some uncertainties and contradictions. The environmental impact of uncertainties in energy policies is a research topic that has just begun to be investigated by researchers. This study examines the effects of energy policy uncertainty (ENERPU) on renewable energy R&D (RR&D), energy efficiency R&D (EER&D) and renewable energy consumption in the four countries with the highest RR&D expenditures (USA, Germany, Japan, and Spain). The study uses the novel multivariate quantile-on-quantile (M-QQR) approach from 2003 m1 to 2022 m9. The results of the study show: (i) The impact of ENERPU varies by quantile and country. (ii) ENERPU causes a decrease in renewable energy consumption and hinders RR&D expenditures. (iii) ENERPU increases EER&D. The Fourier quantile causality test confirms the robustness of the empirical results. Based on these findings, policymakers are recommended to minimize ENERPU and implement stable energy policies to develop the renewable energy sector and technologies.

Optimal operation strategy predictive control for an integrated radiant cooling with fresh air system based on machine learning

Radiant cooling systems are widely valued for their great comfort and energy-saving potential. However, they still face the risk of condensation in the early stages of operation, especially in case of random occupancy and intermittent operation. This study aims to avoid unacceptable discomfort durations in randomly occupied rooms that installed integrated radiant cooling and fresh air system while consuming as little energy as possible. This paper firstly compares the effects of adopting only the setback or standby cooling strategy in a randomly occupied conference room by simulation. The simulation results demonstrate the necessity for predicting optimal operation strategy. Subsequently, optimal operation strategy predictive models were built using three machine learning algorithms on three datasets. The evaluation results of the models indicate the feasibility of using data from neighbouring cities to improve the generalisation ability of the target city model. Finally, the best one of models was used to predict optimal operation strategy and achieved good results: discomfort durations of 97.56% of the conferences were within the acceptable range. Additionally, compared to only adopting the standby cooling strategy, the radiant cooling system operating time was reduced by 8.88%, and the total energy consumption was reduced by 28.85 kWh. In this study, a model to predict optimal operation strategy is proposed. By simulating and analysing from both comfort and energy perspectives, the optimal operation strategy predictive control method effectively limits the discomfort duration and reduces energy consumption and radiant system runtime. This study provides an example of practical engineering and machine learning applications for radiant cooling systems.

Mechanical response, damage constitutive and failure localization characteristics of structural backfills composed of matrixes with different mechanical properties

To investigate the mechanical properties, damage progressivity characteristics, and failure modes of layered cemented paste backfills (LCPB), the unconfined compressive strength (UCS) tests were carried out on LCPB and supplemented with the digital image correlation (DIC) method. The damage characteristics were revealed from the energy perspective, and the damage constitutive equation was established. The results show that the ratio of yield stress to UCS increased with the increase of the c/t ratio and h/H ratio. The intersection point of the dissipation energy and the elastic energy curves could be conservatively considered as a sign that the LCPB is about to enter the accelerated damage stage. The appearance of the intersection point will be earlier with decreasing c/t ratio and increasing h/H ratio. The damage rate curves exhibited an evolutionary characteristic of increasing and then decreasing, and the maximum damage rate gradually decreased with decreasing c/t ratio and increasing h/H ratio; The failure mode showed a significant localization characteristic, and the damage of LCPB was mainly caused by tensile stress generated in the horizontal direction. The findings could provide guidance for the design of LCPB.

Density functional analysis of structural, mechanical, electronic, and hydrogen storage properties of thermodynamically stable lead-free hydrides [formula omitted](X = Cs, Fr): A perspective of clean energy and fuel

A density functional theory based calculations are performed to investigate structural, hydrogen storage, mechanical, electronic and thermodynamical properties of lead-free hydride perovskites XGeH3 (X=Cs, Fr). The optimized lattice constant and hence volume against the minimum energy is obtained and found to be 4.176 Å and 4.184 Å for CsGeH3 and FrGeH3 respectively. The gravimetric and volumetric hydrogen storage capacity of 1.43% and 1.00%, 72.81(g.H2/L) and 73.21(g.H2/L) for CsGeH3 and FrGeH3 respectively. The density of states and electronic band structure predicted the metallic nature of both hydrides which was affirmed by the Fermi Surfaces. The calculation of Poisson’s, Pugh’s ratio and Cauchy’s pressure suggested their brittle nature. The Debye temperature decreases with the increase of temperature while volume and entropy increase by increasing applied temperature. The present study shows the potential of lead-free hydride perovskites in hydrogen storage applications due to rather suitable gravimetric hydrogen capacity and high stability.

Comprehensive assessment of waste heat recovery mismatch and renewable energy integration in data centers: A multifaceted energy, economic, and environmental perspectives

The integrated utilization of free cooling sources, waste heat recovery from information technology equipment, and renewable energy emerges as a pivotal method for conserving energy and mitigating carbon emissions in data centers. However, there is limited research on systems that integrate these three technologies. A notable mismatch arises between the waste heat generated and the requirements for building heating, but it is often overlooked. Moreover, a discernible lack of comprehensive analysis concerning the multifaceted influences associated with using renewable energy exists. Therefore, this paper employs a range of metrics to comprehensively assess a renewable energy integration system considering the mismatch of the waste heat recovery in data centers. The results indicate that due to mismatch characteristics, the energy-saving rate of heating systems will not constantly climb with the increase in energy savings. It causes only 45.5% of waste heat available for heating purposes achieving a power usage effectiveness of 1.17 and the rest will be abandoned. Similarly, its economic performance doesn't absolutely improve with the expansion in heating volume, the payback period doesn't continue to fall but increases after reaching the optimal level of 5.7. The proposed system accomplishes a 45.8% reduction in energy consumption for the cooling system, a notable decrease of 90% in carbon emissions, and a 55.7% reduction in annual cash flow. It is also important to note that while integrating battery systems aids in stabilizing grid disturbances, with a minimum disturbance index of 0.2, it introduces significant economic costs for the data centers.

Nash Equilibria and Undecidability in Generic Physical Interactions—A Free Energy Perspective

We start from the fundamental premise that any physical interaction can be interpreted as a game. To demonstrate this, we draw upon the free energy principle and the theory of quantum reference frames. In this way, we place the game-theoretic Nash Equilibrium in a new light in so far as the incompleteness and undecidability of the concept, as well as the nature of strategies in general, can be seen as the consequences of certain no-go theorems. We show that games of the generic imitation type follow a circularity of idealization that includes the good regulator theorem, generalized synchrony, and undecidability of the Turing test. We discuss Bayesian games in the light of Bell non-locality and establish the basics of quantum games, which we relate to local operations and classical communication protocols. In this light, we also review the rationality of gaming strategies from the players’ point of view.

Biohydrogen upgradation and wastewater treatment in 3-chambered bioelectrochemical system assisted with H2/O2-based redox reactions

The current need for the upgradation of biohydrogen generation and contaminant removal in two-chambered microbial electrolysis cells (MECs) compels the design of alternatives i.e. bioelectrochemical systems (BESs) to conventional reactors. In this study, a novel three-chambered design of MEC (BES-1) was developed with a common anodic chamber and a two-cathodic chambers at both ends of the anodic chamber, separated by a membrane (MEC–MEC). To facilitate electricity recovery, a microbial fuel cell (MFC) was integrated with an MEC in BES-2. Cathodic hydrogen recovery of 8.89 and 4.81 mL/L.day, and organic matter removal of 82% and 76% were obtained in BES-1 and BES-2, respectively, demonstrating their capabilities for bioremediation. Electrochemical analyses also revealed that cathodic reduction reactions improved with the effective utilization of protons during integration. Our design regulates H2/O2-associated electrochemical reactions and is beneficial for maintaining pH equilibrium. From cost and energy perspectives, the integrated BES provides a platform for two different reactions simultaneously and is capable of boosting overall hydrogen recovery and organic matter removal. Moreover, the compactness and competitiveness of such an integrated BES increase its scope for real-world applications.

Study on the damage cause of tunnel junction under different component earthquakes based on on-site investigation and numerical simulation

The Shengli tunnel sustained significant damage during the 2022 Luding earthquake (Mw 6.6), with numerous circumferential and inclined cracks observed in the tunnel lining. This paper develops a three-dimensional numerical model to examine the tunnel junction's dynamic responses to three seismic components: east-west (EW), north-south (NS), and up-down (UD). It also analyzes the causes of tunnel damage. A comparison between the numerical simulation results and the on-site investigation findings shows a high degree of agreement, with damages predominantly concentrated at the junction between the right tunnel and the branch tunnel. The tunnel cross sections' plastic damage areas, damage parameters, K values, and convergent deformation are significantly larger during horizontal vibrations (EW and NS components) than during vertical vibrations (UD component). The stiffness differential between the right and branch tunnels results in varying dynamic responses, leading to geometric incompatibility at the junction as the primary cause of damage. Under horizontal earthquakes, tunnels aligned perpendicular to the vibration direction exhibit significant lateral deformations. Consequently, the extent of damage development in the right tunnel is greater than in the branch tunnel under an EW component earthquake, and the extent of damage development in the branch tunnel is greater than that in the right tunnel under an NS component earthquake. In contrast, damage under the UD component is confined near the junction, without extending into the right or branch tunnels. From an energy perspective, the tunnel system accumulates the least inelastic strain energy during UD component earthquakes, resulting in minimal damage despite the highest Peak Ground Acceleration in the UD direction.

Enhanced thermally integrated Carnot battery using low-GWP working fluid pair: Multi-aspect analysis and multi-scale optimization

Thermally integrated Carnot battery (TICB) emerges as a promising technology for long-duration energy storage. This study aims to improve its multi-dimensional performance from the optimization design level, thereby promoting its competitiveness. Firstly, a refined system architecture is developed, integrating subsystem layout modification and advanced thermal integration mode. Sixteen potential working fluid pairs are formed by screening low-GWP refrigerants as drop-in substitutes for R245fa. Then, a comprehensive evaluation framework is established to characterize this technology from energy, exergy, and economic perspectives, and a collaborative optimization method is introduced to facilitate integrated optimization. Finally, a whole cycle cumulative exergy analysis is conducted to explore directions for further improvement. Results indicate that, compared to the basic architecture, the round-trip efficiency (RTE) of the proposed system is elevated by over 30%. The use of different alternative refrigerants in the charging and discharging cycles makes the TICB not only sustainable but also more efficient. The thermodynamic dilemma of determining the heat pump evaporation temperature disappears with a closed-type heat source. To maximize overall thermo-economics, sufficient heat pump subcooling and evaporator internal superheat are necessary, and the ideal storage temperature span and pinch point temperature difference of heat exchangers must be identified. The collaborative optimization displays that the first-rank working fluid pair is R1234ze(Z)-R1224yd(Z), with an RTE of 85.2%, a volumetric energy density of 3.10 kWh/m3, and a levelized cost of storage of 0.303 $/kWh, respectively. Furthermore, the RTE is highly sensitive to the insulation quality of storage tanks. A mere 2.5% performance degradation can lead to a 10% points decline in RTE. Internal exergy destruction is primarily caused by poor heat transfer matching, while external exergy loss mainly results from underutilized heat sources during non-charging periods. Therefore, we recommend the district heating network as the target heat source for the dual-period TICB. These achievements offer a valuable reference for the research and development of efficient, affordable, and sustainable TICB.

Understanding molecular geometric phase effects with exact effective force: case study of a model system

In this work, molecular geometric phase effects are studied using the idea of exact factorization (EF) (Abediet al2010Phys. Rev. Lett.105123002) and exact effective force (Liet al2022Phys. Rev. Lett.128113001). In particular, we performed dynamics simulations for a two-state vibronic coupling model, and interpreted the results in three different perspectives: the Born-Huang expansion, the exact time-dependent potential energy surface (TDPES) and the exact effective force. We find that (i) at particular moment, while the vanishing nuclear density that occurs periodically in space is conventionally attributed to destructive interference of the nuclear wave packet owing to the geometric phase, such phenomenon can be equally well interpreted through the energy perspective, as manifested in the exact TDPES in the EF scheme; (ii) when combined with trajectory-based classical dynamics, the exact effective force obtained through EF qualitatively reproduces the correct nuclear density, while the adiabatic force gives the wrong density, particularly in the interference region. Our results suggest that the exact effective force is a potential starting point for making approximations and improving trajectory-based computational methods towards an accurate description of geometric phase effects.

Comparative analysis of eight urea-electricity-heat-cooling multi-generation systems: Energy, exergy, economic, and environmental perspectives

The Haber-Bosch process for urea production is known for its significant carbon emissions. While the chemical looping ammonia generation method presents a potential alternative, its technical and economic feasibility still requires further investigation. This paper conducts a comparative analysis of eight renewable energy-driven urea-electricity-heat-cooling multi-generation systems by developing their energy, exergy, economic, and environmental evaluation models. Considering the fluctuation in renewable energy resources, an annual evaluation of the different systems is conducted based on a monthly time scale. The results indicate that systems based on the Haber-Bosch process have higher average energy and exergy efficiencies of 60–80 % and 40–50 %, respectively. For the chemical looping ammonia generation process, the respective efficiencies are 50–70 % and 30–40 %. Additionally, the system integrating the Haber-Bosch reaction, reduction reactor, and solid oxide fuel cell yields the highest energy and exergy efficiencies among the eight systems, at 68.2 % and 45.78 %, respectively. However, it is inferior to the multi-generation system integrating the chemical looping ammonia generation process in terms of economic and environmental performance. In addition, the system integrating the chemical looping ammonia generation process and solid oxide fuel cell has the shortest discounted payback period of 8 years, with annual revenue and net present value of 32.63 and 11.66 MUSD, respectively. While the operating expenditures of the Haber-Bosch (12.6–15.7 MUSD) are lower than those of the chemical looping ammonia generation process (14.0–17.5 MUSD), its capital expenditures (382.0–410.8 MUSD) are significantly higher than those of the chemical looping ammonia generation process (302.4–307.3 MUSD). Furthermore, the conducted environmental evaluation shows that the multi-generation system integrating the chemical looping ammonia generation process and reduction reactor exhibits lower overall carbon emissions (0.013 t CO2/t urea) compared to the state-of-the-art method of oxy-fuel coal-fired power plant for urea synthesis.

A Mass, Fuel, and Energy Perspective on Fixed-Wing Unmanned Aerial Vehicle Scaling

A Mass, Fuel, and Energy Perspective on Fixed-Wing Unmanned Aerial Vehicle Scaling

Regulating the surface area increase of zero-valent iron (ZVI) during ball milling: A study of the mechanical mechanism and low-carbon milling

This study investigates the effect of milling parameters on the specific surface area (SSA) increase of zero-valent iron (ZVI) powder, which is crucial for its environmental applications. Combining experimental and orthogonal design methodologies, the research explores how the parameters modulate the SSA. The operational factors are analyzed from the perspectives of bead momentum, kinetic energy, and energy efficiency. A regression model is proposed for the precise fabrication of ZVI with predetermined SSA. Furthermore, the study identifies optimized parameters that minimize energy consumption and carbon emissions. The results suggest that the optimal milling time is 10 min, with larger beads (2.0 mm), higher quality beads (0.75 kg), and higher shaft rotational speed (2000 rpm) significantly enhancing SSA. Discrete Element Method (DEM) simulations reveal micro-mechanical interactions, supporting the parameter selection scheme for maximizing SSA. The findings contribute to optimizing the milling process of the ductile ZVI powder for environmental clean-up.

Exergy Analysis in Highly Hydrogen-Enriched Methane Fueled Spark-Ignition Engine at Diverse Equivalence Ratios via Two-Zone Quasi-Dimensional Modeling

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH4). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO2) emissions. Given that using neat hydrogen (H2) containing nil carbon still possesses several issues, blending CH4 with H2 constitutes a stepping-stone towards the ultimate goal of zero producing CO2. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH4 to 50% vol. fraction H2, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H2 percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H2 and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H2 or EQR, the work transfer exergy curves acquire slightly higher values the higher the H2 and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H2 or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H2. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H2 fuel, which can prove to be game changer to attaining a clean energy environment transition.

Hydrogen-powered enzymatic valorization using multi-enzyme co-immobilization reactor with polypeptide-based cofactor swing-arm

The chemical valorization of organic matter into high-energy products through reduction using oxidoreductase is a pivotal aspect from an energy perspective. Enzymatic valorization, utilizing the reduction potential of hydrogen contained in inexpensive resources such as coke oven gas (COG) and certain gasified plastics, enables environmentally friendly processes. Here, a strategy was proposed utilizing hydrogenase (H2ase), particularly soluble hydrogenase (SH), for selective utilization of H2 from mixtures without the separation processes. The co-immobilization of SH, elastin-like polypeptide (ELP)-based cofactor swing arm, and mannitol dehydrogenase (MDH) in a microreactor system were demonstrated for enzymatic valorization. The swing arm length and in-resin concentration were optimized to enhance electron mediation efficiency, leading to an improvement in productivity of about 3 mM/hr. Comparable productivity was observed in simulated COG and plastic waste-derived gas, which are promising results for the utilization of such low-purity H2 sources. Furthermore, the system demonstrates robustness and recyclability across maintaining productivity over 6 repeated batch reactions, highlighting its potential for industrial applications. Overall, our study provides valuable insights into the development of sustainable enzymatic microreactors for chemical valorization processes, contributing to greener and more efficient industrial practices.

Research on virtual inertia of energy storage systems under different grid-forming control strategies

Abstract To reasonably evaluate the support capability of grid-forming energy storage in power systems characterized by “double high” characteristics, it is essential to investigate the factors influencing the virtual inertia of grid-forming energy storage. This paper delves into the relationship between two control strategies of grid-forming energy storage and virtual inertia from an energy perspective. Initially, the operational principle and technological advantages of grid-forming energy storage are analyzed. Subsequently, based on the principles of two grid-forming control strategies, mathematical models for both types of grid-forming energy storage are established, elucidating the physical significance of virtual inertia in grid-forming inverters and revealing the adjustability of virtual inertia. Finally, a microgrid simulation system is constructed in PSCAD to validate the theoretical analysis.

Comprehensive evaluation of a new integrated ORC-VCR system with a thermoelectric generator unit combining sustainable energies for hydrogen production

Recently, there has been a growing emphasis on the efficient generation of energy from sustainable sources. This study aims to evaluate a new combined Organic Rankine Cycle-Vapor Compression Refrigeration (ORC-VCR) system from energy, exergy, economics, and environmental perspectives. The system has been designed to cogenerate power, heat, cooling, and hydrogen using solar and biomass energy. To enhance efficiency, a Thermoelectric Generator (TEG) unit has been integrated into the system. The power produced by the TEG is used to generate hydrogen in the Proton Exchange Membrane Electrolyser (PEME). To ensure the continuous operation of the solar collector, especially under conditions of unstable and intermittent solar radiation, a thermal storage tank and a biomass-fired boiler utilizing four different types of biomass (wood, paper, municipal solid waste, and sawdust) have been incorporated. The primary objective of this research is to investigate the impact of employing various biomass types on the system's performance. The results indicate that in terms of energy and exergy, municipal solid waste yields the highest system efficiency. However, from an environmental viewpoint, paper incurs lower pollutant emissions. The proposed hybrid system can produce 145.5 kW of cooling, 513.6 kW of heat, 37.93 kW of electricity, and 0.756 kg/h hydrogen with energy and exergy efficiencies of 32.73% and 14.18%, respectively. The estimated total equipment cost is 7.67$/h, with a CO2 emission of 0.0029 kg/s.

The high-low seedbed cultivation increases crop yield, economic benefit, and energy efficiency while reducing the carbon footprint of winter wheat

It is critical to develop sustainable approaches to growing more grain yield while reducing environmental pressure. The high-low seedbed cultivation (HLSC) pattern can enhance crop productivity in the semi-humid North China Plain (NCP), but comprehensive assessments of its advantages from economic, energy, and environmental perspectives relative to traditional cultivation (TC) are still limited. Therefore, two-site field experiments with two cultivation patterns (i.e., HLSC and TC), one for 3-years (2017–2020 wheat season) and another for 2-years (2020–2022 wheat season), were performed to determine the economic benefits, energy balance and carbon footprint (CF) in the NCP. Results showed that, on average, the HLSC pattern exhibited 16.2 ± 6.3 % higher grain yield, 27.5 ± 13.1 % higher biomass yield, and 61.0 ± 23.7 % higher net profit over the TC pattern. Meanwhile, the HLSC have obviously increased net energy (28.8 ± 13.9 %), energy use efficiency (24.8 ± 12.2 %), and energy input intensity (14.7 ± 6.3 %), while decreased specific energy (15.3 ± 4.8 %). Furthermore, the CF per grain yield and biomass yield under HLSC decreased by 10.9 ± 5.6 % and 20.5 ± 4.5 % relative to the TC, respectively. The results suggest that HLSC is a promising wheat cultivation practices to cater to the demands of crop production with environmental sustainability in the NCP.

Investigation of tribological behavior of polytetrafluoroethylene/graphene composite

AbstractIn this study, we constructed molecular friction models for polytetrafluoroethylene (PTFE)/graphene composites with various defect ratios to represent their different wear stages and simulated their friction processes under different load conditions. The friction and wear mechanisms were revealed by analyzing the variations in their molecular architectures and energies during friction. The results indicate that the friction coefficient decreased with increasing load. When the load was constant, the friction coefficients of the composites containing defections were resemble, indicating that they remained unchanged in the different wear stages. The composite wear continued to increase during friction. However, the wear increment decreased gradually. In addition, by analyzing the changes in MSD, wear can be divided into initial, stable, and accelerated wear stages.Highlights Construct PTFE/Gr molecular models to represent their different wear stages. Simulate the dynamic changes of PTFE/Gr molecular structure during friction. The influence of PTFE/Gr dynamic structural changes was revealed. Reveal the normal force variation from an energy perspective.