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•Battery pack equalization strategy based on UCCVC hypothesis is proposed.•The convergence of equalization is obtained in different inconsistent conditions.•The equalization strategy ...is simulated in fresh and aged scenarios.•The equalization strategy is embedded in a real BMS for practical application analysis.
Lithium-ion battery pack capacity directly determines the driving range and dynamic ability of electric vehicles (EVs). However, inconsistency issues occur and decrease the pack capacity due to internal and external reasons. In this paper, an equalization strategy is proposed to solve the inconsistency issues. The difference of inconsistency for lithium-ion battery pack equalization is determined based on the uniform charging cell voltage curves hypothesis. Stability of the sampling voltage interval and convergence of equalization are analyzed experimentally. Finally, the results of simulation and experiment both show that the equalization strategy not only maximizes pack capacity, but also adapts to different consistency scenarios. Pack capacity and consistency in the fresh or aged state are significantly improved after battery equalization. In the real battery module experiment, the maximum absolute errors of open circuit voltage (OCV) and state of charge (SOC) are 21.9 mV and 1.86%, and the capacity is improved by 13.03%. Importantly, the equalization strategy has high precision and competitive simplicity with low computation, making it suitable for on-line equalization in EVs.
Based on the porous electrode and concentrated solution theory, a thermal model is developed for lithium ion battery pack. The accuracy of predicted battery temperatures is validated by ...charge–discharge cycling experiments under natural and forced convection conditions. The heat generation and dissipation rates of battery under different conditions are simulated by the proposed model and the results indicate that: (1) the SOC change has a significant effect on the reversible heat generation rate but has almost no influence on the irreversible heat generation rate; (2) the generation rates of reversible and irreversible heat during charge are almost equal to that during discharge with the same SOC and current rate, but the effect of reversible heat on battery temperature is opposite; (3) for enhancing heat dissipation with a given input power of cooling fan, there always exists an optimum value for the resistance coefficient of battery pack, and the optimal coefficient is increased when the input power of fan increases. In addition, the comparisons between the predicted and measured battery temperature indicate that, the reversible heat has significant influence on battery temperature during continuous charge and discharge, especially under low current rate, but the influence can't be observed during charge–discharge cycles.
► We developed a theoretically based thermal model for lithium ion battery pack. ► Increasing current rate has more obvious effect on irreversible heat generation rate. ► The change of SOC mainly affects the reversible heat generation rate. ► There always exists an optimal resistance coefficient for battery pack. ► Reversible heat affects battery temperature only during continuous charge and discharge.
In this study, plug-in and wireless charging for an all-electric bus system are compared from the life cycle energy and greenhouse gas (GHG) emissions perspectives. The comparison of life cycle GHG ...emissions is shown in the graph below. The major differences between the two systems, including the charger, battery and use-phase electricity consumption, are modeled separately and compared aggregately. In the base case, the wireless charging system consumes 0.3% less energy and emits 0.5% less greenhouse gases than plug-in charging system in the total life cycle. To further improve the energy and environmental performance of the wireless charging system, key parameters including grid carbon intensity and wireless charging efficiency are analyzed and discussed in this paper. Display omitted
•Compared life cycle energy and GHG emissions of wireless to plug-in charging.•Modeled a transit bus system to compare both charging methods as a case study.•Contrasted tradeoffs of infrastructure burdens with lightweighting benefits.•The wireless battery can be downsized to 27–44% of a plug-in charged battery.•Explored sensitivity of wireless charging efficiency & grid carbon intensity.
Wireless charging, as opposed to plug-in charging, is an alternative charging method for electric vehicles (EVs) with rechargeable batteries and can be applicable to EVs with fixed routes, such as transit buses. This study adds to the current research of EV wireless charging by utilizing the Life Cycle Assessment (LCA) to provide a comprehensive framework for comparing the life cycle energy demand and greenhouse gas emissions associated with a stationary wireless charging all-electric bus system to a plug-in charging all-electric bus system. Life cycle inventory analysis of both plug-in and wireless charging hardware was conducted, and battery downsizing, vehicle lightweighting and use-phase energy consumption were modeled. A bus system in Ann Arbor and Ypsilanti area in Michigan is used as the basis for bus system modeling. Results show that the wirelessly charged battery can be downsized to 27–44% of a plug-in charged battery. The associated reduction of 12–16% in bus weight for the wireless buses can induce a reduction of 5.4–7.0% in battery-to-wheel energy consumption. In the base case, the wireless charging system consumes 0.3% less energy and emits 0.5% less greenhouse gases than the plug-in charging system in the total life cycle. To further improve the energy and environmental performance of a wireless charging electric bus system, it is important to focus on key parameters including carbon intensity of the electric grid and wireless charging efficiency. If the wireless charging efficiency is improved to the same level as the assumed plug-in charging efficiency (90%), the difference of life cycle greenhouse gas emissions between the two systems can increase to 6.3%.
The low thermal conductivity and liquid-phase leakage of phase change materials seriously hinder their large-scale applications. Porous materials have been identified as an effective way to address ...the leakage and provide a thermally conductive network. Therefore, we designed an expanded graphite-based multifunctional composite phase change thermal storage materials for personal thermal management and antimicrobial in medical protection. Expanded graphite (EG) was used as the matrix, silver nanowires (Ag NWs) as the functional enhancement materials, and
n
-octadecane (OD) as the thermal storage materials. OD and Ag NWs were adsorbed in the porous structure of EG by vacuum-assisted impregnation. Finally, EG/Ag NWs/OD were combined with non-woven fabrics (N) by one-step hot pressing method to obtain EG/Ag NWs/OD-N composite with excellent comprehensive performance. With the mass ratio of EG to Ag NWs of 13:7, EG/Ag NWs/OD-N exhibited a thermal conductivity of 2.0130 W m
−1
K
−1
, which was improved by 1070.3% compared with pure OD. EG/Ag NWs/OD-N has a melting enthalpy of 137.85 J·g
−1
and a crystallization enthalpy of 128.97 J·g
−1
. In addition, EG/Ag NWs/OD-N display great antibacterial properties, thermal cycling stability, shape stability, and cycling persistence and showed excellent temperature control in protective clothing applications, offering great potential for large-scale applications.
Solar‐driven evaporation using hydrogels and photothermal materials is a promising freshwater harvesting technology. However, due to the difficulty of removing volatile pollutants through evaporation ...and the fact that the evaporation efficiency has reached its limit, further improving efficiency becomes challenging. Therefore, a material simultaneously possessing low water evaporation enthalpy as well as the ability to inhibit volatile pollutants is desired. In this work, a dense inhibitory layer on the hydrogel framework of polyacrylamide introduced into polyvinyl alcohol is designed to enhance its suppression of volatile pollutants and regulate the water state. This not only reduces the energy demand for evaporation but also makes it more effective in treating wastewater containing volatile pollutant ammonia nitrogen. Finally, a high evaporation rate of 3.0 kg m−2 h−1 and an excellent ammonium rejection rate of 90% for high concentration ammonia wastewater are obtained under 1 kW m−2 illumination. This work opens up new avenues of application for the use of photothermal materials in the use of clean solar energy for the separation of freshwater and volatile small molecules.
A dense positively charged auxiliary layer is uniquely designed to enhance the hydrogel's repellence toward ammonium and regulate water state. The resulting hydrogel has achieved an ammonium rejection rate of up to 90% facing high concentration ammonia nitrogen wastewater, and under 1 kW m−2 illumination, a high evaporation rate of up to 3.0 kg m−2 h−1 is achieved.
Gas-to-liquids (GTL) as an alternative to diesel is considered to be one of the technical options to reduce petroleum consumption in the on-road transportation sector. Between May and August 2007, a ...joint demonstration program by Tsinghua University, Beijing Transit, Cummins Corporation and Shell Corporation was carried out in Beijing. The program focused on the supply systems and vehicle use of GTL fuel. The demonstration fleet was formed by four transit buses fueled with GTL and four with diesel. It was demonstrated that GTL has good compatibility with diesel in terms of fuel supply system and vehicle use. This paper compares the energy consumption and GHG emissions of diesel and GTL fuel supply chains by life cycle analysis based on demonstration results. The results indicate GTL’s large range (reported 54–70%) in synthesis efficiency, as the key factor in determining energy consumption and GHG emissions within the GTL fuel supply chain. For the probable case (GTL synthesis efficiency: 65%), the life cycle energy consumption and GHG emissions of GTL fuel are 42.5% and 12.6% higher than that of diesel. For two sensitivity analysis cases (GTL synthesis efficiency: 54% and70%), energy consumptions are 74.2% and 31.2% higher and GHG emissions are 27.3% and 7.4% higher than that of the diesel fuel supply chain. If the efficiency of the GTL synthesis process is improved to 75%, then the GHG emissions level of the GTL fuel supply chain can be reduced to the same level as the diesel fuel supply chain.
In this paper, citric acid was used as a ligand for getting a transparent homogeneous precursor solution and further ensured homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, ...K-30) was used as a binder and a structure guide reagent because it could form one-dimensional structure in the electrospinning process if the viscosity of the sol was suitable. Finally, the novel orthorhombic InVO4 nanofibers were prepared successfully by annealing electrospun precursor fibers at 700°C. Photocatalytic experiment on methyl orange solution under visible light showed that orthorhombic InVO4 nanofibers had a potential application in wastewater-treatment. Display omitted
► In this paper, orthorhombic InVO4 nanofibers were successfully prepared by annealing the electrospun precursor fibers. ► Citric acid was used as a ligand, it could react with metal salts to get a clear homogeneous precursor solution. ► PVP (K-30), one kind of water-soluble polymers, was used as a binder. Meanwhile, PVP was used as a structure guide reagent.
The novel orthorhombic InVO4 nanofibers have been successfully synthesized by annealing electrospun precursor fibers. Citric acid was used as a ligand for it could react with metal salts to get a transparent homogeneous precursor solution and homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, K-30) was used as a binder and a structure guide reagent because it was one kind of water-soluble polymers. It is easy to gain one-dimensional materials while the viscosity of the citrate/PVP sol was suitable. The structure, morphology and photocatalytic properties of the nanofibers were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electron microscopy (SEM) analysis, UV–vis spectrophotometer and fluorescence spectrophotometer. The nanofibers calcined at 700°C were orthorhombic InVO4 with a width in the range of 30–100nm and length in micron-grade. This one-dimensional pure orthorhombic InVO4 had the higher photocatalytic activity under visible light irradiation. The photo-degradation rate of nitrobenzene aqueous solution under visible light reached 69% after 6h. It is obvious that the orthorhombic InVO4 nanofibers have a potential application in wastewater-treatment.
A spark discharge plasmatron was designed. Hydrogen was produced through partial oxidation reforming of DME by spark discharge plasma at atmospheric pressure and ambient temperature. The effects of ...voltage of electric source, arc frequency, air-to-DME ratio (by mole), DME feed flow rate and arc length on gas concentrations (Vol%), output power of electric source, energy consumption and thermal efficiency were investigated. The experimental results show that when arc frequency is 120
Hz, air-to-DME ratio is 2, DME feed flow rate is 20
mL/min, voltage of electric source is 12
V and arc length is 9
mm, hydrogen concentration is 7%, hydrogen yield is 8.5%, energy consumption is 75.5
kJ/L-H
2 and thermal efficiency is 4.2%. The output power of electric source is different at different arc frequency.
•An intelligent SOH estimation framework for EVs big data platform is presented.•The capacity estimation model is established based on neural network algorithm.•The dataset is generated from ...real-word data of EVs under actual operation.•Big data analysis is used for extraction of health feature parameters and selection of training data.•Accurate SOH evaluation can be obtained by using the historical operating data.
State of health (SOH) of in-vehicle lithium-ion batteries not only directly determines the acceleration performance and driving range of electric vehicles (EVs), but also reflects the residual value of the batteries. Especially, with the development of data acquisition and analysis technologies, using big data to realize on-line evaluation of battery SOH shows vital significance. In this paper, we propose an intelligent SOH estimation framework based on the real-world data of EVs collected by the big data platform. Defined by the more accessible detection, the health features are extracted from historical operating data. Then, the deep learning process is implemented in feedforward neural network driven by the degradation index. The estimation method is validated by the one-year monitoring dataset from 700 vehicles with different driving mode. The result shows that the proposed framework can effectively estimate SOH with the maximum relative error of 4.5% and describe the aging trend of battery pack based on big data platform.
Hydrogen production from partial oxidation of methane under the combination of dielectric barrier discharge (DBD) plasma and NiO/γ-Al2O3 catalyst with cordierite honeycomb monoliths as substrate was ...investigated. The results showed that obvious synergistic effect was generated between DBD plasma and catalyst. Compared with the DBD plasma reactor without catalyst, the CH4 conversion and H2 yield increased from 60.1% and 21.3% to 83.6% and 28.4%, respectively. When the discharge power is above 70 W, the combination of DBD plasma and NiO/γ-Al2O3 catalyst promotes partial oxidation of methane. The catalyst was characterized by X-ray diffraction (XRD). NiO on the surface of catalyst was reduced to Ni because of the introduction of DBD plasma. The activity of catalyst at low temperature was improved, and the generation of oiliness by-products was significantly reduced.
•A combined plasma-catalyst reactor is designed.•The combination of DBD plasma and NiO/γ-Al2O3 catalyst is investigated.•Effects of various parameters are studied.•The CH4 conversion, H2 yield and the activity of catalyst at low temperature are improved.•The generation of oiliness by-products is significantly reduced.
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