Thermal management performances of PCM/water cooling-plate using for lithium-ion battery module based on non-uniform internal heat source

In order to improve the working performance of the lithium-ion battery, the battery module with Phase change material/water cooling-plate was designed and numerically analyzed based on the energy conservation and fluid dynamics. The non-uniform internal heat source based on 2D electro-thermal model for battery LiFePO4/C was used to simulate the heat generation of each battery. Then factors such as height of water cooling-plate, space between adjacent batteries, inlet mass flow rate, flow direction, thermal conductivity and melting point of PCM were discussed to research their influences on the cooling performance of module. And the 5 continuous charge-discharge cycles was used to research the effect of PCM/water cooling plate on preventing thermal runaway. The results showed that the water cooling plate set close to the near-electrode area of battery removed the majority of heat generated during discharging and decreased the maximum temperature efficiently. The PCM between the adjacent batteries could improve the uniformity of temperature field. In addition, the PCM/water cooling plate could limit the maximum temperature effectively and improve the uniformity of temperature field during the 5 continuous charge-discharge cycles. As a result, it prevented the emergence of thermal runaway and increased the safety of module. (C) 2017 Elsevier Ltd. All rights reserved

Investigation of thermal management for lithium-ion pouch battery module based on phase change slurry and mini channel cooling plate

In this paper, the thermal management based on phase change slurry (PCS) and mini channel cooling plate for the lithium-ion pouch battery module was proposed. The three-dimensional thermal model was established and the optimum structure of the cooling plate with mini channel was designed with the orthogonal matrix experimental method to balance the cooling performance and energy consumption. The simulation results showed that the cooling performance of PCS consisting of 20% n-octadecane microcapsules and 80% water was better than that of pure water, glycol solution and mineral oil, when the mass flow rate was less than 3 x 10(-4) kg s(-1). For different concentrations of PCS, if the mass flow rate exceeded the critical value, its cooling performance was worse than that of pure water. When the cooling target for battery maximum temperature was higher than 309 K, the PCS cooling with appropriate microcapsule concentration had the edge over in energy consumption compared with water cooling. At last, the dimensionless empirical formula was obtained to predict the effect of the PCS's physical parameters and flow characteristics on the heat transfer and cooling performance. The simulation results will be useful for the design of PCS based battery thermal management systems. (C) 2018 Elsevier Ltd. All rights reserved

Risk evaluation of internal short circuit for lithium-ion battery based on an active protection method

Internal short circuit (ISC) can lead to thermal runaway and even cause fire. But the traditional passive methods cannot prevent the ISC before it occurs. The active protection method is proposed based on the evaluation of the ISC risk. An evaluation model is built based on the electrochemical model and solved with the Monte-Carlo method. Then, the model is verified with experimental data. The simulation result agrees with the experimental data of accelerated cycle life. Next, the effect of different factors on the probability of ISC risk is studied. It is found that (a) the variation trend of the probability of ISC risk with cycle number is nonlinear. The critical cycle number exists in the long-time use of the battery. (b) The probability increment of ISC risk becomes apparent when the charge rate reaches a critical value. (c) Battery temperature plays a great role in the critical cycle number. A lower temperature reduces the critical cycle number. (d) Effect of factors on the probability of ISC risk is listed as follows: charge rate > cycle number > battery temperature. With the help of the active protection method, ISC risk can be predicted before ISC occurs

Information-Driven Path Planning

Abstract Purpose of Review The era of robotics-based environmental monitoring has given rise to many interesting areas of research. A key challenge is that robotic platforms and their operations are typically constrained in ways that limit their energy, time, or travel distance, which in turn limits the number of measurements that can be collected. Therefore, paths need to be planned to maximize the information gathered about an unknown environment while satisfying the given budget constraint, which is known as the informative planning problem. This review discusses the literature dedicated to information-driven path planning, introducing the key algorithmic building blocks as well as the outstanding challenges. Recent Findings Machine learning approaches have been introduced to solve the information-driven path planning problem, improving both efficiency and robustness. Summary This review started with the fundamental building blocks of informative planning for environment modeling and monitoring, followed by integration with machine learning, emphasizing how machine learning can be used to improve the robustness and efficiency of informative path planning in robotics

Non-uniform effect on the thermal/aging performance of Lithium-ion pouch battery

Non-uniform distribution of current density and temperature is inevitable especially in high C-rate and it can lead to bad performance of battery. Therefore, the non-uniform effect (non-uniform temperature, current density and aging) on the pouch battery performance is studied with experiment and simulation. A new method, which measures the direct current resistance (DCR) based on the discharge curve, is proposed to get more detail of resistance variation. The measurement shows that the resistance of Lithium ion pouch battery with non-uniform temperature is similar to that of average temperature. Then, effect of non-uniform aging is simulated based on the electro-thermal coupled model. It is found that battery suffering non-uniform aging has smaller discharging capacity relatively. The main cause for the discharge capacity reduction between the uniform and non-uniform aging battery is the big difference of local stoichiometry of cathode electrode theta(LiFePO4). The capacity reduction in 1 C rate occupies about 6% of the permissible capacity loss. Finally, tabs of battery are changed in order to acquire uniform temperature distribution. Battery whose tabs are put on the middle of the top side and the bottom side has a better performance in the opinion of thermal analysis. (C) 2017 Elsevier Ltd. All rights reserved

Performance and safety protection of internal short circuit in lithium-ion battery based on a multilayer electro-thermal coupling model

Internal short-circuited lithium-ion battery can generate much heat in a short time and that leads to local high temperature or even explosion. A multilayer electro-thermal coupling model considering the interplay of current at different positions is developed to study the performance of internal short circuit and penetration before the trigger of thermal runaway. The simulation result agrees with the experiment in a certain extent. This study will serve as a guideline for protective design of internal short circuit. It concludes that penetration is not a precise method to simulate the performance of one-layer internal short circuit from view of maximum temperature and effect of cell unit layers. Temperature of large capacity battery is higher relatively when internal short occurs. A new method, in which the battery is forced to external short circuit when the internal short circuit is detected, is proposed to protect the battery from internal short circuit. The battery is within safe range if the external short circuit resistance is small enough. More, the maximum temperature increases with the decrease of battery resistance. Decreasing the resistance may increase the thermal runaway risk while increasing the battery resistance is a good protective method

Thermal management of standby battery for outdoor base station based on the semiconductor thermoelectric device and phase change materials

In order to extend the life span of standby battery for outdoor base station, a semiconductor thermoelectric device/phase change materials (PCMs) coupled battery thermal management system (BTMS), as well as the three-dimensional model of 48 V 80 Ah battery pack, was designed in this paper. The effect of various influencing factors, especially semiconductor thermoelectric device arrangement, temperature range of thermal management, cooling and heating power was investigated numerically. The results showed that the semiconductor thermoelectric devices were arranged at two flanks of minimum size direction could effectively improve the uniformity of battery module temperature field and prolong the heat preservation process. When the temperature difference between upper or lower limit of thermal management temperature range and the phase change temperature of PCMs (T-PCM) was no more than 5K, the maximum temperature difference (Delta T-max) of battery module during the cooling or heating process was lower than 5 K. Both the best choice of cooling and heating power was 200 W. What's more, after 1 C discharging and 0.5 C charging process, the maximum temperature (T-max) of battery module was restrained under the 312 K. During continuous cooling and heat preservation cycle, the cooling time and heat preservation time was about 14 h and 4.15 days, respectively, when the average ambient temperature was 323 K. The simulation results will be useful for the design of PCMs based battery thermal management system for outdoor base station battery

Experimental and Numerical Studies of Fine Quartz Single-Particle Sedimentation Based on Particle Morphology

The sedimentation characteristics of quartz particles affect their separation and settling dehydration processes. Particle morphology determines the sedimentation equilibrium velocity. In this paper, the sedimentation of a single quartz particle is characterized by employing experimental and CFD-DEM approaches. SEM served to examine quartz particles measuring 30–500 μm, and they exhibited flaky–blocky morphologies with an average long–middle axis ratio of 1.6. Consistent with the SEM-detected morphological features of the quartz particles, suggested here is a simpler drag coefficient model, followed by verification of the model with experimental data. The results show that the velocity of a quartz particle in the non-settling direction had a fluctuation of ±0.2 mm/s. The fluctuation reached 0.4 mm/s at varying settlement release angles. The order in which the particles reached sedimentation equilibrium velocity during the settlement process was double-cone, single-cone, and square when the initial velocity was greater than sedimentation equilibrium velocity. Furthermore, the long–middle axis ratio of quartz particles diminished as their equilibrium sedimentation velocities rose. Given that the quartz particles ranged from 30 to 50 μm in size, the long–middle axis ratio wielded no discernible effect on the sedimentation equilibrium velocity

A multilayer electro-thermal model of pouch battery during normal discharge and internal short circuit process

As the electrical and thermal characteristic will affect the batteries' safety, performance, calendar life and capacity fading, an electro-thermal coupled model for pouch battery LiFePO4/C is developed in normal discharge and internal short circuit process. The battery is discretized into many cell elements which are united as a 2D network equivalent circuit. The electro-thermal model is solved with finite difference method. Non-uniformity of current distribution and temperature distribution is simulated and the result is validated with experiment data at various discharge rates. Comparison of the lumped model and the multilayer structure model shows that the temperature non-uniformity Phi of multilayer model is bigger than that of lumped model and shows more precise. The temperature non-uniformity is quantified and the reason of non-uniformity is analyzed. The electro-thermal model can also be used to guide the safety design of battery. The temperature of the ISC element near tabs is the highest because the equivalent resistance of the external circuit (not including the ISC element) is the smallest when the resistance of cell units is small. It is found that increasing the thermal conductivity of integrated layer can effectively relieve the heat spot effect of ISC. (C) 2017 Elsevier Ltd. All rights reserved

Nonuniform current distribution within parallel-connected batteries

An imbalanced current distribution is often observed in cables of parallel batteries, which may limit the release of the energy and power in the battery pack. Hence, it is very important to analyze the homogeneous current distributions within parallel battery batteries and explore the effect on the state of charge and energy loss. Initially, it can be found that a battery near the load will experience a large local current under higher discharge rate. With the discharge, the current distribution will show a surge wave distribution, and the peak is gradually shifted backwards. As discharge continues, local current profile in segments will have different development trends, while current profile with lower initial current values increase, which leads to an entirely different form of current distribution with the initial stage of discharge. The current profile moves in a wavelike form transmission when the total discharge rate is low. The higher the current rate, the more divergent the current distribution. The state of charge distribution is also nonuniform, clearly indicating underutilization of active materials, which will further aggravate the nonuniformity of the local current distribution in the parallel battery pack