An advanced Lithium-ion battery optimal charging strategy based on a coupled thermoelectric model

Lithium-ion batteries are widely adopted as the power supplies for electric vehicles. A key but challenging issue is to achieve optimal battery charging, while taking into account of various constraints for safe, efficient and reliable operation. In this paper, a triple-objective function is first formulated for battery charging based on a coupled thermoelectric model. An advanced optimal charging strategy is then proposed to develop the optimal constant-current-constant-voltage (CCCV) charge current profile, which gives the best trade-off among three conflicting but important objectives for battery management. To be specific, a coupled thermoelectric battery model is first presented. Then, a specific triple-objective function consisting of three objectives, namely charging time, energy loss, and temperature rise (both the interior and surface), is proposed. Heuristic methods such as Teaching-learning-based-optimization (TLBO) and particle swarm optimization (PSO) are applied to optimize the triple-objective function, and their optimization performances are compared. The impacts of the weights for different terms in the objective function are then assessed. Experimental results show that the proposed optimal charging strategy is capable of offering desirable effective optimal charging current profiles and a proper trade-off among the conflicting objectives. Further, the proposed optimal charging strategy can be easily extended to other battery types

Constrained generalized predictive control of battery charging process based on a coupled thermoelectric model

Battery temperature is a primary factor affecting the battery performance, and suitable battery temperature control in particular internal temperature control can not only guarantee battery safety but also improve its efficiency. This is however challenging as current controller designs for battery charging have no mechanisms to incorporate such information. This paper proposes a novel battery charging control strategy which applies the constrained generalized predictive control (GPC) to charge a LiFePO₄ battery based on a newly developed coupled thermoelectric model. The control target primarily aims to maintain the battery cell internal temperature within a desirable range while delivering fast charging. To achieve this, the coupled thermoelectric model is firstly introduced to capture the battery behaviours in particular SOC and internal temperature which are not directly measurable in practice. Then a controlled auto-regressive integrated moving average (CARIMA) model whose parameters are identified by the recursive least squares (RLS) algorithm is developed as an online self-tuning predictive model for a GPC controller. Then the constrained generalized predictive controller is developed to control the charging current. Experiment results confirm the effectiveness of the proposed control strategy. Further, the best region of heat dissipation rate and proper internal temperature set-points are also investigated and analysed

Powering a Biosensor Using Wearable Thermoelectric Technology

Wearable medical devices such as insulin pumps, glucose monitors, hearing aids, and electrocardiograms provide necessary medical aid and monitoring to millions of users worldwide. These battery powered devices require battery replacement and frequent charging that reduces the freedom and peace of mind of users. Additionally, the significant portion of the world without access to electricity is unable to use these medical devices as they have no means to power them constantly. Wearable thermoelectric power generation aims to charge these medical device batteries without a need for grid power. Our team has developing a wristband prototype that uses body heat, ambient air, and heat sinks to create a temperature difference across thermoelectric modules thus generating ultra-low voltage electrical power. A boost converter is implemented to boost this voltage to the level required by medical device batteries. Our goal was to use this generated power to charge medical device batteries off-the-grid, increasing medical device user freedom and allowing medical device access to those without electricity. We successfully constructed a wearable prototype that generates the voltage required by an electrocardiogram battery; however, further thermoelectric module and heat dissipation optimization is necessary to generate sufficient current to charge the battery

Application of a simplified thermal-electric model of a sodium-nickel chloride battery energy storage system to a real case residential prosumer

Recently, power system customers have changed the way they interact with public networks, playing a more and more active role. End-users first installed local small-size generating units, and now they are being equipped with storage devices to increase the self-consumption rate. By suitably managing local resources, the provision of ancillary services and aggregations among several end-users are expected evolutions in the near future. In the upcoming market of household-sized storage devices, sodium-nickel chloride technology seems to be an interesting alternative to lead-acid and lithium-ion batteries. To accurately investigate the operation of the NaNiCl2 battery system at the residential level, a suitable thermoelectric model has been developed by the authors, starting from the results of laboratory tests. The behavior of the battery internal temperature has been characterized. Then, the designed model has been used to evaluate the economic profitability in installing a storage system in the case that end-users are already equipped with a photovoltaic unit. To obtain realistic results, real field measurements of customer consumption and solar radiation have been considered. A concrete interest in adopting the sodium-nickel chloride technology at the residential level is confirmed, taking into account the achievable benefits in terms of economic income, back-up supply, and increased indifference to the evolution of the electricity market

Advanced thermal management system driven by phase change materials for power lithium-ion batteries: A review

Power lithium-ion batteries are widely utilized in electric vehicles (EVs) and hybrid electric vehicles (HEVs) for their high energy densities and long service-life. However, thermal safety problems mainly resulting from thermal runaway (TR) must be solved. In general, temperature directly influences the performance of lithium-ion batteries. Hence, an efficient thermal management system is very necessary for battery modules/packs. One particular approach, phase change material (PCM)-based cooling, has exhibited promising applicability due to prominent controlling-temperature and stretching-temperature capacities. However, poor thermal conductivity performance, as the main technical bottleneck, is limiting the practical application. Nevertheless, only promoting the thermal conductivity is far from enough considering the practical application in EVs/HEVs. To fix these flaws, firstly, the heat generation/transfer mechanisms of lithium-ion power batteries were macro- and microscopically reviewed. Following that, the thermal conductivity, structural stability, and flame retardancy of PCM are thoroughly discussed, to which solutions to the aforementioned performances are systematically reviewed. In addition, battery thermal management system (BTMS) employing PCM is illustrated and compared. Eventually, the existing challenges and future directions of PCM-based BTMS are discussed. In summary, this review presents effective approaches to upgrade the PCM performances for high-density lithium-ion BTMS. These strategies furtherly accelerate the commercialization process of PCM BTMS

Day-Ahead Offering Strategy In The Market For Concentrating Solar Power Considering Thermoelectric Decoupling By A Compressed Air Energy Storage

Due to limited fossil fuel resources, a growing increase in energy demand and the need to maintain positive environmental effects, concentrating solar power (CSP) plant as a promising technology has driven the world to find new sustainable and competitive methods for energy production. The scheduling capability of a CSP plant equipped with thermal energy storage (TES) surpasses a photovoltaic (PV) unit and augments the sustainability of energy system performance. However, restricting CSP plant application compared to a PV plant due to its high investment is a challenging issue. This paper presents a model to assemble a combined heat and power (CHP) with a CSP plant for enhancing heat utilization and reduce the overall cost of the plant, thus, the CSP benefits proved by researches can be implemented more economically. Moreover, the compressed air energy storage (CAES) is used with a CSP-TES-CHP plant in order that the thermoelectric decoupling of the CHP be facilitated. Therefore, the virtual power plant (VPP) created is a suitable design for large power grids, which can trade heat and electricity in response to the market without restraint by thermoelectric constraint. Furthermore, the day-ahead offering strategy of the VPP is modeled as a mixed integer linear programming (MILP) problem with the goal of maximizing the profit in the market. The simulation results prove the efficiency of the proposed model. The proposed VPP has a 2% increase in profit and a maximum 6% increase in the market electricity price per day compared to the system without CAES

A review of thermal management for Li-ion batteries: Prospects, challenges, and issues

Li-ion batteries are essential component in the current generation of electric vehicles. However, further pushing electric vehicles are concerned with battery life. Since the temperature dictates battery lifetime, it is crucial to manage the heat and keep the temperature at an acceptable range within the battery pack. The benefit of a cooling system is to prevent the premature degradation of battery life. This paper provides a critical review of the so far thermal management strategy dealing with temperature within the cells, module, and packs. This paper reviews the advantages and disadvantages of state of the art (traditional) thermal cooling system. In this paper, we have reviewed separately cell, module, and pack level cooling system. The battery thermal modeling techniques and cooling system design challenges are also reviewed. This paper also reviews the future cooling system for future vehicles with rising fast charge rate and these techniques can improve the limitations of the traditional cooling system. This paper also suggests the best suitable and economically viable technology for the upcoming EVs issues