Energy analysis of batteries in photovoltaic systems. Part I: Performance and energy requirements

The technical performance and energy requirements for production and transportation of a stand alone photovoltaic (PV)-battery system at different operating conditions are presented. Eight battery technologies are evaluated: lithium-ion (Li-ion), sodium–sulphur (NaS), nickel–cadmium (NiCd), nickel–metal hydride (NiMH), lead–acid (PbA), vanadium-redox (VRB), zinc–bromine (ZnBr) and polysulfide-bromide (PSB). In the reference case, the energy requirements for production and transport of PV-battery systems that use the different battery technologies differ by up to a factor of three. Production and transport of batteries contribute 24–70% to the energy requirements, and the PV array contributes 26–68%. The contribution from other system components is less than 10%. The contribution of transport to energy requirements is 1–9% for transportation by truck, but may be up to 73% for air transportation. The energy requirement for battery production and transport is dominant for systems based on NiCd, NiMH and PbA batteries. The energy requirements for these systems are, therefore, sensitive to changes in battery service life and gravimetric energy density. For systems with batteries with relatively low energy requirement for production and transportation (Li-ion, NaS, VRB, ZnBr, PSB), the battery charge–discharge efficiency has a larger impact. In Part II, the data presented here are used to calculate energy payback times and overall battery efficiencies of the PV-battery systems.     

Fundamental scientific aspects of lithium batteries(I)--Thermodynamic calculations of theoretical energy densities of chemical energy storage systems

本文主要讨论电池的能量密度.基于热力学数据,根据能斯特方程,可以计算不同电化学反应体系的理论能量储存密度,从而了解化学储能体系理论能量密度的上限,了解哪些体系能够实现更高的能量密度,哪些材料具有更高的电压.     

Requirements for future automotive batteries – a snapshot

Introduction of new fuel economy, performance, safety, and comfort features in future automobiles will bring up many new, power-hungry electrical systems. As a consequence, demands on automotive batteries will grow substantially, e.g. regarding reliability, energy throughput (shallow-cycle life), charge acceptance, and high-rate partial state-of-charge (HRPSOC) operation. As higher voltage levels are mostly not an economically feasible alternative for the short term, the existing 14 V electrical system will have to fulfil these new demands, utilizing advanced 12 V energy storage devices. The well-established lead–acid battery technology is expected to keep playing a key role in this application. Compared to traditional starting–lighting–ignition (SLI) batteries, significant technological progress has been achieved or can be expected, which improve both performance and service life. System integration of the storage device into the vehicle will become increasingly important. Battery monitoring systems (BMS) are expected to become a commodity, penetrating the automotive volume market from both highly equipped premium cars and dedicated fuel-economy vehicles (e.g. stop/start). Battery monitoring systems will allow for more aggressive battery operating strategies, at the same time improving the reliability of the power supply system. Where a single lead–acid battery cannot fulfil the increasing demands, dual-storage systems may form a cost-efficient extension. They consist either of two lead–acid batteries or of a lead–acid battery plus another storage device.     

An analysis of the competitiveness of hydrogen storage and Li-ion batteries based on price arbitrage in the day-ahead market

Acceleration of the hydrogen economy is being observed on a global scale. It is considered to be a potential solution to the problems with high-carbon energy, industry, and transport systems. The potential of production, cost-competitiveness, and opportunities are currently being investigated to provide insights to policymakers, researchers, and industry. In this context, this study makes a quantitative assessment of the competitiveness of hydrogen storage compared to Li-ion batteries based on price arbitrage in the day-ahead market. Two scenarios that form the boundaries of rational decision-making regarding the charging and discharging of energy storage are considered. The first one assumes the charging and discharging of energy storage facilities over the same hours throughout the entire year. The selection of these hours is based on historical electricity prices. The second scenario assumes charge and discharge during historical daily minimum and maximum prices. The results show that NPV is below zero for both technologies when current values of investment expenditure are assumed. The outcomes of sensitivity analysis indicate that only a substantial reduction of investment expenditure could improve the financial results of the Li-ion batteries (NPV>0). The investigation also shows that even simplified charge and discharge over the same hours allows one to achieve 47% (hydrogen) and 70% (Li-ion batteries) of the maximum operating profit when the perfect foresight of prices is applied. In each case, NPV for Li-ion technology is significantly higher than for hydrogen; for example, for a 1 MWh and 1 MWout storage system, NPV is EUR -4.85 million in the case of hydrogen and with Li-ion NPV is EUR -0.23 million. Consequently, the application of expensive decision support systems in small systems may be unprofitable. The increase in profits may not cover the cost of developing and introducing such a system.     

Polymer Electrolyte Membranes for Vanadium Redox Flow Batteries: Fundamentals and Applications

Electrochemical energy storage systems are considered as one of the most viable solutions to realize large-scale utilization of renewable energy. Among the various electrochemical energy storage systems, flow batteries have increasingly attracted global attention due to their flexible structural design, high efficiencies, long operating life cycle, and independently tunable power and energy storage capacity. Although promising, a number of challenges including the high cost of flow battery materials hinder the broad market penetration of flow battery technology. Polymer electrolyte membrane, as a key component in flow batteries providing pathways for charge carriers transport and preventing electrolytes crossover, takes over 25% of the entire cost of the battery system. Apparently, the membrane not only plays pivotal roles in the operation characteristics of a flow battery, but also largely influences the financial cost of the battery system. To provide insights and better understanding of membranes towards enhancing their performance and cost-effectiveness, we therefore present recent advances and research outcomes on the development of polymer electrolyte membranes as well as their applications in flow batteries, particularly all-vanadium redox flow batteries. Various aspects of polymer electrolyte membranes including functional requirements, characterization methods, materials screening and preparation strategies, transport mechanisms, and commercialization progress are presented. Finally, perspectives for future trends on research and development of polymer electrolyte membranes with relevance to flow batteries are highlighted.     

Self-discharge characteristics and performance degradation of Ni-MH batteries for storage applications

The needs for onboard energy storage are practically dependent on the Ni-MH and Li-ion battery packs, because these two power-assisting systems have features of proper energy density, longer cycle lifetime, quick charge acceptance, and proper operating windows for both voltage and temperature. In particular, the Ni-MH power system has a proper tolerance mechanism for overcharge and overdischarge, a lower cost for battery pack maintenance, and a slightly longer cycle lifetime profile. We studied the self-discharge characteristics, state-of-health, state-of-charge, and energy efficiencies at various charge input levels. The end-of-voltages during charge and discharge were evaluated for the Ni-MH storage batteries. The impedance measurements and data analysis have also been conducted for equivalent circuit simulations. The performance deterioration and capacity decay are fundamentally analyzed and discussed in details, including electrode side-reactions, structure degradations, separator weakening, and level changes of electrolyte saturation in the battery. Further battery quality enhancement through cycle duration improvement for onboard energy storage potentially provides more suitable power and energy delivery in order to obtain higher efficiency, save more fuels, and reduce CO₂, SO₂, and NO_x emissions.     

Operation conditions of batteries in PV applications

For a continuous energy supply of photovoltaic operated and off-grid loads, the storage of the solar generated electrical energy is necessary. About 60% of all over the world manufactured solar cells are used for such stand alone systems. In case of photovoltaic systems, mainly electrochemical battery storage systems are used.

The paper describes the requirements for batteries in solar systems. The most important storage systems, such as lead–acid, NiMH and Li-ion batteries are described in detail and further developing trends are discussed.

As it is well known that the operation conditions strongly influence the battery lifetime, this paper reviews photovoltaic operation conditions and experience in performance and lifetime in photovoltaic systems.     

Accurate electrical battery model capable of predicting runtime and I-V performance

Low power dissipation and maximum battery runtime are crucial in portable electronics. With accurate and efficient circuit and battery models in hand, circuit designers can predict and optimize battery runtime and circuit performance. In this paper, an accurate, intuitive, and comprehensive electrical battery model is proposed and implemented in a Cadence environment. This model accounts for all dynamic characteristics of the battery, from nonlinear open-circuit voltage, current-, temperature-, cycle number-, and storage time-dependent capacity to transient response. A simplified model neglecting the effects of self-discharge, cycle number, and temperature, which are nonconsequential in low-power Li-ion-supplied applications, is validated with experimental data on NiMH and polymer Li-ion batteries. Less than 0.4% runtime error and 30-mV maximum error voltage show that the proposed model predicts both the battery runtime and I-V performance accurately. The model can also be easily extended to other battery and power sourcing technologies.     

Charging performance of automotive batteries—An underestimated factor influencing lifetime and reliable battery operation

Dynamic charge acceptance and charge acceptance under constant voltage charging conditions are for two reasons essential for lead-acid battery operation: energy efficiency in applications with limited charging time (e.g. PV systems or regenerative braking in vehicles) and avoidance of accelerated ageing due to sulphation. Laboratory tests often use charge regimes which are beneficial for the battery life, but which differ significantly from the operating conditions in the field.     

Current status of research on optimum sizing of stand-alone hybrid solar–wind power generation systems

Solar and wind energy systems are omnipresent, freely available, environmental friendly, and they are considered as promising power generating sources due to their availability and topological advantages for local power generations. Hybrid solar–wind energy systems, uses two renewable energy sources, allow improving the system efficiency and power reliability and reduce the energy storage requirements for stand-alone applications. The hybrid solar–wind systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. This paper is to review the current state of the simulation, optimization and control technologies for the stand-alone hybrid solar–wind energy systems with battery storage. It is found that continued research and development effort in this area is still needed for improving the systems’ performance, establishing techniques for accurately predicting their output and reliably integrating them with other renewable or conventional power generation sources.     

The automotive battery of the future—the role of electronics

The automotive battery is being asked to carry out more challenging duties than ever before. Many of these duties are a result of new types of electrical load. The way in which a battery is operated and managed within a vehicle can be optimized significantly through the use of battery-related electronics with embedded software. Potential benefits include extended life, early warning of deterioration and failure, greater availability and an improved match to the vehicle's requirements. The impact of electronics in other areas shows that there is considerable potential to go much further in this direction with battery systems. There are, however, important system-wide issues to be considered. The battery system must conform to a wide range of standards and practices applicable to automotive electronic systems and embedded software. The automotive industry is itself trying to come to terms with the inherent difficulties involved in developing, qualifying and upgrading complex networks of software-based controllers within the vehicle. The battery system must be compatible with the results of these initiatives. Cost will always be a major influence, but the cost model is different from that familiar to battery producers. This study outlines the main areas where the battery industry must consider a change from being a component to a system supplier, and makes some recommendations for an industry wide approach to smooth the transition.     

Development,analysis and assessment of fuel cell and photovoltaic powered vehicles

This paper deals with a new hybridly powered photovoltaic- PEM fuel cell – Li-ion battery and ammonia electrolyte cell integrated system (system 2) for vehicle application and is compared to another system (system 1) that is consisting of a PEM fuel cell, photovoltaic and Li-ion battery. The paper aims to investigate the effect of adding photovoltaic to both systems and the amount of hydrogen consumption/production that could be saved/generated if it is implemented in both systems. These two systems are analyzed and assessed both energetically and exergetically. Utilizing photovoltaic arrays in system 1 is able to recover 177.78 g of hydrogen through 1 h of continuous driving at vehicle output power of 98.32 kW, which is approximately 3.55% of the hydrogen storage tank used in the proposed systems. While, using the same photovoltaics arrays, system 2 succeeds to produce 313.86 g of hydrogen utilizing the ammonia electrolyzer system 2 appeared to be more promising as it works even if the car is not in operation mode. Moreover, the hydrogen produced from the ammonia electrolyzer can be stored onboard, and the liquefied ammonia can be used as a potential source for feeding PEM fuel cell with hydrogen. Furthermore, the effects of changing various system parameters on energy and exergy efficiencies of the overall system are investigated.     

Application of superconducting magnetic energy storage in electrical power and energy systems: a review

Superconducting magnetic energy storage (SMES) is known to be an excellent high‐efficient energy storage device. This article is focussed on various potential applications of the SMES technology in electrical power and energy systems. SMES device founds various applications, such as in microgrids, plug‐in hybrid electrical vehicles, renewable energy sources that include wind energy and photovoltaic systems, low‐voltage direct current power system, medium‐voltage direct current and alternating current power systems, fuel cell technologies and battery energy storage systems. An extensive bibliography is presented on these applications of SMES. Also, some conclusive remarks in terms of future perspective are presented. Also, the present ongoing developments and constructions are also discussed. This study provides a basic guideline to investigate further technological development and new applications of SMES, and thus benefits the readers, researchers, engineers and academicians who deal with the research works in the area of SMES. Copyright © 2017 John Wiley & Sons, Ltd.     

Experimental validation for Li-ion battery modeling using Extended Kalman Filters

The battery management systems (BMS) is an essential emerging component of both electric and hybrid electric vehicles (HEV) alongside with modern power systems. With the BMS integration, safe and reliable battery operation can be guaranteed through the accurate determination of the battery state of charge (SOC), its state of health (SOH) and the instantaneous available power. Therefore, undesired power fade and capacity loss problems can be avoided. Because of the electrochemical actions inside the battery, such emerging storage energy technology acts differently with operating and environment condition variations. Consequently, the SOC estimation mechanism should cope with the probable changes and uncertainties in the battery characteristics to ensure a permanent precise SOC determination over the battery lifetime.This paper aims to study and design the BMS for the Li-ion batteries. For this purpose, the system mathematical equations are presented. Then, the battery electrical model is developed. By imposing known charge/discharge current signals, all the parameters of such electrical model are identified using voltage drop measurements. Then, the extended kalman filter (EKF) methodology is employed to this nonlinear system to determine the most convenient battery SOC. This methodology is experimentally implemented using C language through micro-controller. The proposed BMS technique based on EKF is experimentally validated to determine the battery SOC values correlated to those reached by the Coulomb counting method with acceptable small errors.     

Nonlinear control and optimization of hybrid electrical vehicle under sources limitation constraints

This work presents a new contribution on energy management of hybrid electric systems for vehicle applications. The studied hybrid electrical vehicle is composed of fuel cell as a main source and the auxiliary system containing the battery and supercapacitor. A programmable load is used to emulate a vehicle load profile. Two methods are combined to smartly and optimally control the energy flow between the used sources. These methods are the Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) and the Hamilton-Jacobi Bellman (HJB) optimization. The source limitation is considered here in terms of the battery state of charge. The experimental works validate the efficiency of the proposed control where the obtained results demonstrate that the used strategy allows regulating the power flow under a realistic load drive profile. The global stability proof is demonstrated using Lyapunov theory.     

The challenge to the automotive battery industry: the battery has to become an increasingly integrated component within the vehicle electric power system

During the time that the automotive battery was considered to be just a passive component in a vehicle electric power system, the battery industry's answer to all new challenges was constructive improvements. The emerging requirements of even higher function reliability cannot, however be met this way. A battery manufacturer of today has to give recommendations for the appropriate choice of the electrical architecture and has to design batteries that suit best the requirements. In addition, manufactures have to be engaged in the technology of battery management, of battery monitoring and state detection, and performance of prediction under future operation conditions. During service on-board a vehicle, battery performance undergoes significant changes, e.g., loss of storage capability, increase in internal resistance, and changes in voltage characteristics. These ageing processes have to be considered when the electrical architecture is being designed and management strategies are being formulated. Battery monitoring and state detection must be able to identify and quantify battery degradation. Moreover, performance prediction as well as management strategies have to be corrected on account of the changing battery characteristics.     

VRLA automotive batteries for stop&go and dual battery systems

The electrical power requirements for vehicles are continuing to increase and evolve. A substantial amount of effort has been directed towards the development of 36/42 V systems as a route to higher power with reduced current levels but high implementation costs have resulted in the introduction of these systems becoming deferred. In the interim, however, alternator power outputs at 14 V are being increased substantially and at the same time the requirements for batteries are becoming more intensive. In particular, stop&go systems and wire-based vehicle systems are resulting in new demands. For stop&go, the engine is stopped each time the vehicle comes to rest and is restarted when the accelerator is pressed again. This results in an onerous duty cycle with many shallow discharge cycles. Flooded lead–acid batteries cannot meet this duty cycle and valve-regulated lead-acid (VRLA) batteries are needed to meet the demands that are applied. For wire-based systems, such as brake-by-wire or steer-by-wire, electrical power has become more critical and although the alternator and battery provide double redundancy, triple redundancy with a small reserve battery is specified. In this case, a small VRLA battery can be used and is optimised for standby service rather than for repeated discharges. The background to these applications is considered and test results under simulated operating conditions are discussed. Good performance can be obtained in batteries adapted for both applications. Battery management is also critical for both applications: in stop&go service, the state-of-charge (SOC) and state-of-health (SOH) need to be monitored to ensure that the vehicle can be restarted; for reserve or back-up batteries, the SOC and SOH are monitored to verify that the battery is always capable of carrying out the duty cycle if required. Practical methods of battery condition monitoring will be described.     

Development of a long life 35 Ah capacity VRLA battery for load-leveling applications

A load-leveling (LL) system is needed for the effective use of electric power to preserve the environment in Japan. Although the valve regulated lead-acid (VRLA) battery is considered to be one of the suitable candidates, high requirements of long cycle life such as 2000 cycles or a calendar life of 7 years needed to be solved. We are currently developing a new VRLA battery for this application, and have succeeded in achieving over 2000 cycles with a 35 Ah class VRLA battery. It was confirmed by the detailed investigation after a cycling test of the battery that this cycle performance was achieved by improving the charge acceptance of the negative plate, avoiding the grid corrosion by applying an optimized charge condition.     

A Li-ion battery management system for large-capacity energy storage

应用锂离子电池进行储能已成为大容量储能技术研究的重点,但为保证电池组的可靠性、安全性、一致性及使用寿命,必须设计电池管理系统来对锂离子电池进行有效管理。本文提出了一种适用于大容量储能技术的锂离子电池管理系统,该管理系统采用分层采集和管理的方法,分别对单体电池、电池组和储能子系统进行管理。文章详述了分层管理系统的结构、功能和管理策略,其中着重介绍了单体电池数据采集功能、电池状态估计功能和均衡管理功能,并进行了实验验证,给出了实验结果分析。实验结果证明了该管理系统可以满足实际的大容量储能应用需求,可以实现锂离子电池的高精度状态估计功能和高效均衡控制策略,具有很好的应用前景,为后续产业化发展提供了一种技术和思路。     

Design of a grid-connected PV system with hybrid energy storage

由于国内的储能技术起步较晚,分布式电源中应用单一储能介质很难满足系统运行要求.基于某公司的光伏储能并网系统示范项目,以具有快速响应特性的超级电容器和具有大容量储能特性的锂离子电池为混合储能系统,以储能控制器为控制核心统一协调控制,使电能以可控功率按需送入电网.该系统可有效提高储能系统的功率输出能力,优化储能系统的充放电过程,延长储能电池的使用寿命,具有良好的应用及推广价值.