Battery Characterisation and Management - the key to Smart Grids and the Integration of Electric Vehicles

就在2012年11月9日，英国财政大臣乔治奥斯本先生在皇家学会的一次演讲中说：“为电网储存更多电力是一个挑战。电力需求峰值约为60吉瓦，而我们的电网容量约为80吉瓦，但储能容量仅为3吉瓦。更大的电力储存能力对于这些能源的可行性至关重要。它承诺到2050年每年节省英国能源支出高达100亿英镑，因为高峰负荷的额外容量不那么必要。相比之下，中国的电网容量超过1,000吉瓦，电力需求年增长率超过11%，2011年安装的风电容量超过世界其他地区的总和。与此同时，清洁交通部门排放的计划正导致扩大电动汽车使用的雄心勃勃的计划，这既将挑战电力系统，因为电池充电的大量需求，但也提供了机会，因为这些电池可用于提供能量存储。因此，英国和中国面临的挑战是，认识到目前全球电动汽车市场预计将从2012年的170万辆增长到2020年的530万辆，如何利用电动汽车电池的巨大总电能存储容量来提供基本的电网服务，如频率支持，负载均衡、可再生能源发电的“稳固”等等。这种车辆能量存储的双重用途（当连接到网络进行充电时提供其核心车辆运输任务和电网支持）被称为车辆到电网（V2 G）操作。V2 G有许多技术挑战需要克服，并且需要对电池的增加的充电/放电循环的影响以及相关的退化与所实现的电网支持益处进行仔细的成本效益分析。电动汽车电池的双重用途，以提供电网支持将提供非常快速的行动（<5秒），至关重要的是，低成本（22欧元/千瓦）总储能，成本大大低于专用电网电池装置（例如，俄勒冈州塞勒姆的PGE 5兆瓦、1.25兆瓦时锂离子电池电网支持项目为3180欧元/千瓦（@$1= 0.75欧元），美国）或竞争的储能技术，如压缩空气储能（CAES）。关键的是，该提案旨在从电池角度“向上”而不是从网络级别“向下”关注V2 G操作，因为与V2 G成功相关的关键因素是与电池技术有关的因素。这项工作确定的研究挑战是：1）确定与特定电网支持功能（例如频率支持、调峰等）的驱动和V2 G操作相关的电池循环的预期模式。2）调查预期V2 G操作对电池单元、模块和电池组循环寿命、故障和热行为（即热循环和对冷/热电池充电行为的影响）的影响。此外，还需要更准确地确定电池充电状态（SoC）和健康状态（SoH），包括确保电池组内的电池平衡。3）研究从电池管理系统（BMS）到电网控制系统的通信和控制时间和物理信息要求，并反之亦然。4）在不同的英国和中国环境中演示V2 G操作，采用具有循环/热控制的新BMS软件，并改进SoC/SoH预测。

As recently as the 9th November 2012, the UK Chancellor, Mr George Osborne, stated in a speech to the Royal Society that "there is the challenge of storing more electricity for the Grid. Electricity demand peaks at around 60GW, whilst we have a grid capacity of around 80GW - but storage capacity of around just 3GW. Greater capability to store electricity is crucial for these power sources to be viable. It promises savings on UK energy spend of up to £10 billion a year by 2050 as extra capacity for peak load is less necessary." China, by contrast, has a grid capacity of over 1,000GW and an electrical demand growth rate of over 11% p.a, and in 2011 installed more wind capacity than the rest of the world put together. Concurrently, plans to clean up emissions from the transport sectors are leading to ambitious plans to expand the use of electric vehicles which will both challenge the electricity system due to the substantial need for battery charging, but also provide opportunity as these batteries can be used to provide energy storage.Hence the challenge for both the UK and China is, recognising the current global EV market is forecast to grow from 1.7 million units in 2012 to 5.3 million units in 2020, how to utilise this massive aggregate electrical energy storage capacity from EV batteries to deliver essential power network services such as frequency support, load levelling, 'firming' of renewable generation and so forth. The dual use of such vehicle energy storage (to provide its core vehicle transportation duty and grid support when connected to the network for recharging) is referred to as Vehicle-to-Grid (V2G) operation. V2G has many technical challenges to overcome as well as requiring careful cost benefit analysis of the effect of increased charge/discharge cycling of the battery, and associated degradation, versus the grid support benefits achieved. The dual use of EV batteries to provide grid support will make available very fast acting (<5 sec) and, crucially, low cost (Euro22/kW) aggregated energy storage, at cost levels significantly below dedicated grid battery installations (e.g. Euro3180/kW (@$1=Euro0.75) for the PGE 5MW, 1.25MWh Li-ion battery grid support project in Salem, Oregon, US) or competing energy storage technologies like compressed air energy storage (CAES).Critically this proposal aims to focus on V2G operation from a battery perspective 'upwards' and not from a network level 'downwards', as the key factors relating to the success of V2G are those concerned with the battery technology. The research challenges identified with this work are:1) Determining the anticipated patterns of battery cycling associated with driving and V2G operation for specified grid support functions e.g. frequency support, peak shaving etc.2) Investigating the impact of the anticipated V2G operation on battery cell, module and pack cycle life, failures and thermal behaviour (i.e. thermal cycling and impact on cold/hot battery charging behaviour). Additionally more accurate determination of battery state of charge (SoC) and state of health (SoH) is required, including ensuring cell balance within the battery pack.3) Investigating the communication and control temporal and physical information requirements from the battery management system (BMS) to the grid control system and vice versa.4) Demonstrating V2G operation within distinct UK and Chinese environments, employing the new BMS software with cycling/thermal control, and improved SoC/SoH prediction.