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表示：“为电网储存更多的电力是一个挑战。电力需求在60千兆瓦左右达到峰值，而我们的电网容量约为80千兆瓦--但存储容量仅为3千兆瓦左右。更大的存储能力对这些电力来源的可行性至关重要。它承诺到2050年，英国每年节省高达100亿GB的能源支出，因为高峰负荷的额外容量是不必要的。”相比之下，中国的电网装机容量超过1000千兆瓦，电力需求年增长率超过11%，2011年风电装机容量超过世界其他地区总和。与此同时，清理交通部门排放的计划导致了雄心勃勃的计划，扩大电动汽车的使用，这既会挑战电力系统，因为对电池的巨大需求，也会提供机会，因为这些电池可以用来提供能量存储。因此，英国和中国面临的挑战是，认识到目前的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累积电能存储容量来提供基本的电网服务，如频率支持、负载平衡、可再生能源发电的加强等等。这种车辆储能的双重用途(在连接到网络进行充电时提供其核心的车辆运输职责和电网支持)被称为车辆对电网(V2G)运行。V2G有许多技术挑战需要克服，还需要仔细分析电池充放电循环增加的影响以及相关的降级与实现的电网支持好处之间的成本效益。电动汽车电池的双重使用提供电网支持将使非常快速的行动(&lt；低成本(22欧元/千瓦)的聚合储能，其成本水平远低于专用电网电池安装(例如美国俄勒冈州塞勒姆的PGE 5兆瓦、1.25兆瓦时锂离子电池电网支持项目的3180欧元/千瓦(@1美元=0.75欧元)或与之竞争的储能技术，如压缩空气储能(CAES)。这项工作面临的研究挑战包括：1)针对特定的电网支持功能，如频率支持、调峰等，确定与驾驶和V2G操作相关的电池循环的预期模式。2)调查预期的V2G操作对电池单元、模块和组件循环寿命、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的荷电状态(SoC)和健康状态(SoH)，包括确保电池组中的电池平衡。3)调查从电池管理系统(BMS)到电网控制系统之间的通信和控制时间和物理信息需求。4)演示V2G在不同的英国和中国环境中的运行，采用新的具有循环/热控制功能的BMS软件，并改进了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.