Electrochemical energy storage system has the characteristics of convenient and flexible installation, fast response speed and good controllability, which can significantly improve the power grid consumption capacity of renewable energy sources such as wind and light, improve power quality, smooth the power grid flow, reduce power asset investment, and play an important role in promoting the transformation and development of energy transformation. In recent years, lithium-ion battery energy storage systems have been able to flourish in the power industry in countries around the world due to their significant advantages such as high energy density, large discharge rate and declining cost. At the same time, the preparation and release of energy storage related standards are also constantly updated with the development of the energy storage industry. These standards and specifications have actively guided and promoted the development of the energy storage industry, but there are still some problems in the specific application process. Among them, the most critical impact on the lithium-ion battery industry is the safety-related standard specifications.
At present, the internationally influential lithium-ion battery energy storage system safety standards are UL1973 and IEC62619, Japan, Australia, South Korea and other countries have referenced or compiled their domestic applicable standards according to these two sets of standards, and China issued a number of national standards related to energy storage systems in 2017 and 2018. Despite this, the safety of lithium battery energy storage power stations is still relatively prominent, from August 2017 to May 2019, there were 23 fires in energy storage power stations in South Korea; In April 2019, a fire broke out in the energy storage system in Arizona, USA; In August 2018, a fire mountain occurred in the Energy Storage System of Yangzhong in Jiangsu Province. This shows that the standard specifications related to lithium battery energy storage are far from perfect.
In contrast, energy storage power stations in North America and Europe are running better, and there are fewer reported energy storage safety accidents. Although the safety of energy storage is a complex and comprehensive problem, involving many factors such as the technical type, technical level, application scenario, battery quality, local regulations and so on of the energy storage system, advanced and perfect safety standards can ensure the safe operation of the energy storage system. Through the comparative study of the lithium-ion battery safety standards of the main energy storage systems of UL and IEC, this paper systematically analyzes and compares the specific requirements of each clause, explores the advantages and disadvantages of each standard, and puts forward some suggestions for standard improvement, so as to provide a reference for improving and upgrading the safety standards of the new energy storage system.
1.Features of the current energy storage system safety standards
Internationally, the safety standards for energy storage systems mainly include IEC standards and UL standards. Europe and Japan mainly refer to IEC standards to develop corresponding safety standards, such as EN62619 in Europe and JISC8715-28 in Japan, which are revised and compiled according to IEC62619. UL standards are widely used in North America, and their battery safety standards are comprehensive and rigorous, and have considerable influence. Australian standards and IEC standards have been adopted, and the Australian Standards Institute began drafting DRAS/NZS5139 in 2017, and has not yet seen the official release. In order to cooperate with South Korea’s new energy policy, in 2015, South Korea issued a series of energy storage related standards, including the safety standard KBIA-10104-01, which mainly refers to IEC related standards, the biggest difference is that there is less drop test and internal short circuit /thermal runaway diffusion test, and more extrusion, immersion, external short circuit control and overcharge control test.
In terms of lithium battery transportation safety, UN38.3 is the more common standard in the world, requiring lithium batteries to transport, must pass high simulation, thermal test, vibration, shock, 55 °C external short circuit, impact test, overcharge test, forced discharge test, in order to ensure the safety of lithium battery transportation. Most countries around the world adopt this standard. Compared with the UN38.3 standard, the main difference between IEC62281 and the UN38.3 standard is that the number of test samples and the requirements of the live state are different, and the test items are basically the same.
1.1 IEC safety standards for energy storage systems
IEC safety standards for energy storage system products are mainly formulated and promulgated by the IEC Standards Working Group TC21/SC21A and TC120 of the International Electrotechnical Commission, TC21/SC21A focuses on the safety standards of all secondary batteries, while TC120 focuses on the electrochemical energy storage (EES) system related standards for power grid applications. The main safety standards for IEC energy storage systems are as follows:IEC 62619, IEC 62485-5, IEC 62933-5-1, IEC 62933-5-2, IEC 63056, IEC 62281.
IEC62619 regulates the common test items and minimum safety requirements of secondary lithium batteries in industrial use, and iec positions it as an “umbrella standard” for a wide range of industrial product applications, including communication base stations, uninterruptible power systems (UPS), energy storage systems, emergency power lamp fixed installation products, as well as stackers, golf carts, unmanned vehicles (AGVs), railways, sea freight, excluding land transportation for power applications. For various product applications, IEC further develops dedicated lithium battery safety standards to cope, such as IEC63056 for energy storage systems.
IEC62619 emphasizes that battery systems should be evaluated safely under reasonably foreseeable abuse, including external short circuit tests, impact tests, drop tests, thermal abuse tests, overcharge tests, and forced discharge tests. In addition, in the evaluation of the safety of short circuits in the battery, two optional tests are provided: the short circuit test in the battery cell or the thermal diffusion test network of the battery system, which is a more compromise approach.
IEC63056 specifies the safety requirements for secondary lithium batteries and battery packs for energy storage systems with a rated voltage of less than 1500V (DC). IEC62485-5 regulates the safety requirements for the installation, use, inspection, maintenance and disposal of lithium batteries in fixed applications, focusing on the operation safety of fixed lithium batteries 7: IEC62933-5-2 regulates the system safety requirements for electrochemical energy storage systems including lithium battery applications when they are integrated into the power grid. IEC62281 regulates the safety requirements for primary and secondary lithium batteries and battery packs in transit.
In summary, the IEC energy storage safety standard level is relatively clear and covers a comprehensive content. However, due to its being an international standard, the organization and member relationship involved in the preparation are complex, involving more national interest disputes, slow progress, and lagging behind the development of the industry, in addition to IEC62619, IEC62281 has been released.