Application of energy storage battery technology in power systems

　　With the promotion and application of new technologies such as smart grids and distributed power supply, the role of energy storage has further emerged. Our country has also launched a wind and solar energy storage demonstration in Zhangjiakou, and a 5MW all-aluminum redox flow battery energy storage device has been built at Faku Wind Farm in Liaoning. Building energy storage devices in the power grid can be simply compared to a circuit that only has power supply and resistors (users). The circuit is not stable enough. Adding capacitors greatly improves the stability of the circuit. In order to gain an in-depth understanding of the current status and development trends of international energy storage technology, and as a reference for the rapid development of my country's energy storage industry, we now summarize the application, positioning and value analysis of energy storage technology in power systems, the current status of energy storage applications at home and abroad, and industrial policies, etc. relevant circumstances.

　　About various energy storage technologies

　　According to the application fields of power systems, energy storage can be divided into two types: power energy storage and energy energy storage. Energy energy storage is mainly used for the deployment and management of high energy (electric energy). Typical applications include peaking power stations; power energy storage. Energy storage is mainly used in instantaneous high-power input and output situations. Typical applications include power grid frequency regulation.

　　According to the type of technology, energy storage technology mainly includes physical energy storage and chemical energy storage. Physical energy storage mainly includes pumped water energy storage, compressed air energy storage and flywheel energy storage. The first two energy storage systems have the advantages of large scale, long life, safety and reliability, and low operating costs. The construction scale is generally above 100 megawatts, and the energy storage time ranges from a few hours to a few days. They are suitable for peak shaving and filling of the power system. Valley, emergency backup capacity and other applications. Among them, pumped energy storage is currently the most widely used energy storage method in the power system, with a global total installed capacity of 127GW, accounting for 99% of the total installed energy storage capacity. But both energy storage technologies also have construction limitations. Flywheel energy storage has the advantages of fast response, high conversion efficiency, and high specific power. It can realize real-time high-power compensation with the power system. It is especially suitable for power-type energy storage technology in power systems. However, the current technology has not reached practical requirements and has not yet been implemented. It requires technology accumulation and industrial supporting development.

　　Chemical energy storage includes lead-acid batteries, lead-carbon batteries, flow batteries, sodium-sulfur batteries, lithium batteries and metal-air batteries. Compared with physical energy storage technology, it has the advantages of simple system, convenient installation and flexible operation mode. The construction scale Generally in the kilowatt to hundreds of megawatts level, it is suitable for distributed energy storage equipment in power systems. It is currently the focus of the application and development of power energy storage in wind power, solar energy and other fields.

　　Among chemical energy storage technologies, lead-acid batteries are a relatively mature technology and have the advantages of low price, safety and reliability. However, they have short cycle life, cannot be deeply discharged, and have high operation and maintenance costs. Lead-acid batteries can only operate in It is mainly used as a backup power supply for the power system under shallow charging, shallow discharge or backup conditions. Lead-carbon batteries are an improvement on the traditional lead-acid electrodes, which improves the battery charge and discharge life to a certain extent and are used in power system backup and short-term power conditions. Sodium-sulfur battery is a high-temperature battery that uses metallic sodium and liquid sulfur as active materials and operates at 300°C. It has the advantages of high energy storage density and high conversion efficiency, and is suitable for peak shaving and frequency modulation applications in power systems. Currently, the cumulative installed capacity of sodium-sulfur batteries is about 304MW. However, two fire and explosion incidents in 2011 made users pay attention to their safety risks. Lithium batteries have the advantages of high specific power and high conversion efficiency, and are particularly suitable for mobile energy storage methods such as electric vehicles. In recent years, their applications in power system backup power supplies and grid frequency regulation have also attracted much attention. Flow batteries have developed rapidly in recent years. Their advantages such as good safety, long life, and flexible system design make them have broad space as energy storage devices for power system peak shaving, frequency modulation, renewable energy grid integration, and distributed energy supply. .

　　Chemical energy storage technology is suitable for decentralized and flexible energy storage layout of power systems. The current development of technology is flourishing. Flow batteries, lithium batteries, sodium-sulfur batteries, and lead-carbon batteries are the mainstream energy storage technologies for power systems. High safety, high reliability, high cost performance, high energy efficiency, and long life are the development directions of energy storage technology.

　　In recent years, the proportion of renewable energy power generation such as solar energy and wind energy in the power system has gradually increased, which has brought new challenges to the safe operation and efficient dispatch of the existing power grid. Smart grids have become an important factor in promoting the development of new energy and ensuring grid security. carrier. Energy storage technology, especially large-scale energy storage technology, is a means to achieve the main goals of smart grids in the four major aspects of power generation, transmission, distribution, and power consumption, such as regulating power quality and optimizing energy efficiency. It has gradually become an indispensable key link in building smart grids. .

　　It can be seen that the role of energy storage in the entire power system is reflected in "adjustment, optimization, improvement, and guarantee", that is, adjusting the efficient and flexible distribution of electric energy within the entire system, optimizing the resource allocation and utilization of the entire system equipment, and improving the efficiency of the entire system. operation efficiency and power quality, ensuring the stability and safe operation of the entire system. Among them, the necessity of energy storage is reflected in ensuring the security of the power grid, realizing system-wide energy management, and accepting renewable energy; the economy is reflected in optimizing the configuration of equipment and improving the efficiency of the entire network; and the technological advancement is reflected in the comparison with traditional peak load regulation. , frequency modulation, rotating backup equipment, its outstanding advantages in terms of fast, accurate responsiveness and high efficiency.

　　At present, the application of energy storage in the power system subdivisions mainly includes renewable energy access energy storage, grid peak regulation/frequency regulation energy storage, distribution side distributed energy storage and user side distributed microgrid energy storage. It has direct and indirect economic value in these applications.

　　In summary, when investors (power generation companies, grid operators, users) measure the value of energy storage, in addition to considering the direct benefits under each application mode, they must also measure the comprehensive value of energy storage to the entire system, including equipment. Reduced investment, lower operating expenses, improved power generation/power consumption efficiency, etc. In addition, open power trading will also increase the market competitiveness of energy storage. Through the accumulation of running energy storage demonstration projects, we can establish system economic models under different modes and grasp the overall situation of industrial policies to promote the development of the energy storage industry.

　　About the application status of chemical energy storage technology

　　At present, the total installed capacity of energy storage equipment operating in the power system worldwide reaches 127GW, 99% of which is pumped storage technology. The total installed capacity of chemical energy storage technology is about 520MW, including 304MW of sodium-sulfur batteries and 116MW of lithium batteries. , flow battery 20MW, lead-acid battery (including lead-carbon battery) 80MW.

　　Sodium-sulfur batteries are currently the chemical energy storage technology with the largest installed capacity. They are mainly used in distributed energy storage in distribution networks to delay investment in expansion and upgrading of distribution network equipment and lines when load increases. Lithium batteries and flow batteries have developed rapidly in technology in recent years, and their applications in power systems have gradually increased. The mainstream technologies of lithium batteries include lithium carbonate, lithium iron phosphate, lithium polymer batteries and lithium manganese oxide batteries, etc., which focus on power applications in power systems, including frequency regulation, voltage regulation and fluctuation control. The most mature technology among flow batteries is the all-vanadium flow energy storage battery, and there are also research institutions studying iron-chromium flow batteries. Mainly energy-based applications in the power system, including improving the efficiency of renewable energy generation, grid peak regulation and distributed energy storage. Lead-carbon batteries are currently mainly used to improve the power quality of the power grid.

　　The application of chemical energy storage in power systems in the United States, Japan, Europe and China is at the leading level. Japan is a highly urbanized country, with large peak and valley load differences in electricity consumption. The investment in power grid expansion is huge. The role of energy storage is to improve the utilization efficiency of the power grid, delay investment in capacity expansion and upgrades, and provide household backup power. The power trading business in the United States The market level is relatively high, and the application of energy storage is mainly for distributed microgrid and power frequency regulation applications. Renewable energy is developing rapidly in China and Europe, and the main role of energy storage is to strengthen the ability of existing power grids to accept renewable energy.

　　Chemical energy storage technologies such as flow batteries, lithium batteries, and sodium-sulfur batteries are used in all aspects of the power system, and their comprehensive value is gradually reflected, and the number and scale of projects are increasing year by year. The United States, China, Japan, and Europe have different emphasis on energy storage applications due to different power grid structures. The implementation of more application projects will guide and promote the improvement of technology and the commercialization of the market.

　　Energy storage technology industry policy

　　Regarding the development planning of renewable energy and the improvement and optimization of the existing power system to improve the overall energy utilization efficiency, major countries in the world have policies and measures to support the development of energy storage technology.

　　The U.S. Department of Energy released the "2011-2015 Energy Storage Plan" in February 2011, focusing on how to install energy storage systems to achieve their maximum effectiveness; the cost, safety and life cycle of energy storage systems, research and development and application issues; and promoting technology research and development It also builds demonstration projects to demonstrate the value chain of energy storage, and guides scientific research directions through the construction and operation feedback of demonstration projects; it also conducts industrial design of energy storage equipment to achieve large-scale industrial production. The California government of the United States promulgated the energy storage bill "AB2514" in 2010 to evaluate the advantages of various energy storage systems and application models in the power system, formulate feasible and cost-effective energy storage system installation standards, and implement an energy storage quota system, 2020 The annual energy storage installed capacity reaches 5% of the maximum load.

　　The Ministry of Industry and Commerce of Japan issued the "Amendment to the Energy Conservation Law" in November 2011, encouraging the use of independent power generation equipment and batteries as a countermeasure against peak electricity consumption; requiring the use of self-service power generation equipment in factories and buildings, and carrying out energy-saving renovations on buildings. Building energy management system; lithium batteries, photovoltaic power generation systems, fuel cell systems are installed in residential buildings and house energy management systems are installed.

　　What it brings to the power system is system-level comprehensive value, and the development of its commercial market requires the support of industrial policies. How to formulate effective and specific industrial policies has become a question that energy departments around the world are beginning to think about. Energy storage industry policies generally include tax reduction subsidies, one-time investment subsidies, participation in commercial electricity price competition, electricity price subsidies and other subsidy forms.

　　Energy storage is an indispensable part of the power system. In order to better guide and promote the commercialization market of energy storage, it is crucial to formulate energy storage industry policies that suit the national conditions of the country. These policies should include but are not limited to tax exemptions, electricity price subsidies, one-time investment subsidies and participation in commercial power transactions.

　　About the current status of flow energy storage battery technology

　　Compared with other chemical energy storage technologies, all-vanadium redox flow energy storage batteries have many advantages in terms of safety, lifespan and environmental protection, and are considered to be one of the promising technologies for energy storage in power systems. Currently, the cumulative installed capacity of all-vanadium redox flow energy storage batteries worldwide is about 20MW.

　　In 2002, the Austrian company Cellstrom began to develop vanadium batteries, which mainly include 10kW/100kWh system and 200kW/400kWh system. The products are mainly used in conjunction with solar photovoltaic cells for power supply, communication and backup power supply in remote areas. In 2005, Japan's Sumitomo Electric Corporation (SEI) built the world's largest 4MW vanadium battery energy storage system in Tomamae Town, Hokkaido, to match 30.6MW wind power generation. The system continued to operate for 3 years and accumulated a large amount of valuable data and experience. In 2011, SEI applied its new generation vanadium battery technology to target urban smart microgrids and built demonstration projects in Yokohama and Osaka, with good application results.

　　Since 2010, with the continuous maturity of technology and the driving force of the market, all-vanadium redox flow energy storage batteries have gradually entered the demonstration application stage from the research and development stage. In 2012, industrialization began gradually with the efforts of several major vanadium battery manufacturers. China Dalian Rongke Energy Storage Technology Development Co., Ltd. (Rongke Energy Storage for short) is based on independent research and development, has mastered independent core technologies such as battery materials, stacks and battery systems, and management control, and has carried out kilowatt-megawatt vanadium battery design and application. In 2012, the first domestic and world's largest 5MW/10MWh battery system built by Raycom Energy Storage was successfully connected to the grid and put into operation at Guodian Longyuan Shenyang Faku Wind Farm.

　　All-vanadium redox flow energy storage battery technology is considered to be one of the promising technologies for energy storage in power systems. The technology has become increasingly mature through the accumulation of application projects and is gradually accepted by the market. The industry is in the early stage of industrialization, and technical standards and industrial supporting facilities are gradually taking shape.

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