Lithium batteries are important energy storage devices in China, widely used in various fields. Due to their mature application technology, they have great development potential. In order to achieve green production, recycle green energy reasonably, and improve the efficiency of energy storage equipment, energy storage equipment companies need to strengthen research on energy storage equipment and achieve equipment upgrades. Related enterprises need to strengthen research on related technologies, while standardizing existing usage technologies, in order to improve the efficiency of lithium battery usage and promote the progress of energy storage technology.
1. The latest policies in the energy storage industry
Energy storage is a new type of power system, mainly based on new energy. It is an important technology and equipment support to ensure national energy security. Provided strong support for achieving carbon peak, carbon neutrality, and occupying new international strategic heights. It has now become a strategic, fundamental, and pioneering industry for the development of China’s national economy and society. The Implementation Plan for the Development of New Energy Storage during the 14th Five Year Plan period (hereinafter referred to as the “Plan”) marks the flourishing development of a new industry.
The Plan focuses on discussing the guiding principles and basic principles for the development of new energy storage during the 14th Five Year Plan period, and determines the main goals and work priorities for development. This is a guiding opinion for promoting the high-quality development of the new energy storage industry during the 14th Five Year Plan period. At the same time, it also provides strong reference for the innovation demonstration and improvement of the industrial structure of the new energy storage industry, and provides guidance for industrial innovation and sustainable development.
The Plan summarizes the situation of China’s energy storage industry’s stable improvement in technological level and installed capacity, gradual expansion of application fields and business methods, and gradual improvement of systems and market mechanisms. And it is believed that the 14th Five Year Plan is an important stage for the large-scale development of China’s new energy storage industry, and there is an urgent need to build a market-oriented and sustainable new energy storage industry system that is in line with China’s national conditions as soon as possible. For example, combining new energy storage with the development requirements of power systems, new energy, etc., formulating long-term stable incentive measures, expanding new energy storage business models, and promoting market development; Strengthen technical guidance for energy storage projects, strengthen safety management of new energy storage, improve quality control of energy storage and other weak links, and make up for deficiencies in the next five years, striving to achieve new breakthroughs.
During the 13th Five Year Plan period, China’s new energy storage industry is in the initial stage from research and experimentation to commercialization. Significant progress has been made in research and development of technical equipment, construction of demonstration projects, exploration of business models, and establishment of policy systems. The scope of market applications has steadily increased, providing strong support for the transformation of energy structure. At the end of 2020, China had a total installed capacity of approximately 3.3 million kilowatts of new energy storage, ranking first in the world.
Overall, the development status of China’s energy storage industry has tended to improve, but there are still many problems in commercial operation. The safety and business model of electrochemical energy storage are still in the process of exploration and experimentation. Therefore, the Plan suggests that by 2025, the total installed capacity of new energy storage in China will exceed 30 million kilowatts; The performance of electrochemical energy storage technology has been greatly improved, while also reducing the operating cost of the entire system by 30%; New energy storage technologies based on traditional power sources, such as cascade power station energy storage, thermal power and nuclear power extraction energy storage, have been widely applied in engineering; Technologies such as 100 megawatts of compressed air energy storage and megawatt level flywheel energy storage are gradually improving; Breakthroughs have been made in long-term energy storage technologies, such as hydrogen energy storage and thermal (cold) energy storage.
2. Power system and energy storage equipment
The future power system must have flexibility in supply and demand, be able to adapt to large-scale renewable energy integration, and be able to solve intelligent control in energy production, storage, transmission, and consumption processes. Energy storage power sources play a crucial role in four aspects: generation, transmission, distribution, and utilization. Therefore, it is necessary to continue promoting the diversified development of energy storage technology and market, improving energy quality, ensuring supply and demand balance, reducing energy consumption, and allowing consumers to truly appreciate its economic and safety value.
2.1 Energy storage system requirements on the power generation side
After a power outage in the power grid, thermal power units cannot operate normally, and the energy storage system can serve as an auxiliary power supply. Usually, only 1-10MW is needed to provide continuous power supply for 2-3 hours. Renewable energy sources such as wind and solar power generation, due to their intermittent and unstable characteristics, are prone to have an impact on the power system and cannot fully adapt to the scheduling needs of the power system. As a result, a large number of them have been abandoned in the power system. By adopting this energy storage system, the power system can achieve sufficient balance between the power generation side and the grid, improving the utilization rate of renewable energy such as wind and solar energy. Backup power can also be provided in renewable energy power stations.
2.2 Energy storage system requirements on the transmission side
Due to the dynamic changes in the power system and the variation of load cycles, the energy storage system must respond stably to the frequency, voltage, and frequency of the power grid. Frequency modulation energy storage systems typically have an installed capacity of 1MW or larger, with a charging and discharging time of 1-15 minutes, a cycle of 20-40 times per day, and a response time of less than 1 minute. Peak shaving generally has an installed capacity of 10MW or more, with a charging and discharging time of 2-4 hours, once a day, and a response time of less than 1 hour.
2.3 Energy storage system requirements on the distribution side
In the distribution network, when there is a problem with the distribution network, its energy storage system will continue to provide customers. In addition, adjustable loads and controlled power supply methods are used to achieve the power supply quality of the distribution network, solving problems such as voltage fluctuations and harmonics. In order to improve the reliability of the distribution network, energy storage methods with a capacity of 10MW or more are adopted. The duration of charging and discharging is 0.5-2h, and the response time is within 10min. Energy storage systems that improve power quality have a large installed capacity, which depends on actual needs. Generally, they are within 1-40MW, with a charging and discharging time of 1-60s, a cycle of 10-100 times/day, and a response time in milliseconds.
2.4 Energy storage system requirements on the power side
Under the continuous improvement of demand side management, energy storage systems can not only reduce the peak valley load difference for small users, but also greatly solve the current problem of insufficient power grid capacity. On the user side, there are various application areas, such as peak shaving and valley filling, supplementing peak electricity, and emergency power supply in emergency situations. The energy storage system can be designed according to the user’s electricity consumption and load characteristics. Its capacity can supply power for 2 hours during continuous peak hours and 8-10 hours during low periods, with a charging and discharging cycle of 1 time per day.
3. Current application status of lithium battery technology
Currently, domestic research on lithium batteries mainly focuses on three technical aspects, namely titanium oxide type lithium batteries, ternary type lithium batteries, and iron phosphate type lithium systems. In terms of energy storage research, the main consideration is the investment return of batteries, and there is still a large portion of lead-acid batteries in the current market. According to CNESA statistics in Zhongguancun, as of 2016, China’s total chemical energy storage equipment was 243MW, with the majority of batteries being based on lead and lithium-ion technologies, and the installed capacity of lithium batteries accounting for 60%.
In terms of specific energy parameters, lithium iron phosphate batteries can reach over 140 watt hours per kilogram, with a service life of over 3000 times under normal temperature charging and discharging conditions. They have relatively small self discharge and no memory effect, and can support fast charging and discharging. The main mode of operation is to adjust the peak and valley, and the service life can reach 10-15 years. The characteristics of this battery can meet most usage needs. In the second quarter of 2017, China added 21.1MW of electrochemical equipment, and the proportion of lithium batteries has reached 88%, indicating that this battery has been recognized by the majority of users in the market.
Ternary lithium batteries have higher energy than other lithium batteries, but are highly limited by cycling and safety technologies. If this type of battery is subjected to strong impacts, concentrated at a single point, as well as overcharging or short circuit problems, its internal temperature can quickly reach 200-300 ℃, which can easily cause internal reactions in the positive electrode part, leading to overall expansion or even explosion of the battery. Once a problem occurs, it is difficult for the battery to maintain a controllable state. The difference between energy storage technology and new energy vehicles lies in the large space occupied by the system and the low sensitivity to mass ratio. Relatively speaking, energy storage equipment has a large amount of energy, and its safety should be constantly monitored during use. If there is a fire, explosion, or other situation, it may endanger the life and health of surrounding personnel and various property safety. Therefore, most enterprises using this lithium battery remain in the theoretical stage or use it in an ideal environment, And real-time monitoring of battery status is required.
The specific energy value of titanate type lithium batteries is not as high as the other two types of lithium batteries, but this battery performs very well in low-temperature environments, and can be charged and discharged tens of thousands of times under high magnification conditions. Many companies use this technology as their main research route, and the battery is widely used in public transportation vehicles in Northeast China. In energy storage applications, the voltage platform of the battery is 1.5V. To match the PCS DC section, it is necessary to increase the number of batteries in series. Due to poor battery consistency, the management system is relatively large, and control strategies need to be implemented. In addition, it is necessary to achieve cost control by reducing the high rate performance while ensuring the service life, and to give full play to the characteristics of low-temperature and high-efficiency use of batteries. This development currently occupies an irreplaceable position in energy storage technology. After years of development and progress, the maturity of storage batteries has been continuously improved. With the increasing variety of batteries, the relevant technical level is also constantly improving. Traditional lead carbon batteries have greatly improved their cycling capacity in the continuous development, but the results are mostly obtained under experimental conditions and have few practical applications. At the same time, in order to create a green development path, the production of lead and related products in China is also continuously decreasing. At the same time, with the development of lithium battery technology and production capacity, price advantages are gradually becoming prominent, especially for iron phosphate lithium batteries, which have significant price advantages and may replace traditional lead batteries in the market after continuous development.
4. Development trend of integrated technology for industrial energy storage power supply systems
Most power storage products in the form of industrial energy storage are loaded into containers. During use, it is necessary to choose a reasonable battery pack and energy management system based on actual usage needs. The development trend of its key technologies is as follows.
(1) Transforming from modular batteries to packaged ones, thereby increasing the energy storage capacity of individual battery boxes while maintaining a constant volume. Fixed storage methods typically use functional module designs, with a single battery box storing up to 1MW of energy. A power technology company in Shanghai has designed high-density integration technology through research and innovation, which can support a 1MW power storage system. By introducing package hierarchy, various problems such as insulation, address protection, system stability, and safe use of high-voltage direct current are reduced to a certain extent. This effectively reduces the risks caused by external work of wire harnesses and reduces workload. At the same time, the use of plug-in design perfectly avoids process related issues during battery installation, making it easy to maintain.
(2) Developing from fixed to mobile. With the maturity of technology, the use of energy storage equipment has become increasingly widespread, and it is no longer limited to fixed usage scenarios such as power service work and adjustment of electricity peaks and valleys. It is gradually being applied in civil disaster prevention work, oil extraction work, airport applications, and other aspects. With the development of mobile energy storage devices, they will be applied in more application scenarios, able to replace most diesel power generation applications, and achieve the goals of developing green seaports, green airports, and so on.
(3) The market’s demand for hot swapping, floating charging power supply, and high current stable technology is increasingly prominent. In recent years, with the good development of energy storage equipment related fields, it can be seen that its development momentum is good. By using this technology, it can ensure long-term stable operation of the system in work and obtain sustained benefits. Hot swapping technology is the process of plugging and unplugging modules or connectors while the system is running normally.
Float charging power supply is a special battery chemical design that promotes charging work under special electrical pressure, thereby achieving automatic and balanced protection effects. It can avoid self discharge and increased charging depth in most cases, and is an effective method to ensure long-term stable use of batteries, which can improve their service life. Normally, the balancing current in power batteries is measured in milliamperes, and the system requires a current of 10A or even stronger to accelerate the balancing speed.
5. Development factors of energy storage power supply system industry
5.1 Security
The energy storage equipment used in the development of power grid work is theoretically safer than the energy storage equipment of electric vehicles, but it still requires the use of extremely expensive supporting equipment to keep it in a safe operating environment. In addition, battery power supply belongs to the DC form, which requires high safety requirements.
5.2 Economy
The usage time of batteries is proportional to the cost to a certain extent. Currently, the energy conversion capacity and management technology of batteries are relatively mature, and there is great development space in cost compression. If the system integration can be improved, more profits can be obtained.
5.3 Convenience
It is best to achieve plug and play energy storage in use, with a focus on the construction of distributed systems to facilitate the integration of users into the power system used in the market, while also taking into account user satisfaction.
6. Conclusion
In the application of energy storage equipment, power enterprises should fully leverage the role of equipment, combine the current situation of lithium battery application and the development trend of industrial energy storage power system integration technology, strengthen research on related technologies, combine development factors, and improve the safety, economy, and convenience of energy storage power sources.