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1. Introduction

With the continuous promotion of the use of renewable energy around the world, the installed capacity of intermittent energy such as solar and wind energy is growing rapidly. As a key link to smooth these energy fluctuations and improve the stability and reliability of energy utilization, the importance of energy storage system has become increasingly prominent. With a long history of development, mature production technology and specific performance advantages, lead-acid batteries occupy an important position in the field of energy storage. An in-depth analysis of the application of lead-acid batteries in energy storage systems is of practical significance for optimizing energy storage configuration and promoting sustainable energy development.

2. Working principle and characteristics of lead-acid battery

(1) Working principle

The charge and discharge process of lead-acid battery is realized by electrochemical reaction. When charging, under the action of external power supply, the lead sulfate on the positive plate is oxidized to lead dioxide, the lead sulfate on the negative plate is reduced to lead, and the sulfuric acid concentration in the electrolyte is increased. The discharge process is on the contrary, the material on the positive and negative plates reacts with the electrolyte to regenerate lead sulfate, the sulfuric acid concentration is reduced, and the chemical energy is converted into electrical energy and released.

(2) Performance characteristics

1. ** Cost advantage ** : Compared with many new energy storage batteries, lead-acid batteries have a wide range of raw materials and mature production technology, making their initial acquisition cost low, and good cost controllability for large-scale energy storage projects, which is attractive in cost-sensitive application scenarios.

2. ** High technical maturity ** : After more than 100 years of development, lead-acid batteries from manufacturing to maintenance management, the entire industry chain has perfect standards and specifications. Its performance is stable, the fault mode is clear, and the technicians have accumulated rich experience in operation and maintenance in long-term practice, which provides a strong guarantee for its reliable operation in the energy storage system.

3. ** Power characteristics ** : Lead-acid batteries can provide a large charge and discharge power in a short period of time, which can meet the needs of the energy storage system in coping with the peak load of the power grid, rapid power regulation, etc., and perform well in power-type energy storage application scenarios.

4. ** Energy density and cycle life ** : The energy density of traditional lead-acid batteries is relatively low, which means that when storing the same energy, its volume and weight are large, and there are certain disadvantages in space-limited energy storage projects. And its cycle life is limited, generally about 300-500 times, frequent charge and discharge will accelerate the aging of the battery, affecting the long-term use of economic. However, in recent years, through technological improvements, such as the use of new plate materials, optimization of electrolyte formulation, etc., some lead-acid battery products have been significantly improved in terms of energy density and cycle life, and the application range has been broadened to a certain extent.

3. Application scenarios in energy storage system

(1) Distributed photovoltaic energy storage

In the distributed photovoltaic power generation system, photovoltaic power generation is affected by factors such as light intensity and weather, and the power generation fluctuates greatly. Lead-acid batteries can store excess power when the light is sufficient, and release power when the light is insufficient or when the power consumption is peak, so as to ensure the stable supply of power to users and reduce the dependence on the grid. For example, small distributed photovoltaic power stations in some remote areas, due to the distance from the main grid, high access costs, equipped with lead-acid battery energy storage, can achieve self-use, effectively improve energy utilization efficiency, reduce electricity costs.

(2) Wind farm energy storage

Wind power generation is intermittent and fluctuating, and its output power is unstable, which is easy to impact the power grid. The lead-acid battery energy storage system can quickly adjust the power of wind power when the wind speed changes. When there is a surplus of wind power, the electricity is stored; When the wind power is insufficient, the power is released to supplement the power grid, smooth the output power curve of the wind farm, improve the stability and power quality of the wind power grid connection, and help the wind farm to better participate in the power market trading.

(3) power grid side energy storage auxiliary services

1. ** Peak loading ** : there is a peak-valley difference in the power grid load within a day, and the lead-acid battery energy storage system can be charged during the off-peak period of electricity consumption to absorb excess energy; Discharge during peak hours, inject electric energy into the grid, relieve the pressure of peak power supply, reduce the demand for new installed power generation capacity, and improve the operation economy of the grid.

2. ** Frequency modulation ** : the frequency of the power grid is affected by the real-time balance between power generation and electricity consumption, and the lead-acid battery can quickly respond to the frequency change of the power grid, adjust the power through charge and discharge, maintain the stable frequency of the power grid within the allowable range, and ensure the safe and reliable operation of the power grid.

4. Application challenges

(1) Environmental pressure

Lead and acid electrolyte are involved in the production, use and recovery of lead-acid batteries. If the environmental protection measures in the production process are not in place, it may lead to lead pollution, endangering human health and ecological environment; When the waste battery recycling system is not perfect, it will also cause serious environmental pollution if it is discarded at will or not handled properly. Despite the continuous efforts of the industry to strengthen environmental supervision, improve production processes and improve recycling systems, environmental pressure is still an unavoidable challenge for lead-acid battery applications.

(2) Life and maintenance

Limited cycle life makes lead-acid batteries need to be replaced frequently in long-term energy storage applications, increasing operation and maintenance costs and resource waste. At the same time, it is more sensitive to the use of ambient temperature, too high or too low temperature will affect the battery performance and life. In practical applications, a temperature control system is required to maintain a suitable environment, further increasing the complexity and cost of the system. In addition, the daily maintenance work of lead-acid batteries is more complicated, including regular inspection of the electrolyte level, density, monitoring of battery voltage, internal resistance and other parameters, which requires high professional quality of operation and maintenance personnel.

(3) Energy density limitation

The low energy density limits the promotion of lead-acid batteries in applications with compact space and strict requirements on the weight of energy storage equipment, such as some distributed energy storage projects installed on roofs or narrow Spaces, as well as mobile energy storage fields such as electric vehicles, lead-acid batteries are difficult to meet the demand for high energy density, and are facing fierce competition from other new energy storage technologies.

5.Coping strategies and technical improvement direction

(1) Strengthen environmental management and recycling system construction

The government should continue to strengthen the environmental supervision of lead-acid battery manufacturers, strictly implement environmental standards, and encourage enterprises to adopt cleaner production technologies to reduce pollution emissions from the source. At the same time, social capital is encouraged to participate in the waste battery recycling industry, establish a wide coverage, standardized and efficient recycling network, improve the recovery rate of waste lead-acid batteries, realize the recycling of lead resources, and reduce the risk of environmental pollution.

(2) Improve battery performance and intelligent operation and maintenance

1. ** Research and development of new materials and processes ** : Research institutions and enterprises should increase research and development investment, explore new plate materials, electrolyte additives, etc., to improve the energy density, cycle life and low temperature performance of lead-acid batteries. For example, the use of lead carbon composite technology, activated carbon into the negative electrode, effectively improve the battery charging and discharging performance and cycle life.

2. ** Intelligent Management System ** : Use the Internet of Things, big data and artificial intelligence technology to build an intelligent management platform for lead-acid battery energy storage system. Real-time monitoring of battery operating status, through data analysis to predict battery life, hidden trouble, achieve accurate maintenance, reduce operation and maintenance costs, improve system reliability and operation efficiency.

(3) Expand the application field and hybrid energy storage mode

1. Deepening application in specific scenarios ** : Based on the advantages of lead-acid batteries, such as cost and power, further expand its application in scenarios with low space and weight requirements, cost sensitivity and frequent high-power charging and discharging, such as backup power supply of communication base stations and some industrial energy storage, to consolidate market share.

2. ** Hybrid energy storage ** : The lead-acid battery and other high-energy density, long-life energy storage batteries (such as lithium-ion batteries) are composed of a hybrid energy storage system, giving full play to the advantages of different batteries, making up for the energy density and cycle life of lead-acid batteries, optimizing the overall performance of the energy storage system, and adapting to diversified energy storage needs.

6. Conclusion

With the advantages of cost, technology maturity and power characteristics, lead-acid batteries are widely used in the current energy storage system, and play an important role in the consumption of renewable energy and the stable operation of the power grid. However, the challenges it faces such as environmental protection, life span and energy density cannot be ignored. By strengthening environmental management, promoting technological innovation and exploring new application models, lead-acid batteries are expected to continue to maintain competitiveness in the field of energy storage, and develop in tandem with other new energy storage technologies to jointly build a safe, efficient and sustainable energy storage system, and provide solid support for global energy transformation. It will continue to play an important role in the energy storage stage for a long time in the future.