Under the national "double carbon" strategy, new energy represented by photovoltaic and wind power is booming. With the massive access of photovoltaic and wind power, the demand for frequency modulation and peak load regulation resources of the power grid has risen sharply. The energy storage system plays an increasingly important role in solving the consumption of new energy, enhancing the stability of the power grid, and improving the utilization efficiency of the distribution system. Electrochemical energy storage lithium-ion system, due to its low deployment environment requirements and many applicable scenarios, its application scale is growing rapidly. At the same time of large-scale application, the safety of energy storage power stations has also attracted widespread attention.
New energy power side energy storage, grid side energy storage, large off grid and micro grid energy storage power stations often use container type energy storage. Tens of thousands of electric cells are installed in containers through series / parallel connection. There is only a thin layer of diaphragm insulation between the positive and negative electrodes of lithium-ion batteries. Electrical isolation mainly depends on insulating materials and electrical switches. Insulating materials may be carbonized and become conductive materials at high temperatures, The disconnector may also break down under high voltage, and the power device switch tube may also conduct abnormally under reverse high voltage and surge impact. During thousands of charging and discharging cycles for a long time, especially under the condition of overcharge, over discharge and over temperature, it is possible to cause short-circuit fault of the cell and local out of control. If any cell has a safety problem, if there is no strict safety protection measures to deal with it in advance, it may cause a chain reaction of the system and cause an explosion accident.
Increasing the insulating materials and strength and building an iron wall of the energy storage power station may solve the safety problems of the energy storage power station, but it will increase the cost of the power station and is not conducive to the large-scale promotion and application of energy storage. The safety of container type energy storage needs to start from the system scheme, material selection, security design and other aspects, so as to comprehensively take into account the two important indicators of safety and cost. At present, the main safety technologies and measures adopted by the energy storage power station include: new modular energy storage technology, aerogel gel thermal insulation materials, traditional electrical protection, thermal management and efficient fire safety systems, etc.
1. Modular energy storage technology
The first generation lithium battery simply connected the battery packs in series into clusters, and the second generation lithium battery added some intelligent battery management units on the basis of the first generation lithium battery. However, a series of problems, such as the risk of DC bus high voltage and battery insulation, uneven current discharge between clusters, and the inability to mix echelon batteries, cannot be completely solved in the lithium battery system, which has cast a question mark on the safe and stable application of lithium battery. New modular energy storage. Each battery module corresponds to a BMS battery management system. It is equipped with multiple functions such as electrical and physical double isolation, automatic exit of fault modules, early warning of battery insulation failure, etc., which ensure the safety and reliability of lithium batteries. The modules are self-adaptive and active current sharing, support the mixed use of echelon batteries and batteries of different brands, phased capacity expansion and minute maintenance, and solve many application problems of lithium batteries in one fell swoop.
2. Aerogel gel
Aerogel gel is a kind of solid material with nano porous network structure and filled with gaseous dispersion medium in the pores. It is the lightest solid in the world. Aerogel gel is recognized as the lightest solid material in the world, and it is a new generation of energy-efficient thermal insulation materials. Aerogel gel has the characteristics of high flame retardancy, light volume and low consumption. It has become the best choice of thermal insulation materials for power battery cells. At present, it has been adopted by battery enterprises and new energy vehicle manufacturers.
Aerosol can also achieve three-level fire protection. Taking the battery cluster as the protection unit, the centralized gas detection sampling analysis is adopted. Through the detectors preset in each pack box, the changes in the internal chemical composition of the lithium battery are detected in real time. The chip analyzes and calculates the changes of various parameters, and effectively inhibits and prevents the early fire prevention and control of the cells in the battery box, so as to prevent the uncontrolled expansion of the lithium battery and the explosion of the energy storage cabinet.
