What is the new solution for the energy storage thermal management?
As the proportion of clean energy has gradually increased, energy storage plays a vital role in power generation, power grid, and user of the power system. Due to the advantages of high energy density, flexible application, and rapid response, the energy storage is developing rapidly.
According to CNESA data, by the end of 2021, the cumulative installed scale of global electric energy storage projects put into operation is 209.4GW, and the cumulative installed scale of new energy storage is 25.4GW. Sodium ion batteries dominate the market, with a market share of over 90% and 23.1GW. The cumulative installed scale of electric energy storage projects put into operation in China is 46.1GW, accounting for 22% of the total global market size. The cumulative installed scale of new energy storage reaches 5.73GW. Lithium-ion battery is the mainstream technology route of new energy storage, accounting for 89.7% of 5.14GW.
As the core component of electrochemical energy storage, battery has a great risk of thermal runaway. From the perspective of safety, thermal management of energy storage is extremely important.
1. Thermal management in electrochemical energy storage system
Thermal management is an important part of electrochemical energy storage system, the industrial chain of electrochemical energy storage is divided into three parts: upstream equipment supplier, midstream integrator, and downstream application end.
Upstream devices include battery packs, energy storage inverters (PCS), battery management systems (BMS), energy management systems (EMS), thermal management and other devices; The core of midstream link is system integration +EPC; The downstream scenarios are divided into power supply side, power grid side, and user side.
Most enterprises in the energy storage industry chain are involved in 1-2 segments, while a few enterprises are involved in the whole process from battery to system integration and even EPC.
From 2011 to 2021, a total of 32 energy storage power station fire and explosion accidents occurred globally. From January to May 2022, more than 10 energy storage fire accidents occurred globally. With the rapid development of battery energy storage stations in China, due to the quality problems of batteries and PCS or the uneven construction performance of system integrators, the potential fire hazards of battery energy storage are serious and fire accidents are frequent.
On April 16, 2021, a fire and explosion occurred in Beijing Guoxuan Fuwei Energy Storage power Station. According to the investigation, the cause of the fire was an internal short circuit in the LFP battery, which caused the battery to heat out of control and ignite. In July of the same year, the "Victoria Big Battery" project in Australia, which is equipped with Tesla's Megapack energy storage system, caught fire in the battery compartment due to the leakage of the cooling system during the test.
Battery thermal runaway is the main cause of fire accidents.
Battery thermal runaway refers to the internal short circuit or external short circuit leads to a large amount of heat generated by the battery in a short time, triggering the reaction of positive and negative active substances and electrolyte decomposition, generating a large amount of hot and combustible gas, resulting in battery fire or explosion.
Frequent fire incidents highlight that thermal management has become an essential component to ensure the safe operation of energy storage power stations.
2. Thermal solutions
At present, the relatively mature thermal solutions of energy storage thermal management are air cooling and liquid cooling, among which air cooling is the mainstream in the current energy storage system, and the permeability of liquid cooling scheme is expected to continue to rise in the future.
Thermal management becomes the core of energy storage system, and air cooling and liquid cooling are mature technologies at present. The cooling methods of energy storage thermal management mainly include the following three cooling technologies: air cooling (air cooling), liquid cooling and phase change cooling, and heat pipe cooling.
Air cooling
At present, air cooling technology is mainly used in container energy storage system and communication base station energy storage system with low power density. On the one hand, the air cooling system is simple in structure, safe and reliable, and easy to implement; On the other hand, because the energy storage system is not as restrictive as the power battery system in terms of energy density and space, the number of batteries can be increased to obtain a lower operating rate and heat generation rate.
Liquid cooling
The liquid cooling techmology uses water, or other coolants to dissipate heat through indirect contact with the conductor evenly distributed on the liquid cooling plate.
Its advantages include:
1) Close to heat source, efficient refrigeration;
2) Compared with the container air cooling scheme with the same capacity, the liquid cooling system does not need to design the air duct, which saves more than 50% of the floor area, and is more suitable for the future large-scale energy storage power station of 100 MW or more;
3) Compared with the air-cooling system, the failure rate is lower because the use of fans and other mechanical components is reduced;
4) Low noise of liquid cooling, saving power consumption of the system, and environment-friendly.
Phase change cooling
Phase change cooling is a cooling method that uses phase change materials to absorb heat.
The choice of phase change material has the greatest influence on the heat dissipation effect of the battery. When the specific heat capacity of the selected phase change material is larger and the heat transfer coefficient is higher, the cooling effect under the same conditions is better, otherwise the cooling effect is worse.
Phase change cooling has the advantages of compact structure, low contact thermal resistance, good cooling effect, but the phase change material itself does not have the heat dissipation ability, the absorbed heat needs to rely on the liquid cooling system, air cooling system, etc., or the phase change material can not continue to absorb heat.
In addition, phase change materials take up space and cost a lot.
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