How to Safely Cool Down A Battery Energy Storage System?

As the proportion of clean energy gradually increases, battery energy storage system plays a crucial role in the power generation side, grid side and user side of the power system. The penetration rate of electrochemical energy storage is rapidly increasing due to the advantages of high energy density, flexible application and fast response.

Batteries, as the core component of electrochemical energy storage, have a greater risk of thermal runaway, and thermal management of energy storage is of great importance from a safety point of view. As the core component of electrochemical energy storage, the battery has a greater risk of thermal runaway, and from a safety point of view, thermal management of energy storage is of great importance.

I. Thermal management in electrochemical energy storage systems

Thermal management is an important part of electrochemical energy storage system.

The electrochemical energy storage industry chain is divided into three parts: upstream equipment vendors, midstream integrators, and downstream applications.

Upstream equipment includes battery packs, energy storage converters (PCS), battery management systems (BMS), energy management systems (EMS), thermal management, and other equipment, etc.; the core of the midstream link is system integration + EPC; and the downstream is mainly divided into three major scenarios: power supply side, grid side, and user side.

During 2011-2021, there were 32 fire and explosion accidents in energy storage power stations around the world, and from January to May 2022, more than 10 energy storage fire accidents have occurred around the world.

Battery thermal runaway has become the main cause of fire accidents. Battery thermal runaway refers to a large amount of heat generated in a short period of time due to an internal short circuit or an external short circuit, triggering the decomposition of the positive and negative active substances and the electrolyte reaction, which generates a large amount of heat and flammable gases, leading to a battery fire or explosion. The frequent occurrence of fire incidents highlights that thermal management has become an essential and important component to ensure the safe operation of energy storage power plants.

II. Technology Route

At present, the more mature technology route for thermal management of energy storage is air-cooled and liquid-cooled, of which air-cooled accounts for the mainstream of battery energy storage system, and liquid-cooled program is expected to increase in the future penetration rate.

Thermal management has become the core of the energy storage system, and air cooling and liquid cooling are the mature technology routes. battery energy storage system thermal management cooling methods mainly have the following three major technology routes: air cooling (air cooling), liquid cooling and phase change cooling, in addition to heat pipe cooling.

1. Air Cooling

At present, air-cooling technology is mainly used in container energy storage system with small power density and communication base station energy storage system.

On the one hand, because the air-cooled system structure is simple, safe and reliable, and easy to realize; on the other hand, because the energy storage system is not as harsh as the energy density and space limitations of the power battery system, you can increase the number of batteries to get a lower work rate and heat production rate.

Containerized lithium battery energy storage system, for example, the system consists of a standard container, lithium-ion battery system, battery management system, energy storage converter, air conditioning and air ducts, distribution cabinets, sevoflurane fire extinguishing devices and other components.

The air-cooled heat management system has air conditioning structures including floor-to-ceiling one-piece, roof-mounted one-piece, split and other configurations. Floor-mounted integrated air conditioners are used in energy storage containers that have been reserved for air conditioning space, usually with air coming out of the top, connected to the air duct inside the container, and directly supplying precise air to the battery pack.

If there is no space to install air conditioning inside the energy storage container, a roof-mounted integrated air conditioner is required, which is installed on the top of the container and cools the battery from the top.

Split-type air conditioner installed in the battery pack, front return air back air supply, air conditioning outlet connected to the air ducts, directly to the battery for cooling.

2. Liquid Cooling

Liquid cooling program uses water, ethanol, silicone oil and other coolants to dissipate heat through the liquid cooling plate on the uniform distribution of the infusion groove and indirect contact with the battery cell. Its advantages include:

(1) Close to the heat source, efficient cooling;

(2) Compared with the air-cooled solution for containers of the same capacity, the liquid-cooled system does not require the design of air ducts and saves more than 50% of the floor space, making it more suitable for future large-scale energy storage power stations of more than 100MW class;

(3) Compared with the air-cooled system, the failure rate is lower due to the reduction of the use of mechanical parts such as fans;

(4) Liquid-cooled low noise, saving system self-consumption of electricity, environmentally friendly.

In the future, with the new energy power station, off-grid battery energy storage system, such as larger battery capacity, higher system power density of the energy storage power plant needs to start, the energy storage system energy density and heat generation is greater, the security and life requirements are higher, will promote the industry more turn to use liquid cooling program.

3. Phase Change Cooling

Phase change cooling is a cooling method that utilizes phase change materials to absorb heat.

The biggest influence on the cooling effect of the battery is the selection of phase change materials, when the selected phase change materials, the larger the specific heat capacity, the higher the heat transfer coefficient, the better the cooling effect under the same conditions, and vice versa, the worse the cooling effect.

Phase change cooling has the advantages of compact structure, low contact thermal resistance, good cooling effect, etc. However, the phase change material itself does not have the ability to dissipate heat, and the absorbed heat needs to be exported by liquid cooling system, air cooling system, etc. Otherwise, the phase change material can not continuously absorb heat. In addition, phase change materials take up space and are costly.

The four ways to solve the problems faced by the energy sector are advanced energy network technology, demand response technology, flexible capacity technology and energy storage technology. battery energy storage system technology creates commercial value with active cross-time and cross-seasonal power generation and utilization balancing ability, solves the burden of passive regulation of the power grid, and is the key to support the stable and large-scale development of renewable energy. Thermal management system, is a cross-disciplinary technology.

Thermal management system, is a cross-disciplinary technology integration, integration of technologies including materials science, chemistry, mechanical structure, electrical control. Solving the key core technology to ensure the smooth and healthy development of the electrochemical energy storage industry, and battery energy storage system to solve the problem is to realize the carbon peak carbon neutral one of the important path.