Previously:

Due to the thermal characteristics of batteries, thermal management has become a critical component in the electrochemical energy storage industry chain. Breaking down the value distribution within the industry chain, the cost of batteries in energy storage systems accounts for approximately 55%, PCS accounts for about 20%, BMS and EMS together make up about 11%, while thermal management constitutes about 2%-4%. Although the proportion of thermal management in terms of value is relatively low, it plays a crucial role in ensuring the continuous and safe operation of energy storage systems. Currently, there are two main mainstream solutions for thermal management technology in energy storage systems, namely forced air cooling system and liquid cooling system. This article will be divided into two parts to provide a comparative analysis of these two cooling systems in terms of lifespan, temperature control, energy consumption, design complexity, space utilization, noise, production & installation, after-sales, operation and maintenance, and cost. The Part 2 mainly makes a comparative analysis on 5 aspects of noise, production and installation, after-sales, operation and cost. In the Part 2, a comprehensive comparative analysis will be conducted across five key areas: noise, production & installation, after-sales service, operation & maintenance, and costs.

Explanation of nouns

Thermal management technology: Including forced air cooling, liquid cooling, heat pipe cooling, and phase-change cooling, with the last two still in the experimental stage. Forced air cooling: The main components of the air cooling system include air conditioning, air ducts, and module fans. The fans are installed at the front of the module. The module fans dissipate the heat generated by the module's internal cores and carry it out to the prefabricated cabin air duct. The air conditioning system inside the prefabricated cabin dissipates heat through convective heat transfer. Liquid cooling: Liquid cooling system refers to the use of liquid as a heat-conducting medium, transferring heat directly or indirectly by coming into contact with cooling liquid and heat-generating components. It is a heat dissipation technique that removes the heat generated by the heat-generating components.

Chapter Six: Noise comparison

1. System noise comparison of similar manufacturers

2. Comparison of measured noise

Measured noise data of EnerArk in laboratory: 71.8dB at position 1, 68.1dB at position 2, 67.9dB at position 3 and 69dB at position 4; Field noise measured data at customer A's project site: Maximum 72.8 dB.

(1) The main noise source of forced air cooling: PCS < 75dB, fan < 60dB, air conditioner < 65dB; Liquid cooling main noise source: PCS < 75dB, liquid cooling unit < 75dB;
(2) There is no obvious advantage in the noise comparison of liquid-cooled and forced air-cooled products, and the basic noise is less than 75dB.
Chapter Seven: Production & installation comparison

Comparison & analysis of forced air cooling VS liquid cooling in production and installation:

Liquid cooling is more complex than the forced air cooling in production and installation, and the overall installation work requires more time than air cooling system.

Chapter Eight: After-sales service comparison

1. Comparison & analysis of fault points for the forced air cooling VS liquid cooling:

2. Comparison & analysis of failure points for the forced air cooling VS liquid cooling:

3. The difference of battery PACK after-sales service:

(1) Regarding the after-sales service of the battery PACK, the workload, the number of tasks, and the difficulty of the steps for forced air cooling differ significantly from the liquid cooling system, with the forced air cooling presenting a clear advantage.

(2) Preliminary estimates indicate that, excluding the battery PACK component, the disassembly and assembly time for air-cooled battery PACK is within 20 minutes, while the time control for disassembly and assembly of liquid-cooled battery PACK is set at 2h+.

Chapter Nine: Operation & maintenance comparison

1. Forced air cooling and liquid cooling system maintenance contents and cycle:

(1) The maintenance workload for the forced air cooling system is relatively low, with a longer maintenance cycle and lower labor costs and travel expenses.

(2) The maintenance workload for the liquid cooling system is higher, with a shorter maintenance cycle. It involves more operational steps and precautions, demanding a higher level of experience and qualifications from the operations and maintenance personnel. Specialized knowledge and skills are required, and at times, collaboration with personnel from the liquid-cooling unit manufacturer may be necessary.

2. Maintenance requirements for forced air cooling and liquid cooling systems include:

(1) The forced air cooling system has relatively low requirements for maintenance equipment, with fewer specialized tools needed.

(2) In addition to regular tools, the liquid cooling system requires specialized tools for maintenance. The maintenance process involves additional steps, including drainage, injection, and replenishment of liquids. This demands a higher level of expertise and professionalism.

The maintenance of the liquid cooling system is relatively complex and requires more steps and precautions. The maintenance of the forced air-cooled system is relatively simple and the cost is low. For example, there are 5 100kW/215kWh air freezers and liquid freezers, and the operation and maintenance time of liquid freezers is 2-3 times that of forced air cooling.

Chapter Ten: Cost comparison

1. Taking 215kWh C&I battery energy storage cabinet as an example, the proportion of cooling system cost:

(1) The mold cost for liquid cooling is relatively high. The design of the water-cooled plate involves mold making, trial molding, verification, and mold adjustment, requiring a significant investment of time and effort in research and development. Although there are standard mold options, considering the patent, and most companies are reluctant to disclose or share such information.

(2) The prevailing market prices for commercial energy storage products are 1.3 yuan/Wh (liquid-cooled) and 1.1 yuan/Wh (air-cooled).

2. In commercial and industrial energy storage systems, the cost difference between forced air cooling and liquid cooling primarily shows in the following aspects:

Environmental adaptability of forced air cooling and liquid cooling systems

(1) Currently, a 50% ethylene glycol solution is widely used as a coolant in the market, with a freezing point of approximately -35°C. The operational lower limit of water-cooled air conditioners in the market is generally ≥ -30°C. Therefore, liquid cooling energy storage systems are not suitable for use in extremely cold temperature regions. Otherwise, the freezing of the coolant may block or burst the pipes, causing damage to the cooling system (with the first startup being particularly affected). The heating function inherent in liquid cooling requires the coolant to be heated to 20°C before normal startup and operation can occur;

(2) Functional industrial air conditioners available in the market can maintain their heating function at temperatures as low as -40°C, heating the air inside the cabinet to 20°C, thereby sustaining the operating temperature for battery systems;
(3) Ethylene Glycol Coolant: It is a colorless, slightly viscous liquid with a boiling point of 197.4°C and a freezing point of -11.5°C. It can be mixed with water in any proportion. Ethylene glycol has a certain of toxicity and can cause damage to internal organs such as the kidneys, liver, stomach, and intestines;
(4) Environmental Friendliness: Ethylene glycol is a substance that can contaminate groundwater. Operators of such equipment must comply with relevant national and local regulations and must not discharge it casually.

Applicable application of forced air cooling and liquid cooling systems

Comprehensive comparison

For the C&I energy storage applications, the forced air cooling system have more advantages than liquid cooling system.