As the development of energy storage technologies matures and the size of deployments increases, one technical point continually comes up in discussions about energy storage technologies: heat. Batteries generate heat during charge and discharge; how you manage that heat is going to determine if your system reliably lasts for 15 years or fails within 5 years due to premature degradation. LZY Energy is leading the charge on this topic with its storage solutions that use advanced thermal management systems including liquid-cooled systems – a new standard for performance and longevity in demanding applications.
This guide will explain what liquid-cooled systems are, their importance, and how to assess whether or not they will meet your application.
Why thermal management is the core challenge in energy storage
Each battery’s temperature range is critical to providing adequate power from the battery. When batteries cool below a specific temperature, the ability to generate power is reduced. However when a battery exceeds its upper limit of acceptable temperature, chemical reactions inside the battery speed up, causing it to wear out earlier than expected and in some instances represent safety issues for persons using those batteries. The issue is that when batteries are performing the electrochemical functions to produce energy, they generate heat as a normal by-product of their operation, and the higher the rate at which the battery charges or discharges, the more heat is generated.
How air cooling compares to liquid cooling
Historically, forced air cooling has been the most widely used method for managing heat in battery storage systems . To help remove heat away from the battery cells, fans circulate the air through the enclosure of the battery; this process makes forced air cooling an easy-to-implement and inexpensive cooling method. For battery systems with low amounts of power density and only moderate temperatures in their operating environment, air cooling methods work well for cooling purposes, which still makes forced air cooling a viable option for many home and light-commercial settings.
However, air will struggle to effectively act as a cooling medium due to several limitations. Firstly, compared to cooling using liquids, air does not have as high of a heat capacity (or, the ability of the coolant medium to absorb and carry thermal energy). Therefore, when used in applications that draw high amounts of power, experience high rates of charge (fast-charge) or operate in hot conditions, a system that only uses forced air cooling will not keep up with the heat being produced; the end results will be higher cell operating temperatures, which means faster degradation of the cells and will reduce the overall life of the system. Liquid cooling directly solves these limitations found with air cooling methods by using a coolant liquid that affords the system with much better thermal transfer properties than the air, thus allowing the battery cells to be kept at a more consistent operating temperature even in harsh operating environments.
What liquid-cooled energy storage systems actually do differently
In liquid cooled energy storage systems, a coolant (normally a water and glycol mixture) is circulated through channels (in direct thermal contact) to dissipate heat to the battery cells or modules. The advantage of this system is that it has far greater heat transfer capacity than air and therefore allows the battery pack to operate at much narrower temperature ranges than with air-cooled storage systems. Consequently, the following effects can be quantifiable.
In addition, the battery cells within any given storage pack will experience a more uniform temperature profile across the pack; thus, all cells will age at the same rate as opposed to some cells aging faster since they operate at higher temperatures than the majority of cells in the pack. The ability to rapidly charge/discharge the battery cells without generating thermal stress opens up additional applications for liquid cooled energy storage systems.
Applications where liquid cooling makes the biggest difference
While there are applications for energy storage that do not require liquid cooling, there is a much larger performance gap (from the perspective of discharge rates, etc.) for certain applications compared to air cooling. If power is critical at your commercial or industrial facility with high demand peaks, using a liquid-cooled system will allow for the discharge to happen at a higher rate, without experiencing thermal issues. When dealing with large-scale utility storage projects (that provide grid services such as frequency regulation) and offering rapid charge and discharge cycles, this will equally benefit from improved thermal performance due to the use of a liquid-cooled storage solution.
The use of liquid cooling becomes especially advantageous for deployments in hotter climates. Locations where ambient air temperatures are regularly above thirty-five degrees Celsius make it increasingly difficult for an air-cooled system to maintain a battery temperature within acceptable operating limits during periods of heavy use. A liquid-cooled system will perform (allow you to use your battery) much longer and at higher levels than an air cooled system. Thus, when operators are looking to invest in a long-term infrastructure solution in a warm climate, this consideration has a direct impact on their return on investment.
How to evaluate a liquid-cooled system for your needs
To select the correct type of liquid-cooled energy storage system you must first know how much energy you will need, and how long that energy will last. The calculation for determining this “energy” requirement can be derived by calculating your peak demand for electricity, the total amount of electricity used daily, and the amount of backup/storage required to sustain operational energy for given periods of time. The three values are then used to create a “baseline measurement” for developing a storage solution.
The last step prior to determining the best type of liquid-cooled energy storage system is assessing the design of the energy management system that must be integrated with the energy storage system. The designs of both the inverter/microgrid and solar infrastructure must be compatible with the energy storage system and must also be capable of providing the monitoring and communication capabilities required by the operation. A well designed liquid-cooled energy storage system that integrates with an existing installed infrastructure will produce much better performance than a technologically more advanced product that causes integration problems.
Long-term value that justifies the investment
When evaluating energy storage options based on long-term financial returns, operators can benefit from analyzing the operational data supporting liquid-cooled technology versus its air-cooled counterpart. The aforementioned benefits are substantial and have been validated through both technological advancements and operational performance over the last several years. In addition, the market has matured, and reliability is no longer an issue; therefore, operators will find that there is a compelling business case for utilizing liquid-cooled technologies for energy storage purposes.
FAQs
1. What kind of coolant are you using with this style of battery?
Most systems will be utilizing a mixture of both water and glycol (anti-freeze) since it provides excellent heat transfer properties and can both resist freezing as well as work correctly with the metals being used within the cooling circuits.
2. Is the maintenance of these units more complex compared to an air-cooled unit?
While these systems do require periodic checks of cooling level and re-filling from time to time, the design of newer systems minimizes both the frequency and volume of these tasks. Therefore, although there is a slightly higher level of maintenance required when maintaining these types of batteries as compared with those that are cooled by air, the reliability of the liquid-cooled battery will outweigh this extra maintenance effort.
3. Will a liquid-cooled battery last longer than an air-cooled battery?
High-demand or extreme-temperature applications can enhance the service life of liquid–cooled batteries by many years than liquid-cooled batteries that are typically used in air-cooled programs. Liquid cooling allows the cells to be maintained at their ideal operating temperatures throughout their entire operational time by minimizing the effect of high temperatures when used.
4. If there is a leak within the cooling system, what will happen?
Quality systems will be equipped with leak detection sensors and will have features to automatically turn off the cooling system and isolate the leak from the battery cell if a leak is detected by the leak detection system. This prevents the battery cell from being damaged by lack of cooling and provides time to correct the issue prior to further damage being done.
5. What effect does liquid cooling have on charging time?
By maintaining the cell temperature within the ideal range during charging, there should be an opportunity to charge at higher
