For decades, lead-acid battery technology has been the workhorse of data centre UPS, but newer technologies offer new opportunities to improve performance, safety, sustainability, and total cost of ownership. Lithium-ion and nickel-zinc (NiZn) chemistry are the primary competitors in the marketplace, displacing lead-acid. Both have a smaller footprint and a longer life expectancy than lead-acid batteries. While lithium-ion battery trade-offs are more well-known due to their widespread use in other energy storage applications, NiZn technology offers distinct advantages in terms of reliability, safety, and sustainability over both lead-acid and lithium-ion solutions in data centre UPS facilities. These benefits can result in a lower total cost of ownership for data centre operators.
High Power Density with Small Size and Weight
The size and weight of lead-acid batteries are two of their most obvious disadvantages. NiZn batteries have a significantly higher energy density than lead-acid batteries, both in terms of weight (Watt-hours per kilogramme) and volume (Watt-hours per liter). To demonstrate the benefits of NiZn batteries, we compared a 50kW NiZn UPS backup system to comparable lead-acid systems and discovered the following benefits for the UPS facility:
- 42 – 63 percent smaller footprint
- 55 – 60 percent less floor loading
- 110 – 197 percent higher watts/lb
- 91 – 194 percent higher watts/sq. ft.
More Reliable Performance
To take advantage of this increased power density, the data centre operator must ensure that the battery backup system is extremely reliable. The primary factor to consider is the reliability of the battery string. When a lead-acid or lithium-ion battery cell fails, an open circuit is created, effectively shutting down the string. On the other hand, a weak or depleted NiZn cell remains conductive, allowing the string to continue operating. This effectively transforms an emergency situation involving other battery chemistries into a straightforward battery replacement during the next scheduled maintenance cycle, with minimal cost and no operational impact. Additionally, NiZn battery strings are more tolerant of string imbalances than lead-acid or lithium-ion battery strings.
NiZn battery chemistry enables rapid recharging and excels at high discharge rates while maintaining thermal stability in mission-critical applications such as data centre backup. It eliminates the need for trickle charging in order to maintain capacity performance, simplifying system design and increasing energy efficiency. Additionally, unlike lead-acid batteries, NiZn is an alkaline battery that does not sulphate over time, resulting in a significantly longer service life with minimal maintenance. When these reliability behaviours are combined, they result in a direct reduction in TCO.
Safer Data Center Facilities
Apart from maintaining continuous uptime, data centre operators are accountable for the safety of their facilities and personnel. NiZn battery technology clearly outperforms lead-acid batteries in terms of safety, as it eliminates the need for caustic chemicals and routine maintenance to keep the batteries fully functional. Additionally, NiZn batteries do not outgas as lead-acid batteries do during normal operation.
While data centre operators may wish to consider lithium-ion technology as a viable alternative to lead-acid systems, they may have read about thermal runaway events at utility energy storage facilities. They can consult the results of any battery or energy storage system that has been tested to the UL9450A Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems to determine the relative safety of new battery technologies. Testing in accordance with the UL 9540 Test Method can take place at any of the method’s defined levels, including the cell, module, unit, or installation level. Cell-level testing is the only way to determine whether a battery’s chemistry is capable of propagating a thermal runaway. ZincFive’s NiZn batteries have been rigorously tested at the cell level by UL using the UL9540A Test Method, and they passed all five arduous and destructive test types without exhibiting thermal runaway.
Lithium-ion battery systems that pass higher-level unit tests rely on a controlling mechanism (referred to as a Battery Management System, or BMS) that is designed to prevent the propagation of a cell-level thermal event. Mechanical and electronic devices are known to fail and may not preclude a thermal event if they do, illustrating the superior safety value provided by a battery chemistry capable of being tested at the cell level and exhibiting no thermal runaway.
Advantages for Sustainability
With the rapid expansion of the size and number of data centres worldwide, operators are under increasing pressure to mitigate their environmental impact. This is another reason to replace lead-acid batteries, which contain significant amounts of hazardous materials and must be recycled in a highly polluting manner. Indeed, environmental organisations have identified used lead-acid battery recycling as a major source of pollution on a global scale.
Lithium-ion batteries do not yet have a well-defined, self-funded path to recyclability at the end of their useful life. They necessitate additional transportation safety measures due to the fact that they contain both a chemical and an electrical hazard. They are carefully treated to avoid fires and toxic outgassing.
NiZn chemistry outperforms both of the alternatives in terms of sustainability. NiZn batteries are non-flammable and fail-safe because they are made primarily of readily available materials. Additionally, because they have a useful life of up to three times that of lead-acid batteries, data centre operators do not have to replace them nearly as frequently.
Additionally, NiZn batteries are one of the most recyclable battery chemistries available. Indeed, the California Department of Transportation (Caltrans) has defined a Green Technology Battery Backup System (GT-BBS) standard that specifies the use of NiZn battery-based backup systems as a more environmentally friendly alternative to lead-acid battery backup systems.
NiZn Attributes that Lower TCO
The total cost of ownership (TCO) of UPS backup includes more than just the initial capital expenditures (CapEx) on battery solutions and storage facilities. For lead-acid batteries, operating expenses (OpEx) can be more expensive than capital expenditures (CapEx) over the life of the UPS system. NiZn solutions significantly reduce OpEx due to their significantly longer useful life and ease of maintenance.
There are additional significant factors that affect the TCO of data centres. NiZn batteries’ size and weight advantages over lead-acid batteries can help reduce the investment required to build UPS facilities within data centres. Additionally, NiZn batteries operate over a wider temperature range than other technologies, reducing the demand on data centre cooling systems and allowing UPS backup to be placed closer to the load.
ZincFive solutions reduce TCO by up to 28% when compared to lead-acid-based UPS products over the course of the UPS’s useful life.
The Battery Technology for Safer, High Performing Data Center Backup
NiZn technology has emerged as the best option for data centre backup in place of lead-acid batteries. NiZn-based batteries are the heart of reliable high-performance UPS systems due to their high power density, small size and weight, longer life, and higher temperature operation. These batteries are more environmentally friendly and safer to operate than both lead-acid and lithium-ion backup batteries. In general, NiZn technology can assist data centre operators in lowering the total cost of ownership (TCO) of data centre backup.