This week, Industry Outlook asks Patrick Donovan about lithium-ion batteries and their potential use in the data center. Patrick is a Senior Research Analyst for the Data Center Science Center at Schneider Electric. He has over 20 years of experience developing and supporting critical power and cooling systems for Schneider Electric’s IT business unit, including several award-winning power-protection, efficiency and availability solutions. An author of numerous white papers, industry articles and technology assessments, Patrick's research on data center physical infrastructure technologies and markets offers guidance and advice on best practices for planning, designing and operating data center facilities.
Industry Outlook: Why are lithium-ion (Li-ion) batteries being touted for data center applications?
Patrick Donovan: Lithium-ion battery chemistries and how their cells are constructed have evolved quite a bit. In just the last few years, performance, safety and cost have all improved dramatically. The electric-vehicle market as well as demand from other non-data-center applications has driven this evolution in the larger-format batteries that a three-phase UPS would use. On the other hand, the lead-acid batteries that UPSs traditionally use have remained much the same as they were decades ago in terms of performance. But industries beyond the data center have innovated new types of energy storage for smartphones and electric cars, and the time has never been better—technologically speaking—for UPSs to take advantage of these recent advancements.
New customer challenges across the data-center, critical-building, industrial-process and critical-infrastructure arenas are also driving a need for UPS energy-storage innovation.
IO: What challenges are data center managers and the industry facing today that make Li-ion batteries a suitable and beneficial alternative to VRLA (valve-regulated lead-acid) batteries?
PD: The key challenges include the following:
Maximizing the available IT floor space to support the line of business or rent to tenants
Minimizing operating expenses; particularly UPS cooling-energy, battery-maintenance and battery-replacement service costs
The li-ion battery holds the key to addressing these issues.
IO: Why has it taken so long for Li-ion batteries to become a viable option in the data center industry?
PD: Although Li-ion batteries have been used commercially for over 20 years in various applications, they have seldom been used for data center UPSs because of cost. Just a few years ago, they cost 5–10 times more than lead-acid. Now, the cost premium is only 1.5 to 3 times more. Although this capital-expense premium might still sound like a lot, it’s important to understand all of the operating-expense benefits of using Li-ion versus the VRLA batteries that are common today. In fact, in our TCO analysis, we are seeing a 10-year savings of about 10% for Li-ion. We recently published a TradeOff Tool to help people make their own comparison quickly and easily using their own inputs.
I think concerns over safety have been another reason that has limited their use in data centers. Much progress has been made over the years, however, making these batteries very safe and much more similar to other common battery types in this area:
Chemistry changes and cell-packaging improvements have made them more stable
Manufacturing processes are mature and the materials used are more durable
Battery-management schemes are well tested and field proven to keep lithium-ion batteries from overcharging or over overheating.
The prolific use of lithium-ion batteries in hundreds of millions of portable electronics, smartphones and electric vehicles is positive evidence for their safety.
IO: How do Li-ion batteries compare with traditional VRLA batteries in size, charging, price and heat sensitivity?
PD: First, Li-ion batteries pack a lot of energy into a much smaller footprint. As a result, they take up only about one-third of the space (or less) of a comparable VRLA-based solution that delivers the same power. This benefit helps customers increase the footprint available for IT systems while also reducing cooling requirements, saving both capital and operating costs.
At least for the types of Li-ion batteries being selected for use in larger data center UPSs, they are also less sensitive to temperature fluctuations and can accept temperature spikes with little effect on battery life. This capability allows customers to reduce cooling capacity as well as the size of the room that houses the UPS.
Additionally, Li-ion batteries always come with sophisticated battery-monitoring systems (BMSs) that provide a clear picture of battery run time and health. It’s essentially the same technology that enables you to easily see how much battery life is left in your smartphone.
Last, the lifespan of a lithium-ion battery is 10 to 15 years, whereas a VRLA battery typically lasts between 4 and 6 years. A longer shelf life greatly reduces the cost and maintenance burdens of performing battery replacements.
IO: What about recycling? Is it similar to VRLA?
PD: Both battery types are recyclable; at present, however, it’s much easier in most regions of the world to recycle lead-acid than larger-format Li-ion batteries from UPSs and electric vehicles. But thanks to growing demand, new recycling facilities are beginning to come online that can handle these larger-format Li-ion batteries. By the time a battery system bought today would need to be recycled in 10 years, I would expect there to be plenty of options for recycling locally.
IO: Do Li-ion batteries use the same management system as VRLA batteries?
PD: Although Li-ion batteries have very low maintenance requirements, safety is top of mind when it comes to batteries, especially Li-ion batteries. Because lithium-ion battery systems are much more sensitive to how they are charged and discharged, all Schneider Electric Li-ion battery systems come complete with a battery-management system (BMS). This technology—which consists of microprocessors, sensors, switches and their related circuits—automatically collects and reports all the required data to accurately understand the battery system’s health and status, further reducing maintenance burdens. This data includes battery temperature, charge level and charge rate to protect against short circuits and overcharging. The system is also instrumental in protecting the cells from damage by preventing the voltage from going too low on discharge. The BMS provides the UPS and user with accurate information about battery status, health and available run time.
IO: What impact will these battery types have on the future of the data center industry?
PD: Lithium-ion batteries, for sure, are upping the technology ante in the UPS industry. Compared with traditional valve-regulated lead-acid batteries, they offer double the lifespan at significantly less weight and space.
Right now, however, they are still roughly two to three times the price of lead-acid systems, which will likely remain the dominant and low-cost solution for UPS energy storage, at least in the short term. But beyond these simple spec comparisons, lithium-ion batteries could have a greater impact on the data center industry in the future. That’s especially true as a growing number of companies look to employ Open Compute–based architecture, which specifies Li-ion batteries as part of the consolidated server power supply in the rack.
Some types of lithium-ion batteries are optimized for high-capacity storage (aka “energy cells”) that can deliver longer periods of run time. Could these lithium-ion systems appear in data centers as longer-term energy-storage devices that potentially replace traditional generators? Does software and application fault tolerance reach the point where hours and days of backup are no longer needed? Or could these systems be used for peak shaving to lower utility bills? These are some of the more interesting possibilities for lithium-ion battery systems in data centers of the future.
