For years, data centers have been haunted by the threat of power outages and the associated costs of such events. This situation is getting worse, with the most recent numbers from a 2016 report by the Ponemon Institute indicating that the average costs of a data center outage rose from $505,500 in 2010 to over $740,000 in 2015, while the maximum cost increased from $1.0 million to $2.4 million. The number one cause of such outages (representing about one-quarter of all events) was uninterruptible power system (UPS) failure.
The traditional back-up solution of lead-acid batteries and UPS have a poor track record, and are often a weak link, with multiple strings of lead acid batteries requiring high maintenance and frequent replacement.
One approach is to employ super-capacitors as a bridge
Super-capacitors can be combined with the typical UPS arrangement to help address the situation, as they can instantaneously respond to outages or power quality issues without initial voltage drops that may occur as a result of battery resistance. This bridging ability protects the data center until longer-term solutions (batteries, back-up generation, or even shifting of data and operations to different locations) can kick in. They can also allow data centers to use batteries more frequently for peak shaving, thus cutting monthly utility demand costs (demand charges are typically levied on data center users in the form of a monthly kW charge, based on the highest peak demand achieved each month). Such hybrid systems also hold the promise for extending the lifetime of the lead-acid batteries. The advantage of super-capacitors is their high availability rates, relative lack of required maintenance, and long lives.
Lithium ion batteries may represent a longer-term superior and cost-effective solution
Another technology – lithium ion storage - is rapidly emerging as a potential new approach to addressing the reliability challenge. It may soon push aside both lead-acid and super-capacitor solutions, principally because costs are falling rapidly even as the technology continues to improve.
Some lithium-ion providers are already offering products into the marketplace, including a UPS integrated with used electric vehicle batteries. While this is currently suitable for IT rooms or smaller data centers, larger lithium storage arrays – combined with intelligent oversight systems - may soon be the norm.
Soon, these lithium ion systems will likely be the standard offering into the data center marketplace, especially because costs are falling so quickly. These systems were estimated to cost between 1.5 to 3 times more than a traditional lead-acid UPS system in 2016. Just last year, though, costs declined an estimated 24%, (driven by economies of scale associated with electric vehicles).
If costs continue to decline, they will soon reach cost parity with lead-acid systems, if they have not already. Although the upfront costs are higher, operating costs are less. In fact, one total cost analysis from a leading supplier already shows lithium ion solutions as yielding a 10% savings over a decade of operation. But they also have other significant advantages: they have longer cycle lives, long run-times, and the ability to operate at higher ambient temperatures. They have significantly higher power densities, so they take up about one-third the space, freeing it up for other uses. Lithium ion batteries also have the ability to respond instantaneously, thereby obviating the need for combined lead-acid and super-capacitor solutions.
Finally, lithium ion systems combined with UPSs are generally manufactured with intelligence systems that are integrated into the entire package, thus more easily enabling monitoring of variables such as voltage, state of charge, current, temperature, and other critical variables. In this regard, they are far superior to traditional UPS systems incorporating lead-acid.
Ultimately, as the global lithium ion battery industry continues to scale and cut costs, we will likely see this new solution emerge as the dominant approach to ensuring reliability, and relegating lead-acid batteries to the scrap heap of history. Ultimately, they may also be increasingly used for peak shaving and could potentially replace traditional back-up generators.