Data centers have to operate with extreme availability targets which are dictated by artificial intelligence (AI) workloads. Increased reliance on digital infrastructure is putting further pressure on the availability of data centers.
To meet these expectations, battery energy storage systems (BESS) have become a foundational element of data center power architecture. Yet much of the industry conversation still centers around “why” BESS is needed, not “how” it should be designed to function effectively in complex, high availability environments.
This requires identifying the correct “stacked use cases,” which is the practice of designing a BESS to perform multiple functional roles within a data center power system – often simultaneously or under different operating conditions – instead of serving a single, dedicated purpose. In this context, “stacked” refers to “functional stacking” rather than physical stacking of equipment.
“Everyone now knows that BESS is a critical part of data centers, but we need to focus on exactly what kind of stacked use cases these energy storage systems need to provide,” according to Chinmay Morankar, vice president of Systems Engineering at WSP in the U.S.
Stacked reliability functions
There are two critical scenarios when it comes to data center resilience: loss of load and loss of generation. While both demand a swift response, they also place different – and sometimes competing – requirements on a BESS.
Designing multiple reliability roles introduces challenges related to state-of-charge management, response time and control strategy. The problem is that a system optimized for one scenario may be poorly positioned to support the other if these tradeoffs are not addressed early.
“Meeting these requirements often requires close coordination with primary generation equipment suppliers and working with BESS original equipment manufacturers to design an appropriate system,” Morankar said. “Reliability isn’t simply about capacity. It’s about intentional design that anticipates overlapping operational demands.”
System stability and renewable integration
Battery energy storage systems typically don’t operate in isolation. In many cases, they interact closely with large rotating equipment such as gas turbines, as well as with renewable generation resources. These interactions introduce system level considerations that extend beyond the data center boundary.
“Pairing BESS with rotating equipment requires careful coordination between storage and generation assets to ensure system stability,” Morankar said.
At the same time, data centers face growing pressure to integrate renewable energy. BESS enables this transition by stabilizing intermittent generation. . In hybrid generation systems, segmenting BESS roles and assigning different BESS assets to different functions can improve both reliability and performance.
The value of battery energy storage extends beyond steady state operations, as one often overlooks the role BESS can play to support commissioning and early project phases.
“BESS can support commissioning activities along with the load bank, including gas turbine commissioning and transformer energization if designed appropriately,” Morankar explained.
“Furthermore, deploying storage early can reduce project risk, improve schedule flexibility and deliver benefits before full data center load is online.”
Design principles going forward
When evaluating BESS in data center applications, several high level design principles emerge for organizations. These include:
- starting with clear assumptions when load profiles are uncertain
- accounting for AI driven load volatility
- aligning BESS architecture with the site’s generation mix.
“Early stage uncertainty is a defining challenge,” Morankar said. “Most of the time you don’t have clear visibility on load patterns of data centers,” which makes flexibility and upfront assumptions essential. Decision makers should consider whether multiple BESS systems are required to serve distinct functional roles, especially for hybrid generation environments.
Organizations that plan for stacked use cases in modern data centers can reduce operational risk, improve system performance and gain greater flexibility across the project lifecycle. As data center loads become more volatile and power systems more complex, intentional BESS design will be a defining capability.
“Those who treat energy storage as part of a coordinated system, rather than as an isolated component, will be best positioned to meet future reliability demands,” Morankar said.
