Architecting Efficient Peak Power Shaving Using Batteries in Data Centers

Abstract

Peak power shaving allows data center providers to increase their computational capacity without exceeding a given power budget. Recent papers establish that machines may repurpose energy from uninterruptible power supplies (UPSs) to maintain power budgets during peak demand. Our paper demonstrates that existing studies overestimate cost savings by as much as 3.35x because they use simple battery reliability models, Boolean battery discharge and neglect the design and the cost of battery system communication in the state-of-the-art distributed UPS designs. We propose an architecture where batteries provide only a fraction of the data center power, exploiting nonlinear battery capacity properties to achieve longer battery life and longer peak shaving durations. This architecture demonstrates that a centralized UPS with partial discharge sufficiently reduces the cost so that double power conversion losses are not a limiting factor, thus contradicting the recent trends in warehouse-scale distributed UPS design. Our architecture increases battery lifetime by 78%, doubles the cost savings compared to the distributed design (corresponding to $75K/month savings for a 10MW data center) and significantly reduces the decision coordination latency by 4x relative to the state-of-the-art distributed designs.