Power Electronics Architectures for Extreme Efficiency Data Centers

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Energy usage of data centers is becoming an increasingly important concern, as the energy-related operating costs of data centers have become a dominant part of the total cost of ownership, and their power demands represent some of the fastest growing loads on the electric grid. Consequently, data centers today are a significant contributor to global carbon emissions, making the design of data centers with improved efficiency an important societal need. The goal of this project is to reduce the power conversion losses in data centers through innovations in power electronics and system control, with the aim of extreme efficiency. This research program is expected to have far-reaching consequences for the economic and environmental impact of data centers. If successful, the large-scale adoption of the proposed power delivery architecture could save 4.44 billion kWh of energy in US data centers, based on conservative 2010 data and preliminary experimental results from an early proof-of-concept demonstration. These energy savings would in turn reduce harmful emissions equivalent to removing 850,000 cars from U.S. roads. Research will be conducted by undergraduate and graduate students who will be provided with opportunities to develop broad research and education skills. The research will complement existing educational efforts, and will help enhance community outreach programs. Additionally, educational activities include the development of power and energy focused educational modules for middle school teachers. This research will explore a radically different power delivery architecture that is designed specifically for multi-machine environments such as racks of servers, and provides significant improvement both in terms of volume savings and power efficiency. The proposed power conversion architecture exploits the large number of servers available in today's data centers, and achieves extreme power conversion efficiency by electrically connecting servers in series, similar to solutions developed for solar PV and battery applications. Stringent voltage regulation and operational requirements will be met through the combination of a) isolated, high-efficiency, high power density differential power converters that maintain each server voltage within specifications, b) hardware circuitry that enables safe and reliable isolation and hot-swapping of malfunctioning servers, and c) system control that achieves high efficiency, and which handles start-up and shutdown of individual servers and racks of servers. The research plan includes major research components in the areas of power converter topologies; design, fabrication, and testing of high density switched-capacitor power converters; development of isolation and hot-swapping circuitry for safe and reliable operation; bidirectional hysteresis control for improved light-load efficiency; and evaluation and benchmarking against existing solutions.