The face of data centers is changing. Power density demands continue to climb with new computing technologies, ever-growing user bases, and expanding networks. At the same time, efficiency concerns are top of mind for companies, regulatory bodies, and individuals the world over. Data center operators and engineers have approached the pursuit of more efficiency from many angles and have made strides. Although data centers worldwide still use more energy than some countries [1], the estimated overall share of global data center consumption hasn’t changed much since 2010 thanks to innovations from those in the industry [2].
Still, the global reliance on data centers will continue to rise, and energy consumption will rise alongside it unless power specialists and data center operators identify new ways to boost efficiency and scale their facilities more effectively. To do so, they may need to reimagine data center power from the ground up, starting with their power architecture.
At present, most data centers utilize a centralized uninterruptable power supply (UPS) to convert alternating current (AC) power from the grid to direct current (DC) for use throughout the facility. It makes sense: AC distribution has dominated the power sector since its inception, engineers are familiar with its use, and equipment designed for AC input is the norm. However, it may not be the best option to meet today’s data center demands.
The Sustainable Solution
In the 1890s, the War of the Currents saw power pioneers Thomas Edison and Nicola Tesla go head-to-head as engineers and officials worked to standardize power distribution for the construction of the first U.S. grid [3]. Eventually, Nicola Tesla’s and George Westinghouse’s argument for their AC system beat out Edison’s DC proposal. The AC model was determined to be the most appropriate choice at the time, thanks to its ability to travel long distances at a high voltage, its position as the safer option for in-home use, and its simpler conversion process.
As technology has progressed, though, the case for using DC in certain environments has been made time and time again. Just decades after AC’s adoption, high-voltage DC (HVDC) came along to challenge AC’s status as the better choice for high-voltage transmission over large distances [4]. Computers, automobiles, and landline telephones, for example, have used DC for years. Solar panels and wind turbines deliver DC power as both rely upon batteries to store and transmit loads to users. All of this is to say that positioning polyphase AC power as the superior option across applications is a bit of a stretch.
This is especially true in today’s technological environments, which demand precise and varied power to run properly. When power is coming in one way, is stored in another, and needs to run varied equipment with diverse power needs, it must be converted time and time again. And each conversion comes at a price: lost energy.
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In large-scale, power-hungry facilities like data centers, the need for conversion can make maintaining efficiency complicated. In facilities with centralized AC, the cabinets and racks rely on power conversion to ensure critical infrastructure gets the precise power load required. However, with hundreds of cabinets per site and incremental power lost at each conversion step, the total energy losses and inefficiencies start to add up. Performing the final conversation to DC power earlier in the chain can eliminate one or more conversion steps, mitigating energy loss and improving efficiency throughout the facility.
** Note: Slight graininess, best at smaller sizes
New Power for a New World
Shifting to a distributed DC architecture can also help data centers address rising demand, the other pressing concern in the sector. We use a lot more power now than we once did, and existing centralized UPS architectures may soon reach their capacity limits—stunting their ability keep up with demand as it continues to rise. Traditional wisdom tells us that a data center’s scalability is constrained by three factors:
- Physical footprint
- Cooling system
- Power capacity
However, characterizing power capacity as the third factor ignores the real deciding factor: its power architecture.
AC UPS architectures are inherently capacity-constrained. The systems are large, complex, and tailored to fit specific power needs at the time the data center is constructed. This makes scalability quite difficult and results in stranded white space in the data center. Decentralized DC power architectures, however, are not limited in the same way. Decentralized DC power systems connect directly to the AC utility feed to power additional equipment without stressing existing UPS systems. This approach allows operators to scale their output by deploying equipment-specific resources tailored to a facility’s unique design.
Decentralized DC equipment can be slotted into otherwise unused white space on the data room floor, increasing capacity within existing footprints. These decentralized architectures can facilitate the installation of more servers, routers, firewalls, switches, storage, and cooling equipment so operators get the most out of every square inch of their floorplans. Adopting decentralized DC architectures allows operators to add power and load at the same time—and helps them to keep pace in today’s ever-growing market.
Time to Look Ahead
The ubiquity of AC power can be traced to a fascinating piece of history. At the time, it made perfect sense. Its advantages met the needs of the moment and formed the basis for the reliable power grid we now have.
However, in modern applications, AC power’s dominance has as much to do with its widespread use as its inherent qualities. Years of fine-tuning and technological development have made AC the default choice across applications, but that does not necessarily mean it’s the best option across the board. With demand growing, footprints shrinking, and technology forging ahead, the case for more widespread use of DC is steadily growing stronger—and data center power architectures provide a compelling example of where that might start.
As with any change to the status quo, shifting to decentralized DC architectures in data centers will be a process. It will require innovation, investment, and creative thinking to get right. However, the reliability, scalability, and energy savings that come along with the technology can help set the industry on a path toward more efficient and responsible operations for years to come.
REFERENCES
[1] https://www.dw.com/en/data-centers-energy-consumption-steady-despite-big-growth-because-of-increasing-efficiency/a-60444548
[2] https://energyinnovation.org/2020/03/17/how-much-energy-do-data-centers-really-use/
[3] https://www.energy.gov/articles/war-currents-ac-vs-dc-power
[4] https://www.powermag.com/benefits-of-high-voltage-direct-current-transmission-systems/
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ABB Power Conversion | www.abbpowerconversion.com
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • DECEMBER 2022 #389 – Get a PDF of the issue
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Vito Savino is the data center and wireline segment leader for ABB Power Conversion, where he works with data center and telecommunications customers to provide advanced solutions for their dynamic power challenges.
