Bringing DC Power Into The Workplace



When the United States initially became electrified, it appeared as if the nation might run on direct current (DC). Early electric motors and the first incandescent lights were engineered to work best with DC power, although alternating current (AC) devices were also used.

But DC could not travel great distances effectively due to lack of equivalent transformer technology that allows AC to be transmitted at higher voltages and then stepped down at the point of use. Construction of the nation’s first large-scale power plant — the hydroelectric dam at Niagara Falls — confirmed the use of AC power because of its better transmission capabilities to the surrounding community of Buffalo.

So for more than a hundred years, the United States has used alternating current. Increasingly, however, the devices we use to perform daily tasks run on DC power: computers, cell phones, lighting and more. Even DC motors are coming back into vogue. One result of this trend has been the formation of the EMerge Alliance, an industry coalition that is encouraging direct current use via a DC open standard for commercial space.

Why DC Matters

“As a nation, we used to do much of our work using large-horsepower motors that used AC power, but that was 50, 75 years ago,” says Brian Patterson, EMerge Alliance board member and general manager of Armstrong World Industries’ new business development program. “Our work now is mostly digital, and the power requirements have changed as well.”

This shift in how Americans work has created mismatches in power. When AC enters a building, it goes through a series of power converters, rectifiers and inverters. It even goes through several steps of AC-specific voltage transformations. All of the transformations and conversions reduce energy efficiency.

If buildings relied on a combination of AC and DC power, energy efficiency gains would be in the low double digits, says Patterson. For energy-intensive data centers, gains could be as high as 30 percent. Added benefits the Alliance touts include increased flexibility for high-churn interior space and increased sustainability in the use of native DC devices like LED lighting and on-site renewable energy sources like solar and wind.

EMerge Standards

The EMerge Alliance aims to solve some of today’s inefficiencies in part by moving power transformation from the device level to the room or building level. Most power cords for devices that use DC have a small “box” on the charging/power cord. That box is a converter that transforms 120v AC power to DC power. A similar transformer is found in the electronic ballasts and drivers of fluorescent and solid-state lighting.

Under EMerge standards, DC power could be supplied to devices via a distributed network within a building.

The first EMerge standard calls for a distributed bus system at the room level in the form of a suspended ceiling grid. Other standards in the works will address data and telecom centers, building services and utilities, and outdoor power.

“Power in the ceiling can be isolated and everything in the ceiling plane can be controlled by DC,” says Bruce Graham, EMerge Alliance board member and president of projects/design and construction services for global workplace solutions at Johnson Controls.

The result of making DC power available in the ceiling, say EMerge proponents, is increased flexibility. With DC power available throughout the ceiling, interior churn would not force facility managers to face the added cost of relocating wiring for lighting, sensors and other commonly moved devices.

“One of our objectives was to create a safe, bus-like plug and play power infrastructure that could be easily reconfigured during office moves,” says Patterson. “It’s easy to place power in the ceilings because that’s where power is concentrated.”

“For occupiers of the space where DC power is found, they’ll see no difference,” says Graham. “It will look just like a modern building, and standard AC outlets are there for housekeeping or other AC requirements.”

AC outlets will remain because EMerge members envision a hybrid building power infrastructure, with both DC and AC power. Even though buildings will use a hybrid approach, EMerge says wiring will not be redundant or require two systems. “There might be some minor duplication of wiring, but that wouldn’t be required on most installations,” says Patterson. “I believe we’ll see a gradual but constant conversion over to DC equipment.”

Looking to the Future

Future iterations of the standard will evolve to include interior finish infrastructure beyond the ceiling plane. “The topology of this is that it will move down the walls, into raised floor systems, and to occupants’ desktops as well,” says Paul Savage, EMerge Alliance board member and CEO of Nextek Power Systems.

The standard is also expected to evolve and include DC-specific devices; as part of that undertaking, the EMerge Alliance is beginning to conduct third-party compliant product evaluation in conjunction with the California Lighting Technology Center at the University of California-Davis.

With the increasing development of DC-based electronic communication and wireless control systems, the Alliance anticipates updates in control technology during future iterations of their standard.

All this change won’t exactly be easy, and members of the EMerge Alliance know it. “The AC infrastructure has been around for 100 years,” says Patterson. “But it’s like the Internet in some ways: The change will be gradual and the conversion happens a layer at a time.”

Nevertheless, certain industries and forward-looking facility managers are clamoring for increased DC use in their facilities. “So far we’ve seen a pretty big appetite from operators and owners,” says Graham.

Building owners who embrace this technology do so because they know it has quantifiable cost benefits and gives them a progressive edge, especially where constant space repurposing is a way of life, says Patterson.

“The first implementations will really be wearing the badge of leadership,” he says. “I think this technology has the potential to change the building power world the way the Internet changed the computer world.”

About EMerge

The EMerge Alliance is a not-for-profit industry association formed in 2008. The EMerge Alliance was established to promote the rapid adoption of safe, low-voltage DC power distribution and use in commercial building interiors. EMerge is developing open standards that integrate interior infrastructures, power, controls and a wide variety of peripheral devices, such as lighting, in a common platform. The Alliance is a member of the U.S. Green Building Council and is in the first phase of testing DC-specific components with a third-party laboratory.

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  posted on 5/26/2010   Article Use Policy

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