With new generation capacity becoming both more difficult to get approved and expensive to finance, electric utilities are looking at more creative strategies for squeezing inefficiency out of customer-side distribution systems. One idea gaining attention—direct current (DC) distribution—actually represents a step backward to practices common during the days of Thomas Edison. However, new standards and products now under development could bring such designs back into a range of commercial facilities.
Edison’s first generating plants, in New York City, were built to produce DC. This scheme worked well when distribution loads were low. However, as electricity use grew, utilities began seeking new ways to provide power that could be transmitted over longer distances and more easily transformed to meet varying needs. In response, Nikola Tesla developed alternating current (AC) technology to address these concerns. George Westinghouse bought out Tesla’s patents and took Edison on in the “War of the Currents,” a head-to-head tech battle that Westinghouse won.
Now, today’s business and industrial reliance on DC-driven electronic devices is forcing utilities and electrical designers to reconsider this earlier battle. Instead of an either/or approach, perhaps—at least at the facility level—both distribution technologies have a role to play. Proponents of such a mixed approach say that significant energy savings are available by transforming power once, at the building or floor level, rather than at each individual device. Additionally, DC designs could make it easier for site-based renewable energy—produced as DC power—to serve a building’s own energy needs directly.
“The world at both ends has changed,” said Brian Patterson, chairman of the EMerge Alliance, an association of electrical and building system manufacturers, along with several utility participants, working to develop standards for distributing low-voltage DC power in buildings. “On the power-generation side, all the renewable schemes are DC producers. And, on the other end, more likely than not, you’re using DC power.”
In October 2009, EMerge released its first standard, for occupied spaces in buildings. Some of its members already are getting products certified to the standard and preparing marketing efforts. For example, Armstrong—where Patterson is general manager of business development for the company’s building-products division—is planning to release its DC FlexZone ceiling-grid system this spring. The product incorporates a 24V bus into standard suspended-ceiling grids, creating a plug-and-play connection opportunity for ceiling-based lighting and controls.
Patterson said standards’ developers likely will be looking at plug-load applications to address the needs of computers, task-lighting fixtures and other common office equipment. Such attention could aid efforts of furniture makers, such as EMerge members Herman Miller and Steelcase, to produce compliant office cubicles and other systems-based designs.
Gathering data on data centers
Potential DC-related power savings also are being explored in high-voltage installations. Lawrence Berkeley National Laboratories (Berkeley Lab), along with the California Energy Commission and the Electric Power Research Institute (EPRI), is investigating the use of DC power in data centers, at both the facility level and at individual server racks. Servers, like other computer equipment, operate on DC power, which now is transformed at each individual connection.
Because data centers have become such enormous electricity consumers, utilities are beginning to offer incentives to their owners to reduce demand. The Berkeley Lab study developed a prototype design and identified areas where standardization will be required to move broader DC applications forward. Electric utilities—through the involvement of EPRI, the industry’s research arm—are interested in seeing a successful research outcome because of the impact resulting savings could have on their generation profiles.
“This is a readily available technology for reducing demand,” said Brian Fortenberry, program manager in EPRI’s Energy Utilization group. “We wanted to look at this technology to see if there was measurable reduction in demand.”
Bill Tschudi, program manager at the Berkeley Lab’s Environmental Energy Technology Division and who manages the research in DC-based data center design. He said a DC approach is probably only financially feasible for a newly designed facility because rewiring an existing one is prohibitively expensive. But for new construction, DC design offers savings potential beyond the monthly electricity bill.
“From a practical point of view, it should result in less equipment,” he said, leading to a smaller overall building footprint. Plus, fewer AC-to-DC transformers means less waste heat for cooling systems to manage, which is significant, since air conditioning systems can use as much, if not more, electricity than the equipment they are intended to keep cool.
Since the effort’s initial proof-of-concept demonstration, research team members have worked with stakeholders to reach agreements on voltage levels, at 380V, and to create UL-listed connection components. Berkeley Lab researchers also are reaching out to the EMerge Alliance, to address points of common interest, Tschudi said.
“There is interest in merging what we’re doing,” he said.
ROSS is a freelance writer located in Brewster, Mass. He can be reached at firstname.lastname@example.org.