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As power consumers such as big-box stores start to install more solar panels and energy-storage devices, smart transformers could be key to integrating power from these sources and the grid, Maitra says. Storage systems and distributed energy can allow stores to decide when to draw power from the grid and when to send power back to it, depending on the price of electricity at a given moment. Smart transformers could coordinate this potentially rapid change from buying to selling power, while keeping the grid stable and preventing neighbors’ lights from dimming. They could even allow people to buy electricity from their neighbors, Huang says. “If you plug in your electric car at night, you could charge it by negotiating with those in your neighborhood who have excess power,” he says. “You actually pay him. You don’t pay the utility.”

Other kinds of devices can do many of the same things, but the idea of coordinating a large number and variety of consumer-owned devices makes utilities nervous about their ability to keep the grid stable. The new transformers would simplify the system and be utility-owned, making it easier for grid operators to keep the lights on, Maitra says.

Another potential benefit of smart transformers—or what the Electric Power Research Institute is starting to call smart-grid interfaces—is saving energy. For one thing, they can set the voltage of electricity at any given time so that it is at the minimum level appliances need to perform properly. One recent study suggested that doing this could reduce power consumption in the United States by up to 3 percent, which is equivalent to several times as much power as is now generated by all solar panels in the U.S. Even larger energy savings could be seen if smart transformers supplied DC power rather than AC to servers in data centers. Ordinarily, the servers convert the AC to DC themselves—and they do it inefficiently. (Other inefficient conversions, too, are involved in the uninterruptable power supply.) A recent demonstration of such a system by Duke Energy, a large utility company, and the Electric Power Research Institute found that supplying DC could cut power consumption at data centers by about 15 percent.

Smart solid-state transformers are still in the development stage and likely are a few years away from being ready for market—researchers are still working on their efficiency and cost, for example. Taking advantage of their DC capability will require developing new construction standards for homes and businesses. Mark Wyatt, the vice president of smart-grid and energy systems at Duke Energy, cautions that solid-state transformers will need to be supplemented with other devices for controlling power on the grid, and they may not prove cost-effective in many areas. “It’s not one size fits all,” he says.

Yet in the long term, Huang says, smart transformers and other smart solid-state devices could enable an unprecedented amount of two-way power flow. “It could be revolutionary to how we construct the grid,” he says.

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Credit: EPRI

Tagged: Energy, energy, solar, smart grid, energy storage, power electronics, transformers

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