For Immediate Release: June 29, 2012

Batteries to help power homes in Sacramento

For the next 18 months, 42 Sacramento Municipal Utility District (SMUD) households will help determine what happens when a home is partially powered by a large battery. SMUD officially launched the project at the Anatolia subdivision, a SolarSmart HomesSM community in Rancho Cordova, California.

The $5.9 million demonstration project will determine how battery storage can help provide extra capacity during times of peak demand, such as the hottest hours during the summer. The project is funded by a $4.3 million grant from the Department of Energy, with the remainder coming from SMUD, the California Energy Commission and SunPower, Corp.

Under the program, 15 homeowners had large lithium-ion batteries — the technology that powers hybrid autos like the Toyota Prius — installed in their garages. Another 27 homes will share three batteries located in common areas in their neighborhood.

During the hottest afternoon hours when power is the most expensive, the homes will draw electricity from the batteries to supplement what they get from the grid and from the solar panels installed on their roofs. And late at night, when demand is down and power costs fall, the SMUD grid will recharge the batteries for use the next day.

“The aim of the program is to learn whether or not batteries can ease load demand and provide more electricity when renewable energy sources such as solar and wind power aren’t sufficient,” said SMUD Assistant General Manager for Power Supply & Grid Operations, Paul Lau.

“The project will also help us better understand how battery storage and solar mesh with time-of-use rates, where customers pay more for electricity during peak hours and less during low-demand times. The batteries provide power during peak demand, so customers could save money by not drawing all their power from the grid during those hours,” Lau said.

Finally, because the homes in the demonstration project are high-efficiency SolarSmart Homes with the latest in rooftop solar, the project will provide a better sense of how photovoltaic systems can be integrated to take advantage of the smart grid.

“We hope to learn what benefits accrue to customers from their ability to shift load to the battery when electricity prices are highest,” Lau said. “And we want to see what benefits SMUD gains from load-shifting and having the batteries and rooftop PV available to smooth out our load.”

Even though it’s an unfamiliar concept, customers were eager to participate in the program. The pilot was fully subscribed within a week of SMUD holding informational sessions in the neighborhood.

The batteries have been approved by Underwriters Laboratories, which develops safety standards and certification for electrical products. They are the first large, residential lithium-ion batteries to earn the UL seal of approval.

The batteries for the homes are about the size of a mini fridge and can power a home for 2 to 3 hours depending on loads. The batteries being shared by multiple homes are 4-by-4-foot cubes that sit adjacent to distribution transformers and have approximately three times the capacity of the in-home batteries.

Along with the batteries and other hardware, SMUD has installed scores of monitoring devices — in the homes, on the batteries and at a substation — to help keep track of how and when energy is being used, and even how specific weather conditions affect energy use on a minute-by-minute basis. Homeowners also have in-home displays that will show them how much energy they are generating and are using. SMUD grid operators have the ability to monitor and manage these batteries individually or as a fleet through a web application.

“Energy storage is potentially a game changer in our industry,” Lau said. “After this study is complete, we hope to have a much better idea whether energy storage benefits the customer and the utility, and how best to operate the system.”

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Contact SMUD News Media Services at:
(916) 732-5111