Silent Power’s Neighborhood Solar Batteries

Solar panels make electricity when the sun shines, but the suburbs start using the most power when the mases come home from work (ie. night falls). How can utilities shift that solar energy from day to dusk, when it’s most needed?

This week, Sacramento’s utility SMUD turned to startup Silent Power for help. The Baxter, Minn.-based startup was named as a partner, along with GridPoint, SunPower (s SWPR) and lithium-ion battery maker Saft, in a project funded with a $5.9 million Department of Energy smart grid stimulus grant. In its first utility pilot project, Silent Power’s “OnDemand” system will hook up about 15 houses in the Sacramento suburb of Rancho Cordova with inverters that connect rooftop solar panels with batteries, controlling the flow of power between them and the grid at large, CEO Todd Headlee told us in an interview.

“Local firming” is what Headlee calls the service that Silent Power seeks to provide. For about $5,000 more than a typical solar installation, the startup can add its inverter-energy storage system as an on-call service for utilities to balance reactive power and voltage fluctuations on the grid in the short-term, or for homeowners to store cheap self-produced power for later in the day.

In the Sacramento project, Saft will be supplying cells for 10-kilowatt-hour batteries — enough to ride most homes through several hours — that can be stored comfortably in basement or garage, Headlee said. SunPower will provide the solar panels, GridPoint will manage the flow of information between the systems and the utility, and Silent Power will keep an eye on household power via sensors at the main circuit panel.

“This is a very consumer-friendly type solution,” Headlee added, since it allows the battery or the solar panel to take the place of shutting down air conditioners or appliances in response to brownout conditions. Key to the whole enterprise is Silent Power’s inverter, which can also disconnect the house from the grid when there’s a power outage, Headlee said. That would let them keep the lights on with battery power while other solar-powered homes go dark — utility industry standards now require solar panels to shut off in a blackout, mainly to avoid having their power run back up a downed line and electrocute a utility worker.

Utilities are looking for ways to better control customers’ rooftop solar panels to integrate them into neighborhoods where they make up a significant portion — say, 10 percent or more — of the power carried on the local portion of the grid. Beyond the SMUD pilot, Silent Power is working with partners including General Electric (s GE) and several unnamed utilities, as well as advanced lead-acid battery makers and other energy storage providers, Headlee said. The company is expecting to announce more utility projects shortly and is seeking some $7 million in a Series A round to augment its $5 million in angel investment to ramp up production to meet anticipated demand.

Image courtesy of Silent Power.

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