Before grid-tied solar, many people bought a battery along with a solar system to keep the lights on during cloudy days. Once solar connected to the grid, that expensive component went by the wayside, but now it could be returning.
Both SolarCity and Panasonic are developing small batteries for homes or small businesses to guard against power outages, either from intermittency issues, as in Germany, or to protect against natural disasters in the US.
In the US, SolarCity is starting sales of a back-up lithium battery for its solar PV systems.
Tesla’s Chairman, Elon Musk, who sits on SolarCity’s board (and is first cousin of the owners), adopted the advanced batteries it uses in its premium electric vehicles for use as back-up for solar.
The small, powerful battery is small enough to hang on the wall and comes with a 10-year warranty.
When fully charged, it powers basic needs for several days – running lights and refrigerator, charging cellphones and keeping home security systems working. If it’s charged by rooftop solar it can run indefinitely, depending on the weather.
The California Public Utility Commission (CPUC) awarded Tesla and SolarCity $1.8 million to research the energy storage device, and they have filed 70 applications for systems under CPUC’s Self-Generation Incentive Program to supply energy in areas served by Pacific Gas & Electric (PG&E). That would make the companies eligible to receive rebates from the state of California.
Panasonic Starts in Europe
This month, Panasonic is beginning mass-production of a similar battery for European homes.
The company says cuts in the feed-in tariff in Germany and other countries will make selling excess solar energy from their rooftops to the grid less attractive, and homeowners will focus on using the energy for themselves.
The 1.35 kilowatt-hour lithium-ion battery system stores excess energy generated from rooftop solar PV during peak hours and discharges the energy as needed. It will also enable households to reduce dependence on grid power.
"In Germany, there is a concern that the integration of renewable energy sources, such as wind and solar, into the power grid could cause instability in power distribution because of their unpredictable nature," says Fumitoshi Terashima, Director, Smart Energy Systems Business Unit, Energy Company of Panasonic.