SMUD, an early green leader and pioneer among utilities, is starting a demonstration project to find out if it makes sense for homeowners to use batteries as a supplement for the grid during peak, summer energy demand.
SMUD, short for Sacramento Municipal Utility District, is the sixth largest community-owned utility in the US, and has been planning this energy storage project for a couple of years.
Over the next 18 months, 42 homes in one of its SolarSmart communities - where homes are extremely energy efficient and topped with solar - will be partially powered by a large battery.
15 homeowners have large lithium batteries - the size of a mini-refrigerator - installed in their garages, which can power a home for 2-3 hours, depending on the load. Another 27 homes are sharing three big, 4- square-foot batteries in common areas in their neighborhood. They provide about triple the capacity of the in-home batteries.
During the hottest afternoon hours when power is most expensive, the homes will draw electricity from the batteries to supplement what energy from the grid and from their rooftop solar panels. And late at night, when demand is down and power costs fall, the SMUD grid will recharge the batteries for use the next day.
SMUD has installed smart meters in 600,000 homes, which will help the utility and homeowners evaluate this program. SMUD is one of a handful of US utilities to complete such a large deployment.
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 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 show them how much energy they are generating and 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. 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," says Paul Lau, SMUD Assistant General Manager for Power Supply & Grid Operations.
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, and to better understand how battery storage and solar mesh with time-of-use rates.
If the batteries can adequately provide power during peak demand, customers will be able to save money by not drawing all their power from the grid during those times, and the utility can charge accordingly.
They also want to see what benefits SMUD gains from load-shifting and having the batteries and rooftop PV available to smooth out its load.
And 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 solar PV systems can be integrated to take advantage of the smart grid.
After holding informational sessions in the neighborhood, the project was over-subscribed by eager residents. The Saft batteries being used are the first large, residential lithium batteries to earn the seal of approval from Underwriters Labs for safety standards.
The $5.9 million project is funded with a $4.3 million grant from the Department of Energy, and the rest comes from SMUD, the California Energy Commission and SunPower Corp.
SMUD leads the nation in new homes built with integrated solar. In 2006, SMUD launched SolarSmart Homes, working with 18 local, regional and national homebuilders to construct 1041 homes that combine solar energy and advanced energy efficiency design.
Energy features include efficient HVAC systems, radiant barriers in attics, added insulation, duct sealing and compact fluorescent lighting.
SMUD provides incentives to builders to buy down the cost of solar PV systems and provides rebates for energy efficiency upgrades. These rebates and incentives, along with attractive tax credits, make these homes an affordable option for more homebuyers. Residents save as much as 60% on energy bills.
SMUD also has its own feed-in tariff, which maxed out at 100 MW in one week when it launched in 2010. Google partnered to acquire a portfolio of solar PV plants that serve SMUD, which serves the program. SMUD also contracted for 128 MW of wind.