APS testing BESS, a trailer-sized battery to back up solar

APS testing BESS, a trailer-sized battery to back up solar generationArizona Public Service Co. (APS) is testing Electrovaya’s Battery Energy Storage System (BESS). It’s a 1.5 megawatt-hour lithium-ion battery that’s the size of a shipping container that can be moved to different locations.

APS is testing the device to understand how such a system can help stabilize the power from solar and renewables and how it can help reduce peaking demand. The device will be tested and studied at two locations over the next two years. It’s now being tested at an electrical distribution substation.

“This has the potential to change how we deliver energy, and we are excited about the benefits for our customers,” said APS spokesperson Dan Wool.

BESS will later be moved a few miles up the road to support the feeder line at the APS Community Power Project, according to Wool. The neighborhood has 125 homes with solar installed, an elementary school with solar and the 500 kilowatt Doney Park Renewable Energy site.

“Part of it is testing how we can reduce the intermittency of solar. If we have a battery located where generation is, the thought is we can fill in gaps [in production] very quickly with the battery,” Wool said. “The second piece is our solar resource doesn’t align perfectly with customer peak usage. It’s close, but our peaks happen late in the day.”

That’s when people are coming home from work, firing up their air conditioners and kicking back to watch TV or cooking food.

“So we’re losing solar generation, but gaining demand. The thought with the battery is we can store energy early in the morning before the sun comes up and release it after the peak,” Wool said.

By adding in storage, APS also hopes to reduce the peak demand impact on its other generation facilities.

“The best way to describe it is like a car. If you’re revving your car at 85 miles an hour for a long time it will stress your engine,” Wool said.

With the battery, the utility is hoping to distribute some energy from the power lines and some from the battery.

At this point the test is slated to last for two years. Afterward, the unit could have other purposes, like becoming a mobile power source used when a line experiences a service disruption or when work is being done on a power line, for instance.