Inside the battery

power on a single line can affect the power quality.

Utilities are required to maintain a certain quality of power on the grid, based on a frequency of 60 cycles per second, or 60 hertz.

Utilities in Hawaii, which has substantially more solar users than other places in the U.S., have struggled to maintain power quality as the use of solar increases. The problem is particularly acute if the solar panels on a power line generate more electricity than what is being used on that line at the moment.

If power quality varies too far from 60 cycles per second, it can damage devices plugged into outlets in a home.

APS’ Solar Partners Program has tested “smart inverters” to address this issue. Inverters are devices that homeowners need to convert the power from their solar panels into usable power in their homes. APS tested advanced devices that also can be used to regulate the quality of power on the grid.

While smart inverters can help regulate power quality, utilities face the same problem with them being located in customer homes and out of their control. APS is trying to learn how large batteries can be employed to do the same thing.

“Hawaii Electric Co. began installing and deploying solar at an incredibly accelerated pace,” said Scott Bordenkircher, APS director of technology innovation. “Then they began having voltage problems all over the place. They said, OK, we are in trouble, how do we fix it? We are trying to avoid that by doing all this work.”

Arizona is different from Hawaii, where the power grids are small and isolated. And Arizona is much hotter with a different peak demand from air conditioners in summer.

But the results of its testing will be closely watched by the utility industry, Bordenkircher said.

“Nobody else has installed two batteries and is doing this kind of research,” Bordenkircher said. “Our end goal is to increase reliability, as always.”

Salt River Project, the other large utility in central Arizona, approved two similar battery projects earlier this year. One of them is planned as a 10-megawatt battery with the capacity to serve about 2,500 homes for four hours. The second project, to be built near Coolidge by NextEra Energy Resources, is the same size, but rather than recharging using the grid

Inside one of the 55-foot long APS battery buildings, several air-conditioners keep the room a constant 75 degrees.

“When you are charging and discharging, you create a lot of heat,” Pinho said.

Racks of batteries line the walls. No workers are needed to maintain the equipment. It is monitored remotely by APS and the manufacturer and controlled by APS from their network operations center.

A large tank of dry chemicals sits at the ready in case of a fire.

APS previously tested a large battery in Flagstaff, installing the unit in 2010 and taking it out in 2012 after it burned down and threatened to ignite a larger blaze.

The Flagstaff battery was made by Canada-based Electrovaya Inc., and was under warranty, APS officials said at the time of the fire.

Alternative solar model

The APS Solar Partner Program might be researching solar and other technologies, but it isn’t without its critics. The program has been controversial because it involves the utility owning the rooftop solar units, rather than customers owning or leasing them.

A group called the Alliance for Solar Choice, or TASC, representing companies such as leasing company SolarCity Corp. of San Mateo, Calif., vehemently opposed the APS plan when it came before state regulators in 2014.

TASC officials said it was unfair for the utility to compete with them for the same customers.

“This is a waste of money,” TASC lawyer Court Rich said in a 2014 hearing. “There is no other way to say it.”

SolarCity officials said at the time that APS could collect the same data from solar panels already installed in its territory.

APS chose to work with Arizona-based installers to construct the solar arrays, and those installers said it has been a worthy program. They said it grows the overall market for solar.

“American Solar and Roofing supported it because there was a limited plan to it,” company President/CEO Joy Seitz said.

Her firm was instrumental in convincing APS to launch the program.

“It was difficult to have APS be invested and have liability on the roof,” she said. “It ultimately helped people get solar, however you want, whether you want to purchase or lease, and that was a win for me.”

The project was proposed to replace a large solar power plant APS planned, but canceled.

“Instead of having it out there in the desert and having to do environmental studies and impacting the animals that have habitats out there, why not bring it to where (solar) is needed,” she said.