Batteries
The batteries are an evolution of the APS Solar Partner Program. About 1,600 participants allow APS to install solar on their homes in exchange for a $30 monthly credit on their bills, worth about $7,200 over the 20-year term of the deal.
The arrangement aims to increase the number of people using solar power while allowing the utility to research how to handle substantial numbers of solar panels feeding a single power distribution line.
In the Festival area, about 13 miles west of the Loop 303 off Bell Road in Buckeye, 68 residents are participating in the APS program and several others have their own solar kits. They all are on a single distribution line.
APS and other utilities have some customers with solar and small, in-home batteries to address energy supply and demand issues, but the systems are expensive, and if they are on a customer’s side of the meter, the utility can’t control them.
The large battery systems can be dispatched when the utility needs them. The drawback is that they add to the expense of running the power grid, and that cost is made up by all ratepayers.
Helping solar
Several of the homeowners in the Festival housing developments are retirees and the properties are often second homes, with many of them vacant during summer, APS officials said.
But even if there are no customers pulling electricity from the grid, the homes’ solar panels generate electricity during the daytime, and APS must manage the fluctuations on the power grid with all of those solar panels making power and dropping off when a cloud passes or the sun sets.
The large battery can take any excess power generated during the daytime and send it to the grid after sunset, when solar panels are not making electricity but homes are drawing lots of power as people turn on lights and other appliances.
The peak demand on the power grid in metro Phoenix often occurs around sunset, so batteries can help match power supply with demand.
The batteries also can help stabilize the grid when clouds pass overhead, causing the output of solar panels to fluctuate.
“Think of it like a shock absorber,” said John Pinho, project integration manager for APS. “They are used to absorb these shocks and flatten out demand on the feeder (power line).”
The two batteries APS is testing in the area have a capacity of 2 megawatthours, and can discharge enough electricity to supply about 500 homes for an hour, or 250 homes for two hours, or other variations of time and power. But they can do more than that. Having several homes supplying solar