During the daytime, solar power generation can tend to wax and wane erratically depending on sun exposure, cloud cover or even dust on solar panels.

This unpredictable pattern is undesirable for electric utilities, which prefer a stabile energy output.

Yet power prices are cheapest during these sun-soaked hours.

So, like harvesting a berry-loaded field by hand instead of basket, power providers can be faced with an excess of cost-efficient power with no means to stockpile.

What to do?

Enter a battery storage system.

“It’s one of the fastest growing technologies on the energy grid,” Central Arizona Project (CAP) Power Program Manager Jeff Ritter said. “One of the problems with solar power is that it can be intermittent. Batteries give us a way to store it. That aspect is extremely desirable to electric utilities.”

Solar battery storage strategy: an explainer

Essentially, a field of larger-than-life batteries, which can appear in extensive columns and rows, is charged during the daytime, especially during duck curve hours when solar generation is at a maximum output and energy prices are cheapest.

Then, battery storage allows for a shifting of that excess energy for use during the higher-priced, late-evening hours.

As an added spark, the batteries allow for this consistent output of energy during the sun-down hours when solar generation plummets.

It’s a strategy of efficiency and stability.

Grid-scale battery storage: a recent phenomenon

The electric industry has realized there is value in a technology that stores renewable energy to be used at times of higher demand on the grid.  Battery storage is one method that can fill this need.

Battery storage projects are becoming a significant investment for states with large amounts of renewable generation (such as California and Texas).  Other states, especially in the Southwest, are following suit with their own projects to incorporate battery storage into the electric grid.

Arizona – including CAP – is one of them.

How CAP is utilizing battery storage

CAP is on track for the commercial operation of battery storage on Dec. 31, 2023 at Origis Energy’s AZ Solar generation field. In 2020, CAP agreed to purchase 20 years of power from this facility located near Salome in western Arizona.

The batteries at this facility are rated to hold energy for 3.5 hours and have a capacity of 60 megawatt hours (17 megawatts x 3.5 hours).

Battery storage can help save CAP stakeholders money by giving CAP the flexibility to sell energy at a higher price than it costs to charge the batteries. CAP has developed a diversified power portfolio, which includes renewable supplies and a combination of long-term and market purchases. It’s another way CAP’s reliable and cost-effective methods of power purchasing affords stakeholders reliable and stable rates.

This next “phase,” which we call AZ Solar 2, will include this technology of battery storage, a steadying addition as we continue to diversify our power portfolio and harness the power of the sun.