CPS Energy has been harvesting more of the power it supplies to customers from solar energy for the past several years. Now, it’s working on finding better ways to store that energy for use when it’s needed most. 

At their June 28 meeting, CPS Energy’s board of trustees approved a $16.3 million agreement to install a 5-megawatt solar array with 10 megawatts of battery storage on Southwest Research Institute’s property at 9800 W. Commerce St. 

The project will help the utility better understand how to store power generated from renewable sources. CPS Energy officials say stored energy also can help maintain the electrical grid’s reliability.

“We’ve been studying energy storage for a while,” said David Jungman, the utility’s senior director of business and economic development.

“We’re really not sure how quickly it’s going to be adopted. We’re not sure which technology ultimately will be adopted. But we feel like investing our efforts in this technology now … readies us for this change.”

As part of what CPS Energy officials are calling the Flexible Path, the utility’s leaders want 5 percent of the energy it generates by 2040 to first be stored in batteries.

Last year, CPS Energy’s generating mix was roughly 45 percent natural gas, 22 percent wind and solar, 18 percent coal, and 14 percent nuclear.

As renewable energy sources make up more of the utility’s power supply, CPS Energy needs to figure out how best to supply electricity when the sun isn’t shining and the wind isn’t blowing. 

Solar generation peaks in the heat of the afternoon from 1 to 3 p.m., Jungman told the board, but electricity demand spikes from 5 to 7 p.m. as people return home from work and turn on their air conditioners, lights, and appliances.

The conventional way to bridge this gap is to start up a small natural gas-fired peaking plant. CPS Energy operates eight of these, all in Bexar County, communications director Melissa Sorola said.

Jungman explained how the batteries might be able to help fill a similar need while avoiding the use of fossil fuels.

“Instead of turning on a peaking unit, or something else, we’ll be using this energy storage that’s being fed by solar,” he said.

CPS Energy’s board unanimously approved an agreement with contractor Renewable Energy Systems to build the storage and battery units. The utility secured $3 million in new technology funding from the Texas Commission on Environmental Quality to offset some of the cost.

SwRI is leasing the land to CPS Energy and will be doing research on the battery’s performance. SwRI, a not-for-profit entity, is one of the largest independent research and development centers in the U.S.

Most of the company’s research has been on batteries for use in vehicles, commercial devices, and in extreme space and underwater environments.

The project marks the first collaboration of this scale between SwRI and CPS Energy, the municipally owned electric and gas utility serving the San Antonio area.

“Southwest Research is by far at the top of their game in terms of applied science, right here in our backyard,” CPS Energy President and CEO Paula Gold-Williams said.

A CPS Energy rendering of the battery storage units to be installed on Southwest Research Institute property.
A CPS Energy rendering of the battery storage units to be installed on Southwest Research Institute property. Credit: Courtesy / CPS Energy

For SwRI, the arrangement will let researchers study how these batteries will perform when used to store energy from a renewable source and then discharge that energy to the grid when power is needed.

Researchers will be able to monitor the battery and “understand what a typical day in the life of that battery is like,” said SwRI’s Terry Alger, who directs the institute’s battery research section.

Though research is a big part of the project, CPS Energy and SwRI staff say the solar and storage system will eventually become a functional power unit supplying energy to customers.

The installation will be built on 48 acres, with the solar panels taking up most of the space, Jungman said. A 9,000-square-foot fenced-in area will hold four battery units, each eight feet by 44 feet.

Each unit will hold enough batteries for 2.5 megawatts of capacity. It takes more than 20,000 lithium-ion battery cells to add up to 1 to 2 megawatts of storage, Southwest Research staff engineer Bapiraju “Bapi” Surampudi said.

On average in the U.S., 1 megawatt of solar electricity can supply 164 homes, according to the Solar Energy Industry Association.

Over time, engineers can study how the batteries perform under a variety of “use cases,” Surampudi said. Power suppliers can use these batteries to meet peak demand or help maintain the right frequency on the grid to avoid brownouts, blackouts, or damage to electronic devices. 

SwRI also can use the project to more finely tune safety measures, he said. Lithium-ion batteries can pose a fire risk if not properly managed and stored.

Jungman also described plans to share an educational center at the site with SwRI with mockup solar arrays and storage units to teach people about renewable energy.

Construction work should begin sometime October through December and be mostly finished by mid-2019, Jungman said.

Brendan Gibbons

Brendan Gibbons is a former senior reporter at the San Antonio Report. He serves as the assistant manager of the Greater Edwards Aquifer Alliance.