San Antonio-based CPS Energy is working on a project that, if successful, will help solve one of its trickiest problems in solar and wind energy production.
The public utility won a $3 million grant from the Texas Commission on Environmental Quality to develop a commercial battery to store large amounts of solar and wind power during peak production, which generally isn’t when people need it the most.
Renewable energy production can be fickle and unpredictable since it relies on the weather. Peak usage in Texas, on the other hand, is almost always in the evenings when people get home and turn on the air conditioning. The trouble with using wind and solar energy is shifting the power produced during the day and at night to peak usage times.
A 1-megawatt storage battery that came online in August regulates the system’s frequency, or the amount of energy flowing through CPS’ grid. Regulating the frequency at 60 hertz helps keep equipment from getting damaged and prevents blackouts, aiding in stabilizing the grid as required by the Electric Reliability Council of Texas, or ERCOT.
The battery sits on the South Side of San Antonio at the 40-megawatt Alamo 1 solar farm owned by OCI Solar Power, sitting quietly next to a transformer station, making noise only when its heating and cooling units turn on.
“This will run 20 to 30 times a day in the summer, but in December we see up to 100 times of deployment of either regulation up or down a day,” Byungwook Lee, OCI’s energy storage systems manager, said during a site tour of the Alamo 1 facility.
The 1-megawatt battery, half the size of a tractor-trailer, is just a preview of CPS’ plans to build a separate 10-megawatt, $10 million lithium-ion battery bank for use during peak power surges. OCI owns the 1-megawatt battery, but CPS will own the 10-megawatt battery bank.
The battery bank will be installed at a 5-megawatt solar farm at a yet-to-be-determined site, said David Jungman, senior director of business and economic development for CPS. The batteries will be able to store and provide up to 10 megawatts of power for one hour, or 5 megawatts for two hours. One megawatt of energy can power between 400 and 900 homes for a year.
“The solar peak is not when the CPS peak is,” Jungman said in an interview. “The solar peak is probably more like when the sun is high noon or 1 o’clock, but what if we could shift that solar power from the solar peak to the CPS peak, from 5 to 7 p.m. when everybody’s going home and turning up their air conditioners?”
Utility-scale battery systems feature stacks of lithium-ion batteries placed within containers that can be as large as a tractor-trailer. Each unit offers a megawatt of power storage. Jungman said the 10 batteries combined will take up about an acre of space, a small amount compared to the 50-acre, 5-megawatt solar farm that will supply the battery system with power. CPS would then use a battery management system, or BMS, to control when the batteries would be used to supply the grid with electricity.
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