CPS develops $10M battery to store renewable power
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.
For CPS, the 10 megawatts of battery storage would allow the utility to cut back on using “natural gas fired peaking units.” Also known as “peakers,” they’re activated during times of high electricity demand, usually during the hottest summer days and cold snaps in the winter.
While effective, natural-gas peakers are an imperfect solution to meeting high demand loads on the electrical grid because they can take 30 minutes to two hours to start producing electricity, said Sam Jaffe, founder and managing director of Boulder, Colorado-based Cairn Energy Research Advisors, a research and consulting firm specializing in energy storage.
“Even though people complain all the time about you can’t use solar and wind on the grid because you can’t control it,” Jaffe said, with natural gas, “you have this lag time between when you need the power and when you can produce it.”
During periods of peak energy consumption, Jaffe said, natural-gas peaking units have to burn fuel continuously to keep the turbine’s steam warm so they can provide nearly instantaneous power when demand outstrips capacity. This is one of the reasons that electricity prices rise as high as $9,000 a megawatt hour when the demand for electricity peaks.
Batteries “can respond within nanoseconds, not within hours or even minutes or even seconds but in nanoseconds, and supply the required amount of electricity,” Jaffe said.
CPS currently operates eight natural-gas-fired peaking units that can produce 46 to 48 megawatts of electricity each. By using power stored in the batteries, CPS can burn less fuel during peak power usage.
Texas ranks first in the country for wind power, generating more than 20,000 megawatts of power from wind farms, while solar projects produce more than 580 megawatts, most of which is supplied to CPS. Despite the rise in renewable energy use in Texas, battery costs have remained prohibitive for large-scale projects.
That’s where the $3 million grant comes in.