DER, DER, Grid Scale, Utility Integration

CPS Energy Plans Solar + Storage Project to Help Tame the Duck Curve

Later this fall, Renewable Energy Systems (RES) will begin constructing a 5-MW solar PV plant and a 10-MW/10-MWh battery energy storage system for CPS Energy in San Antonio, Texas.

This project combines distributed solar generation with strategically sized and configured electrochemical energy storage, according to the companies, because both the solar and the storage technologies will be interconnected at distribution voltage on a common feeder. Once operational, the system will allow for peak mid-day solar production to be stored and injected onto the grid in late afternoon and early evening, resulting in reduced reliance of fossil fuel generators to meet peak demand during these periods.

In California, as the sun sets and people arrive home from work, energy demand spikes while solar PV generation drops off. This phenomenon has been called the “duck curve.” (See image below.)

CPS Energy and RES say this combined solar plus storage approach is scalable and means that peak system electrical demand will be met with lower emissions producing energy and increased flexibility. 

The project is among the first co-located solar and storage projects interconnected at the distribution level within the Electric Reliability Council of Texas (ERCOT).


Image: Graph of California hourly electric load vs. load less solar and wind (the w:Duck curve) along with solar power output. Data is from CalISO and is for October 22, 2016, a day when the wind output was low and steady throughout the day. Credit: ArnoldReinhold