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Energy Storage Surges Ahead

Energy storage is charging ahead, thanks in no small part to the work of two utilities, in conjunction with the U.S. Department of Energy. Duke Energy and Southern California Edison are now operating two of the biggest such projects in North America, with each optimistic that its investment will pay off.  

When most people think of energy storage, they envision a system whereby power is siphoned off the grid at night, harnessed in a device, and then released during the day when the demand for electricity peaks. While that’s the ultimate goal, the more immediate application is to infuse the grid with electrons when the switches trip and the lights would otherwise flicker out.  

“The batteries provide grid support that grid operators would otherwise not have,” says Jeff Gates, Duke’s in-house expert on its Notrees Energy Storage Project in West Texas, where it has installed lead batteries next to a wind farm. 

“A typical fossil-fired generator would take several minutes to kick in and stabilize the grid. But a battery can respond in less than a second and it is good at being fast and accurate with small deviations in frequency.” 

He adds in a phone interview that when the battery storage operator detects any changes in “frequency” as a result of “power surges” that it can immediately respond before the grid operator – Electric Reliability Council of Texas – even realizes that a problem has been averted. Duke is paid the same as any traditional generator that would deliver electrons on demand.  

The “Notrees” project is 36 megawatts that can charge or discharge at full power for 30 minutes. It uses advanced lead batteries. The project, which has been operating since December 2012, cost $44 million. That is split between the utility and the Energy Department and it is part of the 2009 stimulus plan. This specific undertaking can generate 24 megawatts hours.  

Similarly, Southern California Edison just started its two-year demonstration, called the Tehachapi Energy Storage Project. It is located on a wind farm about 100 miles north of Los Angles – an undertaking that is also part of the 2009 federal stimulus plan. Altogether, the deal is projected to generate 8 megawatts for four full hours, which equates to 32 MWhs. It uses lithium-ion batteries.  

“We are trying to solve multiple problems like minimizing congestion and storing renewable energy at night and using it during the day,” says Doug Kim, director of advanced technology for SoCalEd, in an interview. He adds that the device is expected to provide the type of “voltage support” that Duke is now doing, or the ability to instantaneously inject electrons when there is high customer demand. 

Technologies Compete

What’s the main difference between the two utilities’ batteries? Duke’s battery has more power than that of SoCalEd’s system – or the capacity to convert direct current (DC) coming from the batteries to alternating current (AC) that enters the grid. But Duke’s system does not have as much energy, which drives the battery. 

The Energy Department has funded 15 other projects – some $185 million in