Energy storage for renewables: Do we really need it?
By: SGN Staff
By Doug Peeples
SGN News Editor
Energy storage is generally considered a critical tool for integrating intermittent renewables into the electric grid and maximizing their value. The wind doesn't blow constantly and the sun doesn't shine all the time, and neither cooperates with peak demand. As a result, the quest for reliable, practical solutions has boomed and grid-scale storage is coming into its own.
But do we really need it? Panelists at the Smart Energy International conference in San Francisco this week shared some perspectives we don't hear often during a discussion on using energy storage to get the most out of renewables initiatives.
KEMA's Rick Fioravanti, VP for storage applications and support, said he is seeing "excitement across the board" about storage for renewables. In addition to consulting, KEMA also conducts certification and testing. It recently opened its Smart Grid Interop Lab for the specific purpose of testing smart grid technologies in simulated real-world conditions.
Fioravanti said storage is a definite plus for renewable energy in several ways. It can accommodate the impact of intermittent energy sources and it can be used as a "mitigating and excluding tool." In the U.S., he said, a lot of people are preparing for the day when the nation's energy portfolio includes 20-30% renewables, underscoring the value of having a mitigation tool to manage it.
Also, for distribution utilities, storage is protection against buildup on feeders. He added that while renewables developers tend not to look at storage unless they need to, he contended that they will need to if they're going to make their projects practical and economical.
His boiled down argument for why storage is essential for renewables? Grid operations and integration, protection for utilities and a means for developers to get connected to the grid and generate income.
So doesn't that make it necessary?
You can always find different points of view, several shades of them in fact. Here are some, courtesy of Mark Kapner, engineering director for Frontier Associates and a former senior strategy engineer for Austin Energy, and Marc Keyser, projects manager for markets and AGC engineering at Midwest ISO (MISO).
Kapner, while a fan of storage, chose to take the "devil's advocate" position, as he put it. He said the Electric Reliability Council of Texas (ERCOT) has been able to manage major surges of wind energy on its system without relying on storage. "The studies have shown we can keep going without storage," he said.
He did say that during his tenure at Austin Energy, the utility was able to shift the air conditioning loads of buildings and district cooling systems with economical, unsubsidized thermal cold storage, effectively incorporating fluctuating renewables into a system where cooling accounts for 50% of the load during summertime in Austin. He commented that what he would really like to see is storage added to the upstream side of transmission bottlenecks, which could mean less need to build more transmission infrastructure.
Keyser, who also took the devil's advocate position, said MISO has about 10,500 megawatts of wind energy on its system (with a 25,000 megawatt renewable portfolio standard mandate of 25,000 megawatts). To date, MISO has been able to accommodate wind up to a 7,000 megawatt peak with tuned up forecast accuracy and increased operational efficiency. He added that while MISO now manually calls wind farms to shut down or curtail when needed, it is moving to an automated alerts system.
MISO, he said, uses short-term storage with only a regulating reserve, which it controls. He added that MISO has 2,000 megawatts in long-term pumped storage and has taken an interest in compressed air. But it sounds as if MISO does not rely heavily on storage to manage wind resources.
Obviously, it's not a black and white argument. Instead, the comments from the panelists seem to suggest that while storage can be a useful tool, it's not the only way to approach managing renewables. Use the Talk Back form below to tell us what you think.
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