Energy storage for renewables: Do we really need it?

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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Storage

Count me among those who think storage could be useful, but not at any price, and of course, that's the rub. Storage costs range from not cheap to very expensive, and as this weekend's bankruptcy filing by Beacon Power suggests, not even government loan guarantees can bridge the gap between what storage costs and what it's worth. I was a stakeholder reviewer for a report on storage sponsored by the California Energy Commission. Among other things, it surveyed the state of the art and current research. One of the clear conclusions is that many of the most promising technologies still have technical hurdles to overcome. Another is that most of them are too expensive, and the ones that are within the realm of being cost-effective are not mature (CAES), or are suitable in a limited number of places defined by specific geographic or geotechnical features (pumped storage and CAES). The report also pointed out that large-scale rollouts of promising but immature technologies would likely be a waste of money until they are at a more advanced stage of development. Jack Ellis, Tahoe City, CA

Jack Ellis - 10/31/2011 - 10:52

Low Cost Energy Storage

It seems that the lowest cost for energy storage would be to couple the generation output of variable renewable resources to existing large hydro facilities. A renewable generation ramps up or down, the hydro unit could be ramped down or up to maintain a firm schedule for the coupled resources. The stored energy is retained water behind the hydro unit, subject to minimum water release schedules and reservoir storage capacity. Picture Hoover Dam as the storage system to firm schedules for Mojave Desert solar, San Gorgonio and Tehachipi Pass wind farms

Steve Lafond - 11/01/2011 - 13:13

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