Simanaitis Says

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GOT ENERGY? KNOW HOW TO STORE IT? PART 1

AS THE COST of renewable energy comes down, a significant challenge remains in its inherent intermittency of supply. It is well known to science (you’ll excuse the S word) that the sun always shines, but not always in the same place here on Earth all the time. Also, sometimes the wind blows hard; but, unlike some politicians who come to mind, sometimes it doesn’t.

Hitherto, balancing supply and demand of fossil-fuel-generated electricity has been largely a matter of selectively turning generators on and off. It’s a charming conceit that a local utility can just save it up until needed.

A traditional battery can be used to smooth the supply and demand of electrical energy. Not without tradeoffs, however. This and other images from The New York Times, June 3, 2017. Its online schematics are particularly well done.

The New York Times, June 3, 2017, had an article titled “The Biggest, Strangest ‘Batteries’ ” in which Diane Cardwell and Andrew Roberts describe six strategies that enhance electrical-energy storage. This and tomorrow’s SimanaitisSays discuss these strategies, with some added information gleaned from the Internet.

If, at first glance, these options seem a bit Rube Goldberg, let’s first examine traditional battery storage: It begins with things that are anything but benign, lead and acid, or even more bizarre combinations of molecules, ions and electrolytes.

Applying an electrical current forces these things into a configuration that stores electricity. Retrieving the energy, let’s call it “discharging,” undoes this chemistry. Replenishing the energy, called “charging,” comes with inevitable degradation of the molecules and ions. That is, batteries wear out. What’s more, these chemical reactions don’t like extremes of temperature. And replenishing in particular takes some time.

With these tradeoffs in mind, maybe other options for storage of energy don’t seem so strange. Indeed, each treats intermittency of renewables as a virtue, rather than a vice.

Pumped-hydro energy storage.

Two Lakes and a Hill. This one has already been discussed here at SimanaitisSays back in October of 2015. When renewable energy is abundant—daytime for solar, breezy conditions for wind—the excess is used to pump water from a lower location to a higher one. When the renewable isn’t abundant—nighttime, periods of calm—the water powers turbine-generators as it flows from the high lake to the low one.

In a sense, think of it as a Boulder Dam with human-crafted geography.

The Machlyn Reservoir, Elidir Mountain facility’s upper lake. Image from theregister.co.uk.

Britain’s Elidir Mountain pumped-hydro facility, the largest of its kind in the world, has been in operation since 1984. The New York Times notes that it could supply all of the electrical needs of Wales for six hours. However, its critical use has been uniquely British: The facility meets “the sharp spike in electricity demand when popular TV shows end—and millions of people plug in their kettles to brew tea.”

Compressed air stored underground.

Compressed Air in a Cavern. As its name suggests, this one uses off-peak energy to compress air that’s then stored underground until required.

CAES facility in McIntosh, Alabama. Image from powersouth.com.

In 1978, a compressed-air facility opened in Huntorf, in northern Germany. A key advantage is its quick response to sudden peaks of demand. Another CAES (Compressed Air Energy Storage) facility in McIntosh, southeastern Alabama, has been in operation since 1991.

Four additional energy storage concepts are described in The New York Times piece. Are they Rube Goldberg or real? Read about them here tomorrow. ds

© Dennis Simanaitis, SimanaitisSays.com, 2017

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