Thursday, August 22, 2013

Hawai`i Energy Storage 6: Some of the chemical batteries

There is no shortage of announcements of a new, cheap, powerful battery technology that will transform the energy industry.

Indeed,  when it comes to chemical battery, the number of variations seems endless.

In this, our sixth installment in Hawai`i Energy Storage, we’ll look at some of the options.

Just to consider the media hype around the issue, there’s this MIT promise of  cheap, power-dense flow battery. 

Here is a cool-sounding technology from Valence Technology, which it promises “can result in significantly lower operating costs when compared with lead-acid batteries.”

It’s easy to find news of research that is improving current technologies, like lead-acid and lithium-ion, as well as entirely new chemical battery formulations.

The cost of energy numbers below come from the Sandia-EPRI-NRECA 2013 EnergyStorage Handbook.

A sodium-sulfur battery is much-talked-about. It needs to operate at high temperature: more than 300degrees C. It has a long discharge time, which is good, and has a number of high-value utility applications. Levelized cost of energy is in the $275/megawatt hour range.

Sodium nickel chloride is another high-temperature battery with utility applications. It’s just coming onto the market this year. The levelized cost of energy is high and ranges widely, from $300 to $900 per megawatt hour, according to the handbook.

You’ll hear a lot about vanadium redox flow batteries. They being made for large scale storage applications now, but they are also not cheap, and they likely will never be cheap, because the vanadium is and is likely to remain expensive. And there are other problems, like power fade as compounds from one of its two electrolytes migrate into the other.

That said, vanadium redox batteries have a very long life, and “are capable of stepping from zero output to full output within a few milliseconds.” There’s value in that quickness. But you pay for it with a levelized cost of energy running from $400 to more than $800 per megawatt hour.

A company called EOS reports it is getting ready to ship in 2014 a Zinc-Air battery that is a fraction of the cost of lead-acid.  Properly it is a zinc-potassium hydroxide-oxygen battery. It is much more energy-dense than lithium-ion battery technology, meaning it’s smaller. They’re already working with ConEdison on prototypes. The handbook puts the levelized cost of zinc-air  at $150 to $200.

Lithium ion batteries are increasingly common, and there’ s still a lot of work being done to improve them. They are expensive, $500-$600 per kilowatt hour, and although they can take repeated deep discharge.

One concern: You’ve heard of lithium ion batteries overheating, and rarely, exploding. Considerable research is underway on a number of techniques to control this, including cooling systems, so they can’t heat up at all. And many researchers say that the overheating isn’t a problem with lithium-ion, if they’re properly manufactured and properly charged and discharged.

There is a manganese oxide ion battery about to be marketed by a company named Aquion Energy. It’s being built now on a small scale.

Its initial indications are impressive, but caution: it’s still early. That said, the Aqueous Hybrid Ion (AHI) chemistry sounds impressive. It is composed of a saltwater electrolyte, manganese oxide cathode, carbon composite anode, and synthetic cotton separator. It operates at room temperature.

The makers say it is 85 percent efficient and can go more than 5000 cycles while maintaining better than 80 percent efficiency. It is now cheaper than lithium-ion and cheaper than lead-acid at $300-$400/kWh, and founder Jay Whitacre, who addressed a June engineering conference on utility-scale energy storage conference, said  they hope to get it down to 100/kWh. They can get half a megawatt into a 20-foot shipping container.

Another promising battery: Michael Aziz of Harvard talked about a super-cheap flow battery using an organic molecule called a quinone, but there are still significant issues to be solved.

Sri Narayan of the Department of Energy’s ARPA-E program said the best looking technology right now is iron-air chloride . They still have some problems to solve, but their preliminary indications are that it could meet all the other requirements, AND come in at less than $100 a kilowatt hour. Iron and air, after all, are both abundant and cheap.

Sodium sulfur batteries, storage conference participants said, have a number of excellent features. They operate at high temperatures—550 degrees F.,--and there have been fires as recently as two years ago in Japan.  The technology is not cheap, at roughly $500/kWh.

Some of the other technologies being studied are sodium-nickel, sodium zinc, nickel-zinc, nickel-hydrogen. Each has strengths and weaknesses.

Nobody is predicting when some of these batteries might become available, and even the ones that promise they’ll get to the ARPA-E $100/kilowatt hour level—well, they’re not there yet.

There is a lot of work going on, and lots of promise, but it will take years before one or more of these technologies prove themselves able to meet all the really important criteria for a utility-scale storage system.

© Jan TenBruggencate 2013

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