The AlwaysOn Network has selected its GoingGreen 100 — the 100 top companies in greentech, based on "innovation, market potential, commercialization, stakeholder value creation, and media attention or ‘buzz.’"

Here’s the category I’m watching:

Energy Storage
A123 Systems
Bloom Energy
Cobasys
Deeya Energy
EEStor
GridPoint
Jadoo Power
Lilliputian Systems
ZPower

(Gridpoint was the top company in AlwaysOn’s overall rankings. Good to see a smart grid company win the gold medal!)

Note the enigmatic EEStor, which doesn’t even have an operational website. It claims to have developed an ultracapacitor that will revolutionize the plug-in hybrid and electric car markets and render electrochemical batteries all but irrelevant for most applications. After it made that initial claim, it clammed up — it’s done almost no press and has kept its cards extremely close to its vest. There’s serious venture capital behind it and legit people running it. It certainly isn’t acting like a fraud.

Nevertheless, the claims it’s making seem almost fantastical. I read quite a bit about the company while I was researching a little blurb for Wired. Here’s a bit from a longer version of that piece:

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Most attention in the energy storage world goes to batteries, particularly next-gen lithium-ion batteries. But one storage tech is superior to batteries in almost every way: electrochemical double-layer capacitors, or ultracapacitors (or if you have a flair for the dramatic, supercapacitors). Where batteries store electricity via a chemical reaction, ultracapacitors store it directly in an electric field, enabling them to charge much faster and provide large bursts of near-instantaneous power (added bonus: no moving parts!). Batteries degrade steadily over charge cycles, get hot with use, and contain toxic chemicals; ultracapacitors last virtually forever, have no thermal discharge, and meet RoHS standards.

So what’s the problem? The Achilles heel of ultracapacitors is their specific energy density — they don’t hold nearly as much energy per unit weight as batteries. Lithium ion batteries produce around 120 watt hours per kilogram, whereas commercially available ultracapacitors produce around 6 Wh/kg, some 20 times less. That won’t cut it for vehicles, must less for industrial-grade renewable energy storage.

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EEStor says it can do better — way, way better. From Tyler Hamilton’s piece in Technology Review:

EEStor’s system–called an Electrical Energy Storage Unit, or EESU–is based on an ultracapacitor architecture that appears to escape the traditional limitations of such devices. The company has developed a ceramic ultracapacitor with a barium-titanate dielectric, or insulator, that can achieve an exceptionally high specific energy–that is, the amount of energy in a given unit of mass.

For example, the company’s system claims a specific energy of about 280 watt hours per kilogram, compared with around 120 watt hours per kilogram for lithium-ion and 32 watt hours per kilogram for lead-acid gel batteries. This leads to new possibilities for electric vehicles and other applications, including for the military.

So EEStor’s battery replacement would be smaller, lighter, cooler, cheaper, and more powerful than the most advanced hybrid batteries on the market. The company has struck a deal with ZENN Motors, giving it, at least initially, exclusive access to EESUs to power small- and medium-sized electric cars.

That’s supposed to happen by the end of this year, so we’ll see soon enough whether the hype is justified. Needless to say, skeptics abound.

You can read more about EEStor in this recent AP story, on Tyler’s blog, or on the Energy Blog.