Breakthrough grid storage tech?

Company to watch: Applied Exergy Inc. These guys are privately owned right now. What they appear to have, however, is what looks like a breakthrough grid storage technology. Basically they work with the concept of Exergy.

If I horribly bastardize the physics concept of Exergy what we're talking about is the amount of work potential available when a component of a thermodynamic system goes from one temperature to another.

How they appear to have harnessed this, is by taking energy from renewable sources such as wind, solar etc and attempting to store it in the form of slushy ice-water. So when power is abundant (i.e. when the wind is blowing or the sun is shining), much of that energy is stored.

Now the advantage of this system is basically comparative. If you look at the (massive) amount of stored energy just sitting there in fossil fuels, it's massive. The dirty (no pun intended) little secret of fossil fuels, however, is that though it's got somewhere on the order of 4x the energy density of our most prevalent technical storage solution (lithium-ion batteries), what we're missing is that by the time you get it out of the ground, process it, refine it, transport it and finally burn it inside of an internal combustion engine you only have about 18% of the stored energy actually available for useful work.
It's horribly inefficient.

Compare that, however, with batteries. Your electric motors are some 90% efficient and batteries return also on the order of 90% of their stored electricity out. So if you use an electric motor driven vehicle powered by batteries you get 90% of 90% of 90% which is 73%.
That's a whopping FOUR times more efficient than fossil fuel powered vehicles.
That also, by the way is the reason why fuel cells are a non-starter technology from an energy perspective. Splitting water into hydrogen and oxygen by electrolysis, collecting the hydrogen and then compressing it, then transporting it, then burning it in fuel cells takes you down to somewhere around 30% of the original energy.
Which is why I rag on fuel cells as not being competitive in almost all use-cases.
(Which is not to say there are no viable use cases for fuel cells, there *are* but mass transportation of personal vehicles is not one of them).

So.... that brings us to Applied Exergy's solution: The efficiency of their exergy based process is about 80% on returned energy. So 90% of 80% of 90% is 65%. Which is not too too far off what we get out of lithium ion batteries, if you were using it for electric transportation. Which is pretty decent in fact.

That said, obviously electric transportation itself is a horrible use-case because you'd have to transport the ice-water, store it etc etc so you would get nowhere near the energy efficiency back.

Where it shines, however, is in grid storage. We're talking about large format batteries than can stored megawatt hours (or greater at a time). Lithium Ion batteries can do this, but they cost a significant amount. Water on the other hand is pretty cheap. So these puppies make what I think is a very, very compelling case for a grid storage solution.

So... where are we on this one?

Well Applied Exergy is a private company and it looks like they might be a startup also. They're not listed on any stock market exchange and they may also never actually bring anything to market. But, and here's the but... If they *do* have what they say they have then this little company could be a game changer for renewable power. Definitely one to watch.