"...cram 20 to 40 kilowatt hours of energy into a package about the size of a refrigerator...
"...batteries expected to sell in the neighborhood of $2,000..."
I know "a package about the size of a refrigerator" -- a refrigerator! And it sells for (unless you go super-skimpy) $800-$1600. And it is mostly empty space, the rest is old-tech stuff that doesn't change for years at a time. (Except for the tail-fin on top, my new $1,200 GE icebox is the same as their 1998 model.)
And reefers install cheap. This has to tap your fusebox, usually a union job.
"...a chunk of solid sodium metal ... operate below 90 degrees C."
Even if the ceramic is dirt-cheap, even if the sulphur compound is low-cost, even if they get sodium re-cycled (from a nuke plant? yuk!), I think it is quite unrealistic to clean, assemble, and distribute a reefer full of sodium for not much more than a reefer full of shelves.
We were supposed to have Nuclear energy "too cheap to meter" by the 1970s. We were supposed to have superconductors by the 1980s. We have nuke-- a penny cheaper than coal at best (Salem), and sometimes ruinously costly (LIPA). Superconductors never got into wide use, and the recent atom-smasher coolant leak shows why.
I'll believe it when I see it in Home Depot.
And what after this 10 year life? I can't put a reefer full of sodium at the curb for trash pickup. I can't put a reefer out any more, because it has a pound of non-toxic gas... what about many-many pounds of explosive toxic sodium? I assume they will buy-back sodium, but what economics for pick-up and re-processing?
What happens when the sodium-battery truck gets hit by a beer truck? I've seen runaway gravel and garbage truck accidents, people killed, other vehicles crushed. Not common, but how tragic when it does happen? Heck, I can't ship spray-paint without special precautions.
It _IS_ a deal-changer in places with irregular energy flow. Solar don't work half the time. Windmills (outside Nebraska) don't work 2/3 of the time. Dams sometimes have to "waste" water to maintain downstream flow. A good bucket for electricity changes these situations.
But many of us are on massive nuke or coal generators. They have evolved to supply the quasi-constant demand. Only a small part of the total could be battery-shifted from evening peak to 3am slack. The only immediate effect would be that the natural gas peak-load generators would not run much. Oh, and smaller distribution losses at peak hour. Such changes in load-pattern might maybe save 10% on total cost. For most people, that would not justify this battery, even at $2K with zero percent loan.
It's great news for people far off the utility grid.
It may (in larger form) be good news for a utility with adequate base capacity but pinched at peak load.