[Tade0]

If anyone's interested here's an actual company selling a real Zinc-air product:

https://eosenergystorage.com/about-eos/

Two largest downsides of this technology are:

1. Round-trip efficiency of 75%.

2. Low power density.

Cost and cycle life are great though - should be great for grid storage.

[WhoIsJohnnyGalt]

75% isn't great, but if solar continues its 70 year exponential trend of dropping by half every 3-4 years for another two decades, then round-trip efficiency may not much matter in the long run. Too, the 75% is at 100% Depth of Discharge - it may be better at lower total discharge. Lifetime 15 years / 5,000 cycles is almost perfectly balanced for one full cycle per day (5,475 days in 15 years). Doesn't give the price, though, so hard to calculate cost per cycle. https://eosenergystorage.com/products-technology/