Yes in that it's utilizing compressed gas for energy storage, but no in that in how they're addressing the issue of adibiatic heating and cooling of gas -- the fact that gasses heat when compressed and cool when expanded -- they're actually using this heat itself as the energy storage mechanism, with argon as the working fluid.

Light Sail's approach harvests the provided heat and cooling, but utilizes those for what is effectively a coordinated heating/cooling service. The heat itself isn't part of the energy storage/recovery process.

Both are interesting approaches to the heating/cooling problem.

If you don't allow for the heating and cooling, you run the risk of explosions or of excessive thermal loss from your compressed gas. Explosions are possible if you're storing large volumes of gas in underground former natural gas reservoirs -- injecting large volumes of high-temperature N2 + O2 atmospheric gas risks igniting the residual methane. You also have the problem of icing over your recovery apparatus. As a consequence many CAES (compressed air energy storage) designs incorporate a natural gas burner on the exhaust side which both heats the expanding gas and adds additional energy to the process. The resulting systems are a hybrid of natural gas generation plus energy storage.

The heat is certainly part of the energy storage in lightsail, if the heat generated by the compression wasn't being stored in water and then fed back in during expansion then that energy would be lost.

Is just that with lightsail it is a minor part of the storage, the majority being pressure. They are two very different solutions that approach two similar but differently structured thermodynamic problems, lightsail's system being high pressure/low temperature, and these folk doing a low pressure/high temperature store.

According to their website it looks quite early stage/small scale/experimental. Anybody know how far from feasible and commercial scale they are?

In the case of the OP, even they are at least 5 to 6 years out according to the founders.

Last summer LightSail announced they had completed a full-pressure test of their containment structure at 200 atmospheres. [1] And Danielle Fong tweeted that their pressure tank survived the 'gunfire test'.[2]

The last update I saw showed complete cycle pilot tests in 2015 with deliveries to customers EOY 2015 / early 2016. They should be to market much faster than the OP version since LightSail is working on ~.5MW - 1MW installations and OP is working on much larger versions.

[1] - https://twitter.com/DanielleFong/status/474369529326219264 [2] - https://twitter.com/DanielleFong/status/523188555988746240