You are spot on - the real answer is readily available: nuclear. We have reactor designs that if the active systems fail the reactors shut down naturally instead of running away. We have designs that can be burning all that "spent" fuel we are currently trying to bury for 10,000 years (!). Modular reactor designs in particular have incredible promise to provide for infinite scaling (just add more modules as needs increase), deal with the inefficient building, maintenance and decommissioning costs of todays light water reactor designs, and being modular provide far more granularity in power delivery further negating the need for energy storage to smooth out spikes and troughs in demands; allowing energy producers to far better match generation to power requirements.

Sadly I think it will be far more feasible to develop energy storage technologies than hope we can ever get enough people to be rational about nuclear. I mean how asinine is it for Germany to have turned off perfectly working and economically viable nuclear plants to then be dependent on RUSSIA for natural gas? How dumb do you have to be to be to think that's a REMOTELY good idea? Yet here we are (thankfully France seems to be far more rational - you don't hear them even suggesting they plan to be equally idiotic).

Many battery storage studies don't account for replacement/maintenance, or the infrastructure that would be required to sustain replacement/maintenance at grid scale, let alone the resources required to scale up to handle initial deployment of batteries in sufficient quantities to support the entire grid. Where are we going to get the manufacturing capacity, let alone materials? The scale here is pretty mind boggling if you start to do the math.

Our current battery tech is nothing more than a transitory technology - they are far from sustainable long term. Personally I think super capacitors will be our ultimate solution, but in the meantime if these guys really have dealt with the seepage issues of compressed air, this is are next best bet for MASS energy storage at scale. You only have the privilege of worrying about efficiency if you have a working system. Wood driven steam sucked, but it drove the industrial revolution because there was literally no other viable alternative at the time that could have remotely scaled in the same way.

Remember grid scale solutions require MASSIVE energy capabilities. The scale here is ridiculous compared to home or vehicle energy requirements. If you don't think Goldman Sachs took all of this into account before they made their investment - well, you are grossly mistaken. You don't get to be their size by continually placing bad bets.

If I am going to put on my conspiracy theory hat on for a moment, here's the only reason I would think the investment is sound: Goldman Sachs knows our government will throw money at this despite it being a bad idea. Therefore, the company will make money on paper by effectively becoming yet another subsidized entity of sorts...all in the name of saving the planet (or some other popular delusional statement).

Nuclear is probably the only path to long term clean energy. I hope people eventually wake up to that reality. Sadly, we are going to burn lots of time, money and resources before we get to that moment.