I suspect you are aware of the grid scale experiment that informed my comment (Falkenhagen): I used to work for the company concerned. Technically it works a treat, as long as you don't mind the losses.
Actually, no so thanks for the tip.
Lossy closed-loop systems make more sense where you can take producer/consumers off the grid. This would have the advantage of helping to reduce gross base load and insulating the wholesale market from the the problems associated with excess renewables.
Who knows what continued research will come up with? Got to be better than pouring more billions into things like carbon sequestration.