These look almost there (I know, I know, "almost"): https://ambri.com/ https://ambri.com/ (liquid metal battery) https://www.hydrostor.ca/ https://www.hydrost

These look almost there (I know, I know, "almost"): https://ambri.com/ https://ambri.com/ (liquid metal battery) https://www.hydrostor.ca/ https://www.hydrostor.ca/ (compressed air)