From Erik Spek
The vanadium flow battery has its attractions for electrical energy storage, but it is certainly not the only system that is practical (13 January, p 39). A quite large nickel-cadmium installation with a capacity of about 7 megawatt-hours is still, as far as I am aware, working in Alaska.
There are other technologies, too. Japan has over 100 large sodium-sulphur systems, with capacities up to 70 megawatt-hours, supporting its electricity grid. There are now three such installations in the north-east US. There is also a pilot ZEBRA (sodium-nickel-chloride) installation of 100 kilowatt-hours in Ontario, Canada.
All these systems have their pluses and minuses, but all will be needed to help the ageing and weary electric grid systems on every continent.
Midhurst, Ontario, Canada
