You disagree it is a waste of money to prop up renewables? We all know that is the main reason grid batteries are being targeted vigorously.
Grid batteries have been pursued by electric utilities for decades, completely separate from renewables. The main goal of flattening out the demand curve is independent of the supply.
As the economics approached a usable figure, other uses such as non-dispatchable power supply, ie renewables and also industrial co-gens, have found reasons to use them. The renewables have gotten the recent press, but that is not all the industry is after.
In fact, the very first sentence says it The power sector has long viewed batteries as the answer to the challenges of the modern electric grid — from intermittent wind and solar resources to power surges to demand spikes —
Are you really surprised a current article includes discussion of current issues?
Renewables fail when long transmissions make their installation less commercial,
All power sources have this issue. Nobody ever wanted the Nuclear Power Plant located inside the big city limits.
which I assume is the definition of what they call a 'modern grid'. Are there so called 'modern grids' being constructed to accommodate nuclear, coal or gas powered transmission lines?
Modern gird is a heck of a lot more than just long transmission lines. They operate on tighter margins and controls, far more electronic noise, faster changing load profiles, etc.
Peak shaving can also be made by water impoundments, gas-fired generators, etc. rather than batteries, can't they?
Sure they can work but the economics are swinging to the batteries. And if you can find then permit thousands of acres with sufficient height differential the water works typically at 75% compared to 90% of the battery. Gas fired peakers are expensive, you build the whole infrastructure to operate a few hours where the battery system can be tied into existing substations as they essentially flatten out the load profile adding demand when demand is low and releasing power when demand is high.
The other massive advantage is how fast the battery systems can react, milliseconds. Upset conditions such as power plants or refineries tripping off-line can be balanced as fast as they happen. The modern battery systems become a significant improvement to stability in the grid rather tripping units or shedding customers.