Here's the dilemma: Wind and solar are very clean compared to most other sources of energy, but they produce electricity intermittently, so something must be done to make sure that there's enough supply to meet demand. Figuring out what is the best way to mitigate that intermittency is more complex than it might first seem. The most obvious choice is to build storage, but building a pumped hydro station or a large quantity of lithium-ion batteries uses resources and energy. By calculating the EROI of all the options, researchers have found that it can often be better to simply build more wind turbines or solar panels, or even transmission line to move power from somewhere where the sun is shining or the wind is blowing to somewhere where they're not, than to build storage.
This could lead to big energy surpluses at time, which might mean that more wind and solar power would be wasted, but when production slows down, the larger total capacity would mean that we could still produce enough to match demand.
The authors conclude, "Attempting to salvage energetically cheap power (e.g., wind) using energetically expensive batteries is wasteful from a societal perspective." Elsewhere, they note, "if society aims to increase output of (say) wind energy with the least energetic investment, it is better in many cases to just build another wind turbine, or possibly transmission lines, than to build a battery to store power that arrives at off-peak times."
I think the bottom line is not that one or the other is always best, but that we should always do the math to figure out what makes most sense. But this doesn't mean that energy storage never makes sense, or that it won't start making more sense as the technologies improve:
After looking over why their model gave this output, the authors conclude that the simplest way to change the situation is to give batteries a longer usable lifetime. Simply doubling the usable life of a lithium battery would be enough to start shifting battery storage of wind power into the break-even territory (increasing capacity and the ability to sustain larger drains would also help).
And developing technologies like grid-scale liquid metal batteries could have massively better EROI at scale, making storage a no-brainer once the technology matures.
But it's also possible that if we build huge surpluses of wind and solar, we'll find good uses for the extra energy rather than waste it on sunny & windy days. Dynamic electricity prices could provide an incentive for energy-intensive industries to produce more goods on surplus days and stockpile it for low-energy days when electricity is more expensive. I'm sure good ol' human ingenuity could figure out what to do with cheap, clean energy...