They have(in just this one example) - 35 turbines at 16MW each - that's half a gigawatt of power. Having the kind of battery storage that could provide this amount of power for more than a few minutes is.....well, not impossible, but extremely expensive, especially for something that will just sit there unused(hopefully). Gas generators are comparatively very cheap, easily available, and if fuel is being fed into the system can operate for days on end.

And you'd need an insane amount of solar panels to actually recharge those batteries in any kind of reasonable time too, so you expose yourself to a massive risk if you had two out of power events within say 12 hours. So you'd probably build all of those batteries and solar panels but you'd still need to have emergency generators ready to go anyway.