“Net Zero” — That’s the two-word slogan that has been adopted as the official goal of every virtuous state or country for decarbonizing its energy system.  The “net” part is backhanded recognition that some parts of the energy system (like maybe air travel or steelmaking) may never be fully de-carbonized.  Thus some kind of offsets or indulgences may need to be accepted to claim achievement of the goal.  

But the “net” thing is not for the easy parts of decarbonization.  And by the easy parts, I mean the generation of electricity, and the powering of anything that can be run on electricity or batteries.  In electrifiable parts of the energy system, there is to be no tolerance for “net”; only “zero emissions” will do.  The official line is that zero emissions electricity is easy and cheap because it can be provided by the wind and sun.

The official line is wrong.  As the build-out of these wind and solar generation systems continues to progress, it has become increasingly obvious that there will never be a zero-emissions electricity system powered mainly by wind and sun.

The reason should be obvious to everyone although, for some reason I cannot understand, it is not.  The reason is that the intermittency of wind and solar generators means that they require full back-up from some other source.  But the back-up source will by hypothesis be woefully underused and idle most of the time so long as most of the electricity comes from wind and sun.  No back-up source can possibly be economical under these conditions, and therefore nobody will develop and deploy such a source.