Also keep in mind that these are energy spikes that cause negative prices, whereas most industrial uses need a constant and even supply. These spikes are countered by periods of little to no energy.
This is the biggest problem with (most) renewables, they cannot entirely replace coal or nuclear energy for that reason. Energy storage (at cost) is an unsolved problem.
Super-true. It's actually pretty fascinating how it's currently done in the grid; storage of energy is often done by converting it (at significant efficiency loss) to a mechanical format.
Those formats can get very creative---traditional is "pump a bunch of water uphill into an artificial reservoir," but in areas where big dry mines are available, capping the mine and pressurizing the air inside is also used, which feels super-weird but apparently works?
The periods of "little to no energy" take up less time than periods of "more than little". Such periods are not as your phrase suggested, the norm broken up by occasional spikes.
Total energy supply and demand is never constant or even, it varies throughout days, weeks and seasons. That variation has always had to be accommodated.
Even without more storage (hydro, battery, future??) the grid can use almost all of the input which renewables can throw at it, and use existing plants to fill in gaps.
But there will be more storage, and long range transmission lines, better solar panels, batteries and windturbines. There is no major unsolved problem here, like nuclear fusion or Mars habitation has, its just a matter of mobilizing with existing technology. A matter which has been politically delayed for too long...
In the meantime, you address marginal demand at a lower cost.