But there is plenty of peak capacity. Plenty of plant that currently runs more or less in baseload mode burning fossil fuels. Increased intermittent capacity, whether wind or solar, obviously has to take priority because, as you note, the fuel is free.

All that is required is to lower the average load factor of the fossil fuel plants, i.e. burn less fossil fuels in order to burn more solar and wind. Financial compensations are no doubt needed to those plants, to cover the sunk capital costs.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}

Physics mixes it up. If more is consumed than produced, power fails.

That's not a mix-up and not physics, but the separate issue of providing balancing capacity to meet the difference of demand and total baseload production. And how does that not apply to conventional baseload? Baseload never meets demand anywhere near 100% of the time, and the difference can be rather big on occasion (be it a cold spell in a region with lots of electric heating boosting demand like in France in February this year, or a total shutdown of 52 nuclear plants following a natural disaster and subsequent safety concerns like in Japan earlier this year).

_{*Lunatic*, n.
One whose delusions are out of fashion.}