In Germany, solar output is much lower in winter months than in summer months. Unfortunately, energy consumption is higher in winter (and will likely increase as most homes are currently heated with fossil fuels and need to switch to electricity). In summer, there are days when renewables create over 100% of the consumed energy. But just a few days ago, they were at 7%. Without the use of fossil fuels, or a way to store energy produced in summer for consumption in winter, renewables can't come even close to the energy levels needed even for today's demand. And, as fossil fuels are replaced by electricity, it is expected that future demand will double or triple.

As I said somewhere else, wind energy output is much higher (on average) in winter. Also, no one in their right mind will currently switch to electric heating in Germany, why would they? There is natural gas (for now), maybe later on biogas and already now wood pellets for heating.

> Solar is not very volatile

Only if you disregard the fact that that the sun doesn't shine at night.

Volatility in the energy sector means how "forecastable" the source is. Solar at night is perfectly forecastable.

> Only if you disregard the fact that that the sun doesn't shine at night.

Only if you disregard the fact that 'solar' can mean one or both of photovoltaic cells and solar thermal (which peaks around sunset and carries on producing power into the late evening).