How much would it cost to build out batteries which cover entire continent's electricy needs for say three weeks (as there can be 2-3 week lulls of no wind and no sun in Europe in the winter)? Cause that sounds like a lot of batteries. Not to mention, if a freak 4 week lull occurs, we'll go back to Middle Ages for a week.

Australia's CSIRO studied this for Australia, renewables were half the cost of nuclear, factoring in storage and transmission for both renewables and nuclear (yes, nuclear also needs storage because energy demand varies with time). Australia is uniquely endowed with sun and land, so other countries/regions may arrive at different results.

Solar still produces even in overcast conditions, during the day. If it's light/medium overcast, most of which Germany usually is it still produces 50-80% of nominal. It only really doesn't produce anything at night or when it snows.

"But what if thing thing that never happens were to happen?"

We'd probably go deep into hydro, fire up every gas peaker plant, and through skyrocketing prices incentivize everyone to switch to emergency diesel generators where possible.

You're talking about a once-in-100+-years event. We'll deal with it the same way we dealt with the various oil crises.

But what do we do when the sun isn't shining?

Well what are we doing if the straight of hormuz isn't hormuzing?

Demand will adapt via price signals. Same story as in every market.

You would likely get to 97% green energy first with 5-8 hours of storage: https://reneweconomy.com.au/a-near-100-per-cent-renewables-g...

(for Australia it is 5, for other countries it might be 8)

Once you get to that "nice to have" problem of what to do about the remaining 3% of power needs it would probably make most sense to synthesize and store gas (methane/hydrogen) from electricity when solar and wind is overproducing. Gas can be stored cheaply for long durations. The roundtrip efficiency is poor but it's still cheaper than nuclear power on the windiest sunniest day.

The nuclear + carbon lobbies would of course prefer to model green energy transitions by pretending that the wind and sun simultaneously turn off for 2 weeks at a time every year and that electricity can only be stored in very expensive batteries. This is not realistic.

> (as there can be 2-3 week lulls of no wind and no sun in Europe in the winter)

This is simply entirely untrue. Europe's a big place, there's not a single day ever where there is no sun in it.