Wind & Solar are Complementary
I got this wrong - setting the record straight.
I initially posted that Wind & Solar are not complementary. I was wrong. Thank you to chmeee2314 who set me straight.
So let’s first look at the wind and solar generation over the past 30 days. They look pretty independent.
But now lets take a look at the wind power generated by hour over those same 30 days
And we see there’s a ~ 40% difference between the highest and lowest hour’s generation. So within that stochastic looking change in wind energy, it has a pretty strong difference per hour over the course of the month.
In addition the user Sol3dweller provided links to 8 research articles (see here) discussing the inverse correlation between wind & solar. From reading these studies it looks like wind & solar has an even stronger inverse correlation when the land is next to the ocean, sea, or very large lakes (the Great Lakes).
We’re still left with the fact that at any given hour the generated wind can be very high or very low. So we still need to have storage or backup to handle no wind. But it will be less common than random chance.
This is good news in that modeling wind + solar combined, the need for full backup remains (no wind in the evening) but that will be less often and less severe on average than if there was no inverse correlation. And that means fewer batteries can keep gas backup under 5%.
Again, sorry for getting this wrong. This is why I post on reddit and answer any comments there - because it provides very good peer review.
"And that means fewer batteries can keep gas backup under 5%."
What it means is you need the same backup, the same batteries and gas generation, just that it will be used less often.
The goal in generation is to have generation assets generate (and sell) as much power as possible - that lowers unit prices. You can have two, identical, gas turbines. One provides peak power, and one provides baseload. And they will produce power at wildly different costs, because each last 30 years, and the cost is dependent of the number of hours they run each year. The baseload power plant is cheaper just because it runs more.
Wind and solar only need to be out of sync a few days a year. Maybe a week. And you are right back where you started.