> That isn't enough
> you have purchased two systems for providing power.
Precisely! Correct!
Therein lies the problem of renewables few people seem to understand, talk about and want to talk about. Solar and wind require 100% backup for the period of time during which they are not locally available.
BTW, a good deal of what I have been saying is supported with data from this paper [0]. It analyzes 39 years of data from 42 different countries. It does a good job of displaying the difficult relationships between various mixes and solar, wind and storage. Figure 2 is excellent. It takes a bit of study to internalize. After studying these charts almost everyone should have serious questions about solar. This is where the 95% figure for wind comes from.
And, BTW, figure 2 also shows that without overbuilding capacity both technologies are challenging.
There are ways to look at using distant solar and wind to provide for power holes. For example, have wind power brought in from 500 to 1000 miles away. The idea is you know there's a seriously good probability for the weather being different enough that you cover the power holes at location A using power from location B.
That's great. The question then becomes: How do residents of location B deal with their issues when you are sucking-up their power from location A.
No simple answers to this other than to say that both solar and wind have to be overbuilt and require 100% backup --of some form, I don't care what type-- for when they cannot deliver.
And so your question is perfectly valid and one that really needs to be on the table, front and center. I have asked it before. It is usually met with attacks and insults. It can take many forms, the most basic being:
If you need full 100% reliable backup available at a moments' notice, 24/7/365, are these truly the best technologies for the job?
I have argued that nuclear is a solid solution with 100% availability and the power density to deliver our needs. That is met with even more violent attacks and insults. Apparently I am somewhere between a really stupid person and a criminal for suggesting any of this.
Having devoted a significant effort towards understanding the many intricacies surrounding these issues, my thinking has morphed over time. I used to think we had to consider deploying a massive amount of nuclear power (somewhere beyond 1000 new power plants) for a full transition to electric vehicles and homes. That, of course, is as close to impossible as one can get.
I think a sensible path might be to focus on the 95% reliability of wind (which is far better than anything solar can achieve) and provide that 5% backup with regionally shared nuclear power and other power sources. We would still need hundreds of nuclear power plants built over the next, say, 30 to 50 years. Difficult, yes.
Here's the shocking reality of a transition to full electrification (homes and transportation):
We have to, at a minimum, TRIPLE our power generation and transport capacity.
Why triple?
Well, if we are going to go clean, you have to replace all of our existing power generation with 100% reliable clean alternatives.
That means we need to build 1200 GW of new clean power generation.
As we do this, we shut down what we don't want (if we can).
Next, we need another 1200 GW --at a minimum-- to power a full fleet of electric ground vehicles.
If we start talking cargo ships and aircraft, we are likely at another 1000 GW or far more.
The task, then, is to build somewhere around 3000 to 4000 GW of new clean power generation sources. They have to be 100% reliable, or you need to grossly overbuild to compensate for that.
The, question, then: Can we do this? In 25 years? No way. How about 50 years? Maybe? Tough to say. It sure a hell isn't happening in ten or fifteen, which makes the dramatic claims being made by politicians and their supporters nothing less than ridiculous.
[0] https://www.nature.com/articles/s41467-021-26355-z