> Since peak power usage (in the US) tends to be in the afternoon, that's excellent up
> to about 10% market penetration Above that, you need energy storage
40% is a rather selective reading of that article. The article you link states:
"Now, the International Energy Agency has weighed in with a report on integrating renewables. It finds that, as long as intermittent power sources are under 10 percent of the total energy use, they can essentially be added for free."
That's pretty close to what I just said. (The article is talking about wind plus solar, while I was discussing solar alone). It goes on to talk about higher penetration:
"The report lumps wind and solar into a category it terms "variable renewable energy" and then it says "Things start to change as the fraction of power generated by VREs approaches 20 percent, and there are definitely new challenges as it reaches 30 to 40 percent."
So: I said solar is excellent at market penetration up to 10%, and this article says for solar plus wind together the cost changes at power fraction up to 20%, with "new challenges" as it reaches 30 to 40%.
I'd say we're saying the same thing.
As for the 40% you quote, the article says "that would require substantial reshaping of the rest of the grid--something that's much easier to do outside of mature economies."
The U.S is a mature economy, so that part isn't talking about us.