We can deal with intermittencyThe fossil fuel lobby is quick to say that renewables might be nice if they weren't so intermittent; maybe they can provide a few percents of the energy needed by the grid, but more than that and you risk making everything unstable ("What happens when the sun doesn't shine? When the wind doesn't blow?"). They say that the most dangerous lies have a grain of truth in them, and that's the case here. Intermittency is a real issue that must be addressed, just like many issues had to be addressed to to make coal, oil, and natural gas viable sources of energy (the book The Prize by Daniel Yergin is a good history of the oil industry -- we don't always realize how much was invested in the industry, how many huge problems they had to solve, and how long it took to become mature).
So intermittency is a real challenge, but it's solvable, and Germany is proving to the world that it can be done. This is a large country, with a population of over 80 million people, with a lot of heavy industry and high standards of living. Yet a power grid with about 28% of renewable energy, and up to 40% and more in certain areas, and more than that on certain very sunny and/or windy days, is turning out to be more stable than the mostly nuclear and coal-powered grids in France and Poland (outages total 15 minutes in Germany, compared with 68 minutes in France and more than four hours in Poland).
Also check out: This striking chart shows why solar power will take over the world.
Experts say that a much higher concentration of renewables power sources (50% or more) is possible. “There’s a myth among opponents of renewable energy that you need 100 percent backup spinning all the time, and it’s utter nonsense,” said Michael Liebreich, founder of Bloomberg New Energy Finance.
One of the things that will help the transition to more clean energy is the availability of cheaper storage. Thanks to the parallel electric car revolution, batteries are coming down in prices quickly, and companies like Tesla, with its battery gigafactory, will start selling home systems that will help the grid become a lot more flexible and able to handle ups and downs in supply.