Cleaning up Electricity

In our Big Picture page on Energy Emissions, we saw that we need to do two things:

Clean up electricity
Electrify (almost) everything

We also saw that wind power and solar power have become incredibly cheap, and that they’re going to get even cheaper. That makes cleaning up electricity much easier than it was just a few years ago.

But wind and solar power have a limitation. They are intermittent, generating electricity only when the wind is blowing or the sun is shining. So how can we rely on these “variable renewables” to power our electric grid?

⇒ Read this article by Amory Lovins and M.V. Ramana, explaining why this problem is not nearly as difficult as it looks.

You might already have thought of one answer. When wind and solar generate more electricity than we need, we can use batteries to store the extra electricity, and then release that electricity into the grid later, when there’s not enough generation to meet the demand.

In fact, lithium ion batteries (the same kind of batteries that EVs use) are great for doing this during the course of a day. They can cost effectively soak up excess solar generation in the afternoon, or excess wind generation in the middle of the night, and then discharge it in early evening, when demand for electricity is highest and wind and solar generation are lower. (Ten years ago, using batteries this way would have been prohibitively expensive. But as more and more lithium ion batteries have been manufactured for use in EVs, these batteries have traveled along a “learning curve” and become more and more affordable.)

Unfortunately, lithium ion batteries are not cost effective for storing more than about six hours of energy. But solar and wind generation vary on timescales much greater than that. In fact, they both tend to vary seasonally. There are many fewer hours of sunshine in the winter (unless you’re near the equator), and there can also be long periods with little wind. Those cold times are just when we need the most electricity (and will need even more if we succeed in electrifying everything, including building heat). To store enough wind and solar to get us through these long, dark periods, we would need enormous numbers of lithium ion batteries – enough to make our electricity cost many times more than it costs now.

None of this is a problem for us today. Even in the energy markets with the greatest penetration of renewables, there are still plenty of fossil fuel powered plants that can be fired up when there’s not enough solar or wind power. Experts estimate that it will start to become difficult reliably to meet peak demands when variable renewables make up about 80% of electricity generation in a given market. They make up about 10% of generation globally now, so we have a long way to go before we begin to really feel this problem. For the next decade, our main task is just to deploy as much wind and solar as we can build, as fast as we can. But we also need to start working now on the solutions we will need when we reach 80% variable renewables and we want to decarbonize the remaining 20% of the grid.

Fortunately, there are many potential solutions for the final 20%, and many smart people are taking shots on goal. Some solutions are technologically feasible right now, but face steep social and political obstacles. Others are still being proven out technologically and economically. So, it’s an open question what mix of these solutions we will end up deploying. (The answer will be different in different parts of the world.) But enough of these technologies are far enough along that we can be confident that, by the time we need them, a range of solutions will be ready for us to draw on.

⇒ Here’s a video of a short talk by energy systems modeler Jesse Jenkins, explaining the different roles that different kinds of generation will need to play in a 100% clean grid.

⇒ Here’s a great overview article by Jenkins and others on the technology roadmap to decarbonized electricity worldwide.