Intermediate Physics for Medicine and Biology: Here Comes The Sun

Here Comes The Sun,
by Bill McKibben

I recently finished Bill McKibben’s excellent book Here Comes The Sun (McKibben and I are about the same age, so we both like the Beetles reference. The page just before the Table of Contents has a single line of text: “And I say, it’s all right.”). The subtitle is “A Last Chance for the Climate and a Fresh Change for Civilization.” It’s one of the most optimistic climate change books I have read. After summarizing his past angst-ridden pronouncements on global warming, McKibben writes in the introduction to Here Comes The Sun “And yet, right now, really for the first time, I can see a path forward. A path lit by the sun.”

The heart of his argument is that now, finally, wind power and especially solar power have gotten so cheap that the change to green energy will be not only virtuous but also economically advantageous. In his book, McKibben addresses four questions that are often asked by green energy skeptics. I’ll look at them one by one.

Can We Afford it?

McKibben writes

Sometime in those 10 years [between 2014 and 2024] we passed some invisible line where producing energy pointing a sheet of glass at the sun became the cheapest way to produce power, and catching the breeze the second cheapest... As the energy investor Rob Carlson put it recently, continuing to burn fossil fuel is a “self-imposed financial penalty” that will “ultimately degrade America's long-term global competitiveness.”

The gist of his argument is that with fossil fuels, you have to pay for the fuel each and every time you use it to get energy. Year after year you keep paying for coal or oil or gas. With solar and wind energy, you pay once to set up the technology and then the fuel (the sun and wind) is free. FREE! FOREVER! (Or at least for the lifetime of the solar panel or wind turbine.) I’m an cheapskate and I love free stuff. And you save the planet as a bonus. As McKibben points out, one problem is that energy becomes so cheap that energy companies can’t make money supplying it. What a wonderful problem to have.

But Can the Poor World Afford It?

It turns out that the developing world is leapfrogging straight to solar power, skipping the centralized fossil fuel phase. Why?

The switch is being driven by the desire for reliable and affordable power.

McKibben compares it to how cell phones allowed poor countries to skip the expensive land line infrastructure and go straight to mobile communication. Countries in Africa and the Middle East are right now putting up solar panels, with the process starting at the grass roots rather than from the top down. Who do they buy their solar panels from? China.

But Is There Enough Stuff?

McKibben thinks the concerns about having enough raw materials such as lithium to build the solar panels, wind turbines, and batteries is a legitimate problem, but probably not an insurmountable one.

Yes, you have to mine lithium to build a battery. But once you've mined it, that lithium sits patiently in the battery doing its job for a decade or two (after which, as we will see, it can be recycled). If you mine coal, on the other hand, you immediately set it on fire—that's the point of coal. And then it’s gone. And then you have to go mine some more.

He says we should compare the risks and cost of mining and recycling green energy materials to the much greater risks of mining and dealing with the left over from fossil fuels, such as coal ash.

Do We Have Enough Land?

The land needed for solar and wind is surprisingly small, especially compared to that taken up by fossil fuels. McKibben quotes an estimate that oil and gas wells, coal mines, pipelines, power plants, and the like take up about 1.3% of America’s land. Green energy will require far less. McKibben compares a solar array to a corn field.

Converting some of these [corn] fields to solar panels makes enormous ecological sense. That's because one way to look at a field of corn (or any other crop) is that it’s already an array of solar panels. A plant is a way to convert sunshine into energy through photosynthesis... Somewhere between 1 and 3 percent of the sunlight falling on a leaf actually becomes energy. The photovoltaic panel works considerably better [20, and possibly some day up to 40, percent]...
You could supply all the energy the US currently uses by covering 30 million acres with solar panels. How much land do we currently devote to growing corn ethanol [not the corn we eat, but the corn we use to help fuel our cars]? About 30 million acres.

The biggest threat is not a lack of land, but the not-in-my-backyard attitude so common in the USA.

Because this is a blog about my textbook Intermediate Physics for Medicine and Biology, let’s do one of those estimation problems that Russ Hobbie and I encourage. The solar constant is 1390 W/m². That’s how much light energy from the sun per square meter that reaches the earth (or, at least, the top of our atmosphere). The cross-sectional area of our planet that intercepts this light is πR², where R is the earth’s radius (6.4 × 10⁶ m²). That gives 1.8 × 10¹⁷ W, or 180,000 TW (the “T” is for tera, or 10¹²). Humanity’s worldwide average power consumption is about 18 TW. So, we only need 0.01% of the solar energy available. Granted, some of that sunlight is reflected or absorbed by the atmosphere, some is incident on the ocean, and no solar panel is 100% efficient. Still, the land area needed for solar and wind farms, while not small, is reasonable.

The Final Word

When I can, I like to give authors the final word in my blog posts. So, here is how McKibben ends Here Comes The Sun

I end this book saddened, too, of course—saddened by all that happened in the last 40 years, and by all that we haven’t done. But I also end it exhilarated. Convinced that we’ve been given one last chance. Not to stop global warming (too late for that) but perhaps to stop it short of the place where it makes civilization impossible. And a chance to restart that civilization on saner ground, once we’ve extinguished the fires that now both power and threaten it.

I’ve changed my mind. I’m gonna give George Harrison the final word.