Friday, August 19, 2022

How Big a Problem Is Siting for U.S. Renewable Energy?

To eliminate fossil fuels, the U.S. will need to build a lot of wind and solar farms, and these are going to cover a lot of real estate. For example, here’s a map of the 100% renewable scenario from the Net-Zero America study (click to enlarge):

And here's a great visualization from Bloomberg, showing how much land those wind and solar farms would cover if you put them all next to each other:

That dark blue region in the middle of Kansas shows the total footprint of the wind turbines themselves. But in this scenario new wind farms (which can be shared with other agriculture) would cover an area equal to all of Kansas, Nebraska, Oklahoma, Arkansas, Illinois, and Kentucky, plus part of Indiana and 15 million acres offshore. Compare that to the area of all existing (as of early 2021) wind farms, indicated by the similarly colored segment of Iowa. Meanwhile, new solar farms would cover an area equal to most of Indiana, with only minor opportunities for shared use of that land.

As another comparison, that big green area that covers all of Missouri and a slice of Iowa represents all the land we’re already using for production of ethanol and other biofuels. (This scenario assumes that the amount of land used for bio-energy production would remain the same, but that the biomass would be used more efficiently to produce hydrogen while sequestering carbon.)

The Net-Zero America study includes other zero-carbon scenarios for 2050 that make somewhat smaller demands on land use, through heavy reliance on nuclear energy and/or fossil fuels with carbon capture and sequestration. On the other hand, demand for wind and solar power could continue to grow beyond the year 2050 due to growth in the U.S. population or in our per-capita energy demand. I find it hard to imagine a future in which U.S. wind and solar farms end up expanding by less than a factor of 10.

Which brings us to the big question:

  • Can we actually find sites for that many wind and solar farms?

Physically, the answer is an unambiguous yes. Expanding solar farms by a factor of 10 or even 20 wouldn’t eat up any more land than we’re already using for inefficient biofuel production. Expanding wind farms by a similar factor would essentially mean a lot more shared use of agricultural lands.

But there are going to be issues. In fact, there already are issues.

Everyone agrees that industrial-scale wind and solar farms aren’t appropriate in every physically feasible location. Cities and national parks come to mind, for example. So there needs to be a process for deciding whether any particular location is appropriate. In a democracy, everyone gets a chance to participate in that process. By the same token, not everyone will be happy with every outcome.

Indeed, it’s easy to find stories about local opposition (pejoratively, “NIMBYs”) putting the brakes on solar and wind projects. Local opponents killed the Cape Wind offshore farm in Massachusetts and the Battle Born solar farm in Nevada. They’ve delayed the Icebreaker pilot attempt to put wind turbines on Lake Erie. They’ve enacted sweeping bans on utility-scale renewables in Madison County, Iowa, and San Bernardino County, California.

What’s less clear is whether these local efforts to block wind and solar development have made much of a dent in total U.S. renewable energy deployment. There are now more than 5000 utility-scale wind and solar farms operating in the U.S.:

If the number that have been blocked or significantly delayed by local opposition were more than a few percent of 5000, I should think we would have heard more about it. Here’s a study that lists 23 wind projects and 23 solar projects that have run into major local conflicts (though the study doesn’t claim that the list is comprehensive). Here’s a report on local zoning restrictions on renewable energy that gives about a dozen examples (again not claiming to be comprehensive). Until I see evidence to the contrary, my working assumption is that the number of examples of these sorts is still in the dozens, not the hundreds.

Of course, there must also be plenty of potential wind and solar projects that were scrapped on account of anticipated local opposition, before being publicly proposed. Apparently wind developers have given up on the whole state of Vermont, and I’m getting the sense that an awful lot of the desert Southwest, especially in California, is effectively off limits. Local opposition to renewable energy projects has become a very big deal in a few particular regions, but doesn’t yet seem to be a huge obstacle nationally.

So what’s the prospect for the next few decades, as we scale-up wind and solar generation by an order of magnitude? On one hand, siting should get more difficult as the best sites (both physically and in terms of local support) get developed. On the other hand, developers may be learning how to better navigate local siting conflicts, while renewable-friendly officials at the state and federal levels may enact policies that take some legal tactics away from the NIMBYs.

One example of such a policy could be the federal “permitting reform” that Congress has promised to take up in the coming weeks. I don’t doubt that there’s room to improve federal permitting procedures, though I’m not going to endorse a bill I haven’t seen. Whatever ends up in the bill, I’m skeptical that such a move will make as big a difference as its proponents are suggesting, given that most of the legal obstacles to renewable energy projects are being erected at the local—not federal—level.

Naturally I hope that enough reasonably uncontroversial sites can be found for the big buildup of wind and solar that’s in our country’s near future. I’m sure it won’t be easy, yet I remain very unsure of just how difficult it will be. My sense is that the siting of renewable energy projects is a ripe subject for more investigation and reporting, both by academic researchers and by journalists who specialize in energy and climate.

I look forward to reading and learning more.

Thursday, August 4, 2022

One Billion Americans?

One Billion Americans, by pundit Matthew Yglesias, is mostly a book about politics, international relations, and public policy—none of which are a focus of this blog. But as the title indicates, the book is also ostensibly about demographics. Could or should the U.S. try to increase its population to one billion or thereabouts? If so, how long would it take? These are fun questions to think about.

Let’s start with a look at current U.S. demographic trends. Here’s a plot of annual births (green), deaths (red), net migration (blue), and net population change (black, equal to births minus deaths plus net migration):

The left half of the graph shows the past, while the right half, from 2022 on, shows the latest projections of the United Nations Population Division. Notice the spike in deaths and dip in immigration from the Covid pandemic, which have combined to take a sizable bite out of our population growth over the last couple of years.

Looking forward and hoping for no more deadly pandemics, the projection shows our population continuing to grow through 2100, but more and more gradually, approaching 400 million by century’s end. Nowhere near a billion.

If we want to increase this we would need to increase the number of births and/or the number of immigrants. (Let’s assume we won’t have the technology to significantly postpone the deaths.)

Notice that we’re currently at around 4 million births and 3 million deaths each year. But the number of deaths is rising rapidly (as our population ages) and is expected to surpass the number of births about 20 years from now. After that, population rises only because of immigration.

In the book, Yglesias proposes that the U.S. encourage more births by enacting a universal child allowance, guaranteed parental leave, publicly funded child care and preschool, and other pro-family policies. He’s vague about how much difference he thinks all this will make, but others have pointed out that the countries he holds up as good examples for these kinds of policies (Finland, Scotland, Sweden, Germany, Belgium, Japan) tend to have fertility rates that are even lower than ours. (Sweden’s is infinitesimally higher.) In an interview with Kelsey Piper of Vox, Yglesias responded by noting that Americans tend to be more religious than Europeans, and religious people tend to have more children than those who are not religious.

Let’s suppose, then, that through pro-family social programs we can lift the U.S. fertility rate somewhat higher than that of the rich countries in Europe and Asia. Exactly how much higher might that be? Yglesias cites a New York Times summary of data from the General Social Survey, claiming that “The gap between the number of children that women say they want to have (2.7) and the number of children they will probably actually have (1.8) has risen to the highest level in 40 years.” The suggestion, then, seems to be that the social policies listed above might raise the U.S. fertility rate up to something like 2.7.

I think this is a fantasy. For one thing, both the average GSS survey response and the actual fertility rate have dropped somewhat since 2018, when that New York Times article was published. But more importantly, the actual wording of the GSS survey question was not “How many children would you like to have?”, but rather, “What do you think is the ideal number of children for a family to have?”. Some respondents are likely to answer this question from the perspective of a child instead of a parent—especially if they personally have no wish to start their own families—and the number of children in an average child’s family will always be larger than the number of children born to an average adult. The trend in these survey responses over time can still teach us something, but I don’t see how we can use the numerical level of the average response to predict how many children people would have if they could afford them.

Nevertheless, let me err on the side of being overly generous and assume that somehow the U.S. might raise its fertility rate from the current value of 1.66 children per woman back up to the replacement value of 2.1. Then the green curve on the chart above would jump up by about another million, and the U.S. would get a boost of a few tens of millions of births over the next few decades. In the long term, though, the green and red curves would merge, and any further population growth would come entirely from (net) immigration.

Next question: How high might we raise the annual U.S. immigration numbers? Yglesias doesn’t say. The average over the last two decades has been about a million a year, and that’s what the U.N. projections assume going forward. At that rate it would take us 600 years to add another 600 million Americans. (The exact time required would depend on how many children the immigrants have after they arrive, which in turn would depend on their distribution in age, sex, and education level.)

But immigration has been higher at times in the past. In the 1990s the annual rate reached almost 2 million a year. That was the all-time high in absolute terms, and immigration rates were much lower throughout most of the 20th century. But before World War I immigration rates were fairly high, especially relative to the population at the time.

Here is a plot (data here) of the annual number of people obtaining lawful permanent resident status in the U.S., as a fraction of the population at the time, since 1820:

In the heyday of U.S. immigration, from 1847 through 1914, we were taking in nearly 1% of our population each year, on average. If we wanted to do that today, we’d need to triple our recent legal immigration rate.

Before continuing that thought, I should point out that U.S. fertility rates were also much higher in the past. So even when immigration rates were in the vicinity of 1% of our population each year, the high birth rate meant that the fraction of U.S. residents who were born in other countries never exceeded 15%. Today that fraction is about 14%, despite our much lower immigration rate (as a percentage of population), because our birth rate is also much lower. If we were to raise our immigration rate to 1% of population over a sustained period, our foreign-born fraction would rise to a level never before seen in the U.S. as a whole, though familiar in places like California and Australia.

So in today’s political climate, increasing the immigration rate may be another fantasy. But let’s forget politics and suppose that the U.S. were to admit 1% of our population as immigrants every year. That would be 3.3 million immigrants per year initially, rising over time as our population increases. If we could sustain it, this immigration rate would bring our population up to one billion in about 100 years. (Again the exact time would depend on the demographics of the immigrant pool.)

Is this close to what Yglesias has in mind? We can only speculate. He devotes considerable space in his book to arguing that the U.S. can hold a billion people, while neglecting to say how long he thinks it might take us to reach that level. But putting a specific time scale on the target adds clarity to some issues the book raises, while inviting us to ponder some further questions.

For instance, a hundred years is considerably longer than the time scale—just a few decades—over which the world needs to transition away from fossil fuels. So we needn’t let the prospect of a much higher population clutter our thinking about how to carry out that transition here in the U.S. Then, after a few decades, we’ll have a much clearer picture of what it might take to scale up the fossil-free energy system to meet the needs of the hypothetical one billion Americans.

On the other hand, a hundred years is about the same time scale over which the world as a whole will (probably) transition from rapid population growth to likely decline. Projections suggest that this transition will be especially dramatic in Asia and Latin America, the origins of most U.S. immigrants in recent years. Meanwhile, a century of further economic development is likely to bring the wealth level of much of the world closer to that of the U.S.

So although there seems to be no shortage of people who would like to migrate to the U.S. today, we shouldn’t assume that this will be the case a full century into the future, as we (hypothetically) seek the hundreds of millions of immigrants we would need to reach the one billion level. Already we compete with places like Europe, Canada, and Australia to attract many of the world’s migrants. In a hundred years the list of other rich countries that are eager to attract migrants could be much longer.

Of course there’s nothing sacred about a 1% annual immigration rate. Could we raise it significantly higher still? That would shorten the time needed to reach one billion, but would also bring us into truly uncharted cultural territory, with immigrants arriving so fast that they could soon outnumber native-born Americans. And although I said I’d forget politics, I have to draw the line somewhere on such politically far-fetched speculations.