America by Air: Powering Homes With Molten Salt

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

Our collection of power plants for this photo series keeps growing: a nuclear one over Michigan, another one along the Cali coastline, a bunch of wind turbines over Colorado, a pair of coal-fired plants in Iowa, solar panels with crop circles in Arizona—and now a massive solar plant in Nevada that looks like a moon base or a SETI satellite:

Roberto T. Martins

The stunning image was sent by Roberto, a reader in Georgia:

This is the Crescent Dunes Solar Energy project, in the Nevada desert, as seen on a flight from Denver to San Francisco last November. I had just heard about it on NPR when I saw it right under our flight path. (If I hadn’t listened, I would have no idea what it was.)

Here’s the NPR story that he’s likely referencing. It provides some fascinating details into the unique nature of the Crescent Dunes solar plant, which can generate electricity for up to 10 hours even after the sun goes down. What’s the secret? Molten salt:

“It actually looks like water. It’s clear — it flows like water,” Smith says. He says the molten salt has to remain above 450 degrees Fahrenheit to stay liquid. It’s sent up the tower to the glowing tip, where it’s heated further. When the salt comes back down, it is 1,050 degrees. The molten salt is used to make steam to power a generator.

Here’s a closer view of the plant from Roberto, with the central tower casting a sundial-like shadow across the desert floor:

The plant generates enough electricity to power 75,000 Nevada homes. But it’s had some blemishes: “During a test [of Crescent Dunes last year], observers recorded a video of birds flying into heat from the mirrors and being incinerated.” The group Basin and Range Watch is now suing the agency to get more information on the dangers to wildlife. But flaming fowl isn’t unique to Crescent Dunes; the Ivanpah Solar Electric Generating System in California is another example of a broader problem for solar plants. Here’s an explanation from Emma Roller via our archives:

First, insects are drawn to the reflective light of the solar mirrors. That draws small, insect-eating birds, which in turn draw larger predatory birds. The rays of the mirrors’ reflected light produces temperatures from 800 degrees to 1,000 degrees Fahrenheit. Any animal caught in the intense glare of the mirror’s rays may catch fire and plummet toward the ground, or spontaneously combust altogether.

That beam of fiery death is called a “solar flux.” The bigger threat to birds, however, comes from wind turbines. As my colleague Clare Foran noted, “Research published in the peer-reviewed scientific journal Biological Conservation [in 2013] estimated that between 140,438 and 327,586 birds — or a mean of 234,012 — are killed annually due to collisions with turbines across the U.S.” Petroleum is another big danger:

In the six months after the BP oil spill in 2010 — when 4.9 million barrels of crude oil leaked into the Gulf of Mexico — more than 7,000 birds were collected in the spill area, and more than 3,000 were coated in oil, according to the National Wildlife Federation. Up to 23,000 birds could have been killed by the spill, according to an estimate in Audubon Magazine. It’s also estimated that 225,000 birds died from the Exxon Valdez spill in 1989.

An Atlantic reader has some firsthand perspective on the petroleum threat:

I worked for many years with seabirds in California and Hawaii, and I wanted to add something about the differing impact of mortality between oil and wind. Oil affects predominately seabirds, whereas wind turbines affect mostly land birds. Land birds and seabirds have much different reproductive lives; seabirds live much much longer and produce fewer young each year. [...]

The relevance of this to oil and wind? Adult mortality in seabirds is generally much lower than for land birds, under normal conditions. But increases in adult mortality are much less sustainable. In a situation where you have a significant die-back of adults, land birds can sustain that die-back longer and rebound back much faster once that problem has been eliminated. The recovery time of seabirds is measured, however, in decades.

As Todd Woody points out in this Atlantic post, windows are probably the greatest scourge for wild birds—even excluding windshields:

Every year as many as 988 million birds—that’s not a typo—or nearly 10 percent of the United States’s avian population, die from colliding with windows, according to a study published in March [2014]. In other words, you and I have bird blood on our hands just from sitting inside our offices and homes.

Circling back to Crescent Dunes and happier thoughts, if you lived in New York City two years ago, as I did, you may have noticed that solar plant while walking past Lincoln Center—or, rather, an artistic representation of Crescent Dunes:

Hopefully no birds barreled into that projection. Its artist, John Gerrard, spoke with Motherboard at the time:

Gerrard and a team of programmers used Unigine, a real-time virtual 3D program typically used in gaming, to place the sun, moon, and stars as they would appear over one year at Crescent Dunes. The perspective cycles through ground level, satellite, and various other vantage points. “No view is precisely the same at any point during the course of the exhibition,” according to the official description.

The artist told Motherboard he was interested in the Crescent Dunes facility because it resembles a solar disc from above and its solar tower reminded him of a light house, two technologies that depend on the sun. “I was interested in transplanting these ancient, iconic shapes into New York City with an alternate reality,” Gerrard said. “Most people ignore public art, but it’s stimulating the public in this enormous way to document it. If you look at the #SolarNYC images on Instagram, people are creating these images within images and wonderful hyperlapse videos of Solar Reserve.”

A closeup image of the tower I captured on Instagram looks like a robotic Mad Hatter: