America by Air: Powering Homes With Molten Salt

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: