Except from the higher points of Tonopah like up top of the Mining Park, you can't see the Crescent Dunes plant from Tonopah. You have to head down the mountain and get around the low hills that block the view, after which it's very visible when the thousands of mirrors are focusing the sun's rays on the power tower. I first thought I was seeing brush fires in the hills beyond the plant, but then we realized that it was probably water vapor coming off the plant, as there have been thunderstorms in the area increasing the humidity a little bit.
Although all of these photos are geocoded at the plant itself, we actually stopped along Gabbs Pole Line Road several times because you can get better pictures on the 7-mile approach to the plant. When you get up too close, the fencing around the plant gets in the way.
Over to the right of the road are the actual Crescent Dunes from which the plant takes its name.
Remember that the tower is actually black when it is switched off. This is the light of the sun focused on the tower by more than 12,000 computer-controlled mirrors. The moisture in the air makes it easier to see how the light heats up the tower.
The various heloistats (mirrors) track the sun and keep it focused on the tower.
The heat is used to melt salt, heated to around 600°C. The hot salt goes through a heat exchanger to boil water to create steam that turns a conventional turbine to generate electricity. The steam is then condensed back into water to be reused, and the now-cooler-but-still-molten salt is pumped back up the tower to repeat the cycle.
A very important thing about this kind of plant is that, unlike a solar-voltaic array, this plant doesn't stop generating power when a cloud passes in front of the sun, or even after sunset. This full-scale trial plant does not apparently have the capacity to run all night long, but the long-term plans are to build plants with sufficient molten-salt storage to operate round-the clock. Still, plants like this are "dispatchable" and can be used toward base-load power, rather than "intermittent" like photovoltaic power. Also, while the control systems are complicated, and working with molten salt is a challenging engineering problem, plants like this are expected to last longer and produce far more power per unit time per unit area (say, kilowatt-hours per year per square meter) than PV panels, which wear out faster and use more complicated materials than solar-thermal plants do.
Individual mirrors can be defocused for maintenance, and also to create a "ring of fire" in the airspace around the plant, which discourages birds from flying into the zone where they would be vaporized.
At this time, solar-thermal plants like this cost more up front and, as I mentioned, have technical challenges. But they can be built with domestic materials (steel and glass and concrete) and are not dominated by countries that have bottled up all of the rare earths. They're not a panacea for energy problems, but we think they have a promising future. I'm glad to see that this plant is working again. The solutions developed here can be used to build more and better such plants in the future.