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The vast and glittering Ivanpah solar facility in California will soon start sending electrons to the grid, likely by the end of the summer. When all three of its units are operating by the end of the year, its 392-megawatt output will make it the largest concentrating solar power plant in the world, providing enough energy to power 140,000 homes. And it is pretty much smack in the middle of nowhere.
The appeal of building solar power plants in deserts like Ivanpah’s Mojave is obvious, especially when the mind-blowing statistics get thrown around, such as: The world’s deserts receive more energy beamed down from the sun in six hours than humankind uses in a year. Or, try this one: Cover around 4 percent of all deserts with solar panels, and you generate enough electricity to power the world. In other words, if we’re looking for energy—and of course, we are—those sandy sunny spots are a good place to start.
But statistics are one thing, building a few thousand gigawatts of solar power is quite another. Deserts are dusty, windblown and remote. So far, only a few hundred megawatts of utility-scale desert solar power have been built. Most projects are in the American Southwest, with a few in the Middle East and north Africa as well. Though progress has been slow and significant technical challenges remain, experts and industry leaders seem to agree that engineering difficulties alone are not holding us back from a big desert solar build-out. “From the technical side, I think we can do it. In fact, I know we can do it,” says Seth Darling, a solar researcher at Argonne National Laboratory near Chicago. “I don’t know that we can do it from a policy side, but I sure hope we can.”
Water and dust
On the engineering side, though, Darling says that there are one or two challenges that still could be “deal breakers,” at least for some technologies. The big one is water. Concentrating solar power (CSP) plants, like traditional power plants, need to be cooled to run, and cooling takes water—lots of it. And of course, if water were abundant in the desert, it wouldn’t be the desert. At Ivanpah, on-site wells supply the plant with water, but that solution won’t always be feasible. “I can’t think of any technical way around that unless a dry cooling technology that’s effective and affordable is developed,” Darling says. “No one has really come up with a way to do that.”
For photovoltaics (PV), water is only needed to clean the panels, which brings up the second large problem with desert solar: dust. Solar panels and mirrors need to be cleaned almost daily if efficiencies are to stay where they need to be. Dust is not transparent, so even just one gram of dust per square meter of solar panel area can reduce efficiency by around 40 percent. At that rate, it doesn’t take long in a dusty desert for the problem to become intractable.
In the desert near Abu Dhabi in the United Arab Emirates the Middle East’s first large CSP plant recently faced down the dust issue. In order to reach the 100-megawatt-capacity goal of the Shams 1 plant, developers had to add substantially more mirrors to the plant than planned due to dust in the atmosphere. Scott Burger, an analyst at Greentech Media’s GTM Research who focuses on the region, said the plant probably ended up costing three times the initial estimate, thanks in part to dealing with that dust. And now that it is built, Shams 1 sends a series of trucks up and down the lines of 250,000 mirrors every day, using robot arms to spray that precious water and clean away the dust.