While every day in the desert tends to be sunny, the conditions are not always optimal. And questions about solar energy generated in the desert have arisen. These include: Can the sensitive mirrors withstand sandstorms? How exactly does one build lasting structures on shifting sand dunes? Where will the project get the required water -- which will be turned into steam -- in the middle of the desert? Finally, how will the project make power during the hours of darkness?
Solar thermal power has one big advantage over photovoltaic solar power systems. It produces heat, which can easily be stored -- in fact, much better than electricity. Giant tanks containing thousands of tons of potassium and sodium nitrate molten salt are attached to the solar power plant. The chemicals involved are not at all poisonous; they are the same ingredients as can be found in ordinary fertilizer. Some of the heat produced during the day is then stored in the tanks and, at night, this stored heat can keep the turbines going for another 7.5 hours.
As for sand storms in the desert, there are nine power plants working with parabolic dishes in California's Mojave Desert, and they have been there for over 20 years without any issues. As Lars Schnatbaum-Laumann of the company Solar Millennium AG, which is currently building its third solar power plant in Spain, explains, should a sand storm endanger them, the moveable dishes are turned to a defensive position that affords the biggest dishes protection. After the storm, it is also possible to clean the dishes efficiently. "We now have cleaning robots that automatically clean the dishes of dust and sand, with very low water consumption," Schnatbaum-Laumann notes.
Additionally, the desert floor is not a problem. "When people think of the desert they automatically think of sand dunes," he says. "But, in fact, about 80 percent of the Sahara is stone or scree."
As for water issues, a solar power plant can actually do without it, if it needs to. "Water cooling is the optimal choice," Schnatbaum-Laumann says. "But you can also cool with air if you need to. It costs the plant about 4 percent efficiency. But it's a matter of balancing things up and figuring out whether putting a plant in a place where there is more sunshine and less water is better than putting one somewhere where there is less sunshine and more water."