Catching Light, Sunflower Style

At concentrated-solar power plants around the world, massive mirrors are arranged in concentric circles around a steam-producing tower, staggered like seats in a movie theater so that every other row is aligned. However, this pattern takes up an immense amount of real estate and leaves some mirrors in shadow at certain times of day, reducing the efficiency of the installation.

Now researchers at MIT, in collaboration with RWTH Aachen University in Germany, have found that rearranging the mirrors, or heliostats, in a pattern similar to the spirals on the face of a sunflower reduces the overall footprint by 20 percent. It also minimizes shading and blocking by neighboring mirrors and even boosts the efficiency of the installation by half a percentage point.

In the optimized layout pictured at left, each dot represents a heliostat; the redder a dot, the more efficient it is at reflecting light.

“Concentrated-solar thermal energy needs huge areas,” says Alexander ­Mitsos, an assistant professor of mechanical engineering. “If we’re talking about going to 100 percent or even 10 percent renewables, we will need huge areas, so we’d better use them efficiently.”