Solar Power Stations Like Sunflowers are Optimal

RWTH researcher and mathematics professor Manuel Torrilhon and colleagues from the Massachusetts Institute of Technology (MIT) have developed a new way to lay out mirrors in solar power stations, which is both more compact and converts sunlight into energy more efficiently.

Torrilhon collaborated with former RWTH researcher, Alexander Mitsos, currently a professor in the Department of Mechanical Engineering at MIT, on the interdisciplinary project. To optimize the solar power stations, Torrilhon used the arrangement of seeds in a sunflower and transferred that to the arrangement of the mirrors in the power station. With support of the RWTH Aachen Technology Transfer, the researchers registered a patent for their idea. The process is still in the works.

As Torrilhon listened to a presentation by Mitsos about the optimization of solar power energy, one graphic reminded him of a sunflower. "The spiral form arrangement of the sunflower seeds is based on a classical example for optimal arrangement in mathematics, which is not necessarily well-known among engineers," explained Torrilhon. He emphasized, "The result is a good example for interdisciplinary collaboration." Mitsos and his doctoral student, Corey Noone, could use a computer afterwards to prove, that with the new layout, the mirrors lay closer to each other, saved valuable space, and also let the mirrors reflect the sunlight, so that energy is achieved more efficiently.

The researchers oriented themselves on the natural example set by sunflower seeds. "You start in the middle and move outwards in a spiral form, and place the mirrors like the sunflower seeds, always at a set angle," described Torrilhon. "The next mirror is always placed at a 137 degree angle to the previous mirror. As a result, you move outwards spirally."

In Sevilla, one of the largest plants in the world, which already provides 6,000 households with electricity, could be built using less space and to be more efficient. Experts estimate that such power stations have the potential to create enough renewable energy for the United States of America. Until now, the 600 mirrors in Spain, of which each is half as large as a tennis field, are on a surface area of 439,000 square meters. Each mirror takes in sunlight and redirects it into a high tower, where the solar heat is converted into electrical energy. Using a computer model, researchers laid the mirrors out using the sunflower seed pattern. The space needed for the mirrors was reduced by about 20% as a result. "We even increased the energy efficiency," emphasized Torrilhon. That means, the sunlight will be converted into energy even more efficiently and less energy will be loss. "Since large surfaces aren’t always available, it is extremely important to use the available surfaces sparingly. The next step is to apply the theory to hilly landscapes."