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This is the fifth in a series of profiles of our MIT Energy Fellows—graduate students who are supported by MIT Energy Initiative (MITEI) members to participate in faculty-led research and become part of a long-term community of students and alumni.
Remember burning a hole in a leaf by concentrating the sun’s rays with a magnifying glass? Andrej Lenert is working on boosting the effects of solar energy, but on a much larger scale.
Lenert, one of 40 MIT Energy Fellows, is sponsored by MITEI associate member company Ormat Technologies Inc. of Reno, Nevada. He is interested in improving methods of solar thermal power generation.
Two solar thermal systems—solar power towers and parabolic solar arrays—far exceed the energy-collecting capacity of rooftop solar panels. Power towers use an array of flat, movable mirrors called heliostats to focus the sun's rays, like a magnifying glass, on a single point. Parabolic solar collectors are rows of enormous curved mirrors. Both devices use fluids as a heat source to run a power cycle that converts heat into electricity.
One of the challenges facing solar power is its lack of availability when it’s cloudy or dark. These massive collectors aim not only to generate a large amount of power but also to store it for when the sun doesn’t shine.
When he got to the University of Iowa, where he earned a swimming scholarship and his father held a faculty appointment, Lenert sought out “the coolest thing” he could find. This happened to be research aimed at developing better in-flight tools for pilots. After a few test flights that Lenert spent monitoring data on his laptop while crammed in the back of a two-seater doing barrel rolls and wingovers, he decided that he’d find a different field.
Lenert graduated with a degree in mechanical engineering in 2008. His interest in energy has now led him to designing metal- and salt-based nanoparticles that boost the storage and power-generating capacity of large-scale collectors such as power towers and parabolic arrays.
“I like to think of these tools as ways of concentrating solar light into a deep well,” he said. “A well is completely dark; it absorbs all light. The well stores solar energy for when you need it.” By seeding the towers’ and arrays’ fluids with discrete particles of light-sensitive materials, the collectors become more efficient at heat transfer and at absorbing all wavelengths of light, not just those in the visible spectrum.
These new energy storage methods are inside the fluids—oil in the case of power towers, molten salts in parabolic arrays. “The fluids retain the same viscosity but have the added advantage of storing the solar energy as latent heat, which increases the system’s energy storage capabilities,” Lenert said.
In collaboration with Evelyn N. Wang, Esther and Harold E. Edgerton Assistant Professor of Mechanical Engineering, Lenert is working to identify materials for the nanoparticles that remain stable over a large range of temperatures, don’t glom together, and don’t reflect light. “The stability of the suspension, the phase change of the materials, and the optical properties are key to our research,” he said.
The work requires a multidisciplinary approach, and Lenert is convinced that MIT excels at this. When he first looked at MIT, he said he didn’t immediately click with any professors or programs. But when he heard about the MIT Energy Initiative and its multidisciplinary focus, he was sold. “This program is the only reason I’m at MIT,” Lenert said. “This program gave me the flexibility to do exactly what I wanted in the energy field.”