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Slideshow: Solar power, shaped up

3-D shapes covered in solar cells could produce more power than flat panels, MIT researchers find.
Conventional photovoltaic solar panels are flat, and can be installed horizontally, angled to face the average height of the sun, or mounted on a tracking mechanism.
Caption:
Conventional photovoltaic solar panels are flat, and can be installed horizontally, angled to face the average height of the sun, or mounted on a tracking mechanism.
MIT professor Jeffrey Grossman used a computerized system to let possible shapes for solar panels evolve over time, starting with simple basic shapes. This is an example of a shape that was found to be quite effective because it could catch the sun lower in the sky, and also some surfaces could reflect sunlight onto others.
Caption:
MIT professor Jeffrey Grossman used a computerized system to let possible shapes for solar panels evolve over time, starting with simple basic shapes. This is an example of a shape that was found to be quite effective because it could catch the sun lower in the sky, and also some surfaces could reflect sunlight onto others.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
Shapes that were less efficient were culled from the mix, and the best shapes were combined to produce new hybrid forms.
Caption:
Shapes that were less efficient were culled from the mix, and the best shapes were combined to produce new hybrid forms.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
Some of the shapes produced by the computer program were quite complex.
Caption:
Some of the shapes produced by the computer program were quite complex.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
The program explored shapes that included multiple curves and angles.
Caption:
The program explored shapes that included multiple curves and angles.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
The shape on left was one of the most efficient ones generated by the program, but also one of the most complex. That complexity means it would be impractical to make, so the team produced a simplified version (right) that performed almost as well. Such forms could be designed to be shipped flat, then unfolded at their installation site to their full 3-D shape.
Caption:
The shape on left was one of the most efficient ones generated by the program, but also one of the most complex. That complexity means it would be impractical to make, so the team produced a simplified version (right) that performed almost as well. Such forms could be designed to be shipped flat, then unfolded at their installation site to their full 3-D shape.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
Simulations show that the higher the 3-D panels extend up from the horizontal, the greater their power output, and that they produce a relatively stable output over the course of a day (blue lines) as compared to flat, horizontal panels (red).
Caption:
Simulations show that the higher the 3-D panels extend up from the horizontal, the greater their power output, and that they produce a relatively stable output over the course of a day (blue lines) as compared to flat, horizontal panels (red).
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi
These images illustrate how the genetic algorithm used by the researchers -- based on the principles of evolution -- can start from complete randomness and lead to complex, highly efficient shapes.
Caption:
These images illustrate how the genetic algorithm used by the researchers -- based on the principles of evolution -- can start from complete randomness and lead to complex, highly efficient shapes.
Credits:
Image courtesy of Jeffrey Grossman, Bryan Myers and Marco Bernardi

Flat solar photovoltaic panels are becoming more widespread, but the power they produce varies over the course of the day as the sun’s position changes — unless the panels are mounted on tracking systems to keep them pointed sunward, which adds complexity and expense.

Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering at MIT’s Department of Materials Science and Engineering (DMSE), was inspired by the way trees spread their leaves to capture sunlight and wondered how efficient a three-dimensional shape covered in solar cells could be, and what its optimal shape would look like. He worked with a second-year DMSE graduate student, Marco Bernardi, to create a computer program that mimics biological evolution, starting with basic shapes and letting them evolve, changing slightly each time and selecting those that perform best to start the next generation. He found that such systems could produce relatively constant power throughout the day without the need for tracking, and produce significantly more power overall for a given area — for example two and a half times as much as a flat array when the height equals the length and width. He is continuing to work on finding the best shapes and teaming up with Professors Vladimir Bulović and David Perreault (EECS) to build a prototype system. The team believes that solar panels based on this concept could be shipped flat and then unfolded at the site to their complex shapes.

These images show some of the varied shapes with improved efficiency that emerged from the evolving simulation.

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