Right now, designing a solar power installation generally means figuring out how to orient flat or angled panels so that they’ll capture the most light. Or the panels are put onto expensive, swiveling mounts, which move the panels over the day to track the sun. But a team of researchers at the Massachusetts Institute of Technology has a different theory about how to best design solar power systems—by using solar panels to build three-dimensional structures.
One of the models the team constructed is an open-ended cube. It’s made of nine solar panels—four exterior walls, four interior walls, and the bottom inside. Another, an open parallelepiped, took 17 panels to make. The accordion-like towers, with their ridged faces, contain 32 panels.
These 3D structures don’t look like the rooftops and fields of solar panels being erected all over the world. And they don’t behave quite like them, either. For a given base area, they’re up to 20 times more effective at capturing solar energy than a flat solar panel. They also capture more energy when the sky is overcast, and they produce energy at a more even rate throughout the day.
The MIT team designed and tested these models as part of an experiment exploring the possibility of collecting solar energy in three dimensions. Nature collects energy using three-dimensional systems, an inspiration for this project, say team members Nicola Ferralis and Marco Bernardi. Their team had an advantage over nature, though: They could optimize particular designs to access these systems’ potential advantages. They tested those designs both in computer simulations and, using models, in the real world.
The team starting experimenting with 3D shapes with the idea that increasing the efficiency with which solar panels convert sunlight into power—a measure the solar industry has been regularly pushing upwards—isn’t the only way to improve solar systems. "Efficiency improvements can only partially reduce the installation costs and cannot change the pattern of solar energy generation,” they write in the article reporting their results, published this month.
In the past, installing a cube of solar panels wouldn’t have made much sense. In the 3D structures that the MIT team designed, panels shade each other, blocking access to sunlight, and each solar panel generates less energy than it would if it were installed separately. The advantage that the 3D structures have is in energy generated in a given base area, in the consistency of energy generated, and in energy generated on cloudy days. In some situations, these advantages might make the cost of additional solar panels worthwhile. Since the price of solar panels has dropped so rapidly, installation costs make up more than half the cost of a system, anyway, Ferralis and Bernardi point out.
They imagine that 3D structures might be particularly useful in urban environments, where space is at a premium. A solar tower might sit on top of a parking garage and provide power for EVs, for instance. (Or perhaps urban rooftops could do double duty as sites for solar power generation and as green roofs.) With semi-transparent panels (which exist), the structures could be used more effectively in the windows of building than flat solar panels. They also imagine that 3D solar structures could be designed to make optimal use of sunlight at different places around the world, since the same shapes won’t perform identically everywhere. The structures, they say, could potentially be folded up, like origami, and shipping in flat packages, to be unfolded and erected once they reach their destination.
Photo courtesy of Allegra Boverman/Massachusetts Institute of Technology