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Emerging Technology from the arXiv

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How 3-D Photovoltaics Could Revolutionize Solar Power

Replacing flat panels with three dimensional structures can significantly change the economics of solar power generation, say engineers

  • December 16, 2011

The Sun sends some 87 Petawatts of power our way and converting some small fraction of this into usable power is one of the key battlefronts in the fight to free the world from its addiction to oil.

One way to do this conversion is to turn light into electricity using flat photovoltaic panels. This form of power generation is rapidly expanding all over the world.

But it suffers from various problems that prevent its more widespread adoption, particularly at higher latitudes where the amount of energy that can be converted varies dramatically throughout the day and by season too.

This variation can be mitigated by solar tracking mounts but these are expensive and potential points of failure.

Today, Marco Bernardi and pals at the Massachusetts Institute of Technology in Cambridge say there is a simple fix that could dramatically increase the performance of photovoltaics. Instead of two dimensional flat panels, Bernadi and co suggest using three dimensional structures.

They’ve simulated the performance of various shapes and tested several of these on the roof of a building at MIT. Their results indicate that 3D structures can increase the amount of energy that can be generated by a given footprint by as much as 20 times. These structures can also double the number of useful peak hours of generation and reduce seasonal variation to boot.

There are two effects at work. The 3D structure can pick up light when the Sun is at lower angles and internal reflections within the structure help increase the amount of captured light.

These structures needn’t be complex. A simple cube, open at the top and covered inside and out with photovoltaic cells, can generate as much 3.8 times the power of a flat panel with the same footprint. By comparison, a solar tracking mount produces an increases of only up to 1.8 times.

The ultimate test for this idea is in the economics, of course. A cube has a much higher surface area than a flat panel and is more expensive to produce in the first place. But Bernadi and co say the extra power it generates more than compensates up for this.

If the numbers work out as these guys say, 3D structures could significantly change the photovoltaics market. Bernadi and co suggest their 3D structures could be shipped as flat packages that easily “pop up” into 3D structures when assembled.

And there may be significant improvements to be had in future too. They say the inspiration for this work is “the three-dimensionality of sunlight collecting structures found in Nature.” Presumably, they mean trees and plants.

These are far from the box-like shapes studied so far. Instead, nature seems to rely on fractal structures for solar energy capture. Just how much better these shapes are needs to be established. Copying these shapes will also be difficult with today’s methods of manufacture so advances will be needed in this area too.

But clearly, there’s plenty of potential for further work here. .

Ref: arxiv.org/abs/1112.3266: Solar Energy Generation in Three-Dimensions

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