Quantum dots hold promise for energy scavengers

Researchers at the Massachusetts Institute of Technology claim quantum dots may hold the key to building more efficient energy-harvesting devices.

Peter Hagelstein, associate professor of electrical engineering at MIT and co-author of a paper on the new concept appearing this month in the Journal of Applied Physics, said said existing solid-state devices to convert heat into electricity are not very efficient. The research, carried out with graduate student Dennis Wu as part of his doctoral thesis, aimed to find how close realistic technology could come to achieving the theoretical limits for the efficiency of such conversion.

Hagelstein, Wu and others started from scratch rather than trying to improve the performance of existing devices. They carried out their analysis using a very simple system in which power was generated by a single quantum-dot device. By controlling all aspects of the device, they hoped to better understand how to design the ideal thermal-to-electric converter.

A key to the improved throughput was reducing the separation between the hot surface and the conversion device. A recent paper by MIT professor Gang Chen reported on an analysis showing that heat transfer could take place between very closely spaced surfaces at a rate that is orders of magnitude higher than predicted by theory.  The new report takes that finding a step further, showing how the heat can not only be transferred, but converted into electricity so that it can be harnessed.

Although it may take a few years for the necessary technology for building affordable quantum-dot devices to reach commercialisation, Hagelstein said: “There’s no reason, in principle, you couldn’t get another order of magnitude or more” improvement in throughput power, as well as an improvement in efficiency.

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