AEM Researchers Discover New Way to Convert Heat to Electricity
Researchers Vijay Srivastava, Yintao Song, Kanwal Bhatti in Prof. Richard James group at the University of Minnesota have discovered a new way to convert heat directly into electricity using a multiferroic material they also recently discovered. The demonstration is reported in the inaugural issue of Advanced Energy Materials.
|James and researchers with the device.|
At the heart of the device is a new alloy Ni45Co5Mn40Sn10 having a phase transformation between two crystalline phases. The phase transformation is induced by changing the temperature. Prof. James says “Srivastava was applying a strategy we have developed for making transformations more reversible, perturbing the composition of a known NiMnSn alloy, when he discovered a remarkable phase transformation to a strongly magnetic phase.” The researchers then realized that they could surround a specimen of this material with a coil, heat the material through the phase transformation, and, due to Faraday’s law of induction, induce a current in the coil. The device has no moving parts.
As reported in Advanced Energy Materials, “With its low hysteresis and its large and abrupt change in magnetization at the transformation, we conjecture that the natural application area for our device is energy conversion at small temperature difference...[the device could be useful for the conversion of] the enormous reserves of energy on earth stored at small temperature difference, notably, the 20° C difference between surface ocean temperatures and temperatures just below the thermocline in mid-latitude waters.”
Prof. James explains, “Once we could see this possibility, we realized that multiferroic materials could be used in many ways for energy conversion, giving some completely new devices for technological development.” The materials also have fascinating magnetic properties, and the reason why the strong magnetism appears at this particular composition is unclear. James has teamed with Profs. Chris Leighton and Matteo Cococcioni from the Department of Chemical Engineering and Materials Science and Prof. Paul Strykowski from the Department of Mechanical Engineering to learn more about both the alloy and device.
“Martensitic phase transformations, particularly those with an interesting electromagnetic property, have recently exploded into technology,” says James, “in areas as diverse as microelectronics, information storage, actuation and energy conversion. Part of the reason for this is that we finally understand something about how to make them reversible.”
The research of the AEM group is supported by a MURI project managed by ARO, by AFOSR and by the Russell J. Penrose Chair.