Harvesting low grade waste heat through environment friendly n-Ag2Se/p-MgAgSb based thermoelectric module

Abstract

The majority of the primary energy in any process is wasted as low-grade heat (< 373 K). Thermoelectric power generators are ideally suited for conversion of such low-grade waste heat into electricity. So far Bi2Te3-based alloys based thermoelectric generators are commercially ruling such energy conversion applications. From long term commercial sustainability point of view the scarcity of elemental Te in earth crest and the presence of heavy element Bi are issues of concern. Here we report environment friendly and Te free n-Ag2Se and p-MgAgSb combination as an alternative to the Bi2Te3-based alloys. The mechanically strong and low specific contact resistivity electrical contacts based on Ni and Ag were directly bonded on Ag2Se and MgAgSb respectively using deformation bonding method. For a temperature difference (∆T) of ~ 82 K, the uni-leg device displayed a conversion efficiency of ~ 1.9% that is comparable to the state-of-the-art Bi2Te3-based thermoelectric module for a similar ∆T. Finally, a thermoelectric power generator module comprising of 18 p-n legs was coupled with a DC-DC boost converter for demonstration an application by harvesting low grade waste heat.