Abstract
In order to realize further stability of a stack-type thermoelectric power generating module (i.e. no electrical connections inside), flexible materials of metal springs and/or rods having restoring forces were installed between lower-temperature-sides of thermoelectric elements. These flexible materials were expected to play three important roles of interpolating different thermal expansions of the module components, enlarging heat removal area and penetration of any media through themselves. Then, a low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) was also applied for a high-speed direct heat removal via its phase change from the lower-temperature-sides of the thermoelectric elements in the proposing stack-type thermoelectric power generating module. No electrical disconnections inside the module were confirmed for more than 9 years of use, indicating further module stability. The power generating density was improved to about 120 mW·m-2 with SUS304 springs having 0.7 mm diameter. Increasing power generating density can be expected in terms of suitable selection of flexible metal with high Vickers hardness, cavities control on the spring surface, more vigorous multiphase flow with adding powders to the medium and optimization of the module configurations according to numerical simulations.
Highlights
In our previous work, flexible sections were installed to a stack-type thermoelectric power generating module so as to realize reliable electrical connections inside over an extended time period under varying heat source temperatures [1] [2]
Increasing power generating density can be expected in terms of suitable selection of flexible metal with high Vickers hardness, cavities control on the spring surface, more vigorous multiphase flow with adding powders to the medium and optimization of the module configurations according to numerical simulations
A biphasic medium composed of an underlying water-insoluble/ extremely-low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) [3] in small quantity and upper-layered water in large quantity [4] was applied for enabling high-speed direct heat removal via NOVEC phase change from lower-temperature-sides of the thermoelectric elements, expecting a larger-temperature-difference between one side and another of each thermoelectric element [1] [2]
Summary
Flexible sections were installed to a stack-type thermoelectric power generating module so as to realize reliable electrical connections inside over an extended time period under varying heat source temperatures [1] [2]. No electrical disconnections inside the module could be sustained for more than 7 years of use, confirming the module stability, and the power generating density was improved about two thousands fold, compared to that without flexible sections and with only water instead [1]. Two flexible materials of metal springs and/or rods having restoring forces were applied to the stack-type TEG module for highly reliable electrical connections of the module components with different thermal expansion coefficients and high-speed direct heat removal from lower-temperature-sides of thermoelectric elements (i.e. higher power generating density)
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