Transport-Enhanced Thermogalvanic Energy Conversion

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CBET-1236571PhelanWaste heat energy conversion remains an inviting subject for research, given the renewed emphasis on energy efficiency and carbon emissions reduction. Solid-state thermoelectric devices have been widely investigated, but their practical application remains challenging because of cost and the inability to fabricate them in geometries that are easily compatible with heat sources. An intriguing alternative to solid-state thermoelectric devices is thermogalvanic cells, which include a (generally) liquid electrolyte that permits the transport of ions. Thermogalvanic cells have long been known in the electrochemistry community, but have not received much attention from the thermal transport community. This is surprising given that their performance is highly dependent on controlling both thermal and mass (ionic) transport. The proposed project is an interdisciplinary collaboration between mechanical engineering (thermal transport) and chemistry, and is a largely experimental effort aimed at improving fundamental understanding of thermogalvanic systems. Both thermal and mass transport will be controlled by imposing a nanostructured membrane between the electrodes, which will take advantage of previous work that demonstrated very high rates of mass transfer through aligned carbon-nanotube electrodes, and very low rates of heat transfer through randomly oriented carbon nanotubes. This work may enable improved waste heat energy conversion, largely because a fluidic device like a thermogalvanic cell can conform to the shape of a heat source like an exhaust pipe, and because thermogalvanic cells may ultimately be manufactured more cheaply than comparable thermoelectric devices. Finally, an extensive K-12 outreach program will be undertaken as part of the ongoing Science is Fun program, in which simple experiments based on demonstrating the thermogalvanic effect in salt water will be carried out by students in grades 4 through 8.