Thermoelectric power waves from stored chemical energy

Thermopower wave is a new concept of energy conversion where the chemical energy stored in solid fuel is directly converted into electricity. In this review article, the concept and recent progress of thermopower wave investigations were discussed. The self-sustained reaction propagation of fuels coated around thermal conduit was first theoretically suggested and experimentally realized using a shell-core structure of cyclotrimethylene-trinitramine coated multi-walled carbon nanotubes. The exothermic chemical reaction of fuel was guided and accelerated by the thermal conduit with greater thermal conductivity. The temperature gradient at the reaction front also resulted in electrical pulse caused by the Seebeck effect. However, the peak output voltage was limited to 210 mV due to the low Seebeck coefficient of carbon nanotubes. In order to further enhance the peak output voltage after the first discovery, research efforts have been focused on three areas; thermal conduit with greater Seebeck coefficients, geometric structures of fuel/conduits, and different types of chemical fuels. The thermal conduits with greater Seebeck coefficients generally provided higher peak voltages. One-dimensional structure of fuel/conduits generated more efficient thermopower waves than two- or three-dimensional structures. Picric acid with self-aligned one-dimensional structure could also accelerate the reaction propagation. Overall, the peak output voltage was enhanced from 210 mV to 6.2 V in only five years of research demonstrating the rapid advance and bright future of thermopower waves.