Thermoelectric Power Generation in Dynamic Temperature Environments

Thermoelectric materials have long held promise as a critical piece of the sustainable-energy puzzle. The benefits of thermoelectric power are numerous: they capture energy from waste heat (such as that of industrial processes and automobile exhaust) and naturally-occurring thermal gradients (such as geothermal energy), have a small size, degrade slowly, generally consist of nontoxic materials, and operate silently; however, their widespread adaptation has been limited by their low power outputs and efficiencies. Although a large number of thermoelectric applications have been considered, investigated, and commercialized, the thermal driving force remains the same in each: a steady-state, spatial temperature gradient. Here, an alternate source of thermal energy for thermoelectric power – transient thermal gradients, or the fluctuations of an environmental temperature with time – is investigated; this source of power is useful for low-power devices in remote locations. We design and characterize devices that employ a thermoelectric module sandwiched between two heat exchangers with significantly different thermal masses and examine the effects of heat exchanger size and material selection, period of oscillation of the environmental temperature fluctuations, and radiative heat transfer on the thermoelectric power output. We report maximum experimental power generation on the order of milliwatts using standard bismuth telluride thermoelectric modules in devices with a size of about 10 cm³.