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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Thermoelectric supercapacitor for waste heat recovery




Abstract

Waste heat recovery using conventional thermoelectrics suffers from drawbacks such as high cost, low Seebeck coefficient (few hundreds of µV/K), and complicated and costly fabrication processes. Thermogalvanic cells based on redox electrolytes have been demonstrated as potential alternative. However, the absence of energy storing capability in such devices requires additional components such as capacitor or battery elements that cause complexity in design and operation. Here, we demonstrate an integrated thermal energy harvesting supercapacitor that can act as a stand-alone device for storing electrical energy from an applied temperature gradient. After the temperature gradient is removed, the stored electrical energy can be delivered to an external circuit on demand. A thermogalvanic gel electrolyte film exhibiting a thermo-electrochemical Seebeck coefficient of -1.21 mV/K is used in conjunction with high surface area electrodes consisting of graphene petals grown on conductive carbon cloth substrate. The device possesses a high areal capacitance of 10 F cm-2 leading to high energy density. Moreover, its all-solid-state and flexibility endow it with good mechanical characteristics that allow it to accommodate variable heat source shapes. An equivalent circuit model describes the mechanism of energy conversion and storage in the device. Voltage and current measurements are validated with the model. Furthermore, the influence of parameters such as duration of the applied temperature gradient and load resistance are discussed in light of the model in an effort to optimize device performance.

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