Introducing a new concept for enhanced micro-energy harvesting of thermal fluctuations through the Marangoni effect

Santiago Madruga and Carolina Mendoza

Applied Energy, 2022, vol. 306, issue PA, No S0306261921012721

Abstract: We present a new concept to strongly enhance the conversion of ambient thermal fluctuations into electric power using the Marangoni effect. The physics and capability of the concept are demonstrated through simulations of a micro-energy harvester formed by a Thermoelectric Generator (TEG) coupled to a Heat Storage Unit (HSU) filled by a Phase Change Material (PCM) with a free surface. Gradients of surface tension in the PCM liquid phase originate thermocapillary flows that accelerate the heat transfer between TEG and HSU. This concept can be applied to conditions where the PCM has a free surface and is particularly advantageous in spacecraft, where microgravity makes Marangoni flows a dominant heat transfer mechanism. We describe the system layout and apply the concept to micro-energy harvesting under the thermal load experienced in a small satellite orbiting the Earth. Most of the augmented energy production with respect to conductive transport occurs during the PCM heating phase when Marangoni flows are strongest. For large enough HSU to sustain continuous phase change during the harvesting period, the Marangoni effect multiplies by 2.9, 5.6, and 7.3 times the energy harvested from the environment using octadecane, hexadecane, and water as PCMs, respectively. Thermocapillary flows arise naturally at the interface of liquids subjected to thermal gradients, and no additional physical elements that would add weight or complexity are required to exploit this concept. Since it is based on a fundamental principle, it can be used as a foundation for further improvements to optimize the output of thermoelectric devices to power low-consumption electronics.

Keywords: Marangoni; Phase change material; Thermoelectricity; Thermocapillarity (search for similar items in EconPapers)
Date: 2022
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DOI: 10.1016/j.apenergy.2021.117966

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