Ionic thermoelectric effect in nanofluidic membranes for efficient conversion of waste heat into electrical energy

Abstract: Thermoelectric energy harvesting is a promising, environmentally friendly way to generate electricity that could lessen our dependence on fossil fuels and reduce the harmful emissions associated with their combustion. At present, the use of thermoelectricity is severely limited due to the low efficiency of converting low-grade waste heat into electricity, which is about 63% of the total unused thermal energy released into the environment [1]. Thus, the development of new methods for efficient thermoelectric power generation from waste heat is of great importance. In this presentation, we show that the efficient recovery of low-grade heat can be achieved in well-aligned nanochannels with electrically charged walls, based on the ionic thermoelectric effect. The nanochannels, with diameters of approximately 10 nm and lengths ranging from a few micrometers to several millimeters, are created by the two-stage anodisation of aluminium, the chemical treatment of natural wood and other methods. The charge density on the walls of the nanochannels can be increased through surface functionalisation with organic ligands, leading to the formation of overlapping electrical double layers (EDLs). These EDLs can act as ion filters in the presence of a temperature gradient across the nanochannels, allowing ions with a certain charge to move freely through the pores, resulting in the generation of thermopower. Such ionic thermoelectric converters can transform low-grade heat into electricity with thermopowers of up to 3 mV/K, using aqueous electrolytes such as NaCl and KCl, which is higher than that of conventional solid-state thermoelectric converters. By varying the geometric parameters of the nanochannels, e.g. the type and concentration of the electrolyte, surface charge density, higher thermopowers should be achievable in these systems. Ionic thermoelectric power converters therefore have the potential of becoming game changers in the field of thermoelectric power conversion. References [1] K. Zeb et al., Renewable and Sustainable Energy Reviews, 2017, 75, 1142. [2] T. Li et al., Nature Materials, 2019, 18, 608 Additional Information: Dr Ievgen Nedrygailov presented at the 'Sustainable materials for chemical and electrochemical energy storage' at the 2022 European Materials Research Society Fall Meeting on Sept 20th in Warsaw, Poland. This research was supported by Irish Government funding via the DAFM NXTGENWOOD research program (grant agreement: 2019PROG704) and European Union's Horizon 2020 research and innovation program project TRANSLATE. TRANSLATE is a €3.4 million EU-funded research project that aims to develop a new nanofluidic platform technology to effectively convert waste heat to electricity. This technology has the potential to improve the energy efficiency of many devices and systems, and provide a radically new zero-emission power source. The TRANSLATE project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 964251, for the action of 'The Recycling of waste heat through the Application of Nanofluidic ChannelS: Advances in the Conversion of Thermal to Electrical energy’. More information can be be found on the TRANSLATE project website: https://translate-energy.eu