Ionic thermoelectric osmotic energy conversion for harvesting low-grade waste heat from electronic heat sink

Efficient utilization of low-grade waste heat generated from electronic device is synergistically beneficial for its thermal management and power supply. However, the existing technologies of converting waste heat below 100 °C into electricity in electronic device remain challenging. Based on ion-selective transport in nanopores under a temperature gradient, osmotic energy conversion becomes a potential technique to realize efficient thermoelectric conversion. We present an ionic thermoelectric osmotic energy conversion device for harvesting low-grade waste heat from an electronic heat sink. When the heat flux of electronic heat sink is increased from 1000 W/m² to 3000 W/m², the ionic thermoelectric osmotic power density after 90 min’ operation is consolidated from 11.69 mW/m² to 77.01 mW/m² owing to the increased temperature difference from 18.24 °C to 43.60 °C between aqueous solutions across the ion exchange membrane. In addition, the transient ionic thermoelectric coefficient slightly oscillates around 0.5 mV/K under various heat fluxes, exhibiting a stable thermoelectric sensitivity. Furthermore, the optimum ionic thermoelectric coefficient and power density of osmotic energy conversion is achieved at an ion concentration of 0.01 M and 0.05 M, respectively. As the pH value of aqueous solution is increased from 3 to 11 under an electronic heat flux of 3000 W/m², the output power density is enhanced from 46.91 mW/m² to 83.01 mW/m² with a stable ionic thermoelectric coefficient about 0.47 mV/K due to strengthened nanopore surface charge density. This work offers a promising route for efficient management of waste heat from electronic heat sink to realize thermoelectric energy conversion.