Thermoenhanced osmotic power generator via lithium bromide and asymmetric sulfonated poly(ether ether ketone)/poly(ether sulfone) nanofluidic membrane

Abstract

Osmotic energy, existing between solutions with different concentrations, is a sustainable and ecofriendly resource for solving energy issues. However, current membrane-based osmotic energy conversion technologies focus on electricity generation from an “open” system by directly mixing salt (NaCl) solutions at room temperature. For the integrated utilization of thermal energy and higher power output performance, we demonstrate thermoenhanced osmotic energy conversion by employing highly soluble lithium bromide (LiBr) solutions, asymmetric sulfonated poly(ether ether ketone)/poly(ether sulfone) (SPEEK/PES) membranes, and LiMn2O4/carbon nanotube (LMO/CNT) electrodes. The thin top layer of this heat-resistant membrane contains hydrophilic groups (i.e., the sulfonated groups in SPEEK) that are beneficial for ion-selective transport. The thermal effect on each solution is investigated, and osmotic energy conversion can be improved by regulating the heat gradient. The power density is ~16.50 W/m2 by coupling with a temperature gradient (30 °C). This work is a step forward for promoting the performance of osmotic energy conversion with thermal energy assistance and provides the basis for a closed-loop system with regenerated osmotic energy from other energy forms. Moreover, the external field-osmotic hybrid energy conversion system shows powerful potential in the energy harvesting field.