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

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.With the assistant of heat, the osmotic power generator with nanofluidic sulfonated poly(ether ether ketone)/poly(ether sulfone) membrane and high soluble lithium bromide shows excellent ion transport behavior and superior output power density for salinity gradient energy harvesting.Research Summary: For integrated utilization of sustainable energy and pursuing the high performance of the osmotic energy harvesting, the authors propose a strategy to couple the low-grade thermal energy with the salinity gradient energy by employing a thermoenhanced osmotic power generator. In the system, the LiBr with high solubility and the asymmetric sulfonated poly(ether ether ketone)/poly(ether sulfone) (SPEEK/PES) membranes with high stability and ion selectivity are both chosen for the thermo-enhanced osmotic energy harvesting. The proposed generator achieved the output power density of ~16.50 W/m², extremely high value at 50-fold artificial sea water/river water condition, by coupling with the configuration of 30 ºC temperature gradient. Thus, by using the proposed system, the thermal energy, especially low-grade ones, has been well harvested and greatly improve the osmotic energy conversion. Thus, the external field-osmotic hybrid energy conversion system could show its great potentials in different fields with proper coupling. [ABSTRACT FROM AUTHOR]