Harvesting Blue Energy Based on Salinity and Temperature Gradient: Challenges, Solutions, and Opportunities

Abstract

Greenhouse gas emissions associated with power generation from fossil fuel combustion account for 25% of global emissions and, thus, contribute greatly to climate change. Renewable energy sources, like wind and solar, have reached a mature stage, with costs aligning with those of fossil fuel-derived power but suffer from the challenge of intermittency due to the variability of wind and sunlight. This study aims to explore the viability of salinity gradient power, or “blue energy”, as a clean, renewable source of uninterrupted, base-load power generation. Harnessing the salinity gradient energy from river estuaries worldwide could meet a substantial portion of the global electricity demand (approximately 7%). Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are more prominent technologies for blue energy harvesting, whereas thermo-osmotic energy conversion (TOEC) is emerging with new promise. This review scrutinizes the obstacles encountered in developing osmotic power generation using membrane-based methods and presents potential solutions to overcome challenges in practical applications. While certain strategies have shown promise in addressing some of these obstacles, further research is still required to enhance the energy efficiency and feasibility of membrane-based processes, enabling their large-scale implementation in osmotic energy harvesting.

Commercial Nafion Membranes for Harvesting Osmotic Energy from Proton Gradients that Exceed the Commercial Goal of 5.0 W/m2

“…In addition to proton gradient energy, industrial waste heat, known as low-grade heat, shows great potential when coupled with osmotic energy. 24 We found that as the temperature of the electrolyte solution increases, the conversion efficiency of proton gradient energy is enhanced, with a power density of 8.1 W/m 2 at 333 K (5.1 W/m 2 at 293 K) under a test area of 0.2 mm 2 . This work demonstrates the potential application of a low-cost commercial Nafion membrane in proton gradient energy harvesting and provides ideas for large-scale conversion of osmotic energy.…”

“…Even under a large area of 12.5 mm 2 in a strong acidic environment, a power density of 2.1 W/m 2 can be achieved. In addition to proton gradient energy, industrial waste heat, known as low-grade heat, shows great potential when coupled with osmotic energy . We found that as the temperature of the electrolyte solution increases, the conversion efficiency of proton gradient energy is enhanced, with a power density of 8.1 W/m 2 at 333 K (5.1 W/m 2 at 293 K) under a test area of 0.2 mm 2 .…”

Light-Augmented Multi-ion Interaction in MXene Membrane for Simultaneous Water Treatment and Osmotic Power Generation

“…We should note that without solar light osmotic power can still be generated, albeit with lower power density. Moreover, industrial wastewater often has relatively high temperature, which should also promote the Na + selectivity and the osmotic power density. ,,, Such power harvesting is environmentally safe and may offer the possibility of generating net energy and economic profit from the simultaneous treatment of wastewater.…”

Revealing the Effect of the [CoO]6 Microstructure in Pseudocapacitance by Controlled Delithium of LiCoO2

“…Owing to the scarcity of fossil fuels, renewable energy sources and energy storage devices have attracted considerable attention. − Particularly, supercapacitors have received increasing attention because of their high capacitance, good stability, and fast charging and discharging processes. Pseudocapacitor is a type of supercapacitor, − whose mechanism was originally demonstrated by the redox reactions of RuO 2 in aqueous electrolytes. , Notably, the electrode materials play a key role in the performance of supercapacitors; however, their high cost makes them not suitable for mass production.…”