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Excessive discharges of chemical dyes have led to severe contamination of seawater, resulting in significant ecological damage. Thermo-osmotic energy conversion technology, which purifies wastewater and generates electricity under temperature gradients, has garnered considerable interest from researchers. However, the operational efficiency of thermo-osmotic energy conversion is inherently limited by the effective membrane area, and conventional systems typically employ flat membranes as separators, resulting in suboptimal performance for the same floorage. In this study, we introduce a novel system that combines thermo-osmotic energy conversion technology with hollow fiber membranes that possess a high effective membrane area, thereby achieving optimized performance. Driven by the temperature gradient, the water in the dye solution condenses outside the membrane and converted from vapor to liquid. The continuous accumulation of condensed water generates pressure and drives a water turbine for sustainable power generation. Our results demonstrate that at temperature gradient of 40 °C, the system can achieve the power output of 16.75 Wm−3 and the freshwater production rate of 70.29 kg m−3 h−1 under ideal conditions. This study presents a novel water-electricity co-production system based on low-grade waste heat recovery for dye solution treatment, which extends the applicability of thermo-osmotic energy conversion technology and improves its practicality. • Hollow fiber membrane combined thermal-osmosis hybrid system was proposed. • Simultaneous generation of freshwater and electricity was achieved under dye solution. • Optimal operating conditions for the system are discussed. • A theoretical model was developed to optimize water and electricity output of the system. [ABSTRACT FROM AUTHOR]

Low-grade heat energy is enormous and widely distributed around the world, but it cannot be effectively converted to electricity owing to the small temperature difference and fluctuating heat source. As a promising technology that can convert low-grade heat energy into electricity while obtaining additional freshwater, thermo-osmotic energy conversion has attracted attentions of numerous researchers. However, traditional thermo-osmotic energy conversion technologies lack the utilization of the accompanying variation in salinity gradients throughout the process. In this study, a hybrid system was presented to achieve simultaneous freshwater production and electricity generation by combining thermo-osmosis system with a salinity gradient power recovery module. Continuous operation of the thermo-osmosis system will naturally produce a range of salinity differences, which will then be converted into electricity by the salinity gradient power recovery module. Our results show that this hybrid system can optimally increase the electricity output by ∼0.99 W m−2 over the conventional thermo-osmotic energy conversion system. Overall, our research demonstrates a promising device to harvest low-grade waste heat for co-generation of electricity and freshwater. This innovative approach has the potential to broaden the application possibilities of thermo-osmosis technology. • Salinity gradient recovery combined thermal-osmosis hybrid system was proposed. • A theoretical model was developed to predict electricity output of the system. • Comparing to traditional TOEC, increasing electricity output by ∼0.99 W m−2. • Co-generation of freshwater and electricity was achieved under real seawater. [ABSTRACT FROM AUTHOR]