All-Cold Evaporation under One Sun with Zero Energy Loss by Using a Heatsink Inspired Solar Evaporator.

Xuan Wu,Yida Wang,Haolan Xu,Qin Li,Zhiqing Wu,Ting Gao

doi:10.1002/advs.202002501

Abstract

Interfacial solar steam generation is a highly efficient and sustainable technology for clean water production and wastewater treatment. Although great progress has been achieved in improving evaporation rate and energy efficiency, it's still challenging to fully eliminate the energy loss to the surrounding environment during solar steam generation. To achieve this, a novel heatsink‐like evaporator (HSE) is developed herein. During solar evaporation, the temperature on the top solar evaporation surface can be regulated by the fin structures of the HSE. For the evaporators with 5 to 7 heatsink fins, the temperature of the solar evaporation surface is decreased to be lower than the ambient temperature, which fully eliminates the radiation, convection, and conduction heat losses, leading to the absolute cold evaporation over the entire evaporator under 1.0 sun irradiation. As a result, massive energy (4.26 W), which is over 170% of the received light energy, is harvested from the environment due to the temperature deficit, significantly enhancing the energy efficiency of solar steam generation. An extremely high evaporation rate of 4.10 kg m−2 h−1 is realized with a 6‐fin photothermal HSE, corresponding to an energy conversion efficiency far beyond the theoretical limit, assuming 100% light‐to‐vapor energy conversion.

Highlights

Interfacial solar steam generation is a highly efficient and sustainable of the solar-thermal evaporator to increase thermal absorbance, minimize energy loss technology for clean water production and wastewater treatment
The porous nanocarbon composites (PCCs) were synthesized by a hydrothermal method, in which glycerol was applied as the main carbon source, melamine as the template substrate for the nucleation of the carbon particles
The heatsink-like evaporator (HSE) was comprised of a top circular surface connected with fin structures, which were made of bamboo paper coated with cost-effective porous carbon material

Summary

Results and Discussion

The PCCs were synthesized by a hydrothermal method, in which glycerol was applied as the main carbon source, melamine as the template substrate for the nucleation of the carbon particles. It is noticed that the bottom end of the fin presented a slightly higher temperature than the top part (Figure 4d; Figure S10d, Supporting Information), indicating an energy flow from the bulk water to the fins.[32] the energy for solar evaporation (Eevap) could be estimated by using Equation (4): Eevap. To investigate the energy exchange between the 6-fin HSE and the bulk water, the evaporation system was placed in a thermal insulation Dewar flask (Figure S14a, Supporting Information) with a thermocouple inserted to monitor the temperature change of the bulk water during solar evaporation (Figure S14b, Supporting Information). It was noticed that after 8 h continuous outdoor seawater evaporation, no salt crystal was formed and accumulated on the surface of the HSE (Figure S16, Supporting Information), indicating that this evaporator is applicable for practical seawater desalination

Conclusion

Experimental Section

Conflict of Interest