Experimental study of the solar-driven interfacial evaporation based on a novel magnetic nano solar absorber

The solar-driven interfacial evaporation is a local heating method for vapor generation and liquid inspissation, which can significantly increase thermal efficiency. The conventional solar absorbers have complicated manufacture, non-adjustable structure and difficulty in expanding application. A new three-dimensional solar absorber was put forward for the solar-driven interfacial evaporation system. The solar absorber was composed of magnetic nano particles, which were assembled into a porous structure by exerting a magnetic field. This magnetic nano solar absorber (MNSA) could be restructured and recycled by adjusting the magnetic field. The interfacial evaporation system employing the novel MNSA could achieve thermal efficiency of evaporation by 83.1% under 1 sun illumination with the evaporation rate of 1.20 kg m-2h-1. Its evaporation rate was 3.4 times that of the bulk water evaporation. The increase of air speed and light intensity could significantly improve the evaporation performance of the interfacial evaporation system. Under 1 m/s air speed, the evaporation rate of the MNSA could be 1.85 kg m-2h-1 under one sun illumination and 3.30 kg m-2h-1 under 2.5 sun illumination. The change of air relative humidity would impact the evaporation rate significantly, especially under lower relative humidity of air.