Improvement of the efficiency of volumetric solar steam generation by enhanced solar harvesting and energy management

Abstract

Volumetric solar steam generation has attracted substantial interest due to its low cost, minimum carbon footprint and wide application in many areas including clean water production, desalination, and wastewater treatment. However, the efficiency of volumetric solar evaporation is still low and there is an urgent need to investigate the fundamental of the limitation of low efficiency and find a new strategy to improve the solar evaporation efficiency. In the current work, antimony doped tin oxide@carbon (ATO@C) nanofluids were prepared by a hydrothermal approach. The ATO@C nanofluids exhibit broad-band and high absorption in the solar spectrum due to the complementary effect of C (in visible region) and ATO (in the near infrared region). ATO@C nanofluids of 0.3 wt% could harvest 99.9% of the incident solar energy within 1 cm penetration distance. The photothermal conversion efficiency is 97.8%. The coupling relationship between the solar harvesting and the energy distribution was revealed. Increasing mass fraction and reducing thickness can localize the heat in the surface layer of nanofluids and thus minimize the energy consumption in heating water (internal energy) and therefore improve the solar evaporation efficiency. A high evaporation efficiency of 88.6% was achieved in this way.