Anisotropic solar evaporator with low thermal conductivity for desalination, thermoelectric generation and cultivation

Abstract

Solar-driven evaporation technology is considered an effective approach for obtaining fresh water. However, unnecessary heat loss and inefficient energy utilization decrease evaporation rate of solar evaporator. Herein, a multifunctional integrated aerogel-based evaporator is fabricated with anisotropic porous structure and low thermal diffusivity by the freeze-casting method, which not only reduces heat loss in evaporation process but also enables the formation of a power generation system and a desalination and cultivation system. The oriented pores of the aerogel-based evaporator enhance light refraction, promoting light absorption, which is beneficial for capillary action in seawater desalination. Additionally, the aerogel-based evaporator with anisotropic low thermal conductivities (0.066 W m⁻¹ K⁻¹ at axial direction and 0.058 W m⁻¹ K⁻¹ at radial direction) effectively minimizes thermal loss to the surrounding water. Under 1 sun irradiation (1 kW m⁻²), the aerogel-based evaporator exhibits the evaporation rate of 2.00 kg m⁻²h⁻¹ and 92.83 % evaporation efficiency. This effectiveness of the power generation system strategy in thermoelectric generation results in an output power of 1.14 W m⁻², with a voltage of 92.9 mV and a current of 11.04 mA. Furthermore, a desalination and cultivation system are designed to enable concurrent evaporation, condensation, and collection of freshwater, demonstrating its potential for agriculture applications. This work demonstrates the feasibility of achieving high evaporation rates in seawater desalination through the design of an insulating aerogel evaporator with low thermal conductivity and provides a solution for alleviating freshwater shortages in remote coastal areas.