Cover matters: enhanced performance of a multistage solar evaporator with tuned optical and thermal cover properties

Abstract

To address global water scarcity and improve off-grid pure water production, this study focuses on enhancing the performance of inverted solar evaporators by optimizing the design of cover materials. By employing a coupled numerical and experimental approach, we systematically investigated the optical and thermal properties of various cover materials, including thin film, transparent silica aerogel, acrylic, and glass, to guide their rational design under different operational conditions. Silica aerogel, with its high solar transmittance and ultra-low thermal conductivity, demonstrated superior evaporation performance in high-stage device designs and retained cost-effectiveness in high-stage and low-solar irradiation (1 sun) scenarios. However, under single-stage design and low-solar irradiation, thin film emerges as a viable and cost-effective alternative. At high solar concentrations, the performance gap between aerogel and other materials narrows, making acrylic a suitable substitute maintaining both efficiency and cost-effectiveness. Experimental results show that the optimized cover thickness for aerogel was 6 mm achieving an evaporation rate of 6.25 kg m⁻² h⁻¹ under 1 sun. These results highlight the critical role of cover material properties in enhancing solar evaporator efficiency, offering valuable insights for the development of high-performance, sustainable water purification systems.