High-Efficiency Superheated Steam Generation for Portable Sterilization under Ambient Pressure and Low Solar Flux

Abstract

Superheated solar steam generation above 100 °C is critical for many important applications such as sterilization but is challenging to achieve under natural fluctuating low-flux solar illumination and often requires pressurization and the usage of expensive optical concentrators. Herein, we demonstrate generation of superheated steam under ambient pressure and low-flux solar illumination by integrating a recently emerged interfacial evaporation design into a solar vacuum tube. Within the tube, the water vapor, which is generated by a high-efficiency localized heating-based evaporator, is further heated by a heat exchanger into superheated steam without pressurization. The steam generator has shown tunable steam temperature from 102 to 165 °C and solar-to-steam conversion efficiency from 26 to 49% under 1 sun illumination. Owing to the minimized heat loss from the solar vacuum tube and the interfacial evaporation design, it enables stable generation of steam above 121 °C under ambient fluctuating solar illumination with an averaged solar flux of ∼600 W/m 2 . Effective sterilization is verified using both the Geobacillus stearothermophilus biological indicator and Escherichia coli bacteria, making portable solar steam sterilization and other steam-related applications feasible under ambient solar illumination.

A Passive High-Temperature High-Pressure Solar Steam Generator for Medical Sterilization

“…12,15,19,31,33,[49][50][51][52][53][54][55] A few recent studies employed a subsequent superheating stage to boost the steam temperature beyond 100 C in open systems (open symbols in quadrant II). 20,32,48 This work demonstrates that it is possible to generate saturated and pressurized steam with low optical concentration represented by the only filled symbol in quadrant II.…”

“…A few studies have shown the possibility to further boost the steam temperature via a subsequent superheating stage (open symbols in quadrant II). 20,32,48 However, due to the relatively low efficiency, a pressurized saturated steam generation beyond 100 C was only available in quadrant I in previous research. Enabled by the highly efficient thermal concentration approach, this work provides a viable solution for generating saturated and pressurized steam-represented by the filled star in quadrant II.…”

Electrically Driven Interfacial Evaporation for High-Efficiency Steam Generation and Sterilization

“…The Escherichia coli bacteria were used as the indicator in the steam sterilization experiments. 46 The sterile tubes containing the bacterial solution were exposed to hot steam within the sanitizer for 15 min under a heating power density of 18 kW/m 2 (Figure S8). Figure 5d presents that all the E. coli bacterial cells were killed by the LIEH-based steam sanitizer, but many bacteria cells were still alive after treatment in the BEH-based steam sanitizer due to the low vapor temperature.…”

Structure Architecting for Salt‐Rejecting Solar Interfacial Desalination to Achieve High‐Performance Evaporation With In Situ Energy Generation

“…For example, the heat carried by hot water vapor can be recycled for electricity generation via thermoelectric ( Figure a) and thermomechanical effects (Figure 15b), [ 66,83 ] or directly utilized for rapid sterilization. [ 81,150–152 ] Converting downward heat loss into electricity has also been demonstrated through thermoelectric method as shown in Figure 15c, which is achieved by taking the advantage of inherently established temperature difference between hot solar absorber and cool water body. [ 68,79,85 ]…”