TY - JOUR
AU - Yu, Zongfu
AB - Efficient solar vapor generation has been attracting a lot of attention for its potential in various applications, such as desalination, sterilization and chemical purification with a minimal carbon footprint. Tremendous progress has been achieved with materials designs for photon [1–3] and thermal management [4–6]. However, with those improvements, losses related to convection and conduction start to dominate. For this reason, it becomes essential to minimize losses related to radiation, convection and conduction simultaneously for optimal solar steam performance and widespread application. So far, high solar-to-heat conversion efficiency (∼80%) can only be achieved by using complicated structures [1]. In an article published in the National Science Review, the Zhu group from Nanjing University demonstrated a new concept: ‘artificial transpiration.’ The method, inspired by the transpiration processes of trees, uses a 3D hollow-cone structure based on graphene oxide film (black hollow cone in Fig. 1) [7]. In this unique 3D artificial transpiration device, conduction loss was suppressed by designing a 1D water path. The radiation and convection losses were also suppressed by increasing the surface area of evaporation. As a result, this artificial transpiration device enables over 85% solar-to-heat efficiency under one sun irradiation. Figure 1. Open in new tabDownload slide Schematics of different solar steam generators reported by Zhu et al. (a) Traditional 2D direct contact. (b) 3D artificial transpiration device; the red straight and blue arrows represent the direction of heat conduction and water supply, respectively, while the red wavy arrows represent the direction of heat convection and radiation. Adapted from [7]. Another feature of this 3D structure is the ability to collect more sunlight throughout the day compared with a 2D flat horizontal device—about 24% more—because around 10–50% of sunlight is diffusive. Thus it performs even better in the real world than in the laboratory. The total evaporation rate of the 3D artificial transpiration device is 2.52× higher than that of the 2D direct contact device. Zhu's group first applied this structure to the solar waste-water treatment, which includes two pathways, producing clean water (as shown in Fig. 2a) and recycling heavy metals such as copper and cadmium (as shown in Fig. 2b). Figure 2. Open in new tabDownload slide The performance of solar waste-water treatment reported by Zhu and colleagues. (a) Concentrations of different heavy metal ions before and after treatment. The blue colored lines represent the WHO’s drinkable water standards. (b) Output of purified water over irradiation time; inset, an optical image of an absorber with recovered CuSO4.5H2O crystal after 5 h of irradiation. Adapted from [7]. Overall, this approach opens up many new possibilities to harvest and utilize solar thermal energy. In the future, the structure can be further optimized to recycle more heavy metals and increase the device life time. As new challenges arise in optimizing the device's performance, a research frontier for solar thermal energy conversion is emerging. REFERENCES 1. Zhou L , Tan YL, Wang JYet al. Nat Photon 2016 ; 10 : 393 – 8 . 2. Bae K , Kang G, Cho SKet al. Nat Commun 2015 ; 6 : 10103 1–9 . 3. Neuman O , Ferontic C, Neumannc ADet al. Proc Natl Acad Sci USA 2013 ; 110 : 11677 – 81 . 4. Ghasemi H , Ni G, Marconnet AMet al. Nat Commun 2014 ; 5 : 44491 – 7 . 5. Li XQ , Xu WC, Tang MYet al. Proc Natl Acad Sci USA 2016 ; 113 : 13953 – 8 . 6. Ni G , Li G, Boriskina SVet al. Nat Energy 2016 ; 1 : 16126 . 7. Li XQ , Lin RX, Ni Get al. Natl Sci Rev 2018 ; 1 : 70 – 7 . © The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is properly cited. for commercial re-use, please contact journals.permissions@oup.com © The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
TI - Artificial transpiration: an efficient means of waste-water treatment
JF - National Science Review
DO - 10.1093/nsr/nwx088
DA - 2018-03-01
UR - https://www.deepdyve.com/lp/oxford-university-press/artificial-transpiration-an-efficient-means-of-waste-water-treatment-AaUyGQwg04
SP - 120
EP - 121
VL - 5
IS - 2
DP - DeepDyve
ER -