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Enhanced performance of a direct contact membrane distillation (DCMD) system with a Ti/MgF2 solar absorber under actual weather environments

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Abstract

In this study, we report on a solar membrane distillation (MD) system with a 5-stack Ti/MgF2 solar absorber adapted as a heat source under actual weather conditions. The 5-stack Ti/MgF2 solar absorber showed light absorption of 85% over the wavelength range from 0.3 to 2.5 μm. This consequently induced greater heat and a two-fold greater water heating capability up to 80 °C for water in a closed water tank without insulation under a 1-sun illumination. The enhanced solar absorption of the Ti/MgF2 solar absorber showed a 12% improvement in permeate flux of the integrated MD system compared with a system without a solar absorber. Under actual weather conditions, the solar DCMD system with the Ti/MgF2 solar absorber successfully produced distillate water in the range of 0.51–4.78 L/m²·day depending on weather conditions. Despite unfavorable solar irradiance conditions in autumn, the integrated DCMD system with the Ti/MgF2 solar absorber proved superior to a conventional commercial evacuated-tube solar collector in terms of daily production of distillate water and solar energy requirements for certain amounts of distillate.

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... (Wan et al. 2016;Yu et al. 2020;Lu et al. 2020). Silicon dioxide (SiO 2 ) and magnesium fluoride (MgF 2 ) can be used in many fields such as protective multifunctional coatings (Mashtalyar et al. 2017), medical fields (Kao et al. 2011), biomedical applications (Tian and Liu 2015), optical coating fields , antireflective coatings (Zuccon et al. 2014;Lin et al. 2011;Piao et al. 2019), surface corrosion resistance (Sarkar et al. 2020;Mashtalyar et al. 2020), and solar membrane distillation (Shin et al. 2020). These layers together are achieved a graded refractive index from the air for distillation water to verify high transmittance in the visible spectrum (Wang et al. 2012). ...
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In search of new sources of water supply, seawater desalination is increasingly recognized as a viable option. In arid coastal areas, the lack of fresh water coincides often with an abundance of solar energy. Coupling desalination systems with renewable energy technologies is of great importance. Project SMADES funded by the EC has sponsored the development of a so-called “large SMADES” system. The system is designed to provide high quality potable water in remote coastal areas with low infrastructure and without connection to a grid. The energy for the desalination process is supplied entirely by solar thermal collectors in the form of heat on a temperature level of 60°C to 80°C. The desalination units are improved membrane distillation (MD) modules with internal heat recovery function. The electrical auxiliary energy which is required to drive the pumps and valves for the automatically operated systems is supplied by PV panels. The collector area is 72 m2, the hydraulic loop of the collector field comprises a solar heat storage tank of 3 m3 and the collector loop is separated from the seawater loop of the MDdesalination-modules. Automatic controls start up the desalination unit whenever sufficient sunlight is present to provide hot water and electricity for pumping from the solar collectors and PV panels. This paper describes this plant that has been assembled at the Marine Science Station (MSS) of Aqaba, Jordan, and presents the results of the first few months of operation. The feed water was seawater directly from the Red Sea.
Article
This paper presents an assessment of membrane distillation (MD) based on the available state of the art and on ourpreliminary analysis. The process has many desirable properties such as low energy consumption, ability to use low temperature heat, compactness, and perceivably more immunity to fouling than other membrane processes. Within the tested range, the operating parameters of conventional MD configurations have the following effects:(1) the permeate fluxes can significantly be improved by increasing the hot feed temperature (increasing the temperature from 50 to 70°C increases the flux by more than three-fold), and by reducing the vapor/air gap (reducing the vapor air gap thickness from 5 to 1 mm increase the flux 2.3-fold); (2) the mass flow rate of the feed solution has a smaller effect: increasing it three-fold increases the flux by about 1.3-fold; (3) the concentration of the solute has slight effect: increasing the concentration by more than five-fold decreases the flux by just 1.15-fold; (4) the cold side conditions have a lower effect (about half) on the flux than the hot side; (5) the coolant mass flow rate has a negligible effect; (6) the coolant temperature has a lower effect than the mass flow rate of the hot solution. Fouling effects, membranes used, energy consumption, system applications and configurations, and very approximate cost estimates are presented. The permeate fluxes obtained by the different researchers seem to disagree by an order of magnitude, and better experimental work is needed.
Solar absorber material and system designs for photothermal water vaporization towards clean water and energy production
  • M Gao
  • L Zhu
  • C K Peh
  • G W Gim
M. Gao, L. Zhu, C.K. Peh, G.W. Gim, Solar absorber material and system designs for photothermal water vaporization towards clean water and energy production, Energy Environ. Sci. 12 (2019) 841-864.
  • W Li
  • U Guler
  • N Kinsey
  • G V Naik
  • A Boltasseva
  • J Guan
  • V M Shalaev
  • A V Kildishev
W. Li, U. Guler, N. Kinsey, G.V. Naik, A. Boltasseva, J. Guan, V.M. Shalaev, A.V. Kildishev, Refractory plasmonics with titanium nitride: broadband metamaterial absorber, Adv. Mater. 26 (2014) 7959-7965.