Passive solar high-yield seawater desalination by modular and low-cost distillation


Although seawater is abundant, desalination is energy intensive and expensive. Using the Sun as an energy source is attractive for desalinating seawater. Although interesting, current passive devices with no moving parts have unsatisfactory performance when operated with an energy flux lower than 1 kW m−2 (one sun). We present a passive multi-stage and low-cost solar distiller, where efficient energy management leads to significant enhancement in freshwater yield. Each unit stage for complete distillation is made of two hydrophilic layers separated by a hydrophobic microporous membrane, with no other mechanical ancillaries. Under realistic conditions, we demonstrate a distillate flow rate of almost 3 l m−2 h−1 from seawater at less than one sun—twice the yield of recent passive complete distillation systems. Theoretical models also suggest that the concept has the potential to further double the observed distillate rate. In perspective, this system may help satisfy the freshwater needs in isolated and impoverished communities in a sustainable way.

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Fig. 1: Layout of the solar passive distiller during day hours.
Fig. 2: Desalination performance of the modular distiller.
Fig. 3: Salt removal and durability of desalination performance during night hours.
Fig. 4: Comparison of the modular passive distiller with other solar desalination technologies, and its possible application.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information files.


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The authors are grateful to ‘Fondazione CRT—Torino’ under the NANOSTEP project (‘La Ricerca dei Talenti’ call; grant number 911/2015). E.C. acknowledges partial financial support from the Politecnico di Torino through the Starting Grant (grant number 56_RIL16CHE01). The authors also thank M. Bressan and R. Costantino for laboratory support, S. Pezzana (Almeco Group) for providing experimental materials, and P. Ornolio and the Marina di Varazze and Lega Navale Varazze institutions for hosting field tests of the floating distiller. In particular, we acknowledge L. Molin Pradel (Marina di Varazze) for generous hospitality. This work was performed under the auspices of the CleanWaterCenter@PoliTo (

Author information




P.A. initially suggested the study of a passive floating panel exploiting materials with high solar absorptance and hydrophobic microporous membranes for seawater desalination. E.C. conceived the ideas of both the thin hydrophilic layers separated by an air gap as a passive distiller unit (membrane-free solution) and the multi-stage gain of freshwater flux. P.A. developed the theoretical model and suggested the rinse strategy. M.M. and M.F. assembled the prototypes and conducted the computations. M.M. conducted the experiments with the help of F.V. and M.F. E.C. and P.A. supervised the research with the help of M.F. All authors contributed to writing the paper.

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Correspondence to Eliodoro Chiavazzo or Pietro Asinari.

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Supplementary information

Supplementary Information

Supplementary Notes 1–5, Supplementary Figures 1–17, Supplementary Tables 1–4, Supplementary references 1–43.

Supplementary Dataset 1

Raw data on distillate flow rates from lab, rooftop and sea experiments on 1-stage, 3-stage, and 10-stage distillers using either no membrane, 0.1 μm membrane or 3.0 μm membrane.

Supplementary Dataset 2

Raw data on temperatures and irradiance from lab, rooftop, and sea experiments on 1-stage, 3-stage, and 10-stage distillers using either no membrane, 0.1 μm membrane, or 3.0 μm membrane.

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Chiavazzo, E., Morciano, M., Viglino, F. et al. Passive solar high-yield seawater desalination by modular and low-cost distillation. Nat Sustain 1, 763–772 (2018).

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