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Yes—a 2017 laboratory prototype used sunlight to evaporate seawater and produced desalinated water while generating a small amount of electricity. The electricity did not come from desalination by itself: evaporation made the water near a light-absorbing surface saltier than the seawater below, and an ion-selective membrane used that salinity difference to generate electrical output. The study did not establish that the water met a drinking-water standard.
How the prototype made water and electricity
Peihua Yang and colleagues combined two processes in one small device. Carbon-nanotube-modified filter paper absorbed sunlight and heated the water at its surface, concentrating evaporation there. A commercial Nafion membrane sat beneath the evaporator. As water evaporated, the remaining water at the surface became saltier than the seawater below it, creating a salinity gradient across the membrane. The membrane selectively allowed ions to move, separating charge and producing an electrical potential and current at the electrodes. The 2017 paper describes the design and results.
Study leader Jun Zhou explained that the membrane “only allows positive ions to go through, which induces a charge imbalance on the two sides – generating an electrical potential as well as current from redox reactions at the electrodes.” In other words, solar heat drove evaporation, while the resulting difference in salt concentration supplied the gradient used for electricity generation.
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What the study reported
Under one-sun illumination, Yang and colleagues reported about 1 W m−2 of additional electrical power and a maximum solar thermal efficiency of up to 75%. The paper also gave a theoretical real-time salinity-power estimate of 12.5 W m−2 during steam production. That theoretical estimate is not the same as the additional electrical power reported from the device.
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The tested proof-of-concept device had an area of 100 cm2, according to Chemistry World’s 2017 report. These are results from a small research demonstration, not a commercial-scale performance claim.
How to interpret the claimed salinity advantage
Zhou said the salinity difference produced at the device surface could have “six times” the energy density of the difference between river water and seawater. That was his explanation of the local gradient in this concept, not a general estimate for every desalination system or salinity-gradient technology.
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The reported output also needs scale context. Doriano Brogioli, a University of Bremen researcher working on salinity-gradient energy, called the device’s 1 W m−2 power density “relatively good,” but compared it with 10–20 W m−2 for solar panels. That range was his comparison in the 2017 report, not an independent measurement of the prototype.
What the results do—and do not—show
The experiment supports the idea that solar-driven evaporation can create a salt concentration difference that a membrane-based system uses to generate electricity while producing desalinated water. It does not show that the water was certified safe to drink: the reviewed accounts do not report a drinking-water standard test.
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Brogioli also questioned the device’s practical feasibility, warning that its silver electrodes were consumed during operation and that silver dissolution could pollute the water. This was his caution about the design, not a reported lifecycle assessment. The 2017 sources establish the proof of concept and its reported figures; they do not establish later field performance or commercial deployment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What would matter in a practical comparison
A fair comparison with a solar still, photovoltaic-powered desalination system, or another salinity-gradient device would need consistent evidence on several points:
- Water: freshwater yield and measured water quality, including whether it meets a stated drinking-water standard.
- Energy: net electrical output under clearly specified illumination and operating conditions, separated from theoretical estimates.
- Scale and duration: device area and how long the system was tested.
- Materials: membrane and electrode composition, replacement needs, and any contamination risks.
- Readiness: whether the result is a laboratory demonstration, a field-tested system, or a commercial deployment.
The 2017 accounts do not provide enough consistent comparative data to rank this prototype against those alternatives.
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