A research team from Soochow University in China has developed a portable solar-powered device that produces drinking water from turbid, saline, oily and highly acidic water. The prototype produced 1.64 liters of clean water in eight hours using an evaporation surface measuring just 30.72 cm2.
The system uses an electrothermal evaporation process in which an electrically powered heating element heats a surface that absorbs contaminated water, causing the water to evaporate. The resulting vapor is collected and condensed into clean water, while salts and other contaminants remain in the source water.
The device’s main innovation is an interlayer electrothermal evaporator. Instead of heating the entire volume of the wet material, the researchers positioned the heating element within an internal layer of the structure.
This configuration reduces heat losses to the surrounding water and air. According to the study, the design reduced heat losses and energy consumption by nearly two-thirds compared with a conventional electrothermal evaporator based on volumetric heating.
The system also combines two sources of solar energy.
It features foldable solar cells that generate electricity to power the electrothermal evaporator, alongside a foldable Fresnel lens that concentrates sunlight directly onto the evaporation surface. The study does not specify the rated capacity or electrical characteristics of the PV system.
When accounting for concentrated solar energy, the device achieved an apparent energy efficiency of 93.31% and a water production rate of 69.46 liters per square meter per hour.
Outdoor tests showed that the prototype could produce 1.64 liters of drinking water in eight hours using an evaporation surface of 30.72 cm2, smaller than a standard bank card.
The researchers tested the system with different types of water, including sediment-laden water, oil-contaminated water, highly saline wastewater and strongly acidic water.
The tests also included real seawater, with the researchers analyzing water samples before and after treatment. Under concentrated sunlight, the system achieved evaporation rates exceeding 90 kg/m2 per hour.
The device integrates PV modules and an optical solar concentration system, allowing it to operate without a grid connection or external fuel supply. The researchers said the configuration could be used in areas where conventional water supply infrastructure is damaged or unavailable.
They also suggested that the technology could serve as a portable water treatment solution in emergencies, including floods, earthquakes and conflicts, where access to safe drinking water may be disrupted.
The researchers presented their findings in “Solar-operated interlayer electrothermal evaporator enabling instant high-flux freshwater production across multiple scenarios,” published in Nature Water. Outdoor tests were conducted using a small-scale prototype on selected days in January and February 2025.
The results demonstrate the feasibility of the concept, but larger systems and longer-term testing under real-world conditions are still needed to assess its potential for large-scale deployment.
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