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Technology Created in Singapore Uses Narrow Tubes to Generate Electricity from Rain with 10% Efficiency, Lighting LEDs without Turbines or Dams.
A group of engineers from the National University of Singapore has developed an innovative system that efficiently converts raindrops into electricity without the need for large structures.
The new method can already power up to 12 LEDs for 20 seconds with just two small tubes.
The technique utilizes a little-explored physical phenomenon called piston flow to generate electricity directly from rainwater that flows through vertical tubes. The efficiency reaches 10% conversion of the energy from the droplets into electricity.
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Tubes Instead of Turbines
Unlike traditional hydropower plants that rely on dams, turbines, and large volumes of water, the new system developed in Singapore operates with narrow tubes and natural raindrops. It does not require complex installations or large reservoirs.
In a laboratory experiment, the researchers used a tower with a metal needle that released droplets with the same characteristics as natural rain.
The droplets fell into a tube 32 centimeters high and 2 millimeters in diameter, made from a conductive polymer. The tube was connected to wires that allowed for the collection of the electricity generated by the movement of the droplets.
Electricity was produced as the droplets descended, alternating with air pockets inside the tube.
This intermittent flow creates a charge separation that can be captured and transformed into usable energy.
Experiment Results
The system achieved an efficiency of 10% in converting the energy from the droplets into electricity. Compared to a continuous water flow, the piston flow method was five times more effective.
The energy generated by just two tubes was enough to keep 12 LEDs lit for 20 seconds.
This is just the beginning. The expectation is that thousands of tubes installed together could power entire parts of buildings in regions with frequent rain.
Applications in Urban and Rural Areas
One of the strengths of the system is its versatility.
As it does not depend on rivers or dams, it can be installed on rooftops of houses and buildings, green walls, gutters, or any vertical structure.
It can also benefit remote communities that do not have easy access to the electrical grid.
By installing many of these tubes, it would be possible to take advantage of rainy periods to generate additional electricity in a decentralized and continuous manner.
The technology could also be used in conjunction with solar panels, utilizing cloudy and rainy periods to compensate for low solar generation.
Proven Performance and Efficiency
The researchers detailed the advancements of the study in the scientific article “Plug Flow: Generating Renewable Electricity with Water from Nature by Breaking the Limit of Debye Length,” published in the journal ACS Central Science in April 2025.
The work showed that the system surpasses an old physical limit of electricity generation on a millimeter scale, known as the Debye length, which limited efficient charge separation to distances below one micrometer. With the new method, this barrier has been overcome.
In the piston flow system, the liquid moves in columns separated by air, allowing for effective ion separation. The OH⁻ adheres to the walls of the tube, while the more mobile H⁺ carries on with the water. This generates a positively charged liquid and a negatively charged surface, producing continuous electric current at both ends of the tube.
Tests with Different Types of Water
The tests showed that the system works not only with rainwater but also with tap water and even saltwater.
Furthermore, the technology maintained its efficiency even with temperature variations ranging from 4 °C to 50 °C and demonstrated stability for at least seven consecutive days of use.
The average power generated by a single tube was 440 μW, with an energy density of approximately 100 W per square meter.
These numbers represent an improvement of up to five orders of magnitude compared to previous continuous flow methods.
Practical Demonstrations
In addition to lighting LEDs, the researchers demonstrated other possible applications with the generated electricity. These include plasma generation, chemical reactions, surface modification, charging liquids and solids, and detecting radicals through tests with DPPH.
These experiments reinforce the potential of the new technique for diverse uses, both in energy and in industrial or scientific processes.
Another relevant point is that the system does not require pre-charges, advanced electronics, or expensive materials. This makes the method accessible, inexpensive, and easy to scale.
According to the engineers responsible for the study, this approach could represent a new category of energy generation based on intermittent flow and interfacial chemistry, surpassing old theoretical limits.
They believe that this innovation could become a fundamental part of a more ecological energy matrix and adapted to varied urban and climatic realities.
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