Imagine a living plant leaf quietly producing electricity throughout the day—without batteries, solar panels, turbines, or fuel. This may sound futuristic, but scientists have now demonstrated a new form of green energy generation by harvesting electricity from one of nature’s most common processes: leaf transpiration.
In a recent study, Hu and colleagues developed a living leaf transpiration generator using a lotus leaf. Their device directly converts energy associated with water movement through the leaf into electrical power. The experiment reveals a previously overlooked form of the hydrovoltaic effect and could open a new direction for sustainable energy technologies.
What Is Hydrovoltaic Electricity?
Hydrovoltaic electricity refers to the generation of electrical energy through interactions between water and materials, often involving water movement, evaporation, or changes in moisture.
Researchers have explored several ways of producing electricity from water. These include evaporation, droplets moving across surfaces, flowing water, and moisture gradients.
But there is another enormous source of water movement happening around us every day: plants.
Plants continuously transport water from their roots toward their leaves. Once the water reaches the leaves, some of it escapes into the atmosphere through tiny openings called stomata. This natural process is known as transpiration.
Although transpiration is essential for plant life and represents one of the largest water fluxes on land, its potential for directly generating electricity has received comparatively little attention.
Hu and his team set out to explore whether this natural process could be turned into usable electrical energy.
The Leaf Becomes a Tiny Power Generator
For their experiment, the researchers used a lotus leaf as a living energy-generating component.
The basic idea is surprisingly simple.
Water absorbed by a plant moves through its internal vascular system before reaching the leaf. When water evaporates through the stomata, it creates continuous water movement within the plant.
The researchers designed a generator capable of capturing the electrical effects associated with this process.
Instead of cutting the leaf apart or converting it into a synthetic material, the system uses the living leaf itself.
This makes the concept particularly interesting because the energy source is not something artificially supplied to the device. It comes from a biological process that plants naturally perform.
Electricity Generated Throughout the Day
One of the most impressive results was the generator’s ability to produce electricity over extended periods.
The lotus-leaf-based system demonstrated sustained electricity generation throughout the day.
The researchers measured an open-circuit voltage of approximately 0.25 volts and a short-circuit current of about 50 nanoamps.
These values are small compared with the electricity produced by conventional solar panels or other commercial energy technologies. However, the importance of the study is not simply the amount of electricity generated by one leaf.
The experiment demonstrates that plant transpiration itself can be directly connected to electricity generation.
The researchers also found that the electrical output could be amplified by connecting multiple generators together.
Generators connected in series can increase the overall voltage, while connections in parallel can increase the available current.
This suggests that arrays containing many leaves or plant-based generators could potentially produce larger electrical outputs.
Why Transpiration Matters
To understand why this discovery is interesting, it helps to look at what happens inside a plant.
Plants continuously absorb water through their roots. That water travels upward through specialized tissues called xylem and eventually reaches the leaves.
Inside the leaves, water can evaporate through microscopic pores called stomata.
This process creates a continuous exchange between the plant and the atmosphere.
Transpiration also plays a major role in cooling plants and transporting nutrients. In fact, it is one of the fundamental processes that allows terrestrial plants to survive.
The new study suggests that this enormous natural movement of water may also have an electrical dimension that can be harvested.
In other words, a process that plants have been performing for hundreds of millions of years could potentially become part of future energy technologies.
What Controls the Electricity Output?
The researchers did not simply measure electricity generation. They also investigated which environmental and biological factors influenced the generator’s performance.
Their analysis showed that several factors were particularly important.
One was the transpiration rate.
When transpiration increased, electricity generation also improved. This makes intuitive sense because stronger transpiration means greater water movement through the leaf.
Another important factor was stomatal conductivity. Stomata control the movement of water vapor between the inside of the leaf and the surrounding atmosphere. When these microscopic openings become more conductive, transpiration can increase.
Temperature also influenced electricity generation. Changes in temperature can affect evaporation and transpiration, thereby changing the conditions under which electricity is produced.
However, not every environmental factor helped.
The researchers found that higher relative humidity had a counteractive effect. When the surrounding air contains more moisture, the driving force for water evaporation from the leaf decreases. As a result, transpiration can become weaker, reducing the electrical output.
This relationship highlights how closely the generator is connected to the natural physiology of the plant.
A New Type of Green Energy?
The study is important because it expands the idea of what can be considered a renewable energy source.
Solar panels capture sunlight. Wind turbines capture moving air. Hydroelectric systems capture flowing water.
A leaf transpiration generator takes a different approach: it captures energy associated with biological water movement.
Plants are widespread across the planet, and transpiration happens naturally whenever environmental conditions allow it.
This raises an intriguing possibility: could large numbers of leaves or plant-based systems one day be integrated into distributed micro-energy technologies?
For example, future research could explore whether plant-based generators might power extremely low-energy sensors, environmental monitoring devices, or other small electronic systems.
However, it is important not to exaggerate the current results. The demonstrated electrical output is still very small, and significant engineering challenges remain before this technology could become commercially useful.
Why This Discovery Matters
The real breakthrough is not that a single lotus leaf can replace a solar panel.
It cannot—not at present.
Instead, the study reveals a previously underexplored mechanism for harvesting energy from leaf transpiration.
The researchers have shown that a living plant can function as part of a hydrovoltaic electricity-generating system, transforming a natural biological process into measurable electrical output.
This creates an entirely new research direction at the intersection of plant biology, hydrovoltaic technology, materials science, and renewable energy.
Future studies may investigate other plant species, different environmental conditions, improved electrode designs, and methods for combining large numbers of generators.
Nature Could Be Hiding More Energy Sources
For billions of years, plants have been moving enormous quantities of water from soil into the atmosphere.
Humans traditionally viewed this mainly as a biological and ecological process.
The work by Hu and his team suggests that it may also represent an opportunity for energy harvesting.
The lotus leaf experiment demonstrates that natural transpiration can generate electricity, reaching 0.25 V in open-circuit conditions and 50 nA in short-circuit conditions, while multiple units can be connected to enhance the electrical output.
The concept is still at an early research stage, but its significance lies in the question it raises:
How many other natural processes around us are quietly carrying usable energy that we have not yet learned to harvest?
From sunlight falling on leaves to water moving through their microscopic tissues, nature continuously performs energy transformations. The challenge for scientists is discovering how to capture those processes efficiently without disrupting the systems that produce them.
The humble leaf may therefore have another role beyond producing oxygen and supporting ecosystems: it could become a blueprint for a new generation of tiny, biological green-energy technologies.
Reference: Hu, Q., Lin, X., Ren, G. et al. Hydrovoltaic electricity generation induced by living leaf transpiration. Nat Water 2, 988–998 (2024). https://doi.org/10.1038/s44221-024-00311-9
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