Evapoelectrics is an energy harvesting approach that directly converts heat released during water evaporation into electricity using thermoelectric generators (TEGs). Unlike hydrovoltaic systems, which first turn moisture into mechanical energy and then into electricity, evapoelectrics skips this step and relies on direct conversion.1 The technique was first discussed in a July 2025 paper.2
Image Credit: ACS Nano 2025, 19, 28, 26249-26258
Evapoelectrics principles are based on evaporation physics. When water changes from liquid to vapor, it absorbs around 2250 joules per gram, producing a cooling effect. This cooling creates temperature gradients that thermoelectric generators convert into electrical power. 1
The device design is straightforward. It uses a thermoelectric generator placed between two heat sinks, with one heat sink consisting of a porous polyvinyl alcohol (PVA) hydrogel that absorbs water and enables evaporation. The other is kept near ambient temperature. As water evaporates from the hydrogel, the surface cools and creates the temperature difference between the two heat sinks. This gradient drives heat flow, which the thermoelectric generator converts into electricity.1
Performance and Efficiency Advantages of Evapoelectrics
Current evapoelectric devices show measurable improvements over other moisture-based energy technologies. Studies indicate that this direct conversion approach produces roughly twice the output of existing hydrovoltaic systems. In demonstrations, it has been sufficient to power small electronic components such as LCD displays.1
Efficiency remains a limitation. Present systems operate at around 0.1 percent efficiency, comparable to early photovoltaic devices. Researchers acknowledge this challenge but suggest that material and design improvements could increase efficiency levels in future versions.1
The approach also offers some advantages over solar and wind energy. While those depend on weather conditions, evaporation occurs in most environments on a continuous basis. This makes evapoelectrics a potentially useful option for steady, low-level power generation.2
Evapoelectrics: Applications and Market Potential
The most immediate applications for evapoelectrics are in powering small, low-energy devices where conventional batteries or power connections are less practical. Wearable devices, such as smartwatches, fitness trackers, and health monitoring sensors, represent a key potential market. These systems could draw energy from ambient humidity or perspiration, allowing them to operate continuously without frequent battery changes.1
Other opportunities include medical sensors and environmental monitoring equipment. These devices are often deployed in remote areas where replacing batteries is difficult or expensive. Evapoelectric systems could supply a steady source of power from environmental moisture, reducing maintenance requirements.
Market data also supports interest in this area. The global energy harvesting sector was valued at $634.3 million in 2024 and is forecast to grow at 8.8% annually through 2034, driven by demand for sustainable power solutions across multiple sectors.3 This trend suggests a favorable environment for technologies such as evapoelectrics.
Technical Challenges and Future Development
Several engineering challenges remain before evapoelectrics can be widely adopted. One major issue is maintaining a continuous water supply. Current prototypes require regular replenishment, which limits their practicality in many applications. Researchers are testing solutions such as atmospheric water harvesting and integration with existing water systems.1
Material development is another focus. The PVA hydrogel needs improvement to enhance water retention and evaporation rates while remaining durable over time. The thermoelectric generators also require optimization to more effectively capture and convert the relatively small temperature differences produced by evaporation.
Scaling is both a possibility and a challenge. Individual devices provide only modest power suitable for small electronics, but some studies suggest larger-scale implementations, such as floating generators on water bodies or turbine-like structures, could generate more significant electricity.4 The economic feasibility of such large systems, however, has not yet been demonstrated compared to established renewable options.
Industry Implications and the Future Outlook Evapoelectrics
Evapoelectrics fits into the broader trend of distributed energy generation and ambient energy harvesting. As electronic devices become more widespread and energy-efficient, there is growing demand for compact, low-maintenance power sources. This makes evapoelectrics a promising option for supporting the Internet of Things (IoT), where reliable, small-scale power is essential for networks of sensors and monitoring devices.
The technology also highlights ongoing progress in thermoelectric applications. While traditional thermoelectric systems have seen limited adoption due to efficiency challenges, approaches such as evapoelectrics show potential in targeted scenarios where they can be technically and economically viable.3
For the renewable energy sector, evapoelectrics is best viewed as a complementary option rather than a competitor to large-scale solar and wind. Its value lies in applications that require continuous, low-level power derived from ambient conditions.
There are also possibilities for integration with existing infrastructure. For example, evapoelectric units could be combined with solar panels, building ventilation systems, or industrial cooling processes to create hybrid energy systems that capture energy from multiple environmental sources.
Conclusion
Evapoelectrics illustrates how everyday physical processes, such as evaporation, can be used for energy generation. At present, efficiency constraints limit its use to small-scale electronics, but its capacity to deliver continuous power from environmental moisture makes it suitable for specific applications.
Further progress will depend on advances in material performance, system integration, and scaling methods. With improvements in efficiency and reductions in manufacturing costs, evapoelectrics could become part of the broader mix of renewable energy technologies, particularly for sensors and wearable devices that require low, steady power.
Its long-term role will be shaped by whether it can provide cost-effective solutions in situations where continuous operation, ambient energy harvesting, and minimal maintenance are clear advantages over alternatives.
References and Further Reading
- Orf, D. (2025, January 7). In an energy breakthrough, scientists just pulled electricity out of thin air. Popular Mechanics. https://www.popularmechanics.com/science/energy/a65625500/evapoelectricity-evaporation-energy/
- Cao, J., Dong, J., Wu, J., & Suwardi, A. (2025, July 10). Evapoelectrics: Direct harvesting of electricity from evaporation using thermoelectrics. ACS Nano, 19(28), 26249–26238. https://doi.org/10.1021/acsnano.5c10693
- Global Market Insights. (2024). Energy harvesting market size, analysis report 2025–2034. https://www.gminsights.com/industry-analysis/energy-harvesting-market
- Chi, H., Zhao, K., Zhou, W., et al. (2022). Harvesting water-evaporation-induced electricity based on liquid–solid triboelectric nanogenerator. Advanced Science, 9(28), 2201586. https://doi.org/10.1002/advs.202201586
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