Tapping into the Future with TENG by Madison Kidd

 Tapping into the Future with TENG

By Madison Kidd

Imagine a future where rainwater powers entire homes—a concept that sounds like science fiction yet is becoming a reality. Thanks to advances in renewable energy research, triboelectric nanogenerators (TENGs) offer the potential to harness rainwater as a sustainable energy source. Through the continued research into renewable energies to combat climate change, a unique discovery was made and has the potential to generate power with just the use of rainwater and a small system. It is a complex application of charge transferring through TENG, but the charge captured over time could significantly impact the environment. 

This innovative technology has already been applied to wearable systems, such as the 'Self-Powering Smart Suit' developed at the University of Wollongong, Australia. It is powered entirely by these nano generators capturing the kinetic energy of the person wearing it. From the smallest of movements, to swinging your arms back and forth, the smart suit uses a TENG mode, to power multiple LEDs, a remote control, an LCD screen and more.[1]

Figure 1: Self-Powering Smart Suit with TENG

The core principle behind TENG applications is to identify small mechanical forces, like movements in a smart-suit, and amplify them into significant energy sources. Prior to the energy generation application discovery, the nano generators were mainly used for sensing very small mechanical movements, such as cracks in buildings or concrete, water movement and even sound waves. Rudimentary testing began in 2015 for a wide variety of applications for energy generation as unique as structural vibrations, cellular bioelectrical stimulation, and ice and water based TENGs.[2] In May of 2023, a group at a University in China conducted a research project to create a large-scale raindrop energy harvester utilizing the technology of TENG. The team took their knowledge of the natural charge of rain water, and experimented on what additional materials will create the highest potential difference to generate energy.[3] This research cannot be fully understood until we focus on how TENG works and how energy is generated from it. 

There are many different ‘modes’ when it comes to TENG. The different modes are used for different applications. For the smart suit, the contact-separation mode is used when the movement of the person wearing the suit interacts with the nanogenerator technology, causing a charge transfer. Other modes are used for different applications such as sliding or freestanding.[4] For the rainwater harvesting, a new mode of TENG is utilized, R-TENG (rainwater triboelectric nanogenerator). The process has to do with the overall idea of the triboelectric effect, which describes the charge between materials as they make contact with each other and how this charge moves through the system. This charge transfer can be captured and converted into energy. The R-TENG mode is much more complex than the initial modes discovered in 2015 by Wang Zhong Lin in China.[4]

The schematic in Figure 2, generated by the research group, captures the full sequence of this TENG mode, and how the charge is transferred. The grey top layer is a natural electronegative material, such as a plastic or polymer, that does not conduct electricity. This means that this layer of material will always remain negative, which influences the movement of electrons around them. The layer beneath this, the bottom electrode, is often a metal, as it must be an electropositive material, which conducts electricity. This layer is connected to the top small yellow stripe, the top electrode, made of another conductive material through a wired connection and a diode. As rainwater makes contact with the system, the diode facilitates charge transfer between the electrodes, much like a gate, allowing energy to be captured efficiently before the water continues its flow. As the drop begins to contract due to surface tension, the charge begins to flow back through the diode to the bottom electrode. Once the water flows past the system, the bottom electrode gains its full positive charge back and the cycle continues.[3]

Figure 2: R-TENG Process[3]

The charge difference between the top and the bottom electrode are measured and captured when the current is the highest when the water drop is in contact with the top electrode, and used to charge a battery. 

Now, it doesn’t take someone very versed in the triboelectric effect to take away that the power generated from one raindrop cannot be that much. While this is true, think about the sheer amount of rain that falls every year. According to NJ.gov, the average precipitation in New Jersey can vary from 40-55 inches/year. That comes to be around 34 gallons per year per square foot of surface area. Now, how can this be utilized to generate electricity from all of that rain water? My design team at the Stevens Institute of Technology has developed a solution that optimally incorporates insights from this study into a practical application.

Our team was tasked with finding a way to integrate TENG into a roof system to generate electricity for the household. If you think about how a roof works in regards to precipitation, it follows the same cycle: rain hits the roof and slides down the incline, the water collects in the pitched gutter and flows down towards the downspout to be redirected to the ground. In this process, all the water that hits the roof ends up going down the downspout. With an average New Jersey roof size of 1,700 square feet, an average gutter will direct almost 50,000 gallons of water every year to the downspout. 

With all of this in mind, the team set their eyes on integrating the R-TENG design into downspouts, for all 50,000 gallons to flow over the system. Although the team is still in the prototype stage, the results are promising, as the energy output could make up to a calculated 50% of an average household's electricity usage at this stage. A CAD model of the multiple TENG layers alternating down a downspout can be seen in Figure 3 below. As the rain water goes down the first incline, most of the charge is transferred, but in order to get all of the potential out of the raindrop, there are multiple stacked TENGs so the process repeats as the drops falls down. 

Figure 3: R-TENG Downspout Prototype

 

With all of the different forms of renewable energy out in the world today, TENG technology is by far one of the most recent discoveries being found in 2012. It is also by far one of the least expensive. Wind turbines require millions of dollars for the turbines themselves and cause concerns for the aviation population. Solar cells for roofs are expensive and not suitable for all residential houses based on sun-exposure. Hydro-power requires millions of dollars to create the dams and turbine systems to generate energy. Nuclear power is one of the most controversial forms of renewable energy, with the disposal process and the downpayment. Due to the small size needed for these nanogenerators to generate energy and the use of abundant materials, the cost is exceedingly less than other forms. The product created by my team replaces an already existing roof system, and simply integrates the technology into the system to let the rain water work for you. 

The potential of triboelectric nanogenerators (TENGs) to revolutionize renewable energy systems is undeniable. From self-powering wearable technology to rainwater harvesting integrated into everyday infrastructure, it offers an extraordinary glimpse into a future where energy generation is both sustainable and seamlessly embedded in the world around us, without us noticing. By harnessing the power of rainwater through innovative designs like the R-TENG downspout prototype, we can unlock vast amounts of untapped energy. This vision of powering homes with a natural resource as abundant and overlooked as rainwater challenges us to rethink traditional energy paradigms and embrace cost-effective, scalable solutions.
As the world grapples with the urgent need for climate action, TENG technology stands out not just for its ingenuity, but also for its accessibility and affordability. While the journey to full-scale implementation is still underway, the breakthroughs we are witnessing today signal a transformative shift. By continuing to refine and expand on these designs, we are not just creating new energy sources but paving the way for a more resilient and innovative world. TENG represents the future of energy, proving that even the smallest forces—like a single raindrop—can drive monumental change.

Works Cited 

[1] Kim, Seonghyeon, Woosung Cho, Dong-Joon Won, and Joonwon Kim. “Textile-type Triboelectric Nanogenerator Using Teflon Wrapping Wires as Wearable Power Source.” Micro and Nano Systems Letters 10, no. 1 (July 5, 2022). https://doi.org/10.1186/s40486-022-00150-x.

[2] Choi, Dongwhi, Younghoon Lee, Zong-Hong Lin, Sumin Cho, Miso Kim, Chi Kit Ao, Siowling Soh, et al. “Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications.” ACS Nano 17, no. 12 (May 23, 2023): 11087–219. https://doi.org/10.1021/acsnano.2c12458.

[3] Yang, Yaowen, Bao Cao, Chao Yang, Zixun Wang, Haonan Zhang, Lin Fang, Wen He, and Peihong Wang. “A Droplet-based Multi-position and Multi-layered Triboelectric Nanogenerator for Large-scale Raindrop Energy Harvesting.” AIP Advances 13, no. 5 (May 1, 2023). https://doi.org/10.1063/5.0148345.

[4] Kim, Weon-Guk, Do-Wan Kim, Il-Woong Tcho, Jin-Ki Kim, Moon-Seok Kim, and Yang-Kyu Choi. “Triboelectric Nanogenerator: Structure, Mechanism, and Applications.” ACS Nano 15, no. 1 (January 11, 2021): 258–87. https://doi.org/10.1021/acsnano.0c09803.