EPS Nordic Seminar: Efficiency optimization for large-scale droplet-based electricity generator arrays with integrated microsupercapacitor arrays

#energy-storage #energy-harvesting

Water energy, from raindrops, rivers, and waves, is a vast renewable resource. Droplet-based electricity generators (DEGs) are lightweight, nearly metal-free, and offer high power density, making them promising for harvesting this energy. However, two critical challenges hinder their practical application: significant performance degradation, potentially up to 90%, in existing small-scale integrated panels, and low efficiency, often less than 2%, in storing the irregular high-voltage pulsed electricity produced by large-scale arrays. In this walk, I will introduce our recent progress in scaling up DEGs. By tailoring the bottom electrodes so that their area is comparable to the spread area of the impinging water droplets, we double the average output power of individual cells and fabricate large-scale (30-cell) arrays that achieve approximately 2.5 times higher power than state-of-the-art arrays. Furthermore, without using any power management chip, we integrate a large-scale (400-cell) micro-supercapacitor array to store the irregular high-voltage electricity produced by the 30-cell generator array at an efficiency of 21.8%. The integration of large-scale electricity generators and micro-supercapacitor arrays forms a simple, chipless, self-charging power system with an output power of 81.2 μW, which is 27 times higher than current systems based on 30-cell arrays. This work provides important insights towards practical applications of droplet-based electricity generators.

Mr. Zheng Li is a PhD candidate at KTH Royal Institute of Technology, Sweden. He acquired his bachelor's degree from Southeast University, China in 2019, and master’s degree from KTH in 2022. During his master study, he developed a highly conductive metal-free ink based on conducting polymer and graphene to enable the scalable fabrication of high-rate on-paper micro-supercapacitors (MSCs). The research was published in [Advanced Functional Materials 32, 2108773 (2022)] and highlighted by [Nature Electronics 4, 769 (2021)]. In his PhD study, Zheng continues to use the high-rate MSCs to improve the energy storage efficiency of the emerging droplet-based electricity generators, as published in [Nature Communications 16, 8530 (2025)].

Email: zheng2@kth.se 

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• Kistagången 16
• Kista, Stockholms lan
• Sweden 16440
• Building: Electrum
• Room Number: Faculty Lounge

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