Chung-Ang University achieves dual-purpose breakthrough: Turning water into electricity while detecting fires

Various clean energy technologies have been developed to meet the rapidly intensifying energy demand and dwindling fossil fuel reserves. However, many of these technologies are hindered by low efficiency and high costs. Hydrovoltaic (HV) mechanisms, in which electricity is generated by the direct interaction of nanostructured materials and water molecules, have recently emerged as promising, cost-efficient alternatives. HV systems show particular promise for powering electrical sensors, including fire sensors.

Traditional fire sensors rely on batteries to operate during power outages, but these batteries can explode during fires. In contrast, HV systems draw energy from water, where the device is partially immersed in it, making them a safer alternative. Additionally, traditional fire sensors face challenges such as false alarms triggered by cooking smoke, steam, or dust, along with high maintenance needs and limited lifespans. HV systems overcome these limitations by responding only to evaporation-driven changes to water flow, such as those caused by fire. Despite their potential, no studies have yet explored the integration of HV systems in fire-sensing applications.

In a recent study, a research team led by Associate Professor Byungil Hwang from the School of Integrative Engineering at Chung-Ang University developed an innovative HV device that doubles as a fire sensor. “Our hydrovoltaic system can produce up to a few tens of microwatts, making it perfect for small-scale applications like fire detectors and health monitoring systems. This system is self-reliant, requires only a few milliliters of water, and has a fast response time,” explains Prof. Hwang. Their study was made available online on January 04, 2025, and published in the Chemical Engineering Journal on February 01, 2025.

HV systems consist of hydrophilic substrates covered with a nanoporous layer with a highly charged surface capable of attracting protons from water. When immersed in water, protons are drawn to the negatively charged surface of the nanostructure, forming an electrical double layer (EDL). The EDL consists of two parallel layers of opposite charges on either side of a surface, in this case, the HV system’s nanostructure. Evaporation, caused by increased temperature from visible light or infrared light or a fire, acts as a driving force, causing water to flow from this immersed region to the non-immersed region via capillary action. This flow of water generates an asymmetry of proton densities, causing a potential difference along the direction of flow, known as the streaming potential, which can then be harnessed to produce electricity.

The device proposed in the study utilizes waste cotton integrated with Triton X-100 and PPy, collectively termed CPT, as the nanoporous layer. This CPT layer is placed into a cylindrical tube with corrosion-resistant aluminum electrodes at both ends, part of which is immersed in water. The black color of PPy enhances light absorption and therefore evaporation on the non-immersed end, while Triton X-100 induces a high surface charge in the EDL, facilitating a high voltage generation. This design allows electricity generation simply by shining light onto the device.

Testing revealed that the device can generate a maximum voltage of 0.42 Volts and 16 – 20 microamperes of current under infrared light. As a fire-sensing device, it exhibits a fast response time of 5-10 seconds. Furthermore, it maintained excellent stability over 28 days of continuous testing, with no corrosion or degradation in performance, indicating long-term viability. It also performed robustly under varying environments.

“This is the first demonstration of using a hydrovoltaic system in a fire sensing application,” notes Prof. Hwang. “Our HV system has the potential to be a sustainable power source for various sensor systems, such as health and environmental monitoring systems that require uninterrupted operation.”

This innovative device demonstrates how sustainable small-scale energy systems can revolutionize applications like fire detection, health monitoring, and environmental sensing.

***

Reference                                    

Authors: Sujith Lal^a, Sudip K. Batabyal^b,c, Ergang Wang^d, Byungil Hwang^a*

Title of original paper: Photo-sensitive hydrovoltaic energy harvester with fire-sensing functionality

Journal: Chemical Engineering Journal

DOI: https://doi.org/10.1016/j.cej.2025.159281

Affiliations:

^aSchool of Integrative Engineering, Chung-Ang University, Republic of Korea

^bDepartment of Physics, Amrita School of Physical Sciences, India

^cAmrita Center for Industrial Research & Innovation (ACIRI), Amrita School of Engineering, Amrita Vishwa Vidyapeetham, India

^dDepartment of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden

Corresponding author’s email: bihwang@cau.ac.kr

About Chung-Ang University

Chung-Ang University is a private comprehensive research university located in Seoul, South Korea. It was started as a kindergarten in 1916 and attained university status in 1953. It is fully accredited by the Ministry of Education of Korea. Chung-Ang University conducts research activities under the slogan of “Justice and Truth” Its new vision for completing 100 years is “The Global Creative Leader” Chung-Ang University offers undergraduate, postgraduate, and doctoral programs, which encompass a law school, management program, and medical school; it has 16 undergraduate and graduate schools each. Chung-Ang University’s culture and arts programs are considered the best in Korea

Website: https://neweng.cau.ac.kr/index.do

About Associate Professor Byungil Hwang

Byungil Hwang is currently an Associate Professor at the School of Integrative Engineering at Chung-Ang University. His research group focuses on developing novel materials for energy harvesting systems, particularly hydrovoltaic energy harvesters. They investigate various polymer matrix composite materials for applications in wearable systems. The group also emphasizes enhancing material reliability through the implementation of advanced characterization techniques, such as optical fiber sensing, peak force quantitative nanomechanical mapping with atomic force microscopy, and nanoindentation. Prior to joining Chung-Ang University, Dr. Hwang worked at BASF, where he developed a range of nanomaterials for flexible electronics.

Website: https://scholarworks.bwise.kr/cau/researcher-profile?ep=1075