A Fire Alarm That Runs on Water
Researchers developed a hydrovoltaic fire sensor that generates electricity from water, offers fast detection, and eliminates false alarms.
Each year, building fires are responsible for thousands of deaths and tens of billions of dollars in losses in the United States alone. Once a fire gets started, the best hope for a good outcome comes from early detection. A good fire alarm system alerts building occupants that they need to head for an exit immediately, and also gets the local fire department on the way to minimize damage to the structure and its contents.
Current fire detection systems, while effective in many scenarios, are not without a number of flaws. Traditional fire alarms often depend on batteries as backup power sources to operate during electrical outages, but these batteries pose risks of exploding under intense heat. Additionally, many alarms are prone to false triggers caused by everyday activities such as cooking, producing steam, or dust particles, which reduces trust in the system. These false alarms can lead to complacency, delays in response times, and unnecessary costs. Furthermore, maintaining and replacing traditional alarm systems can be expensive, especially in large facilities, as their components degrade over time.
Water: the best friend of firefighters since 1810
Seeking to address these challenges, researchers at Chung-Ang University have turned to an innovative technology that leverages advances in clean energy and materials science. In particular, they are working with hydrovoltaic (HV) systems — technologies that generate electricity through the interaction between water and nanostructured materials. In doing so, they have developed a novel HV device that serves as a fast-response fire sensor. This innovative system not only provides a safer and more reliable alternative to battery-based fire alarms but also offers sustainable, long-term functionality.
The new HV fire-sensing device capitalizes on the unique properties of hydrophilic materials and evaporation dynamics. The system features a nanoporous layer — referred to as the CPT layer — that was created from a combination of waste cotton, Triton X-100, and polypyrrole (PPy). This layer is housed in a cylindrical structure with corrosion-resistant aluminum electrodes at both ends. When part of the device is immersed in water, it forms an electrical double layer (EDL) by attracting protons to its charged nanostructure. As evaporation occurs due to increased temperatures — such as those caused by fire — it induces water movement from the immersed to the exposed region via capillary action. This flow creates a potential difference, known as the streaming potential, which the system harnesses to generate electricity.
The CPT design plays a crucial role in enhancing the device’s efficiency. The black color of PPy optimizes light absorption, increasing evaporation rates, while Triton X-100 boosts the surface charge in the EDL, enabling higher voltage generation. Tests of the device revealed that it could generate up to 0.42 volts and 16 to 20 microamps of current under infrared light, with a response time of just 5 to 10 seconds in fire scenarios.
Better, safer, easier
Unlike traditional fire alarms, this HV device does not rely on external power sources or batteries, making it inherently safer during fires. It also eliminates false alarms caused by non-fire-related activities, as its activation depends solely on evaporation-driven changes in water flow. The system demonstrated exceptional stability over 28 days of continuous testing, showing no signs of corrosion or performance degradation, even under varying environmental conditions.
By addressing the limitations of traditional fire alarms and combining clean energy generation with advanced materials, this device opens up new possibilities for safer, more efficient building safety systems. Beyond fire detection, this technology could extend to other small-scale energy applications, further contributing to a cleaner, more sustainable future.
