Harvard researchers have recently discovered a novel method for fire suppression using electrical fields—a finding that may have implications for firefighting because it does not rely on the rapid delivery of physical suppressants such as water, powder, or carbon dioxide to the site of a flame.
The scientists discovered that by applying an oscillating electrical field, they could trigger stronger interactions between the electrical field and the charged flame particles. The effects were strong enough to put the flame out, according to Ludovico Cademartiri, a postdoctoral fellow in the department of chemistry and chemical biology who worked on the study.
The scientists took a piece of metallic electrode in the shape of thin metal wire and connected it to a high voltage power supply and positioned that wire in the proximity of a controlled methane gas flame. Then, they turned on the high voltage source which sinusoidally raised and lowered the voltage.
“Think of it as blowing out a flame,” said Kyle J. M. Bishop, a former postdoctoral fellow at the George M. Whitesides Research Group who continues to collaborate with Cademartiri and the Harvard team. “The [electrical field] pulls to separate the region that’s hot and burning from the unburnt fuel, so that fuel will not continue to burn.”
In their experiments, the scientists used time-varying electrical fields to extinguish small flames—the kind of electromagnetic radiation that could act at a distance. Their success so far suggests that their novel method may enable firefighters to combat a flame from afar in the future. It also increases speed of address, since it takes electrical fields a matter of milliseconds to put out a fire, said Bishop.
“We like to think that what we have here is essentially a new way to affect fires,” Cademartiri said. “Our hope and belief is that if we can find novel ways to address fires that are more sophisticated than just throwing water at it.”
“It’s certainly a new phenomenon,” said Applied Mathematics Professor Michael P. Brenner, adding that his colleagues’ findings were promising.
At the moment, however, the researchers still need to iron out some kinks and begin to work with electrical engineers and combustion scientists to design an effective firefighting device using electrical fields.
The team faces further challenges when converting its experimental ideas into practical tools. Although the electrical field itself is not dangerous to humans—the magnitude of the field the experimenters used is similar to the experience of a spark when touching the handle of a car—high voltages do carry the danger of making electrical discharges, which could potentially be hazardous.
The Whitesides Lab is also working on an a project that involves the use of sound, or acoustic waves, for flame suppression.
“They’re taking giant speakers and aiming them at flames,” Bishop said. “It’s a testament to [Professor] Whitesides for coming up with these crazy ideas.”