Engineers from the University of Florida (UF) have developed a tiny, self-powered sensor that could make hydrogen fuelled transport safer by detecting leaks and sounding an alarm wirelessly.
The device, called a sensor node because it is designed to work in tandem with dozens or hundreds more like it, has the ability to draw its power from a tiny internal power source that harvests energy from small vibrations. That means future versions could one day operate continuously without batteries or maintenance when affixed to cars, refrigerators, pumps, motors or any other machine that gives off a slight vibration.
“You need lots of hydrogen sensors to detect leaks, but you don’t want to have to maintain them or change the battery every couple of months,” said Jenshan Lin, an associate professor of electrical and computer engineering and the lead investigator on the NASA-funded sensor project. “Our sensor can operate completely independently.”
Lin and his colleagues developed the sensor node over the past two years as a part of the NASA Hydrogen Research Program at UF. The programme spans several research projects. NASA uses liquid hydrogen to fuel the space shuttle, and the goal of the $1 million-plus sensor project is to help the space agency improve the safety and reliability of all its hydrogen systems.
The card deck-sized sensor node has been tested successfully in a UF laboratory, and researchers say the next step is to miniaturise it and test it at NASA labs and in field conditions. But its long-range applications potentially go beyond NASA to the development of hydrogen as an increasingly important fuel source.
“You will need to have sensors all over the place. If there is a leak, you can see which ones light up, and where the leak is, and how quickly it is spreading. That way you can shut off valves and avoid a major problem,” said Steve Pearton, a professor of materials science and engineering and one of the faculty members on the project.
UF materials, electrical and chemical engineering researchers all had a hand in making the node. The materials and chemical researchers came up with the sensor, which is based on zinc oxide nanorods that Pearton called “whiskers” of zinc oxide through which pass an extremely tiny electrical current. The more hydrogen surrounding these whiskers, the more conductive they become, providing a way to measure the ambient hydrogen in the air.
The electrical engineering researchers discovered how to amplify the signal enough to make it readable by a microcontroller. They also developed a tiny wireless transmitter to send the information to a central base station. The electrical engineers further found ways to power the device either through conventional solar cells or a piezo-electric vibrational energy harvesting system that draws on energy from vibrations produced by a variety of mechanical and electrical equipment.
Laboratory tests of the node, attached and powered by the vibrations of a mechanical shaker, showed that it could detect hydrogen concentrations of as little as 10 parts per million and successfully transmit the information as far as 20 metres. Ten parts per million is well below the level at which hydrogen becomes explosive.