Florida Guards Against Leaks in Hydrogen-powered Vehicles

Each sensor node contains two hydrogen gas sensor chips and a ZigBee transceiver compliant with the IEEE 802.15.4 wireless standard. The nodes measure for the presence of hydrogen in the air at a rate of once every five seconds, then transmit those measurements directly to the base station, which is connected to a computer by USB cable. The software on the computer, written by students at the University of Florida, enables it to read the data, then transmit it over the Internet to be accessed by Orlando city officials, as well as by the public. The base station can also trigger an alarm if hydrogen is detected at a quantity higher than 1 percent—but to date, Painter says, no such leaks have occurred.

Installed throughout the 170- by130-foot area in which the 14 vehicles are stored, Ren says, the nodes are mounted on the ceiling above the vehicles, making it easy for them to detect the presence of hydrogen, since hydrogen gas is lighter than air and tends to rise. The nodes are plugged into AC power sources, but each node's built-in battery provides 30 days of power if an outage occurs. The base station and computer also have battery back-up power.

John Painter

Since installing six nodes two years ago, the research team has reduced that number to four. The researchers believe four nodes are sufficient for monitoring the hydrogen levels in the garage, and now use the other two nodes for further experiments at the university. The sensor nodes have a transmission range of up to 328 feet, according to professor Jenshan Lin, who, along with professor Steve Pearton, designed the wireless system, but are positioned within 50 feet of the base station that receives their transmission.

Although the nodes initially contained just one hydrogen sensor, the state found the results confusing because of the temperature fluctuations within the garage. Such fluctuations affect hydrogen readings since warmer temperatures result in higher electrical current readings from the sensor, and the current readings are pivotal to the hydrogen sensor system since the presence of the gas causes a change in current reading as well. To solve the problem, the team installed two identical chips—both providing temperature-sensing functionality, but one with the hydrogen readings deactivated, so that the software system could compare the two results against each other to provide a more accurate hydrogen reading.

The system, Ren says, could be a solution for other companies and organizations to address concerns related to the safety of hydrogen storage for fuel-cell vehicles and generators. The cost of the technology is low, he says, adding, "Our cost was less than $200—and if mass-production is adapted, the cost can be reduced significantly."

The solution also has medical applications, Lin says, in which data could be collected regarding a patient's health and transmitted wirelessly to a doctor's office. A female patient could use a sensor at home, for instance, to test her saliva for the presence of c-erb-2, an antibody present in individuals with breast cancer, thereby providing an alternative to mammograms for cancer screening. As with the hydrogen-sensing system, the results of a saliva test could be transmitted to a receiver with a USB connection to a computer, then sent to a doctor's office via the Internet.