Giving batteries a boost

Nov 1, 2006 12:00 PM, By Mary Rose Roberts

Fuel-cell-based power systems are becoming popular among researchers

Over the last few months, thousands of Sony-made, lithium-ion battery packs have been recalled because of fire-safety concerns — leading some to wonder whether they will be replaced by alternative energy sources. The question is: How soon, and to what degree?

“The quality of the lithium-ion battery is such that there will always be a use for them in some form,” said Dominic Gervasio, an associate professor at Arizona State University's Center for Applied Nanobioscience in the Biodesign Institute, who nevertheless is working on a replacement.

Oddly, the Li-Ion battery is an important component of Gervasio's research on next-generation, micro-fuel cells. Along with a team of chemists, he created a miniaturized hydrogen-gas generator that can develop into a compact fuel-cell package to power portable electronic devices three to five times longer than conventional batteries. The hybrid device consists of the fuel-cell subsystem, a Li-Ion battery and a controller, Gervasio said.

Each fuel-cell subsystem is powered by aqueous alkaline borohydride, an alkaline compound with a high capacity for maximizing the concentration of hydrogen in a fuel source. It has shown promise as a safe, energy-dense, hydrogen-storage solution, Gervasio said. Unlike other fuel sources, borohydride does not require high temperatures in order to release the hydrogen.

“Many people are trying to use methanol as a source of hydrogen or as the fuel itself,” Gervasio said. “To get the hydrogen out of methanol, you have to heat it to about 200 degrees centigrade. That's roughly like sticking your hand in the oven when you're baking.”

In contrast, the hydrogen derived from borohydride “comes out of it at room temperature,” he said. “So there's no chance of the [user] getting burned.”

Academics aren't the only ones experimenting with fuel cells. U.S. Army scientists also are theorizing ways to boost power from existing batteries using methanol as the energy source. Steve Slane, a 21-year veteran of the U.S. Army's Communications-Electronics Research, Development and Engineering Center now heads its battery branch. As chief, he leads team studies on improving battery output specifically for field-deployed military personnel.

“The same radio used by an 82nd Airborne solider will be used differently than by a Striker Brigade combat solider who has access to a vehicle and a battery charger,” he said.

Slane's team takes a hybrid-battery-system approach. Hybrid batteries are a combination of a Li-Ion battery and a methanol fuel cell. For example, a portable radio would run off the battery, and the fuel cell would act as the recharger. This reduces the weight in batteries each solider must carry, he said.

However, Slane said there are some limitations to fuel-cell technologies.

“The limitation in fuel cells right now, especially small fuel cells for the solider, is that they are not very high-powered devices,” Slane said. “So for a transmit on a radio, the fuel cell wouldn't be able to provide the power. The lithium-ion battery would.”

Army researchers also are keeping an eye on cutting-edge technologies. These include energy harvesting, solar, wind, mechanical, piezoelectric (see story on page 60) and conduits that take energy from natural sources and convert it into electricity.

Yet battery power is only one solution to the overall challenge of keeping hand-held devices operational. In Slane's opinion, reducing energy consumption is the key to the development of new power sources.

“The power consumption of the devices and the power management and efficiencies have to get better,” he said. “So as radios draw and consume less power … even a small efficiency in power of these future energy-harvesting techniques could provide solutions.”