The technology is essentially an advanced version of today’s hybrid-vehicle technologies. While GE is developing it to make a cheaper fuel-cell bus, the resulting technology could be applicable to diesel or gasoline hybrids too–and could make it into cars someday. GE’s effort, which will draw on advances in other hybrid projects at the company, is scheduled to produce a prototype in three years.

An existing generation of demonstration fuel-cell buses is now three to four times more expensive than ordinary buses, which, along with the necessary hydrogen fueling stations, makes them too expensive to be practical. But in terms of adopting hydrogen as a fuel, buses do hold clear advantages over cars, says Bill Van Amburg, senior vice president of Weststart-Calstart, a not-for-profit organization currently developing fuel-cell buses. A city bus can been filled at a central location (requiring less infrastructure) and has far more room on board to store hydrogen.

To address fuel-cell cost, which comes largely from the use of expensive catalysts such as platinum, researchers at GE’s labs in Niskayuna, NY, are drastically reducing the size of the fuel cells, which are “by far the most expensive component of the bus”–significantly more expensive than batteries, says Vlatko Vlatkovic, a leader in electronics and energy-conversion research at GE.

For the horsepower needed for acceleration or high speeds, the bus will instead rely on advanced battery technology. In fact, GE will use two kinds of batteries to do distinct jobs: one for the big bursts of acceleration power essential to getting the bus moving from a dead stop, and a second for storing lots of electricity to supplement the fuel cell during high-speed or uphill driving. As with hybrid cars, the power for these batteries would come from energy recaptured during braking and from excess charge from the fuel cell.

For the first job, GE researchers are evaluating new high-power, yet safe, lithium-ion batteries from A123 Systems, whose batteries are now used in a line of professional power tools (see “Safer Lithium-Ion Batteries”). A123 researchers are redesigning their batteries for the much larger packs needed in buses. Vlatkovic says that the company is also considering ultra-capacitors, another type of energy-storage device that can take in and deliver charge very quickly, although it can’t store as much energy as a battery.