The FTA has funded Georgetown University's Advanced Vehicle Development program to help commercialize fuel cell technology to satisfy the nation's need for transit buses that are environmentally sound and operate on non-petroleum fuels. This program is solidly based upon a history of successful analyses, studies, and hardware development that have verified the promise of this technology for the transit bus application.

The need for clean, efficient vehicle power systems that operate on non-petroleum based fuels has been spurred by the continuing dependence on foreign oil and the deterioration of air quality in our urban areas. Shortly after the OPEC oil embargo in the early 1970s, the U.S. government embarked on a program to introduce electric and alternatively fueled vehicles. Currently, the transportation sector accounts for over two-thirds of the petroleum use in the nation. Early electric vehicle attempts relied upon the storage battery for the vehicle power and energy. While the battery is excellent at delivering power, it suffers in the areas of total amount of energy that can be stored and the length of time to recharge. Thus, present battery powered electric vehicles can't go far enough and take too long to recharge.

The fuel cell has emerged as a strong candidate to circumvent the limitations of storage batteries. This technology has proven to be an excellent producer of electrical power in a variety of applications and can derive its energy in the same way that a diesel or gasoline engine does, from a refillable liquid fuel tank. The fuel cell power plant for transportation can operate on non-petroleum liquid fuels, which could significantly reduce this nation's dependence on oil imports. Additionally, it has emission levels well below any projected clean air standards. The fuel cell is quiet, clean, more efficient than internal combustion engines, and should require much less maintenance.

 

Several key elements distinguish the GU Fuel Cell Transit Bus Program; it has been this focused approach that has resulted in the successes to date:

 
1. Transit Bus Application

Transit buses are the correct path to the introduction of fuel cell power plants for automobiles. Fuel cells are clean; urban air quality can be quickly and significantly improved by operating non-polluting transit buses. Fuel cell transit buses will introduce the American public to the real advantages of the technology and further the goal of bringing fuel cell automobiles into the marketplace. Transit buses were selected to lead the way into near-term commercialization for the following reasons:

• Compatible weight/volume constraints are amenable to existing fuel cell technology
• Reduced emission transit buses have immediate environmental benefits to inner cities
• Central fueling stations minimize fuel logistic issues
• Structured routes and maintenance allow quantification of operational and cost issues
• Fuel cell power requires no operational concessions with transit bus routine operations
• Serves as full size operational laboratory to resolve technical issues hindering automotive use
• Transit buses offer ideal opportunity to educate public of the technology

 
2. Focus on Liquid Fuel

The quickest path to widespread acceptance of the Fuel Cell powered transit bus dictates the use of liquid fuel. Transit agencies in the United States are comfortable and familiar with refueling vehicles with liquid fuels at atmospheric pressure. Gaseous hydrogen operation alleviates major concerns with Fuel Cell development (primarily the development of a responsive fuel processor) and yields a more efficient Fuel Cell power plant. However, high-pressure gaseous hydrogen storage consumes a large volume yielding insufficient storage capacity on a transit bus to achieve the range requirements (typically 350-400 miles) of most US transit operators.


Early on, GU selected methanol as the best near-term liquid fuel. Methanol has a well-defined chemical formula (CH₃OH), can be easily reformed with a steam reformer (either low-temperature or high-temperature) or other reforming techniques, will reduce oil imports, can be derived from renewable resources or coal, and can be acquired in quantity at a reasonable price. Transit agencies have experimented with methanol-fueled internal combustion engines to power inner-city transit buses. Although there were problems with engine wear and repair, the logistics of obtaining, storing or handling methanol was not an issue.





 
3. Technology Readiness

The Phosphoric Acid Fuel Cell (PAFC) technology was selected for the initial program because of its commercial legacy in the electrical utility application and proven capability to operate on reformed fuel. UTC Power has delivered over two hundred PC-25 (now called the PureCell 200) stationary power plants to various countries around the world; several have achieved 50,000 hours of operation. These power plants have been operated using natural gas, light naphtha, and liquid methanol as the fuel source. The challenge was to shrink these 200 kW units from 40,000 pounds to a 100 kW package compatible with a transit bus. UTC Power delivered a 100 kW PAFC power system weighing less than 4,000 pounds which fits in the rear of a standard transit bus. This bus (the first of the Generation II buses) was rolled out in May 1998 and is currently in a test and demonstration program being conducted by GU.


The original FTA Grant has since been modified to include the Proton Exchange Membrane Fuel Cell (PEMFC) technology due to the significant progress recently achieved. Major investments are being made around the world to develop PEMFC power plants for the automotive application. This technology holds promise of becoming a robust, lightweight, cost-effective automobile power plant with attractive operational advantages. Georgetown's second Generation II bus uses a PEMFC fabricated by Ballard. This vehicle rolled out in December 2001.





 
4. Series-Hybrid Propulsion Systems

At the inception of the 40-foot Fuel Cell Bus Commercialization Program, there was no certainty that the Fuel Cell weight and volume goals could be achieved. To be sure, the entire rear module of the bus platform had to be dedicated to the 100 kW Fuel Cell. This required placing the electric traction motor forward of the rear axle severely constraining the physical characteristics of that subsystem. It became apparent that a 200 kW Fuel Cell (either PAFC or PEMFC) could not be fitted in the allotted space aboard the bus with near-term technology. It was also not certain that the responsiveness of the Fuel Cell power plants could match the required drive cycle of the transit buses. Thus, traction batteries were needed to provide surge power as well as a means to accept regenerative braking energy.


The five fuel cell buses produced by Georgetown University have all had hybrid electric propulsion systems utilizing nickel-cadmium or lead-acid batteries. Even with the improvements made in fuel cell systems in recent years, there are many important advantages to having an energy storage system on the fuel cell buses, including alleviating the performance requirements of the fuel cell, reducing the maximum power required from the fuel cell, and reducing brake wear. Recent advancements in hybrid vehicle technology (in both automobiles and transit buses) significantly reinforce the advantages of a hybrid system.






 
5. Full Scale Vehicle Demonstrations, Testing, & Analysis

It takes fully-integrated Fuel Cell powered vehicles to identify system-level issues. It is always attractive to optimize each subsystem in anticipation of its function in the larger scheme. Experience at GU has revealed that approach works in the design stages but the learning process truly begins when the rubber meets the road. It's what you learn after you know it all that counts! Demonstrations are key to convince potential customers that technology is fast approaching practicality, but it is vital to get operating test results to guide future developments.