Hydrogen Fuel Car

Army Set to Test Hydrogen Fuel Cells

The U.S. Army took delivery of the crew cab pickup at the GM research facility outside of Rochester, NY, where the vehicle's two fuel cell power modules were made. Marking the occasion was Sen. Hillary Rodham Clinton (D-NY), who was instrumental in securing the funds in the 2005 Department of Defense appropriations on behalf of GM's experimental truck.

When an army goes to war, about 70 percent of the bulk tonnage it moves to the troops involves fuel for vehicles on the battlefield. Obviously, fuel economy is an important part of what the U.S. Army wants its future vehicles to deliver. A secondary goal is to reduce harmful vehicle emissions.

The Pentagon believes that one way to achieve these goals will be in the use of specially developed fuel cell powertrains for its vehicles. General Motors Corp (GM) is lending a hand in this endeavor, and the Army took delivery of its first leased fuel cell vehicle (FCV) on April 1, 2005 at the GM Fuel Cell Center in Honeoye, NY.

The vehicle is a modified Chevrolet Silverado truck fitted with two 94kW fuel cell stacks that have the ability to generate 252 horsepower and 317 lb.-ft. of torque. That amount of torque is about equal to GM's 5.3L V8 gas-fueled engine.

Hydrogen and oxygen are fed thru a proton exchange membrane (PEM) fuel cell stack to generate the electricity needed to drive the electric motors, which power the wheels.

PEM Fuel Cells: How They work There are several kinds of fuel cells, but Polymer Electrolyte Membrane (PEM) fuel cells-also called Proton Exchange Membrane fuel cells-are the type typically used in automobiles. A PEM fuel cell uses hydrogen fuel and oxygen from the air to produce electricity. The diagram below shows how these fuel cells work.

Diagram: How a PEM fuel cell works. 1. Hydrogen fuel is channeled through field flow plates to the anode on one side of the fuel cell, while oxygen from the air is channeled to the cathode on the other side of the cell. 2. At the anode, a platinum catalyst causes the hydrogen to split into positive hydrogen ions (protons) and negatively charged electrons. 3. The Polymer Electrolyte Membrane (PEM) allows only the positively charged ions to pass through it to the cathode. The negatively charged electrons must travel along an external circuit to the cathode, creating an electrical current. 4. At the cathode, the electrons and positively charged hydrogen ions combine with oxygen to form water, which flows out of the cell.

Fuel Cell Stacks

Photo: GM fuel cell stack. Most fuel cells designed for use in vehicles produce less than 1.16 volts of electricity-far from enough to power a vehicle. Therefore, multiple cells must be assembled into a fuel cell stack. The potential power generated by a fuel cell stack depends on the number and size of the individual fuel cells that comprise the stack and the surface area of the PEM.

The overall goal of the Army's exploration of FCVs is to cut mpg ratings by 75 percent. If a successful FCV platform is accepted by the Army, a significant part of its 246,000 non-tactical vehicle fleet could be replaced, resulting in major fuel savings. Presently, the army is testing a number of gas- and diesel-hybrid High-Mobility Multipurpose Wheeled Vehicles (HMMWV, aka "Humvees") and 18-wheelers. But hydrogen is their future fuel of choice.

Early military experience with fuel cell power units is being built by the use of small auxiliary power units (APUs). The Army also recently signed an $88-million deal with GM and the U.S. Department of Energy to build a fleet of 40 hydrogen fuel cell vehicles (HFCVs) to prove out the concept as well as explore the hydrogen infrastructure that will be needed.