The place to begin demonstrating any advanced transportation system is with fleet application, which offers the convenience of centralized fueling and maintenance. We also believe that our program, and the pathway we are following, holds the most promise toward achieving the long-term goal of using hydrogen fuel cell technology in the transportation sector.

—AC Transit’s General Manager Rick Fernandez

The UTC fuel cells in the hybrid buses (earlier post) combine oxygen from the air with hydrogen gas stored onboard the bus, at low, near-ambient pressure, removing the need for a compressor and increasing the fuel efficiency and reliability of the whole system.

Integrating the UTC Power fuel cell with a hybrid-electric drive system has enabled us to achieve twice the fuel efficiency of diesel.

—Dave Mazaika, ISE President and CEO

The Chevron hydrogen energy station uses dual on-site steam methane reformers (SMR) to produce hydrogen from natural gas. It then purifies, compresses, and stores the gas for use as a vehicle fuel. The Chevron hydrogen station will dispense up to 150 kg of hydrogen daily—enough to fuel the three 40-foot fuel cell buses and 10 fuel cell vehicles.

The two Steam Methane Reformers produce a reformate stream typically composed of 75% hydrogen, 20% CO₂ and other trace gases including CO and CH₄ (methane).

The reformate is compressed to approximately 125 psi—the pressure needed to separate hydrogen from contaminants in the gas stream. A pressure swing absorption (PSA) unit accepts the compressed reformate and delivers 99.99% pure hydrogen.

This is further compressed to 6,250 psi, and stored in a series of cascade storage vessels. The 6,250 psi pressure at the pump dispenser is appropriate to fuel vehicle tanks to 5,000 psi.

The HyRoad project is part of the DOE Technology Validation program. The hydrogen production and refueling component is driven by Chevron Technology Ventures—a subsidiary of Chevron that is focused on new energy technologies, including wind and biofuels. The mainstream refinery operation that focuses on the bulk production of hydrogen for use in refining processes isn’t involved.

(A Chevron Technology Ventures engineer described the difference between the two operations as knowing how to build an elephant, and figuring out how to build an ant.)

Another Chevron hydrogen energy station built at the Hyundai-Kia America technical Center in Chino uses autothermal reforming (ATR) rather than steam methane reforming to produce hydrogen from natural gas. This station produces 12 kg of hydrogen per day.

Autothermal reforming uses a process in which natural gas is reacted catalytically at high temperature with oxygen and steam at high temperature to produce hydrogen. The hydrogen gas produced from ATR is a mixture of hydrogen, nitrogen (from the air), carbon dioxide and small quantities of other gases. This mixture must be processed further to produce the essentially pure hydrogen required for use in fuel cell vehicles.

In the future, the station may also use the ATR process to produce hydrogen from ethanol.

Chevron is also working on single-step reforming (SSR): a process presented at the National Hydrogen Association conference in 2005 that converts natural gas and steam into near-pure hydrogen in a single step, with potentially significant cost savings.

AC Transit is one of the largest transit agencies in California, serving more than 64 million passengers a year throughout a 360-square mile region.