The Hydrogen Bus Technology Validation Program
The Hydrogen Bus Technology Validation Program (Davis/Sacramento, California) is a multi-district partnership of the City of Davis, Yolo County Transportation District (YCTD), University of California, Davis (UC Davis), UniTrans (transit authority for the City of Davis and UC Davis), and Collier Technologies, Inc. The purpose of the program is to validate advanced clean fuel technologies in a practical application, thereby reducing emissions by reducing reliance on polluting and toxic diesel fuel. In particular, hydrogen-enriched natural gas buses are a promising technology for two reasons. First, they are expected to meet the California Air Resources Board’s strict transit emissions requirements. Second, they require development of a hydrogen infrastructure that can pave the way to use of fuel cells, widely considered the future of transportation technology.

Collier Technologies, Inc.’s role is to provide conversion of the existing CNG engine to operate on HCNG in an ultra-lean burn mode to reduce controlled exhaust emissions while maintaining engine power output. The purpose of the program is to validate clean, advanced hydrogen fuel technologies in a transit bus application.


Dept of Energy, City of Las Vegas, Air Products and Collier Technologies
The project is designed to bring hydrogen fuels to the marketplace in the short term. Because of the high capital cost and the high purity hydrogen requirements of current fuel cell technology, the successful commercial implementation of hydrogen as a fuel is not now viable. Because of this situation, a strategy is needed for earlier commercial implementation of hydrogen as a fuel. Collier Technologies, Inc. is advocating the strategy to supplement natural gas with hydrogen for use by internal combustion engines. Both light and heavy-duty vehicles can have a significant reduction in tail pipe emissions with this technology. The rate of supplementation ranges between 30 and 50% by volume hydrogen (called HCNG). This range allows for enough hydrogen to significantly enhance the combustion of ultra-lean mixtures of natural gas while remaining within an operational window that does not require extensive engine modifications.

Collier Technologies, Inc.’s role in this project is to provide retrofit of ten light-duty pickup trucks and the re-powering of six buses to operate on HCNG fuel.


Arizona Public Service and Collier Technologies
APS has been operating vehicles on blends of hydrogen between 30 and 50% (by volume) for the past two years.

The F-150 shown below was originally equipped with a factory gasoline engine then converted for gaseous fuels and HCNG operation by Collier Technologies, Inc. This vehicle competed in the Michelin Challenge Bibendum in 2001 where it received one gold and two silver awards.

The vehicle was then converted to burn a 50% HCNG blend. With the above proof testing completed, Collier Technologies, Inc. is finalizing the development of a 32 valve supercharged pure hydrogen engine to be fitted into the vehicle. The vehicles are fueled from the APS Alternative Fuel Pilot Plant developed to dispense gaseous fuels, including CNG, blends of CNG and hydrogen and pure hydrogen. The primary objective of this program is to evaluate the safety and reliability of operating the vehicles on hydrogen and HCNG fuels. Secondary objectives were to quantify vehicle emissions, cost, and performance. Hydrogen engine generators are other areas of interest with APS and Collier Technologies has been developing this technology with APS in 5 –100 kilowatt range.


Dept of Energy and Collier Technologies
Heavy duty HCNG engine development program for diesel and natural gas engine replacements.

Collier Technologies, Inc. is developing engine technology that is applicable for use in heavy-duty vehicle applications. This patented technology deals specifically with the use of mixtures of hydrogen and natural gas (called HCNG). This application of HCNG technology is unique for two reasons. One is the very high brake mean effective pressure required by the engines. The other is the very large reduction in regulated exhaust emissions that can be achieved relative to both diesel and natural gas alternatives. The design strategy uses mixtures of hydrogen and natural gas containing at least 30% hydrogen (by volume) and incorporates lean burn and a fraction of exhaust gas recirculation for charge dilution to control NOx, CO, and NMHC emissions will be controlled by an oxidizing catalyst. At this stage in the project, NRG has developed two candidate engine platforms, ranging from 7.4 to 8.4 liters displacement, of its own for evaluation. A third engine platform of 11 liters displacement is currently under development. Testing on one of these platforms has shown NOx levels of 0.15 g/hp-hr using a weighted eight-mode steady state test with CO emissions essentially eliminated.

The goals for the project are:

  • Develop engine configurations that can replace existing diesel and natural gas engines utilizing HCNG fuel achieving equivalent power.
  • Achieve exhaust emissions of: <0.2 g/hp-hr NOx, <0.01 g/hp-hr CO and NMHC.

The project approach has investigated the following design variables:

  • Compression ratio
  • Combustion chamber design
  • Ignition system
  • Exhaust gas recirculation (EGR)-to-lean burn ratio
  • Exhaust catalysts
  • Water injection