The DOE views this interim time as a period in which to solve remaining technical challenges for hydrogen products. It has an ongoing $1.2 billion program to assist the development of hydrogen technologies through research, demonstration and validation projects. Other federal agencies along with state and local governments are also participating. Technical challenges that the DOE has identified include practical on-board storage options for hydrogen fuel, lowering the generation cost of hydrogen and finding economical ways to create a hydrogen distribution infrastructure. Consequently, the hydrogen industry is at an awkward crossroad. The basic technology has been proven to provide environmental benefits along with energy efficiency but hydrogen-fueled systems are still way too costly and inconvenient for most consumer applications. Deployment of hydrogen-fueled technologies depends, then, upon finding early applications for hydrogen where (1) the technology hurdles are not so significant, (2) the vehicle and fueling systems can be operated and monitored by trained technicians and (3) government participation is available either by operating or partially funding the technology deployment.
Hydrogen for Airport and GSE Applications
For these reasons and others, airports have emerged as excellent sites for demonstration projects that show hydrogen vehicles can be operated safely and reliably in commercial conditions. Airports, particularly in the largest urban centers, contain a variety of vehicle types and applications including fleets driven and maintained by trained operators. Since fueling occurs in central locations and the vehicles are operated in a planned duty cycle, range limitation and fueling infrastructure problems presented in other applications are diminished. Many promising airport sites are in emissions non-attainment areas where low or zero-emissions vehicles are encouraged or mandated by regulators.
In the US, there are already some hydrogen vehicle airport projects in various stages of development. The first operational airport hydrogen fueling station is at Los Angeles (LAX). Projects in development include fleets at Orlando, Dallas/Ft. Worth and Rockford (NW Chicagoland Regional Airport). Additionally, there are a number of military air bases that are considering hydrogen vehicle fleet projects. The vehicles that will be deployed at these and other airports include both off-road and on-road GSE.
Airport Vehicle Applications
Fuel cell tow tractors are being developed for both military and commercial use. A fuel cell powered tow tractor performs similarly to an electric vehicle, but is always "fully charged" without a performance drop-off at the end of a work shift. In many cases, hydrogen fuel could actually cost less than electricity for a battery-powered tractor. Fueling with hydrogen is much quicker than charging a battery and the tow tractor has the potential for doubling as an auxiliary power unit.
Hydrogen can also be used as a fuel for internal combustion engines (ICE). Ford Motor Company has developed a 4.6-liter V6 hydrogen-fueled engine that is being used by a major GSE manufacturer to develop tow tractors as well as other off-road vehicles. The hydrogen ICE has the benefit of providing near zero emissions, using a technology that does not require significant new training for an operating technician. Since ICE technology has a long track record, hydrogen ICE vehicles could quickly be inserted into a fleet as soon as a fuel source is established. While the hydrogen ICE is not as efficient as a fuel cell powered vehicle, the first generation of vehicles would almost certainly cost much less.
Diesel buses can produce emissions equivalent to 65 passenger vehicles. With such an impact on emissions and because they are operated in fleets, they are excellent candidates to demonstrate hydrogen-fueled systems. Consequently, several configurations of hydrogen-fueled buses have been developed by vehicle manufacturers.
Buses that use a compressed natural gas (CNG) blend with hydrogen, ICE hydrogen hybrids and fuel cell electric buses are under development and are being demonstrated around the globe. Any of these configurations could be used in shuttle applications at major airports.
Vehicles for inter-terminal transportation, parking shuttles and rental car shuttles are another good application for hydrogen-fueled airport vehicles. Figure 3 shows a hydrogen fueled ICE airport shuttle vehicle.
By introducing these vehicles at airports - as well as for other fleet applications, a fueling infrastructure will begin to be established, making the eventual deployment of fuel cell vehicles much easier.
Establishing a Fuel Infrastructure
There are three basic alternatives for providing hydrogen fuel for an airport vehicle fleet: (1) hydrogen can be delivered from a remote source, either in liquid or gaseous form and stored on-site, (2) an electrolyzer can generate hydrogen on-site or (3) hydrogen can be generated on-site via natural gas reformation.