Growing the current national retail network of about 60 hydrogen fueling stations to achieve a viable hydrogen infrastructure will take significant investment and technological innovation. Figure 2.1 shows a 2008 snapshot of hydrogen fueling stations. The figure of stations nationwide is approximated at 60 because stations are opening and closing in response to market forces. Appendix A outlines some of the transmission and distribution networks that could help support a hydrogen infrastructure. Table 2.4 at the end of this section summarizes the challenges a hydrogen transition entails. The table in Appendix B shows the challenges facing all non-fossil fuels.
Technology is just one of the challenges a transition to hydrogen faces. There also are public and private sector constraints, commercial issues, safety codes and standards that need to be implemented, safety and emergency response trainings to be developed, as well as sustained commitment to the goal. This section explores each of these areas, the progress that has occurred to date, as well as the remaining barriers to be overcome and/or strategies that need to be decided.
If the country is to reduce significantly the greenhouse gases that threaten the environment, technological innovations in a variety of areas will be necessary. Current Federal research, development and deployment programs are playing key roles in this transition.
A hydrogen infrastructure faces three important technology challenges:
The NRC reported that fuel cell "stack" operating life has grown from about 1,000 hours in 2004 to more than 1,500 hours. In 2008, DOE's National Renewable Energy Laboratory documented an independent validation of 140 fuel cell vehicles that showed nearly 2,500 hours under real world conditions.1 More recently, fuel cells have lasted as long as 7,300 hours in laboratory testing.2 The Federal goal is 5,000 hours, which is equivalent to 150,000 miles of engine life for gasoline-powered vehicles.
Fuel cells also are beginning to match the distances between refuelings for gasoline vehicles about 300 miles. NRC noted that a 2007 Toyota test did exceed the 300-range goal. However, the NRC reported, it did so at an estimated cost of $15 to $18 per kilowatt hour for on-board fuel storage systems, which is much higher than the goal of $2 per kilowatt hour for commercial success.
These benchmarks are important because, according to the NRC, they are the performance measures for consumer and market acceptance of this technology.
Figure 2.2 shows the gaps between current performance and goals for hydrogen storage. Research continues to close the gaps between the different compression systems and pressures for refueling hydrogen fuel cell vehicles or HFCVs. The amount of progress toward goal depends on whether compression agents are cryogenic, chemical or some other compound. To date, liquid hydrogen is the closest to goal, followed by cryo-compressed fuel cells using the higher pressure rate of 700 bars.
NRC also cautioned that the size and weight of current fuel cell systems must be further reduced to match fossil-fueled operating efficiency. It added that this also applies not only to the fuel cell stack, but also to the ancillary components and major subsystems (e.g., fuel processor, compressor/expander, and sensors) making up the balance of the power system.
In its report, Transitions to Alternate Transportation Technologies a Focus on Hydrogen, the NRC assessed the current state of fuel cell technology as:
"Lower-cost, durable fuel cell systems for light-duty vehicles are likely to be increasingly available over the next 5-10 years and, if supported by strong government policies, commercialization and growth of HFCVs [hydrogen fuel cell vehicles] could get underway by 2015, even though all DOE targets for HFCVs may not be fully realized."
Today, alternative fuels account for only 2 percent of the nation's transportation fuels. According to research done by RITA's Volpe National Transportation Systems Center, alternative fuels in 2006 provided about 5 billion of the roughly 184 billion gasoline equivalent gallons needed to move our citizens and commerce. Most transportation fuels are destined for the nation's 238.1 million light vehicles and 9.3 million commercial trucks and buses.3
Figure 2.3 shows a timeline for transitioning to hydrogen fuel cell vehicles. The figure reflects a variety of factors including fuel supply and the time drivers normally own their vehicles. These vehicles include HEV - Hybrid Electric Vehicle, PHEV - Plug-In Hybrid Electric Vehicle, FECV - Fuel Cell Electric Vehicle, FPBEV Full Performance Battery Electric Vehicle, H2ICV Hydrogen Internal Combustion Vehicle, CEV City Battery Electric Vehicle, NEV Neighborhood Battery Electric Vehicle, FCAPUV Fuel Cell Auxiliary Power Unit Vehicles.
Figure 2.4 shows the current mix of U.S. fuels used to power vehicles. At present the United States uses about 140 billion gasoline-equivalent gallons. Of this total, only 41,000 gasoline-equivalent gallons are derived from hydrogen.
According to the NRC, hydrogen fuel cell vehicles are not likely to be cost-competitive until after 2020 when, in a very optimistic scenario, they could comprise about 2 million of the nation's 280 million lightduty vehicles. In that scenario, the number of these vehicles could grow rapidly thereafter to about 25 million by 2030, it added, and by 2050 hydrogen vehicles could account for more than 80 percent of new vehicles entering the fleet. Assuming conventional rates of car buying continue4, it could take another decade or more to complete the transition. The extent of Federal and private contributions needed to bring the industry to maturity is discussed later in this section.
To help popularize hydrogen vehicles, the NRC recommends consideration of Federal incentives to bridge the cost gap5 between HFCV and traditional vehicles.6 "Sustained, substantial and aggressive energy security and environmental policy interventions will be needed to ensure marketplace success for oil-saving and greenhouse-gas-reducing technologies, including hydrogen fuel cell vehicles."7
Just as fuel cell performance needs to evolve to make hydrogen fuel cell vehicles an important tool in controlling greenhouse gases, the source of that hydrogen also needs to undergo technological innovation. Today, most hydrogen is produced from natural gas via steam methane reforming. This technology has limited impact on reducing greenhouse gases and improving the environment. Advocates see it as a first step in transition to a hydrogen economy. Coal and nuclear are expected to have the largest positive environmental impact between 2015 and 2030, with newer technologies contributing to a greener environment after 2030. This evolutionary process is shown in figure 2.5.
To realize the vision of creating hydrogen fuel that produces only heat and water, fuel production methods need to change substantially. DOE is funding research and technologies to produce hydrogen from electricity, nuclear energy and clean coal, including building and operating a zero emissions, high-efficiency co-production power plant that will produce hydrogen from coal along with electricity. Nuclear research includes high-temperature thermochemical cycles, high-temperature electrolysis, and reactor/process interface issues.
The ideal end-state for hydrogen focuses on developing advanced technologies from domestic renewable energy resources that minimize environmental impacts. Key DOE research areas include electrolysis, thermochemical conversion of biomass, photolytic and fermentative micro-organism systems, photoelectrochemical systems, and high-temperature chemical cycle water splitting.
However, uncertainty about how, where and with what technologies hydrogen will be produced necessarily creates ambiguities in developing the infrastructure to support hydrogen transport. If, for example, the primary source of hydrogen is natural gas, then very large volumes of natural gas will be required to convert an appreciable fraction of transportation energy consumption to hydrogen. Beyond the relatively straightforward issue of feedstock availability and cost, a natural gas-based hydrogen infrastructure could take several different forms:
It is not clear, at this point, which model of hydrogen production and distribution is most desirable. For transportation planners, the challenge is that the infrastructure requirements for the various models are vastly different.
The challenge for distribution models is that enabling technologies for each scenario requires different additional research, development, testing and funding to reach maturity. NRC estimates that a $40 billion Federal investment would be needed between 2010 and 2030 to enable hydrogen fuel cell vehicles to have the potential to achieve commercial success. NRC expects private sector investment in a successful scenario would have to exceed $100 billion.8
In addition to the challenges of evolving vehicles and fuels, innovations are needed in how vehicles are refueled. The fundamental quest is to find lighter materials that provide storage rates and refueling times similar to those of fossil fueled vehicles. Figure 2.6 shows the relative volumes needed to travel more than 300 miles.
The energy in 2.2 lb (1 kg) of hydrogen gas is about the same as the energy in 1 gallon of gasoline. A light-duty fuel cell vehicle must store 11-29 lb (5-13 kg) of hydrogen to enable an adequate driving range of 300 miles or more. Because hydrogen has a low volumetric energy density (a small amount of energy by volume compared with fuels such as gasoline), storing this much hydrogen on a vehicle using currently available technology would require a very large tank-larger than the trunk of a typical car. Advanced technologies are needed to reduce the required storage space and weight.
Storage technologies under development include high-pressure tanks with gaseous hydrogen compressed at up to 10,000 pounds per square inch, cryogenic liquid hydrogen cooled to -423F (-253C) in insulated tanks, and chemical bonding of hydrogen with another material (such as metal hydrides).
DOE and DOT are funding research to explore fuel cell bus operations in 14 cities and some of these conveyances will be fueled with hydrogen. They also are studying how innovative composites can permit higher rates of hydrogen storage. The goal is to identify materials that increase the amount of hydrogen a tank holds and facilitate its flow during refueling.
The infrastructure requirements for different vehicle onboard storage designs differ. If the preferred vehicle design is for liquefied hydrogen, this presents a significant challenge for the design of the infrastructure. Gaseous hydrogen has to be cooled, compressed, and stored before delivery to the vehicle at yet to be defined locations conditions and locations. An all-liquefied hydrogen supply chain would be difficult and is probably infeasible. Safety and cost considerations will probably argue for liquefaction relatively close to the point of sale, but probably not at the service station (though this is possible). However, a liquefied hydrogen service station is a much more elaborate facility than a gaseous hydrogen station, and may present somewhat different safety and siting considerations.
Raising storage pressures to 10,000 psi would likely increase the attractiveness of hydrogen vehicles. However, 10,000 psi storage raises design questions for service stations and local distribution. The fundamental question is whether service stations locally compress hydrogen to 10,000 psi for delivery to vehicles, or whether some portion of the supply chain (delivery trucks, for example) ought to operate at higher pressures as well.
As in other cases, the challenge for infrastructure planners is to design an infrastructure when key parameters remain uncertain.
According to DOE, its Hydrogen Learning Demonstration has collected data on refueling rates, which has shown that, on the average, at 350 bar pressure, the refueling rate is 0.81 kg/min (with over 25% at a rate of more than 1 kg/min). At 700 bar pressure, the average refueling rate is 0.59 kg/min (with only 3% over 1 kg/min).
The organizational challenges facing government and others fall into three major components coordination of Federal, State and local governments; land use and site planning; and public perception and education.
NRC notes that one of the most important challenges in a transition from petroleum fuels is a consistent and clear framework of Federal, State and local requirements for the storage and use of alternative fuels. This is especially critical for hydrogen since it requires a separate infrastructure from that used for today's petroleum vehicles.
Because Congress adopted the United Nation's Dangerous Goods Code to govern all hazardous materials moving in U.S. commerce, there is consistency in the requirements governing the transport of these fuels. Federal law requires that only DOT's Pipeline and Hazardous Materials Safety Administration (PHMSA) may grant any deviations or waivers from these international rules.
NRC and others identify standardization of requirements and/or production processes as key to facilitating the widespread adoption of any innovation. The ability to quickly build and deploy hydrogen processing plants and fueling stations across the nation requires that manufacturers have certainty in the products they design and develop for distribution across the nation. Consumers require the certainty that standardization will bring to buying, using, repairing and fueling hydrogen vehicles.
Government, especially the Federal Government, can play a vital role in providing this certainty either through nationwide regulation or strong support of national industry standards. As noted in the Safety Codes and Standards section of this report, DOE, DOT and the other Federal hydrogen agencies are working with the key national standards bodies to:
The planning process for the creation of infrastructure whether a fueling station or a stretch of highway is controlled at the State and/or local levels of government. While the Federal Government may issue guidelines for these activities, there is little Federal control over what are basically local land-use decisions.
Although land use authorities are familiar with the requirements for creating a safe and efficient fossil fuel station, they often are unaware of what exactly is needed for hydrogen fueling station. As DOE has found, this lack of familiarity creates reluctance to approve facilities and makes securing approval longer and more costly. In some cases, local laws would prohibit or deter creation of alternative fuel stations.
Land use and planning are especially critical issues for the building of retail hydrogen refueling facilities. Unlike some other alternative fuels, hydrogen pumps cannot simply be added to existing fossil fueling stations. Because of safety and inherent handling properties, hydrogen refueling stations require separate infrastructure to meet these different handling requirements.
As noted by NRC, a full-size hydrogen refueling unit added to a conventional fueling station with a minimart would an additional 7,200 square feet of space. This would bring the footprint to almost 14,000 square feet (7,200 + 6,500). Even if a smaller (e.g., 100 kg/d) hydrogen fueling unit is used, a station would still require about 2,200 additional square feet. In urban areas, this footprint could limit the number of existing sites that could be used for both purposes. It also opens up the possibility that many of the hydrogen refueling sites will be at nontraditional locations such as shopping malls and big-box retailer parking areas or even auto dealerships.9
If the nation is to lessen its dependence on fossil fuel, then the public, as well as State and local decisionmakers, need to better understand hydrogen, hydrogen infrastructure and the social benefits of making alternative fuel investments. This information is crucial to allaying public concern and opposition to any kind of development.
It will take a large-scale, concerted effort to help overcome this reluctance to invest and build, especially when cutting edge technologies are involved. State and local planners and officials, as well as private sector decisionmakers, will need training, as well as opportunities to collaborate about making safe and smart investments. The public will need similar opportunities to better understand the societal benefits of these investments. Future Federal programs will need to integrate these considerations.
Just as the public sector faces coordination and land use and planning issues, the private sector has similar concerns. These concerns encompass station start-up; network maturity, station standardization, fuel quality and quantity; and insurance and liability. Federal guidance, as well as education and outreach could create the innovative partnerships needed in the transition from a fossil fueled economy.
For infrastructure and its supporting land use and planning activities, an important consideration is whether there will be a transition from portable to permanent stations. Fossil fuels in the late 19th century and very early 20th century were sold at pharmacies. Users then received regular deliveries at home or at their places of business. It took about 15 years from the time the first car was made in the United States for the first public fueling station to open.
Investment strategies for alternative fueling stations including hydrogen have similar variation in cost and level of investment. As shown in a University of California Davis study, A Near-term Economic Analysis of Hydrogen Fueling Stations (Jonathan Weinert, Dr. Joan Ogden), the costs for starting a station can vary greatly based on the type created.10
To facilitate private sector investment in portable and permanent refueling, there needs to be clear public sector direction on the preferred migration strategy as well as on the types of equipment and land-use configurations needed to get there. As mentioned elsewhere in this report, the widespread adoption of national model codes and requirements appear essential to meeting this challenge.
One of the special challenges facing a hydrogen infrastructure is at the retail level. At the bulk level, there are 700 miles of DOT-regulated transmission pipeline and, according to EIA, about 500 miles of distribution pipeline dedicated to hydrogen movements. The fuel also is able to share the liquid natural gas network. However, these benefits are stymied at the retail level, where there are about 60 vehicle refueling stations, most of which are located in California. Network maturity also affects other alternative fuels as outlined in Appendix B.
A key unanswered challenge is how hydrogen distribution and retail networks will grow. As NRC noted, there is debate as to whether specific markets or regions, such as California, should be targeted for hydrogen investment or if a national strategy of a station every 25 miles should be pursued. Coordination of fuel supply with vehicle distribution will be an important area of public/private cooperation.11
Another concern for investors will be standardization of requirements for planning, constructing and operating refueling stations. The use of model national codes for planning and constructing facilities helps investors leverage the lessons learned from earlier activities so that subsequent efforts can be delivered more quickly and cost effectively. Standardization encompasses issues from the performance of pumps and storage tanks to the proper siting of this equipment at stations.
Improving the compatibility and interoperability of station equipment is another way to facilitate deployment because it reduces deployment costs as well as the time needed to build this infrastructure.
Whether fueling their vehicles with gasoline, biofuels or hydrogen, consumers want certainty about the quality of the product they are buying. An important component of the infrastructure maturation process is the development of fuel quality standards and their widespread adoption and implementation by industry.
At present, DOE, International Standards Organization (ISO), the Society of Automotive Engineers (SAE), the California Fuel Cell Partnership (CaFCP), and the New Energy and Industrial Technology Development Organization (NEDO)/Japan Automobile Research Institute (JARI) are working to put in place these standards for hydrogen fuel cells.
This partnership of domestic and international interests has two goals. The first is to identify and exclude potential contaminants from the automotive fuel cell or in on-board hydrogen storage systems. The second is to balance the extremely high cost of providing extremely pure hydrogen with the life-cycle costs of the complete hydrogen fuel cell vehicle "system." Currently, partnership researchers are working together to assess the influence of different contaminants and their concentrations to develop a process whereby the hydrogen quality requirements may be determined and broadly adopted. Their success will determine consumer acceptance of hydrogen fuel cells.
of financial risk (e.g., likelihood and cost of adverse events) based on historical records of frequency and cost impact of an adverse event. The industry then establishes premiums to cover this risk. Insurers generally charge high fees, limit coverage and/or require high deductibles for covering extraordinary situations where historical experience is thin. The burgeoning use of fuel cells for vehicles and conveyances and the development of stations to refuel them is a prime example of such a situation.
Until a record of successful hydrogen station operation is established, insurance and liability requirements could deter many potential investors from financing hydrogen refueling stations. It will take Federal, State and local officials working together with the insurance industry and station investors and operators to overcome this significant practical barrier.
One public/private partnership recommended the following strategies to address the insurance issue:12
Any transition to hydrogen-fueled transportation will require the creation and/or updating of safety codes and standards for the safe handling of the fuel during manufacture, when in transit or at refueling stations. It also will require additional training and tools for emergency responders because of the differences in handling properties between hydrogen and fossil fuels.
Although the process of fueling a hydrogen car is not much different than refueling a gasoline vehicle, hydrogen needs to be handled differently from petroleum fuels. As a result, there is a need for hydrogen specific codes and standards for storage, fueling and emergency response. Table 2.1 outlines the objectives of codes and standards and how each are used.
As with any fueling station, hydrogen stations typically combine bulk storage and dispensing. They may provide gaseous hydrogen, liquid hydrogen, or both to cars, buses, or other vehicles such as forklifts. Like other fuels, hydrogen stations can be on private property or industrial grounds, as well as part of retail fueling stations that also provide gasoline, diesel, or other fuels.
Hydrogen stations are designed with a number of sensors and safety systems to protect against potential hazards. Sensors detect leaks and computers monitor all operating systems to ensure against problems. Flame detectors watch the refueling station at all times.
Hydrogen fires normally are not extinguished until the supply of hydrogen has been shut off due to the danger of re-ignition and explosion. Personnel who work around hydrogen should be trained in the characteristics of hydrogen fires and proper procedures for dealing with them. For example, a hydrogen fire is often difficult to detect without a thermal imaging camera or flame detector. Emergency responders need to let a gaseous hydrogen fire burn, but spray water on adjacent equipment to cool it.
Because of these differences between traditional petroleum-based fuels and hydrogen, safety codes and standards repeatedly have been identified as a major institutional barrier to deploying hydrogen technologies and developing a hydrogen economy. To enable the commercialization of hydrogen in consumer products, new model building codes and equipment and other technical standards need to be developed and recognized by Federal, State , and local governments.
DOE, DOT and other Federal partners are working to identify needed codes and standards, facilitate their development with the pertinent stakeholders and support publicly available research and certification investigations necessary to provide the data and science for promulgating them.
A large number of possible codes and standards can come into play for permitting design and construction of hydrogen fueling stations. Additional Federal, State, and local requirements also may apply. These codes are needed to ensure the safety of employees and customers. They include the proper design, location, and operation of storage and dispensing equipment and the proper installation and operation of leak detection, fire detection, and fire suppression equipment. In addition, incompatible materials or improperly installed equipment can lead to fuel contamination, which can degrade the performance of the fuel cells that power hydrogen-fueled vehicles.
With respect to fueling stations and fuel cell installations, DOE has worked with the National Fire Protection Association to develop the necessary hydrogen codes. An update to current standards is in progress and should be ready by the end of the calendar year. This comprehensive update is aimed at standardizing and speeding up the permitting process.13 In addition, DOE held 15 workshops across the country to educate more than 250 code officials on the permitting process for hydrogen fueling stations.
Continued development and updating of standards, as well as education of officials on the need to adopt and implement them at all levels of government, will be an on-going challenge in planning, building and deploying the network of production and dispensing facilities needed to make hydrogen-based transportation a reality.
A list of the key standards and code organizations include:
egardless of the alternative fuel, the transition from gasoline and diesel will require government to act as convener and facilitator. Congress will need to support basic and applied research, as well as outreach to stakeholders and public sector participation in standard setting bodies. It also will need to provide the Federal agencies with the technical resources to harmonize development of domestic standards with international standards and help resolve conflicts in international requirements, i.e. International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), and Working Party on Pollution and Energy (GRPE). Appendix C provides information on DOE's international efforts.
Among the challenges government faces are:
Hydrogen has been delivered safely for decades, mostly by pipeline or over the road. The current U.S. hydrogen pipeline infrastructure is small - about 700 miles of DOT-regulated transmission lines, compared to more than a million miles of DOT-regulated natural gas transmission pipeline - so hydrogen is often delivered by trucks carrying gaseous or liquid hydrogen in cylinders or tanks.
DOT's Pipeline and Hazardous Materials Administration (PHMSA) administers and enforces Title 49, Code of Federal Regulations requirements for the transport and storage of hydrogen, along with other fuels and hazardous materials. This includes specifying approved shipping containers, including pipelines, defining testing, maintenance, and inspection requirements for safe transport and handling. Aluminum or steel cylinders are a common approved packaging for compressed gases, including hydrogen.
Tube trailers transport bulk quantities of hydrogen gas, while cargo tanks carry bulk liquid hydrogen. Placards and material identification numbers are required to be displayed on bulk transport vehicles to help first responders recognize the material and respond appropriately in the event of an emergency.
Because of the differences in the handling properties of hydrogen and petroleum based fuels, a suitably trained emergency response force is an essential component of a viable infrastructure. Training of emergency response personnel is a high priority, not only because these personnel need to understand how to deal with a hydrogen-related emergency situation, but also because firefighters and other emergency workers are influential in their communities and can be a positive force in the introduction of hydrogen and fuel cells into local markets.
DOE and DOT, working the Occupational Safety and Health Administration (OSHA) and National Fire Protection Association (NFPA), are developing frameworks for hazardous materials emergency response training, and a tiered hydrogen safety education program for emergency responders. In 2007, the first training tools were released. They provided a basic awareness about hydrogen and a high level overview of how to handle these commodities.14 More sophisticated and rigorous materials are in development.
Taking an enterprise view of the transition to cleaner fuels for transportation will involve a long term focus by the Federal Government and its private sector counterparts.
Long term areas of effort15 could include:
Table 2.2 captures key areas of investment for a large scale transition to hydrogen fuel cell vehicles.
NRC estimated the Federal Government's contributions as being roughly $55 billion from 2008 to 2023 (when fuel cell vehicles would become competitive with gasoline-powered vehicles). This funding includes a substantial R&D program ($5 billion), support for the demonstration and deployment of the vehicles while they are more expensive than conventional vehicles ($40 billion), and support for the production of hydrogen ($10 billion). Private industry, it added, would be investing far more, about $145 billion for R&D, vehicle manufacturing, and hydrogen infrastructure over the same period.
NRC further refined this estimate in its Summit on America's Energy Future: Summary of a Meeting. There it notes that the private sector cost for hydrogen infrastructure would be about $400 billion by 2050to support 220 million vehicles. This total also would include 180,000 stations, 210 central plants, and 80,000 miles of pipeline.
In a 2007 paper authored by General Motors Research & Development Center and Shell Hydrogen, the private sector researchers estimate that the cost to construct 12,000 refueling stations is between $10B and $15B. This network would put 70 percent of the U.S. population, now living in the nation's 100 largest cities, within a two-mile radius of a refueling station and connect these cities with a station every 25 miles along the interstate highway system. The authors provided no timelines for funding and deploying these investments.
In its 2009 Action Plan, the California Fuel Cell Partnership estimates its station startup costs at about $3 million to $4 million each. These estimates are shown in Table 2.3.
In summary, as shown in Table 2.4, the challenges of hydrogen infrastructure fall into the following key areas:
Table 2.4 (pp. 24- 28) and Table 3.1(pp. 32-34) highlight where the nation is on transition to a hydrogen infrastructure as well as the remaining barriers and possible strategies that could facilitate the journey.
1 DOE 2008 Annual Report http://www.hydrogen.energy.gov/pdfs/progress08/v_c_1_debe.pdf ; National Renewable Energy Laboratory's latest durability Controlled Demonstration Project (CDP): http://www.nrel.gov/hydrogen/docs/cdp/cdp_1.ppt and completed 2008 CDPs: http://www.nrel.gov/hydrogen/pdfs/44256.pdf slide 4, also the "max projection."
15 Recommendations reflect discussions and proposals included in NRC's Transitions to Alternative Transportation Technologies A Focus on Hydrogen, and its Summit on America's Energy Future: Summary of a Meeting, California Fuel Cell Partnership Hydrogen Fuel Cell Vehicle and Station Deployment Plan and: A Strategy for Meeting the Challenge Ahead Action Plan and National Hydrogen Association The Future of Hydrogen: An Alternative Transportation Analysis for the 21st Century.