Updated: May 25
Co-author: Raqib A. Chowdhury (M.S. Candidate in Energy Policy and Climate. The Johns Hopkins University)
Source: Ricardo Strategic Consulting
Hydrogen (H2) presents a vital opportunity for decarbonizing the road transportation sector in the United States. Since the United States has the world’s largest economy, its decarbonization is essential for attaining global greenhouse gas (GHG) emissions reduction of the magnitude needed to fight climate change. Such efforts need to be undertaken on the federal, state, and municipal levels. Decarbonization is broadly defined as the decrease in the carbon intensity of an economy (Meyer, 2020). The Kaya Identity equation describes carbon intensity as carbon dioxide (CO2) emissions/energy. The Kaya Identity relates the global CO2 emissions to population, Gross Domestic Product (GDP) per capita, CO2 emissions/energy (carbon intensity), and energy/GDP (energy intensity) (Andrews & Jelley, 2007).
According to Economist (2021b), “only a holistic, multifaceted approach to decarbonization is likely to succeed” (p. 12). In other words, decarbonization efforts in all sectors of the economy can help address climate change. Due to the significant dependence on petroleum-based fuels, the transportation sector, in particular, faces substantial hurdles in lowering its carbon dioxide emissions. Gross (2020) states that the sector “is the least-diversified energy end-use sector, dominated by oil” (p. 4). For example, in 2019, petroleum-based fuels accounted for 92% of US transportation. The US transportation sector was responsible for the most significant source (28%) of US emissions versus the power sector, which contributed to a 25% share of US emissions (Saundry, 2021b). Andrews and Jelley (2007) assert that “to obtain deeper cuts in emissions will require lowering the carbon intensity of the fuels” (p. 442). Therefore, eliminating US emissions from the transportation sector will be crucial to meeting IPCC reduction mandates (IPCC, 2022) to avoid climate change.
As a valuable player in reducing carbon intensity, hydrogen may complement other low-carbon technologies and energy efficiency improvements in the US decarbonization efforts, especially in the road transportation sector. From a net-zero target perspective, the importance of hydrogen is manifold. "[While] not in itself the solution to abate all emissions across sectors, hydrogen uniquely complements and enables other decarbonization pathways such as direct electrification, energy efficiency measures, and biomass-based biofuels" (Hydrogen Council, 2021, p.13). Different factors, such as technological, infrastructural, economic, political, and standards (safety and fueling protocols) related to hydrogen deployment in the US road transportation sector, will be vital in achieving favorable decarbonization outcomes.
Hydrogen, the lightest element, is the most abundant element available in the universe. Hydrogen exists in gaseous form at normal pressure and temperature. However, it turns into liquid at minus 253°C (or minus 423°F). In the solar system, Sun consists of hydrogen and helium gases. On Earth, hydrogen exists only in compound form with other elements, such as gases, liquids, and solids (EIA, 2021). As the simplest element, hydrogen has many appealing physical properties. First, it has a high energy density by mass. One kilogram of hydrogen stores about three times (33.3 kWh or 120 MJ/kg) the energy content of one kilogram of gasoline (12.2 kWh or 44 MJ/kg). Tesla's new 4680 lithium batteries may achieve, at a maximum, 300Wh/kg. Some of the future solid-state batteries will only deliver less than 1kWh/kg, which is a tiny fraction of hydrogen's energy density by mass (DOE, 2020a: Neil, 2022). Second, hydrogen has significant environmental and health benefits. For example, hydrogen does not produce carbon monoxide or sulfates when burnt in the air except for a few nitrogen oxides. When hydrogen is used in a fuel cell (described more in Section 3), it emits nothing more than water (Economist, 2021).
Due to the lack of the elemental form of hydrogen on Earth, hydrogen has to be separated from the hydrogen-containing feedstock (fossil fuels, water, biomass, or waste materials) with an energy source (DOE, 2020a). Unfortunately, due to the laws of thermodynamics, it takes more energy to derive hydrogen than hydrogen provides when the element is converted into usable energy (Economist, 2021a, p.19). In other words, the current hydrogen production is a very energy-intensive and costly process. Depending on diverse resources and technological methods, hydrogen can be classified into black (made with coal); gray (made with natural gas), blue (same technologies with added carbon capture and sequestration (CCS)); green (electrolyzers with renewable energy); pink (electrolyzers with nuclear power); and turquoise (pyrolysis through heating methane) (Economist, 2021a). The most common "large-scale production technologies" are the following: natural gas steam methane reforming (SMR); nuclear high-temperature electrolysis (HTE); biomass gasification, and low-temperature electrolysis (LTE), which uses variable renewable energy, and gasification of coal. Other hydrogen production technologies are under development or available with different maturity levels or costs (Ruth et al., 2020; SGH2 Energy, 2022).
The current main uses of hydrogen are concentrated in the following applications: 1) as a catalyst and chemical feedstock, 2) as a chemical in ammonia (fertilizer) production, 3) in petrochemical and refinery processing, and 4) as a hydrogenating agent in drug and food production. Like electricity, hydrogen can be used as an energy carrier (fuel) to move, deliver, and store energy from other sources (DOE, 2020a). Presently, hydrogen is not widely used as a fuel but has enormous potential to emerge as a low-carbon fuel option for electricity generation, manufacturing, and transportation sectors (DOE, 2020a; EIA, 2022).
This research paper focuses explicitly on integrating hydrogen, as an energy carrier, into the US road transportation sector. It primarily focuses on medium-and-heavy-duty vehicles, which travel long distances (regional/intercity buses, trucks) and light-duty vehicles (light-duty trucks and high-utilization rate passenger cars, i.e., taxis). The research paper is structured into five main sections. After the introduction in Section 1, Section 2 describes the qualitative and quantitative methods employed in the paper. Section 3 explains the challenges and opportunities of hydrogen deployment in the road transportation sector. Section 4 outlines the strategy for using hydrogen in the road transportation sector as a part of the US decarbonization strategy. Section 5 concludes, addresses limitations, and offers further research suggestions. The following section describes hydrogen technology and its potentially important role in the US economy.
Section 2: Methodology
The analysis in this research paper builds upon different domestic and international case studies and quantitative indicators to present a strategy of using hydrogen in the road transportation sector as a part of the US comprehensive effort to decarbonize its economy. In addition, the paper’s methodology is informed by the US National Renewable Energy Laboratory’s (NREL) methods for estimation of hydrogen’s economic potential as an energy carrier, a transportation fuel for light-duty fuel-cell electric vehicles (FCEVs), and medium-and-heavy-duty FCEVs in the contiguous United States (Ruth et al., 2020). NREL uses resource analysis (Brown et al., 2016) to estimate the economic potential of hydrogen for the United States. In the analysis, economic potential represents a subsection of technical potential and serviceable consumption potential, which includes only the amount of the resource that can be sold at a profit. Technical potential, in turn, is a part of resource potential, which is constrained by the resource’s energy content and theoretical physical potential. Further, serviceable consumption potential is a subset of the total consumption potential, representing the maximum amount of hydrogen’s theoretical consumption (Ruth et al., 2020). The relationships are illustrated in Figure 1 and Figure 2.
NREL defines the economic potential of hydrogen as "the quantity of hydrogen expected to be available at prices lower than other options to meet each end-use requirement" (Ruth et al., 2020, p.12). Its researchers estimate the economic potential for hydrogen as the market equilibrium between demand and supply by utilizing microeconomic analytical methods (Brownlie and Lloyd Prichard 1963; Schwartz 2010). The researchers calculate the economic potential for every hydrogen application in the national market and find the threshold price at which point hydrogen may compete with other market options. NREL uses 2050 as the single target year for all hydrogen applications in the United States to make the analysis possible. This approach corresponds with the goals of the Long-Term Strategy of the United States: Pathways to Net-Zero Greenhouse Gas Emissions by 2050 (DOS, 2021b). In addition, the hydrogen market sizes are reported on a mass basis (in a million metric tons (MMT) of hydrogen).
Various criteria for ascertaining different resource potentials
Note: Criteria used to ascertain various resource potentials (Figure 7). From The Technical and Economic Potential of the H2@Scale Hydrogen Concept within the United States (p. 10) by M. F. Ruth et al., 2020; Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results. by A. Brown et al., 2016.
NREL constructs demand and supply curves for hydrogen applications in the national market to calculate the economic potential. First, the researchers build demand curves for each hydrogen-consuming market, estimating the quantity of hydrogen every consumer might purchase over a range of prices. The light-duty FCEV’s hydrogen demand curve is obtained by utilizing the MA3T vehicle-choice model to ascertain the vehicle price, fuel price, and vehicle performance impact on consumer choices and further market penetration. NREL uses the economic equilibrium method for mature market estimations, but the MA3T model's estimate for 2050’s potential vehicle stock is not yet available for a mature market. Therefore, the researchers perform necessary changes in their approximations. Namely, NREL uses vehicle penetration when the market share for FCEVs reaches equilibrium in the MA3T vehicle-choice model (corresponding to the year 2075) (Oak Ridge National Library, 2019). The researchers then multiply the total vehicle stock in 2050 by the market share in 2075 to estimate the number of vehicles and corresponding hydrogen demand. So, the researchers calculate the equilibrium light-duty FCEV penetration if that market equilibrium could be reached by 2050 (Ruth et al., 2020).
Categorization of various demand potentials
Note: Categorization of different demand potentials (Figure 8). From The Technical and Economic Potential of the H2@Scale Hydrogen Concept within the United States (p. 11) by M. F. Ruth et al., 2020.
To estimate annual FCEV demands in the demand curve estimates for medium-and-heavy duty vehicles, NREL uses the projected FCEV market shares modeled for light-duty vehicles, as described in Elgowainy et al. (2020). NREL assumes that FCEV penetrations in the medium-and heavy-duty vehicles’ markets might be similar to or exceed vehicle penetration in the light-duty vehicles’ markets due to the performance advantages of FCEVs over the battery-electric vehicles in duty cycles needed for medium-and-heavy duty vehicles (Ruth et al., 2020). NREL constructs supply curves to obtain the quantity of hydrogen each producer would supply at various prices. The supply curves are for hydrogen produced via the following production technologies, namely, natural gas steam methane reforming (SMR); nuclear high-temperature electrolysis (HTE); biomass gasification, and low-temperature electrolysis (LTE), which uses low-cost dispatch-constrained electricity from solar, wind, and nuclear generation. Such supply curves represent the summation of production and delivery costs, so, in the transportation sector, they may be considered as supply prices at the city-gate terminal for transportation demands (Ruth et al., 2020).
Finally, NREL develops five scenarios, which use different combinations of the demand and supply curves, to estimate the range of hydrogen’s economic potential in the contiguous United States, such as Reference; R&D advances plus Infrastructure; Low natural gas resource/High natural gas price; Aggressive Electrolysis R&D; and Lowest-cost Electrolysis. These scenarios depend on market conditions, fueling hydrogen infrastructure availability, hydrogen prices, hydrogen technology R&D, and prices that users will pay for hydrogen due to other competitor technologies without changes to the current state and federal policies. The scenarios do not include potential rebound effects when the price for competing technologies and resources change due to hydrogen's influence on their market shares (Ruth et al., 2020). Such scenarios are described in Table 1.
This research paper uses NREL's economic potential estimation for the road transportation sector (light-duty, medium, and heavy-duty vehicles) calculated in the most ambitious, Lowest-Cost Electrolysis scenario. NREL researchers state that "we identify the economic potentials for several scenarios but do not consider how to reach those potentials" (Ruth et al., 2020, p. 116). This study aims to demonstrate a specific strategy to reach the NRELs’ projected hydrogen economic potential for the road transportation sector in the Lowest-Cost Electrolysis scenario, where hydrogen is used as the preeminent tool for significant decarbonization in the United States.
Five Scenarios Used to Estimate Economic Potential
Note: Reprinted from The Technical and Economic Potential of the H2@Scale Hydrogen Concept within the United States (pp. x-xi) by M. F. Ruth et al., 2020.
Moreover, as a guide, the paper uses the skeleton of the strategic framework laid out by the Fuel Cell & Hydrogen Energy Association (FCHEA) in the Road Map to a US Hydrogen Economy report. In this report, the association describes the specific roadmap for all US economic sectors, organizing it into four important phases: 1) 2020-2022 (“immediate next steps”), 2) 2023-2025 (“early scale-up”), 3) 2026-2030 (“diversification”), and 4) 2031-beyond (“broad roll-out”). Each phase has specific quantitative and qualitative milestones for all hydrogen applications. Also, every phase designates the most important strategy enablers, namely "policy enablers" as well as "hydrogen supply and end-use equipment enablers" (FCHEA, 2020, p.13).
This research paper takes a similar approach to phases and facilitators in devising a specific decarbonization strategy, which uses hydrogen deployment in the US road transportation sector. The strategy in Section 4 consists of four phases: 1) 2022-2024 (immediate steps), 2) 2025-2027 (short-term scale-up); 3) 2028-2032 (mid-term steps), and 4) 2033-2050 (long-term roll-out). The strategy facilitators are 1) policy facilitators and 2) hydrogen fuel and supply chain facilitators. Due to the lack of access to special transportation-related modeling tools, the strategy in this study primarily focuses on qualitative recommendations and provides quantitative indicators whenever possible. The next section describes the state of the current US road transportation sector along with the challenges and opportunities of hydrogen integration into the sector.
Section 3: US Road Transportation and Hydrogen: Challenges and Opportunities
Hydrogen's deployment as an energy carrier is essential for US road transportation segments, especially for medium-and-heavy duty vehicles traveling long distances (intercity/regional buses, trucks, etc.) and light-duty vehicles (light-duty trucks and high-utilization rate passenger cars, i.e., taxis). US transportation consists of highway (road) transportation (81%) and non-highway transportation (19%). Within highway transportation (81% in total), passenger cars occupy 23%, light trucks – 33%, medium/heavy trucks – 24%, buses – 0.8%, and motorcycles – 0.2%. non-highway transportation usage (19% in total) consists of air (8.8%), water (4.2%), rail (2.1%), and pipelines (3.6%) (Saundry, 2021x). The US GHG emissions approximately correlate with energy usage within various segments of its transportation sector due to the prevalence of petroleum-based fuels. Light-duty vehicles account for 59%, medium/heavy-duty vehicles – 25%, aviation – 3%, and rail – 2% (Saundry, 2021b). Decomposition analysis, an environmental and energy analysis tool, has been useful in studying historical GHG emissions and energy use in various segments of the US transportation sector. This analysis uses the Kaya Identity variation for the transportation sector, which decomposes overall transportation CO2 emissions into four primary drivers: fuel carbon intensity, vehicle fuel consumption, population, and travel demand. (Scholl et al., 1996; Lakshmanan and Han, 1997; Mui et al., 2007; Yang et al., 2008; Yang et al., 2009; McCollum & Yang, 2009).
The valuable characteristics of petroleum-based transportation fuels, namely energy density, chemical conversion, and deployability, bring unique challenges in moving away from petroleum-based fuels (Gross, 2020). Since fossil fuels represent the primary energy source for most transportation segments, the sector is considered a difficult one to decarbonize (Meyer, 2020). The magnitude of complexity in decarbonizing road transportation also varies across its parts. Some transportation segments are maybe more complicated to decarbonize than others. For example, the expected fast growth of heavier forms of road transportation intensifies the challenge of displacing petroleum-based fuels in the sector. Per the International Energy Agency (IEA), the oil demand in heavy trucking will increase by 25% by 2040. In contrast, despite the growth of light-duty vehicles on the roads, IEA predicts the peak oil demand from these vehicles in the early 2020s. More efficiency in vehicles and transportation electrification reduce petroleum-based fuel consumption in the light-duty vehicle segment (Gross, 2020).
Electrification is considered the most attractive technology for a light-duty fleet (especially passenger cars) that carry lighter loads while traveling shorter distances. Papadis and Tsatsaronis (2020) advise that "electromobility can be applied to cars and trucks and is included as an option in most scenarios" (p. 7). Namely, the researchers believe that the electrification of transportation may serve as one of the best approaches for the transportation sector. However, the total decarbonization of the transportation sector through electrification may be problematic (IRENA, 2018). Saundry (2021c) also states that "the key variable for EVs is the level of emissions associated with generating the electricity used in the vehicle" (p.7). In other words, the electrification of transportation will only be successful if it is appropriately coordinated with the decarbonization of the power sector. Therefore, Gillispier and Krisher (2021) believe that, in the long-term, hydrogen may serve as an additional vital tool to reduce carbon emissions from the transportation sector, which represents "the single biggest US contributor to climate change" (para. 4). In other words, the hydrogen deployment in the road transportation sector may complement the electrification of vehicles in the broader context of the US energy transition.
Fuel cell electric vehicles (FCEVs) and battery electric vehicles (BEVs) represent the two main options for the zero-emissions US road transportation sector. FCEVs are electric vehicles with refueling times and driving ranges similar to internal combustion engine (ICE) vehicles (IRENA, 2008). Both types can be used for various transportation segments (light/medium/heavy-duty vehicles). BEVs store energy as electricity in batteries, whereas FCEVs store energy (15 kWh/kg) as hydrogen and then convert it to electricity through fuel cells (FCHEA, 2020). The fuel cell is "an electrochemical device that can be used to generate electricity or store energy in the form of hydrogen” (Andrews and Jelley, 2017, p. 405). The suitable materials and chemicals for the anode and cathode, electrolyte and catalyst represent the fundamental challenge in creating an efficient fuel cell (Saundry, 2021a). There are various fuel cells: polymer electrolyte membrane (PEM), solid oxide fuel, molten carbonate, phosphoric acid, alkaline fuel, and alkaline exchange membrane fuel cells. PEM fuel cells usually operate at about 80°C and respond rapidly to changing loads, making them appropriate for various transportation applications (DOE, 2020c).
FCEVs might compete with BEVs in some on-road transportation segments. However, IRENA (2018) asserts that "for each [road transportation segment], there is a clear competitive advantage for either FCEVs or BEVs" (p. 32). Although the FCEV deployment has been focused on the passenger light-duty vehicle segment, the real opportunity for hydrogen deployment exists for heavier vehicles traveling long distances. Goldman Sachs (2022) asserts that "clean hydrogen could be a key competing technology [for heavy vehicles], given its high energy content per unit mass (lighter) and faster refueling time" (p. 89). IRENA (2008) states that FCEVs have potential in the heavy vehicles segment (trucks and buses) in the short-medium term. In addition, FCEV long-term potential exits in the medium/sizeable light-duty passenger cars with high utilization rates (taxis or last-minute delivery vehicles). FCHEA (2020) believes that by deploying FCEVs through 2050, the US road transportation sector will be one of the biggest beneficiaries of hydrogen fuel (Figure 3).
The potential of hydrogen fuel-based vehicles in the US
Note: Exhibit 3 - There are already many industrial applications in motion that are short-term moves. Adapted from Roadmap to a US hydrogen economy (p. 12) by FCHEA (2020).
The following section discusses the challenges of hydrogen deployment in the US road transportation sector.
The lack of adequate hydrogen fuel supply for the road transportation sector, absence of hydrogen infrastructure, economic issues, decarbonization policies' drawbacks, and the necessity to improve safety codes/standards and fueling protocols for medium/heavy-duty vehicles are the main potential challenges for successful hydrogen deployment in the road transportation sector.
Fuel Availability – Technological Barrier
The unavailability of sufficient liquid hydrogen supply for FCEVs represents the first challenge for scaling FCEVs in the US road transportation sector. Neil (2022) notes that "people assume hydrogen is abundant. It isn't – not in a readily usable form" (para. 4). For example, the United States, annually, produces only about 10 MMT of hydrogen (DOE, 2020a). As a chemical feedstock, the primary demand for hydrogen comes from ammonia production and petroleum refining. Small amounts of hydrogen are used in a few industrial applications, namely methanol production (DOE, 2020c). US hydrogen production primarily comes from fossil fuels (99%), natural gas through SMR (95%), and partial oxidation of natural gas through coal gasification (4%). Electrolysis is used only in 1% of US hydrogen. In contrast to the United States, 70MMT of hydrogen is produced globally. Global hydrogen production comes from natural gas through SMR (76%), coal gasification (22%, mainly in China), and electrolysis (2%) (DOE, 2020a).
Table 2 shows the current and future hydrogen economic potential breakdowns in the Lowest-Cost Electrolysis scenario. As seen from the table, in the most ambitious scenario, by 2050, the US needs to increase the supply of transportation FCEVs from a currently negligible amount to 17 MMT. Therefore, the US faces the daunting task of quickly ramping up the hydrogen supply for transportation and other sectors to decarbonize its economy.
Hydrogen Demand Applications in Lowest-Cost Electrolysis Scenario (MMT/year)
Note: Reprinted from The Technical and Economic Potential of the H2@Scale Hydrogen Concept within the United States (p. 10) by M. F. Ruth et al., 2020.
The absence of a reliable public and private hydrogen infrastructure for the road transportation sector is the second challenge in achieving widespread FCEV adoption across the United States. This infrastructure consists of hydrogen transportation, storage, and distribution (dispensing and fueling) (DOE, 2020c). Incidentally, “[hydrogen] transportation, distribution, and storage are the primary challenges of integrating hydrogen into the overall energy economy system” (DOE, 2020a, p.11). Neil (2022) agrees that even if low-carbon hydrogen were plentiful, it would be challenging to develop hydrogen transportation and delivery for the road transportation sector.
Hydrogen transportation and storage are challenging since hydrogen has a low-volumetric density at room temperature (nearly 30% of methane at 15°C, 1 bar) and quality to pervade metal-based materials. There are four primary methods for hydrogen transportation at scale: tube trailers, pipelines, liquid tankers, and chemical hydrogen carriers. Gaseous hydrogen can be transported by pipelines or tube trailers, whereas liquid hydrogen may be moved by liquid tankers or marine vessels. The current portfolio of hydrogen storage options consists of physical-based (compressed gas, cold/cryo-compressed, liquid, and geological) and material-based (metal hydrides, absorbents, and chemical hydrogen carriers). Currently, there are no material-based storage options ready for widespread commercialization. Energy densities in cryo-compressed and liquid hydrogen storage systems may benefit medium/heavy-duty vehicles' infrastructure rollout. However, the need for boil-off, venting, and insulation, which occur from extended dormancy, adds costs and challenges to the system's performance (DOE, 2020c).
Hydrogen distribution (dispensing and fueling) is the last vital part of hydrogen infrastructure for the road transportation sector. Sinha and Brothy (2021) proclaim that "the hydrogen refueling network is the main barrier to FCV adoption because consumers will only purchase an FCV if the stations exist to refuel it" (p.7). In other words, US FCEV drivers require ample hydrogen fueling station (regional and/or nationwide) coverage to reassure them that fueling will not be a problem. There are 48 public hydrogen fueling stations in the US, 47 in California, and 1 in Hawaii (Neil, 2022). Overall, the US will need to invest in significant research and development (R&D) efforts to increase the throughput of hydrogen dispensing systems and other related systems at the fueling stations. Moreover, R&D efforts are required to improve the reliability of materials used in the compressors and develop new designs for cryogenic transfer pumps, compressors, and dispensers to ensure they have sufficient throughout the medium/heavy-duty vehicle fleet (DOE, 2020c). Overall, the demands placed on hydrogen transportation, storage, and hydrogen delivery present challenges for the initial introduction and the nationwide scale-up of hydrogen infrastructure for the road transportation sector.
Economics is the third hurdle to successful hydrogen deployment in the road transportation sector. The three-pronged economics issue is connected to the costs of hydrogen production, fueling infrastructure, and FCEVs. First, the current production cost of low-carbon hydrogen is a costly process. In the United States, gray hydrogen costs $2/kg, blue hydrogen costs between $5-$7/kg, and green hydrogen costs $10-$15/kg, depending on availability (SGH2 Energy, 2022). DOE Hydrogen Program describes that the US might produce hydrogen from polymer electrolyte membranes (PEM) at approximately $5-$7/kg. This calculation assumes grid electricity prices between 5-7 cents/kWh, existing technology, and low volume electrolyzer capital costs (CapEx) at $1,500/kW. Hellstern et al. (2021) stress that the significant hydrogen end-users would consider hydrogen economically viable if the fuel is made at $1/kg in the United States and $2/kg in the European Union. Second, the costs of building hydrogen infrastructure will be prohibitive. For example, Neil (2022) notes that the costs of presently available hydrogen fueling stations during the past decade are much higher than associated costs with traditional gas stations. Such costs usually include the costs of the natural gas reformer on-site to evade the necessity of high-capacity storage tanks and pipelines. Additional costs of hydrogen fueling stations are connected to the compliance costs associated with local, state, and federal safety regulations.
Lastly, the broad adoption of FCEVs also relies on the relatively inexpensive cost to consumers. Compared to ICEVs and even BEVs, the high cost of FCEVs may preclude such widespread rollout of FCEVs in the road transportation sector. For example, the researchers analyzed the cost components for different vehicle types in Austria and Germany in 2016 (Table 3). The results show that, at present, FCEVs and BEVs are more expensive to operate than conventional vehicles. However, BEVs are less costly than FCEVs in investment, fuel, and operations costs. The fuel cell cost accounts for nearly half of the investment cost for FCEVs (Moriarty & Honnery, 2019). The main contributor to the cost of a fuel cell is the catalyst, which is based on the platinum group metals that are highly dependent on imports. Other components also need additional R&D improvements to meet low-cost targets for fuel cells, such as electrolytes or membranes, bipolar plates, etc. The cost reductions for fuel cells need to happen while maintaining efficiency and improving the durability of components (DOE, 2020c). To sum up, high costs of production, fueling infrastructure, and FCEVs may hinder the hydrogen deployment in the road transportation sector.
Cost components for different vehicle types in 2016 (Euros per 100 km).
Note: Reprinted/adapted from Prospects for hydrogen as a transport fuel (p. 16035) by Moriarty & Honnery, 2019.
Drawbacks from Decarbonization Policies
Drawbacks from decarbonization policies might become the fourth roadblock to successful hydrogen deployment in the road transportation sector. The United States, along with various nations worldwide, has implemented internal combustion engine phase-out policies. Biden's administration aims to "50 percent of all new passenger cars and light trucks sold in 2030 be zero-emissions vehicles, including battery-electric, plug-in hybrid electric, or fuel cell electric vehicles" (Saundry, 2021c). Andrews and Jelley (2017) affirm that policy changes may encourage the shift in the transportation modes and assist decarbonization efforts.
However, due to the urgency of the fight against climate change and ambitious decarbonization targets in some states, accurate technology winners might not be discovered quickly enough to justify large-scale hydrogen infrastructure buildout. Gross (2020) warns about the potential policy drawbacks in very ambitious jurisdictions: "Policy has the potential to drive vehicle uptake and infrastructure development, but at the risk of not allowing the technology competition to play out fully" (p. 11). In other words, the policies that encourage the shift to a low-carbon vehicle fleet might stifle the competition to establish an accurate technology winner for road transportation segments. Namely, the California Air Resources Board (CARB) passed a new rule in June 2020, which requires broad adoption of zero-emissions trucks, beginning in 2024, with all heavy-duty vehicle sales being zero-emissions by 2045. The CARB does not stipulate a specific technology in the ruling. Electric trucks are currently ahead of other technologies in research and development efforts.
Furthermore, through the West Coast Clean Transit Corridor Initiative, the US West Coast utilities are ready to offer the charging infrastructure for BEVs. Even though the CARB ruling is technology-neutral, such policy will significantly benefit California's electric medium/heavy-duty trucks. The District of Columbia and fifteen states in the US Northeast also signed a memorandum of understanding to follow California's initiative. Thus, policies may accelerate decarbonization in the road transportation sector by encouraging the electrification of medium/heavy-duty vehicles. However, such policies might leave the deployment of hydrogen infrastructure and FCEVs significantly behind. The policy drawbacks might also be amplified by the miscoordination of federal, state, and local efforts during the hydrogen deployment in the road transportation sector.
Safety Codes and Standards
The implementation of safety standards is the fifth potential challenge in the US hydrogen deployment in its most carbon-intense sector, road transportation. Hydrogen has been safely used in different industrial sectors, such as refining and chemicals, for more than seventy years. Its chemical properties give hydrogen a better standing than fossil fuels inflammability, risk of secondary fires, and quick dissipation. Nevertheless, hydrogen is a flammable, odorless, invisible gas requiring stringent safety measures. The US needs to implement such actions in hydrogen production, use, and handling, namely leak detection systems, storage tanks, and safety valves (FCHEA, 2020). Thus, hydrogen standards need to be constantly revised, in concert with the R&D efforts in the US and abroad, as hydrogen continues to be deployed in the road transportation sector.
Fueling Standards for Medium/Heavy-Duty Vehicles
The rapid development of fueling standards for medium/heavy-duty vehicles might be the last challenge of hydrogen deployment in the road transportation sector. Once hydrogen is transported to the hydrogen fueling stations, it may need to undergo the additional process for conditioning, such as pressuring, cooling, and purification. Hydrogen is usually stored on-site in bulk. Hydrogen fueling stations for all vehicles (light, medium, heavy-duty) usually have high-pressure compressors, dispensers, and storage vessels – all these systems are required to permit hydrogen fueling per specific standard protocols. The fueling standards for light-duty vehicles are currently developed, with the technology commercially deployed in the current FCEV hydrogen fueling stations across the United States. For example, the fueling pressure for light-duty vehicles is typically 10,000 psi or 70 MPa (700 bar). However, the fueling standards for medium/heavy-duty vehicle fleets are yet to be established, and such measures need to inform the equipment requirements for the hydrogen high-throughput stations (DOE, 2020c). The US needs to coordinate its R&D efforts with similar efforts globally (FCHEA, 2022). Thus, the rapid development of reliable fueling standards for medium/heavy-duty vehicles is essential for successful hydrogen deployment in the US road transportation sector.
To summarize, the lack of hydrogen supply and infrastructure, economic issues, the drawbacks of decarbonization policies, the urgency to improve safety codes/standards, and fueling protocols for medium/heavy-duty vehicles are primary potential challenges for successful hydrogen deployment in the road transportation sector. The following section discusses the opportunities for hydrogen deployment in the road transportation sector.
The main prospects for hydrogen deployment in the road transportation sector are the availability of domestic natural resources, technologies, additional resources (storage and liquefication), supportive hydrogen-related policies, and the FCEV’s advantages over BEVs and ICEs.
Availability of Natural Resources, Technologies, and Additional Resources
The United States has various primary energy resources to produce low-cost, low-carbon, secure, sustainable, and large-scale hydrogen, including fossil, biomass, and waste-stream resources (DOE, 2020c). The US possesses sufficient low-carbon and renewable electricity sources for green hydrogen, such as solar, wind, nuclear, and hydropower (FCHEA, 2020). Currently, the country consumes and produces about 10 MMT/year, about one percent of US energy consumption (DOE, 2020c).
At the same time, the US is rapidly exploring and developing hydrogen production technologies, which can utilize these natural resources through natural gas and coal gasification with CCUS, biomass conversion, waste-to-energy technologies, and various water-splitting technologies (Figure 4). Such a wide array of natural resources and technologies spread across the country can help increase its hydrogen supply from "a few hundred to hundreds of thousands of kilograms per day” (DOE, 2020c, p. 15).
Fossil Fuels. Presently, natural gas and coal are the two primary fossil resources utilized for global hydrogen production (DOE, 2020c). Natural gas, produced in rock formations, contains the remains of tiny creatures fossilized under immense heat and pressure throughout millions of years (Andrews & Jelley, 2017). Coal is a "carbon-rich solid, which originated in vast swamps containing large trees and leafy plants" (Andrews & Jelley, 2017, p. 74). Based on the differences in carbon content, coal can be divided into lignite, bituminous, sub-bituminous, and anthracite (Saundry, 2021d). The US remains the largest natural gas consumer despite its decline in the share of global gas consumption (Saundry, 2021e). Due to the relatively recent fracking boom of "unconventional resources," the US currently is the largest global producer (with a 24% share) of natural gas (Saundry, 2021e). Approximately 95% of US hydrogen is produced through SMR methods based on prevailing natural gas infrastructure. FCHEA (2020) claims that the US has ample affordable natural gas and carbon storage capacity to produce blue hydrogen (natural gas with CCUS) on a massive scale. In the near term, CCUS can be utilized with auto thermal reforming (ATR - conversion of steam, natural gas, and oxygen to syngas), partial oxidation of natural gas, and gasification of coal or biomass/coal/plastic waste blends.
Other developing technologies include direct methane pyrolysis into hydrogen and solid carbon. There are currently promising hydrogen production systems that can produce hydrogen for less than $2/kg. One of the successful examples of an SMR/CCUS project is the integrated hydrogen production facility at the Valero Refinery, the Port Arthur (SMR/CCUS project) (Preston, 2018). In the long-term, the reductions in capital and operating costs and further R&D advances in technologies can lead to low-carbon production at less than $1/kg. In addition, steam cracking (cracking natural gas liquids) can also produce affordable hydrogen as a by-product of this process. The current hydrogen production capacity is 2 MMT/year, which will increase to 3.5 MMT/year from the deployment of additional steam cracking plants soon. The DOE estimates that, if properly implemented, this process can provide 35% of current hydrogen demand and provide opportunities to co-locate end-use applications in various US regions (DOE, 2020c).
US Diverse hydrogen production technologies and resources
Note Diverse hydrogen production technologies (Figure 16). From Department of Energy Hydrogen Program Plan (p. 15) by DOE (2020c)
Biomass/Waste-Stream. Primary biomass sources (poplar, willow, switchgrass) and biogas, derived from anaerobic digestion of organic residues from agricultural waste, municipal solid waste, and landfill sources, can be used for US hydrogen production. The feedstock potential for such resources is more than a billion dry tons annually (DOE, 2020c). Biomass is an attractive, sustainable low-carbon energy source due to the basic cycle for bioenergy, which recycles carbon dioxide out of the atmosphere and releases the same carbon dioxide during burning (Andrews and Jelley, 2017). Biomass can be gasified on its own or during the gasification processes for waste plastics and coal. The processing of primary biomass into bio-derived liquids for consequent reforming into hydrogen, together with CCUS, may produce carbon-negative hydrogen.
Furthermore, biogas can be reformed through an SMR-like process into hydrogen after additional clean-up procedures. Through microbial-assisted electrolysis, fermentation, or non-thermal/thermal plasma-based processes, producers can use waste-stream feedstocks for hydrogen production. Based on the availability and costs of biomass/waste-stream resources, producers can commercially deploy some types of technologies (SMR/gasification of biomass and waste streams) in the short term. In the long-term, R&D initiatives in conversion efficiency and the decrease in costs of transporting/pre-treating feedstocks will make this type of hydrogen production economically competitive (DOE, 2020c).
Water-Splitting Technologies for Hydrogen Production. Hydrogen producers can use various water-splitting technologies, which utilize electric, photonic, or thermal energy from US low-carbon and renewable energy resources (DOE, 2020c). Electrolysis is considered a "promising option for carbon-free hydrogen production from renewable and nuclear resources" (DOE, 2022a). Andrews and Jelley (2017) explain that electrolysis serves as vital technology in the energy storage and the synthesis of low-carbon fuels through hydrogen production. The US has abundant renewable and low-carbon electricity resources, crucial for hydrogen production. For example, solar photovoltaics and wind power enable hydrogen production on both distributed and centralized basis throughout almost all US regions. Concentrated solar power (in the south-western region) and solid biomass (in the central and eastern regions) are other potential renewable energy sources that the US may use for hydrogen production. Lastly, present nuclear plants can be co-located next to the large-scale hydrogen production facilities (DOE, 2020c).
Electrolyzers can be coupled with the US electric grid or be integrated with distributed generation assets for hydrogen production for various applications. An electrolyzer is defined as a “system that uses electricity to break water into hydrogen and oxygen” (Cummings, 2020, para. 1). IRENA predicts in its World Energy Transitions Outlook 2022 that the cost of hydrogen electrolyzers will fall at similar rates to onshore wind and solar PV's decrease in the past decade (Collins, 2022). Low-temperature electrolyzers (membrane-based and liquid-alkaline) provide short-term commercial profitability, with units ready for industrial-scale production. The hydrogen cost for low-temperature electrolysis is connected to the US electricity cost. Currently, for electricity priced between $0.05-$0.07/kWh, hydrogen’s cost ranges between $5-$6/kg (DOE, 2020b). Hydrogen becomes cost-competitive, at less than $2/kg, if the electricity cost lowers to $0.02 - $0.03/kWh (due to the increase in solar/wind generation) along with R&D advancements in the durability and efficiency of electrolyzers (DOE, 2020c).
Additional Resources (Hydrogen Storage and Liquefaction). The US possesses more than 1,600 miles of hydrogen pipelines and three caverns, which can be used to store hydrogen on a massive scale. In addition, there are eight hydrogen liquefaction plants (cumulative capacity of 200 metric tonnes/day), with three more additional plants to be built in the near term (DOE, 2020c). These other resources provide tangible opportunities for hydrogen storage and transportation of liquified hydrogen to the end-users, especially in the road transportation sector.
Pro-Hydrogen Domestic Policies
Although the US has not yet announced an official national hydrogen strategy, the country has always supported hydrogen technology. In 1969, the US Apollo 11 mission, which put the first man on the moon, utilized a hydrogen fuel cell system for electricity/ water needs and liquid hydrogen as rocket fuel. Since this historic mission, the US has retained its leadership position in developing and commercializing hydrogen and fuel cell technology. Over the last decade, the US DOE provided funding for fuel cells and hydrogen ($100-$280 million/year) and $150 million/year since 2017 (FCHEA, 2020). More than ten years ago, the DOE's early investment in the forklift and material handling industry represented the US early market success for using hydrogen in transportation. As of 2020, more than 35,000 systems are commercialized by the US private sector without additional DOE funding. Hydrogen is also used in over 8800 commercial and passenger vehicles, with a growing hydrogen fueling infrastructure (DOE, 2020c).
Other developed countries have provided more significant financial support for developing their hydrogen economies. For instance, China declared $17 billion in funding for hydrogen transportation needs through 2023. In 2019, Japan announced hydrogen funding of approximately $560 million. Germany offers $110 million/year towards R&D efforts for hydrogen technologies for various industrial-scale end-uses. Therefore, FCHEA proclaims, "Directing capital to hydrogen is key to enabling its growth in the US" (FCHEA, 2020, p.6). In other words, large-scale government funding is crucial to lay down the foundation for all sectors of the US hydrogen economy, mainly in the road transportation sector.
Recently, the US has undertaken serious steps towards creating the solid groundwork for nationwide hydrogen solutions. For example, in 2020, the US DOE published Hydrogen Strategy and Hydrogen Program Plan, which describes the strategic framework for nationwide hydrogen deployment, H2@Scale. "H2@Scale is a DOE initiative that provides an overarching vision for how hydrogen can enable energy pathways across applications and sectors in an increasingly interconnected energy system" (DOE, 2020c, p. 8). Furthermore, launched on June 7th, 2021, the DOE Hydrogen Shot initiative seeks to reduce clean hydrogen's cost by 80% to $1/kg by 2031 (DOE, 2022b). In February 2022, the US "[entered] the hydrogen policy wave" by announcing $9.5 billion in clean hydrogen funding as a part of the US Infrastructure Investments and Jobs Act (Goldman Sachs, 2022, p. 17). Here are the excerpts from Sections 40313, 40314, and 40315 of this Infrastructure Bill, which are relevant to the road transportation sector (Goldman Sachs, 2022):
· Section 40313 focuses on forming a clean hydrogen R&D plan to 1) further R&D and commercialization of the use of clean hydrogen in transportation and 2) show a standard of clean hydrogen production in the transportation sector by 2040.
· Section 40314 describes additional clean hydrogen programs with vital provisions to the Energy Policy Act, such as:
1) $8 billion over four years (2022-2026) for the creation of Regional Hydrogen hubs for clean hydrogen production
2) Requirement for development of National Energy Strategy for Hydrogen
3) $500 million over four years (2022-2026) towards R&D and demonstration projects for novel clean hydrogen production/processing/delivery/storage/use of equipment manufacturing technologies
4) $1 billion for the Clean Energy Electrolysis Program for funding R&D, demonstration, commercialization, and hydrogen deployment efforts. The federal government will provide grants to entities that can reach the following program goals: a) reduction in the cost of hydrogen production using electrolyzers to less than $2/kg by 2026 and b) any other goals that the Secretary of Energy deems appropriate.
5) establishment of the mechanism for coordination of National Laboratories, namely the Idaho National Laboratory, the National Energy Technology Laboratory, The National Renewable Energy Laboratories, and other research institutes and universities
· Section 40315 defines clean hydrogen as hydrogen manufactured "with a carbon intensity equal to or less than 2 kilograms of carbon dioxide equivalent per kilogram" (Goldman Sachs, 2022, p. 18). The DOE and EPA will readjust this definition no later than 2027 after further consultation between the DOE and EPA.
Furthermore, in March 2022, US Senators Chris Coons (D-Delaware) and John Cornyn (R-Texas) introduced the Hydrogen for Trucks Act to assist with deploying heavy-duty FCEVs and hydrogen fueling stations. This act will 1) provide incentives for FCEV adoption by covering the cost difference between FCEVs and ICEs; 2) encourage parallel deployment of fueling stations and FCEVs, and 3) offer data and benchmarks for various kinds of fleet operations, which is supposed to accelerate deployment and incentivize private investment (Coons, 2022). To sum up, the trajectory of US pro-hydrogen policy and, mainly, the current political environment provides a vital boost for hydrogen deployment in the US road transportation sector.
According to FCHEA (2020), FCEVs have many advantages compared to BEVs and ICEs. Such benefits are based on 1) range/weight/powertrain volume, 2) fueling time, 3) diversification or reduction of raw material dependencies, and 4) performance consistency at various temperatures. Based on such prospects, FCEVs can be instrumental in various US transportation segments, complementing electrification, biofuels, and other powertrain strategies (FCHEA, 2020):
· Range/weight/powertrain capabilities:
FCEVs’ hydrogen storage requires less weight and space than a BEV’s battery. Therefore, FCEVs can have a higher payload and drive further than BEVs. This advantage translates into a longer-range advantage, which is crucial for freight transport and light/mid/heavy-duty vehicles (FCHEA, 2020). Moriarty and Honnery (2019) also indicate that such factors will significantly influence purchasing decisions for vehicle customers.
· Fast fueling time:
FCEV's fueling time matches ICE's (2-3 minutes for 400 miles) faster than the BEV rate (between 30 minutes and 8 hours). This advantage might not be transparent when vehicles are charged overnight in depots. However, FCEV's fueling time is advantageous in the market segments, where customer convenience and high utilization rates are vital, namely for taxis, medium/heavy-duty transport, and autonomous vehicles. Faster refueling time reduces the infrastructure footprint for FCEVs due to the decrease in the number of fuel pumps in warehouses, mines, ports, and public areas (FCHEA, 2020).
· Reduction and diversification of raw material dependencies
The FCEV deployment will have limited supply chain risks on raw materials for manufacturing hydrogen storage tanks and fuel cells for the road transportation sector. Namely, the hydrogen industry in 2005 already limited the usage of platinum content by 80 percent to less than 0.2g/kW (Jacob et al., 2020). Cerium and cobalt are also limited quantities in fuel cell production (FCHEA, 2020).
· Performance consistency at various temperatures:
FCEVs provide the same performance standard across all the geographies and varying climates. This temperature-resistant operation advantage is crucial for the successful deployment in various regions throughout the US road transportation sector.
In essence, the hydrogen deployment in the US road transportation sector might benefit from domestic natural resources, technologies, additional resources (storage and liquefication), supportive domestic policies, and the FCEV's advantages over BEVs and ICEs. The following section discusses the hydrogen deployment strategy in the road transportation sector through 2050.
Section 4: US Hydrogen Deployment Strategy: Road transportation
As discussed in the previous section, the absence of sufficient hydrogen fuel supply and hydrogen infrastructure; high costs; disadvantages of domestic decarbonization policies; the necessity to improve safety codes/standards and fueling protocols for medium/heavy-duty vehicles are potential risks to successful hydrogen deployment in the road transportation sector. At the same time, the abundance of domestic natural resources, the plethora of existing and developing technologies, storage and liquefication resources; supportive domestic pro-hydrogen policies; and the advantages of FCEVs in contrast to BEVs and ICEs represent the prospects for this specific decarbonization strategy in the United States.
Section 2 describes the methodology and the purpose of this study, which is the presentation of a specific roadmap to reach NREL's economic potential for the road transportation sector in the Lowest-Cost Electrolysis scenario, where hydrogen is widely utilized as a vital solution for significant decarbonization in the United States. This scenario results in the most significant reduction in the usage of petroleum (15%) since it has the highest level of FCEV penetration: 5 MMT per year of hydrogen fuels 22% of medium/heavy-duty vehicle fleet, and 12 MMT per year of hydrogen fuels 26% of light-duty trucks and 18% of light-duty vehicles. This maximum level of FCEV penetration is possible due to the highest availability of affordable electrolytic hydrogen. Under this NREL scenario, about 90% of the hydrogen is produced through the LTE process, with the remaining 10% nuclear HTE. NREL researchers state that "an increased hydrogen market size can be realized even if low-cost LTE is unavailable as long as other hydrogen production options are available" (Ruth et al., 2020, p. xiii). Such options are 1) SMR with affordable natural gas, 2) biomass, and 3) low-cost HTE, even if limited to the use of nuclear energy only. The hydrogen market size may increase if HTE hydrogen production technology can employ supplementary cost-competitive energy resources (grid electricity with natural gas-generated heat or affordable, dispatch-constrained electricity from nuclear, wind, and solar generation) (Ruth et al., 2020).
In the conclusion of the report, which informed the methodology of this study, NREL researchers suggest several paths for future analysis of the transition from current infrastructure and market conditions to five future scenarios of hydrogen deployment. The researchers recommend that future analysts identify potential regulatory and market modifications in hydrogen deployment, the timing of R&D investments and initial commercialization of hydrogen applications, specific regions for regional support decisions, and near-term opportunities for hydrogen as a vital energy carrier (Ruth et al., 2020).
This research study strives to extend the NREL research in describing the ambitious decarbonization strategy, which deploys hydrogen in the US road transportation sector. The highly optimistic and aggressive growth strategy consists of four phases: 1) 2022-2024 (immediate steps), 2) 2025-2027 (short-term scale-up); 3) 2028-2032 (mid-term steps), and 4) 2033-2050 (long-term roll-out). The strategy facilitators are 1) policy facilitators and 2) hydrogen fuel and supply chain facilitators. First, policy facilitators play an important role "since they are needed to create the right incentives to help the private sector invest and develop the hydrogen market" (FCHEA, p. 13). Policy facilitators cover policy support (federal, state, and municipal), public initiatives for bridging economic barriers to initial market launches, and the establishment/improvement of hydrogen standards (safety and fueling protocols). Second, hydrogen fuel and supply chain facilitators outline specific steps for hydrogen integration into the road transportation sector, namely technological attempts to increase hydrogen fuel availability, hydrogen infrastructure/FCEVs developments, and initiatives to lower costs throughout the entire hydrogen supply chain. The hydrogen supply chain includes equipment manufacturers, infrastructure operators, FCEVs manufacturers, etc. The next section describes "Immediate Steps" (2022-2024).
Phase I. Immediate Steps (2022-2024)
Under Section 40314 of the Bipartisan Infrastructure Investment and Jobs Act (HR. 3684), policymakers develop National Energy Strategy for Hydrogen during the first phase. The nationwide deployment of hydrogen in the road transportation sector cannot happen without the supportive pro-hydrogen regulatory framework at the federal, state, and municipal levels. This policy framework is also needed to encourage private investment into hydrogen production and the supply chain for the road transportation sector. Hart (2020) explains the federal government's critical role in assisting energy transition and ensuring competitiveness by funding R&D efforts for advanced technologies, supporting financing to the private sector through the tax code, providing debt financing to innovative projects, spreading information about best practices, and purchasing goods and services.
While devising the national strategy, the policymakers rely on the current DOE's Hydrogen Program Plan, namely on established coordination and collaboration with other federal agencies, such as the Department of Defense, to identify areas of common interest and prospects/risks in hydrogen deployment for road transportation (DOE, 2020c). For instance, the Office of Naval Research Global Tech Solutions Program sponsors the Massachusetts Institute of Technology (MIT)'s research to convert aluminum into hydrogen fuel for all kinds of vehicles in expeditionary environments (Eurasia Review, 2022). Such innovative R&D efforts might benefit remote area-hydrogen deployment in the road transportation sector.
The policymakers also draw on the current Program's coordination and collaboration with several state governments to ensure the activities' integration at the federal, state, and municipal levels. Such activities include public outreach and education, real-world demonstrations, and early-market deployments. In addition, the policymakers utilize the best practices from the Program's engagement with the stakeholders from the private and non-profit sectors. For instance, the Program has developed vital partnerships that support the integration of R&D efforts between the government, private sectors, and academia, focusing on the US road transportation sector. Such partnerships are US DRIVE (Driving Research and Innovation for Vehicle Efficiency and Energy Sustainability) and the 21st Century Truck Partnerships with VTO, which focuses on advancing the next generation of medium/heavy-duty trucks, including the usage of hydrogen fuel cells (DOE, 2020c). The policymakers also benefit from the engagement with other stakeholders, such as the Fuel Cell and Hydrogen Energy Association (FCHEA) or private-sector-based associations and coalitions.
Other steps, informed by FCHEA (2020), occur during the initial two-year period. First, the federal and state governments establish solid, technology-neutral decarbonization goals and remove regulatory barriers. However, as Gross (2020) warns, "policymakers must ensure that their actions do not crowd out further advances in new fuels, especially hydrogen" (p. 17). Such awareness helps prevent drawbacks from decarbonization policies, as mentioned in Section 3. Second, dedicated policymakers increase awareness about hydrogen safety through public outreach to the federal and state-level officials and the general public. Third, other changes happen, namely, the implementation of hydrogen codes and safety standards, establishment of fueling standards for medium/heavy duty vehicle fleets, modernization of existing hydrogen-related regulations, and the establishment of hydrogen-related workforce programs.
Lastly, in this phase, California and other Section-177 states implement specific FCEV targets with existing zero-emission vehicles (ZEV) mandates or low-carbon fuel emissions standards. According to FCHEA (2020), Section 177 of the Clean Air Act allows states to adopt California's instead of federal standards. These progressive states can continue encouraging heavy-duty FCEV adoption by supporting FCEV purchase programs and infrastructure. State governments can also lead in FCEV adoption by gradually switching to an FCEV fleet while balancing this procurement with the BEV adoption in specific market segments. Additional policies focusing on FCEV user advantages (public cost-neutral incentives) and compensation policies for FCEV purchase programs support vehicle adoption. Eventually, other states, the follower states, can also follow similar roadmaps in developing clean energy policies and supporting hydrogen deployment. At the end of this phase, National Energy Strategy for Hydrogen helps solidify national targets and approaches for large-scale hydrogen deployment, particularly in the road transportation sector.
Hydrogen Fuel and Supply Chain Facilitators
During the first phase (2022-2024) and in the second phase (2024-2026), the creation of Regional Hydrogen Hubs ($8 billion funding over four years) helps increase hydrogen fuel availability for the road transportation sector. According to John (2022), this law requires at least one of the hubs to be used for pink hydrogen, at least one for blue hydrogen, and two other ones for green hydrogen production. There are multiple proposals for such Regional Hydrogen hubs. For instance, HyDeal LA public-private consortium seeks to produce green hydrogen to replace fossil fuels for transportation and a large portion of natural gas used for power generation and heating. The project needs funding for $27 billion over the next fifteen years, including the cost of new pipeline infrastructure and underground storage (John, 2022). Second, a Utah consortium, the Advanced Clean Energy Storage project, is expected to be the world's largest industrial-scale green hydrogen production and storage project. On April 26, 2022, this project received $504.4BB in debt financing from DOE's Loan Program's office (MP, 2022). Third, nuclear energy producers want to use excess nuclear electricity to produce pink hydrogen in Xcel Energy's Prairie Island and Arizona Public Service's Palo Verde nuclear plants. There are other promising projects for clean hydrogen production in New York and other states (John, 2022).
The federal funding for the Clean Energy Electrolysis Program ($1 billion) and R&D grants ($500 million) during the first and second phases help reduce hydrogen deployment costs. Other steps suggested by FCHEA (2020) also increase hydrogen fuel availability for the road transportation sector: 1) dedicated hydrogen production for ground transportation, 2) scaling up hydrogen production through water electrolysis (10-50 MW electrolyzers); 3) as a bridge technology to LTE-produced hydrogen, usage of large-scale hydrogen production from SMR or ATR with renewable natural gas and mid-scale hydrogen production (SMR/ATR) with CCUS.
The expansion of hydrogen's use for decarbonizing the US road transportation sector is connected with the growth of hydrogen's infrastructure. The current clean hydrogen projects are built on bilateral arrangements between hydrogen purchasers and producers (John, 2022). In the first phase, multilateral agreements for clean hydrogen are arranged for the hydrogen industry to grow to scale. Such arrangements involve multiple producers and buyers in the road transportation sector, preferably developing Regional Hydrogen Hubs. Such mutually-reinforcing networks in various regions can grow hydrogen's supply and demand in the road transportation sector.
Other steps in developing hydrogen infrastructure involve addressing hydrogen transportation, storage, and distribution (dispensing and fueling). The National Academy of Sciences (2008) advocates the "phased introduction" of FCEVs and fueling stations, starting from major cities and moving to other cities in phases. In so doing, "the so-called lighthouse concept reduces infrastructure costs by concentration the development in relatively key areas termed 'lighthouse cities'" (p. 78). During the first phase, liquid and gaseous distribution are developed throughout "lighthouse cities" and pioneer states.
In addition, according to FCHEA (2020)'s suggestions, the following immediate steps take place: 1) integration of hydrogen-tolerant equipment, 2) rollout of second-generation FCEVs and hydrogen fueling stations for buses and light-duty vehicles, and 3) rollout of heavy-duty FCEVs and related fueling stations. R&D efforts are also essential in overcoming the infrastructure challenges described in Section 3, namely, improving the reliability of materials used in the compressors and new designs for cryogenic transfer pumps, compressors, and dispensers to ensure they have sufficient throughout the medium-heavy-duty vehicle fleet. The following section describes "Short-Term Scale-Up" (2025-2027).
Phase II. Short-Term Scale-Up (2025-2027)
In the second phase, aggressive expansion of hydrogen production and infrastructure helps maintain momentum in hydrogen deployment in the road transportation sector. Federal support remains critical in removing any regulatory barriers toward using hydrogen in the US decarbonization, as per the country's broader Nationally Determined Contributions (NDC) declarations (DOS, 2021a). The private sector is incentivized to implement NDC goals to create a resilient, net-zero future. In pursuit of such targets, informed by FCHEA (2020), state policies remain essential in the pioneer states and the follower states, which have started pursuing decarbonization goals on a larger scale. In the pioneer states, local governments support the minimum hydrogen infrastructure expansion for coverage in its core markets. Such efforts can be undertaken through technology-neutral subsidies, joint ventures funded by large industrial conglomerates, market-based policies, or request-for-proposal (RFP) funding. In addition, the follower states pursue the pioneer states’ strategies, focusing on measures covering the FCEV cost difference with the incumbent technology (ICE) and supporting the expansion of hydrogen infrastructure. In other words, in the second phase, federal and state incentives, primarily in the early pioneer markets, assist in transitioning from government support to large-scale market-based mechanisms.
Hydrogen Fuel and Supply Chain Facilitators
During the second phase, the utilization of Regional Hydrogen Hubs continues to grow the large-scale hydrogen fuel supply for the road transportation sector. The federal funding for R&D and demonstration projects for novel clean hydrogen-related technologies and the increase in demand from the road transportation sector also decrease hydrogen costs. The Clean Energy Electrolysis Program proves to be successful as the federal grant recipients reach the main Program's goal – a reduction in the cost of hydrogen production using electrolyzers to less than $2/kg by 2026. The mechanism for coordination between US National Laboratories, research institutes, and universities instills additional innovation into clean hydrogen production. In general, during this phase, the US witnesses the growth in the industrial-scale hydrogen production, a reduction in the cost of electrolyzers, and an increase in hydrogen demand from its road transportation sector.
Other strategies, informed by FCHEA (2020), continue expanding the hydrogen supply and improve all parts of hydrogen infrastructure for the road transportation sector. For example, as economic factors connected to electrolyzers continue to improve, industrial companies can ramp up large-scale LTE hydrogen production of more than 50 MW and the smaller production facilities at remote fueling stations. This development fosters the usage of hydrogen for the integration of variable renewable electricity production and transportation demand on a large scale. At the same time, innovations occur, such as successful industrial-scale demonstrations of SMR or ATR with CCS, which can also be dedicated to hydrogen production for the road transportation sector.
On the hydrogen infrastructure side, informed by FCHEA (2020), the following steps take place: 1) the introduction of pure hydrogen-tolerant equipment and 2) the integration of dedicated hydrogen delivery systems in industry clusters. The road transportation sector continues to transform as new and improved FCEVs are brought to market, for example, to meet the California Fuel Cell Partnership goal of 1 million FCEVs by 2030. Heavy-duty vehicle infrastructure grows as fueling stations get introduced through the follower states, and second-generation heavy-duty vehicles are presented throughout the US. Multiple hydrogen producers and buyers from the road transportation sector continue arranging multilateral arrangements for the buildout of clean hydrogen projects in additional Regional Hydrogen Hubs.
In addition, federal grants toward R&D efforts in the Infrastructure Investments and Jobs Act support innovation in the second phase, reducing fuel cells' costs. The cost of a fuel cell accounts for nearly half of the investment cost for FCEVs (Moriarty & Honnery, 2019). As mentioned in Section 3, the main contributor to the cost of a fuel cell is the catalyst, which is based on the platinum group metals that are highly dependent on imports. Promising R&D projects lead to the commercialization of technologies. For example, in 2020, the multi-institutional group discovered the non-platinum catalyst that can lead to longer-lasting and cheaper power (The Source, 2020). Another promising project from UCLA/Caltech found out that altering fuel cell catalyst shape can lower costs since it requires only 1/50 as much platinum as a regular smooth one (UCLA, 2016). In the second phase, it is assumed that these technologies are commercially ready for widescale deployment within the US. The following section describes "Mid-Term Steps" (2028-2032).
Phase III. Mid-Term Steps (2028-2032)
By the end of the third phase, the US achieves emissions reductions of 50% below the 2005 levels, which is critical for the decarbonization of the road transportation sector (DOS, 2021b). The following developments are informed by FCHEA's (2020) futuristic projections. First, the full-scale deployment of medium/heavy-duty vehicles is scaled up, supported by the strategic placement of fueling stations along the high-usage of freight corridors. The regional infrastructure networks start connecting to create a nationwide network to assist the coast-to-coast travel. Light-duty vehicles and buses continue to disseminate beyond the pioneer states. More importantly, "hydrogen production has been scaled up, the critical infrastructure has been put in place, and hydrogen equipment is manufactured in scale" (FCHEA, 2020, p. 73). In other words, the US is on the stable trajectory of deploying hydrogen broadly in its road transportation sector.
Such developments are possible due to the continuing federal and state policies, which support the transition from direct government support to large-scale market-based mechanisms. In the pioneer states, industrial conglomerates, supported by tax incentives and FCEV targets, expand the fueling network through investment in critical locations. Local governments develop dependable ZEV strategies and targets in the follower states, including FCEVs in all market segments.
Hydrogen Fuel and Supply Chain Facilitators
During the third phase (2028-2032), the DOE "Hydrogen Shot" initiative reaches its goal of slashing the costs of clean hydrogen (green, pink, blue, or turquoise) to $1/kg by 2030. The LTE-based hydrogen production increases in the states, where dedicated variable solar and wind generation keeps electricity costs low. Moreover, a nationwide portfolio of small modular nuclear reactors (SMRs), which will start replacing the traditional reactors in the 2030s, produces pink hydrogen at a stable, affordable cost and a high-capacity factor. Andrews and Jelley (2017) describe various types of SMRs under consideration, such as LWRs and fast neutron reactors (FNRs) in addition to molten salt reactors (MSRs). Within an MSR, the operators use the uranium fuel and dissolve it in a sodium fluoride salt coolant, which circulates through a graphite moderator. The high-level waste is reduced due to the continuous removal of fission products and recycling of the actinides. The plant maintains a high operating temperature for hydrogen production during the process. Since there is a passive cooling of a core, the safety of the SMR is also improved.
Informed by FCHEA (2020), other steps in the roadmap, which increase hydrogen fuel availability and infrastructure for the road transportation sector, occur. For example, electrolyzer production costs reduce capital and operating costs due to the increasing volume of manufacturing processes. Blue hydrogen also scales up as CCS and CCUS technologies develop to support increasing hydrogen demand in the road transportation sector.
Hydrogen infrastructure expands as the production of fueling station components and fuel cells for all types of FCEVs scales up. The private sector also gets fully involved in developing FCEVs and hydrogen dispensing (fueling stations). The road transportation players learn best practices from the Hydrogen Mobility Europe project (H2ME) initiative, which supports the deployment of FCEVs and fueling stations across the European Union (Hydrogen Mobility Europe, 2022). In addition, hydrogen distribution has expanded further since dedicated hydrogen pipelines began to connect industrial-scale clean hydrogen sites with demand centers focused on the road transportation sector. The next section describes "Long-Term Roll Out" (2032-2050).
Phase IV. Long-Term Roll Out (2032-2050)
By the end of 2050, the US is very close to achieving net-zero GHG emissions goals articulated in The Long-Term Strategy of the United States - Pathways to Net Zero Greenhouse Gas Emissions by 2050. Such accomplishment is possible due to the coordinated action based on four strategic pillars: federal leadership, innovation, non-federal leadership, and all-of-society action (DOS, 2021b). It is anticipated that specific transport segments, especially the FCEVs, achieve cost parity with fossil-fuel alternatives. Additional policy support fully corrects for externalities between FCEVs and ICEs. Figure 5 shows how, from 2020-to 2050, electricity and alternative fuels (hydrogen, bio-energy) will become primary fuel sources in the road transportation sector.
On the policy front, consistency and acceleration in policy implementation remain crucial in achieving net-zero GHG emissions in the United States. During this phase, informed by FCHEA (2020), federal policymakers focus on building a comprehensive hydrogen code and standardizing hydrogen practices across the country to enable broader deployment in the road transportation sector. Federal regulations also recognize LTE-based hydrogen production as one of the leading technologies in increasing hydrogen fuel supply for the industry. In addition, best practices and lessons from the pioneer states are disseminated across the rest of the country to deploy hydrogen in the road transportation sector in the most efficient way. Lastly, carbon tax proposals get broader support across the US as an efficient way to increase revenues while encouraging lower GHG emissions past 2050, especially in the road transportation sector.
US Transportation Final Energy Usage: 2005-2050
Note: US. Transportation Final Energy Use 2005-2050 (Figure 8). From The Long-Term Strategy of the United States: Pathways to Net-Zero Greenhouse Gas Emissions by 2050 (p. 30) by DOS (2020b)
Hydrogen Fuel and Supply Chain Facilitators
After 2032, according to the FCHEA (2020), hydrogen is being deployed broadly throughout the US economic sectors, especially in the road transportation sector. This expansion of hydrogen usage leads to further cost reduction across the entire value chain in hydrogen deployment, particularly in the road transportation sector. Both production and hydrogen infrastructure for the road transportation sector reach maturity and continue to expand to meet the increase in the US transportation demand. According to FCHEA (2020), other steps happen, such as 1) retrofitting SMR/ATR capacity with CCUS due to policy incentives or climate regulations and 2) competition between LTE production and SMR/ATR plus CCS production due to the search for lower-cost production.
Hydrogen infrastructure continues to evolve as efforts are made to upgrade existing gas infrastructure to withstand high hydrogen integration. At the same time, if required, new hydrogen-compatible pipelines are built throughout the nation. The full hydrogen deployment into the road transportation sector is complete as the US obtains a large-scale clean hydrogen production network and an efficient infrastructure. The variety of vehicle models for light/medium/and heavy-duty markets are readily available for US customers.
Section 5: Conclusion
This research paper describes a specific strategy to decarbonize the US economy: unlocking hydrogen’s potential in the US road transportation sector. The strategy is intended to become a potential part of the US portfolio of decarbonization approaches to reach net-zero GHG emissions by 2050. The study affirms that hydrogen is a crucial piece of the US decarbonization puzzle. It also shows that, given many opportunities, challenges, interdependencies, and tradeoffs, the decarbonization of the US road transportation sector is a complex issue. The analysis in this paper draws on domestic/international case studies and quantitative indicators to describe challenges and opportunities for hydrogen deployment in the road transportation sector. The study’s methodology is also informed by NREL methods to estimate hydrogen's economic potential as an energy carrier, a transportation fuel for light-medium-heavy duty FCEVs in the contiguous United States. This research study uses NREL’s economic potential estimation for the road transportation sector, calculated in the most ambitious, Lowest-Cost Electrolysis scenario. NREL researchers warn that “we identify the economic potentials for several scenarios but do not consider how to reach those potentials” (Ruth et al., 2020, p. 116). This paper aims to extend NREL’s research by describing a four-phase ambitious decarbonization strategy that deploys hydrogen in the road transportation sector from 2022 to 2050.
As with every research, this paper is not without limitations. The limitations of the study’s methodology are connected to the limitations of NREL's methods for estimating hydrogen's economic potential as a transportation fuel in the road transportation sector. In acknowledging NREL’s analysis limitations and needs for additional analysis, its researchers describe the necessity for 1) the supplementary analysis of the threshold prices for hydrogen applications; 2) the cross-cutting analysis of the light-duty vehicle market; 3) a construction of the supply curve for HTE integrated with grid electricity and heat generation from natural gas, biogas or another feedstock, 4) detailed cost estimates for future HTE and LTE technologies to increase the confidence in supply curves, 5) supplementary analysis to ascertain the economics of regional hydrogen markets and to estimate exports/imports across the US regions, 6) analysis of potential policy implications on both regional and national hydrogen demand and supply curves, 7) sensitivity analyses for price variations (natural gas and petroleum prices) and impact of regional hydrogen exports/imports on hydrogen market sizes, and, lastly, 8) incorporation of effects of the competition for hydrogen-producing/enabling resources (land, water and variable renewable/clean electricity sources) on hydrogen prices (Ruth et al., 2020).
In Section 3, the research paper may benefit from an additional discussion about the impact of lifespan challenge on hydrogen deployment in the road transportation sector. Lifespan challenge for vehicles is a critical issue since ICE vehicles, especially in the medium/heavy-duty segment, can stay around for a long time. Gross (2020) claims that heavy trucks have a lifespan of 15 years. Therefore, it might take decades for a novel technology to be spread throughout the vehicle fleet, especially if introduced slowly (McCollum et al., 2009).
The proposed decarbonization strategy has limitations as well. First, as acknowledged earlier, this strategy represents the most ambitious pathway for quickly ramping up the hydrogen deployment in the road transportation sector. All barriers (technological, infrastructural, economic, political, and standards-related) need to be surpassed to achieve favorable decarbonization outcomes. Undoubtedly, it would be challenging to achieve NREL's targets for hydrogen production under the Lowest-Cost Electrolysis scenario. Under the scenario, about 90% of the hydrogen is produced through the LTE process, with the remaining 10% nuclear HTE (Ruth et al., 2020). Perhaps, during the first two phases, the US might employ an alternative mix of technologies (proposed by NREL) to ensure a rapid scale-up of hydrogen fuel supply for the road transportation sector. Second, due to enormous decarbonization challenges, a longer deployment time might be necessary to scale hydrogen deployment in the sector. Third, the paper only focuses on hydrogen deployment in the road transportation sector, disregarding the roll-out of other decarbonization technologies, like vehicle electrification. Perhaps, a multi-technology approach, a scale-up of both FCEV and BEV charging infrastructures, will lead to faster decarbonization that is faster and more cost-effective, serving all US customers based on their specific needs. Lastly, due to the lack of access to special transportation-related modeling tools, the strategy's authors primarily focus on qualitative recommendations and provide quantitative indicators whenever possible. The rigorous modeling assumptions and outcomes, incorporating all NREL methodology limitations, may have led to better decarbonization approaches.
Regardless of the presented shortcomings in this research paper, this study extends the current literature concerning decarbonization in the US road transportation sector. Also, the study underscores the urgency of hydrogen deployment in the sector by presenting a specific detailed strategy to decarbonize the US economy. The authors of the study agree with Hart (2020)’s belief about the necessity of rapid energy transition in the US, “The longer we resist the future, the more time is lost. Time is limited before we are technology followers in the next generation of clean energy power generation and transport technologies” (p. 20).
Finally, this closing section proposes a few future research directions about hydrogen deployment in the US road transportation sector. First, the researchers can build upon this study's ideas and incorporate rigorous transportation modeling tools to develop better projections and recommendations regarding the integration of hydrogen in the road transportation sector. Second, the analysts may devise a similar strategy that includes potential rebound effects when the prices for competing technologies and resources change due to hydrogen's influence on their market shares. Lastly, as hydrogen production/infrastructure-related technologies continue to improve and develop, future researchers may propose strategies for coordinating hydrogen-related decarbonization in the power and transportation sectors.
Andrews, J., & Jelley, N. (2017). Energy science: principles, technologies, and impacts (3rd ed). Oxford University Press.
Brown, A., Beiter, P., Heimiller, D., Davidson, C., Denholm, P., Melius, J., Lopez, A., Hettinger, D., Mulcahy, D., & Gian Porro (2016). Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results. NREL/TP-6A20-64503. Golden, CO: National Renewable Energy Laboratory. https://www.nrel.gov/docs/fy15osti/64503.pdf
Brownlie, A.D., & Prichard, M.F (1963). Professor Fleeming Jenkin, 1833–1885 Pioneer in engineering and political economy. Oxford Economic Papers 15(3), 204 – 216.
Collins, L. (2022, March 22). Cost of hydrogen electrolyzers to fall this decade at similar rates to solar and wind, says IRENA. Recharge News. https://www.rechargenews.com/energy-transition/cost-of-hydrogen-electrolysers-to-fall-this-decade-at-similar-rates-to-solar-and-wind-says-irena/2-1-1192868
Coons, C. (2022, March 10). Bipartisan group unveils hydrogen energy bill to tackle emissions from heavy-duty transportation. Chris Coons. https://www.coons.senate.gov/news/press-releases/bipartisan-group-unveils-hydrogen-energy-bill-to-tackle-emissions-from-heavy-duty-transportation
Cummings (2020, November 16). Electrolyzers – 101: what they are, how they work, and where they fit the green economy. https://www.cummins.com/news/2020/11/16/electrolyzers-101-what-they-are-how-they-work-and-where-they-fit-green-economy
Department of Energy (DOE) (2020a, July). Hydrogen strategy: enabling a low-carbon economy. Office of Fossil Energy. US Department of Energy. https://www.energy.gov/fecm/downloads/hydrogen-strategy-enabling-low-carbon-economy
Department of Energy (DOE) (2020b, September 22). Cost of electrolytic hydrogen production with existing technology. US Department of Energy. https://www.sgh2energy.com/top-coverage
Department of Energy (DOE) (2020c, November). Department of Energy. Hydrogen program plan. US Department of Energy. https://www.energy.gov/articles/energy-department-releases-its-hydrogen-program-plan
Department of Energy (DOE) (2022a). Hydrogen production process: electrolysis. US Department of Energy. https://www.energy.go /eere/fuelcells/hydrogen-production-electrolysis
Department of Energy (DOE) (2022b). Hydrogen shot. US Department of Energy. https://www.energy.gov/eere/fuelcells/hydrogen-shot
Department of State (DOS) (2021a, April). The United States’ Nationally Determined Contribution: Reducing Greenhouse Gases in the United States: A 2030 Emissions Target. US Department of State. https://www4.unfccc.int/sites/NDCStaging/pages/Party.aspx?party=USA
Department of State (DOS) (2021b, November). The Long-Term Strategy of the United States: Pathways to Net-Zero Greenhouse Gas Emission by 2050. US Department of State. https://www.whitehouse.gov/wp-content/uploads/2021/10/US-Long-Term-Strategy.pdf
Eurasia Review (2022, February 28). Making hydrogen fuel anywhere: ONR test prototype to power Marines in expeditionary environments. Eurasia Review News and Analysis. https://www.eurasiareview.com/16022022-making-hydrogen-fuel-anywhere-onr-tests-prototype-to-power-marines-in-expeditionary-environments/
Elgowainy, Amgad, E., Mintz, M., Uisung Lee, U., Stephens, T., Sun, P., Zhou, Y., Zang, G., et al. (2020). Assessment of the Potential Demand for Hydrogen in Vehicle and Industrial Applications. Argonne National Laboratory. https://greet.es.anl.gov/publication-us_future_h2
Economist (2021a, October 9). Creating the new hydrogen economy is a massive undertaking and a delicate one. The Economist. https://www.economist.com/briefing/2021/10/09/creating-the-new-hydrogen-economy-is-a-massive-undertaking
Economist (2021b, October 30). Japan: global climate cooperation. Advertisement in the Special report: Stabilizing the climate. The Economist. http://impact-japanglobalclimatecooperation.economist.com/sustainability/projects/japan-global-climate-cooperation/
EIA (2022). Hydrogen explained. US Energy Information Administration (EIA). https://www.eia.gov/energyexplained/hydrogen/
Fuel Cell and Hydrogen Energy Association (FCHEA) (2020). Road map to a US hydrogen Economy. FCHEA. https://www.fchea.org/us-hydrogen-study
Fuel Cell and Hydrogen Energy Association (FCHEA) (2022). Hydrogen fuel cells codes/standards. FCHEA. http://fuelcellstandards.com/
Gillispie, M. & Krisher, T. (2021, August 13). Hydrogen-powered vehicles: a realistic path to clean energy? ABC News. https://abcnews.go.com/US/wireStory/hydrogen-powered-vehicles-realistic-path-clean-energy-79439859
Goldman Sachs (2022, February 4). Carbonomics: The clean hydrogen revolution. Goldman Sachs. https://www.goldmansachs.com/insights/pages/carbonomics-the-clean-hydrogen-revolution.html
Greene, D.L, Leiby, P. N., & Bowman, D.L. (2007, June) Integrated Analysis of Market Transformation Scenarios with HyTrans. The US Department of Energy – Office of Scientific and Technical Information. https://doi.org/10.2172/930960
Gross, S. (2020, October). The challenge of decarbonizing heavy transport. Brookings Institution. https://www.brookings.edu/wp-content/uploads/2020/09/FP_20201001_challenge_of_decarbonizing_heavy_transport.pdf
Hart, C. A. (2020). Strategy for the future: energy transition, competitiveness, and the future Midwest. Pulte Institute for Global Development – ND Energy Center for Sustainable Energy at the University of Notre Dame. https://pulte.nd.edu/assets/351519/report_strategy_for_the_future_craig_hart.pdf
Hellstern, T., Henderson, K., Kane, S., and Rogers, M. (2021, October). Innovating to net-zero: An executive's guide to climate technology. McKinsey Sustainability. Retrieved from
Hydrogen Council (2021, November). Hydrogen for Net-Zero: A critical cost-competitive energy vector. The Hydrogen Council. https://hydrogencouncil.com/wp-content/uploads/2021/11/Hydrogen-for-Net-Zero.pdf
Hydrogen Mobility Europe (2022). Hydrogen Mobility Europe. https://h2me.eu/
International Renewable Energy Agency (IRENA) (2018). Hydrogen from renewable power: Technology outlook for the energy transition. IRENA. https://www.irena.org/publications/2018/sep/hydrogen-from-renewable-power
The Intergovernmental Panel on Climate Change IPCC (2022). Sixth Assessment Report. The Intergovernmental Panel on Climate Change. https://www.ipcc.ch/assessment-report/ar6/
Jacob S., Kathi M., and Dimitrios P. (2010, March 23). Platinum Group Metal loading. US Department of Energy. https://www.hydrogen. nergy.gov/pdfs/9018_platinum_group.pdf.
John, J.S. (2022, February 22). Which states will win out on $9.5B in federal clean hydrogen funding? Canary Media. https://www.canarymedia.com/articles/hydrogen/which-states-will-win-out-on-9-5b-in-federal-clean-hydrogen-funding
Lakshmanan, TR & Han, X. (1997, March). Factors underlying transportation CO2 emissions in the USA: a decomposition analysis. Transportation Research Part D 2 (1), 1 – 15. https://doi.org/10.1016/S1361-9209(96)00011-9
McCollum, D.& Yang (2009). Achieving deep reductions in US transport greenhouse gas emissions: Scenario analysis and policy implications. Energy Policy 37, 5580-5596
Meyer, T. (2020). Decarbonizing road freight transportation–A bibliometric and network analysis. Transportation Research Part D: Transport and Environment, 89, 102619.
Mitsubishi Power Americas (MP) (2022, April 26). Advanced clean energy storage project receives a $500 million conditional commitment from the US Department of Energy. Mitsubishi Power Americas. https://power.mhi.com/regions/amer/news/20220426#
Mui, S., Alson, J., Ellies, B. Ganss, D. (2007, April). A wedge analysis of the US transportation sector. US Environmental Protection Agency. https://nepis.epa.gov/
Moriarty, P., & Honnery, D. (2019, May 22). Prospect for hydrogen as a transport fuel. International Journal of Hydrogen Energy 44, 16029-16037. http://doi.org/10.1016/j.ijhydene.2019.04.278
National Academy of Sciences (2008). Transitions to alternative transportation technologies: a focus on hydrogen. National Research Council of National Academy of Sciences. https://nap.nationalacademies.org/catalog/12222/transitions-to-alternative-transportation-technologies-a-focus-on-hydrogen
Neil, D. (2022, February 12-13). Dude, where is my hydrogen-powered car? The Wall Street Journal. https://www.wsj.com/articles/hydrogen-powered-cars-11644519367
Oak Ridge National Laboratory (2019). MA3T. 2019. Oak Ridge National Laboratory. https://teem.ornl.gov/ma3t.shtml.
Papadis, E. & Tsatsaronis, G. (2020). Challenges in the decarbonization of the energy sector. Energy, 205 (118025). doi: 10.1016/j.energy.2020.118025.
Preston, C. (2018, October 26). The Carbon Capture Project at Air Products' Port Arthur Hydrogen Production Facility. 14th Greenhouse Gas Control Technologies Conference in Melbourne 21-26 October 2018. http://dx.doi.org/10. 139/3365795
Ruth, M.F, Jadun, P., Gilroy, N., Connelly, E., Boardman, R., Simon, A. J., Elgowainy, A., & Zuboy, Jarett (October 2020). The Technical and Economic Potential of the H2@Scale Hydrogen Concept within the United States. https://doi.org/10.2172/1677471
Saundry, P. (2021a). Module 10. Energy Storage and Integration Issues. [Lecture notes of fuel cells and hydrogen]. AS.425.601.81 Principles and Applications of Energy Technology. Blackboard. https://blackboard.jhu.edu/
Saundry, P. (2021b). Module 13: Energy and Transportation. [Lecture notes on transportation in context]. AS.425.601.81 Principles and Applications of Energy Technology. Blackboard. https://blackboard.jhu.edu/
Saundry, P. (2021c). Module 13: Energy and Transportation. [Lecture notes on electric vehicle transport.] AS.425.601.81 Principles and Applications of Energy Technology. Blackboard. https://blackboard.jhu.edu/
Saundry, P. (2021d). Module 9: Conventional Fossil Generation. [Lecture notes on coal] AS.425.601.81 Principles and Applications of Energy Technology. Blackboard.https://blackboard.jhu.edu/
Saundry, P. (2021e). Module 9: Conventional Fossil Generation [Lecture notes on natural gas in context.] AS.425.601.81 Principles and Applications of Energy Technology. Blackboard. https://blackboard.jhu.edu/
Scholl, L., Shipper, L., Kiang, N. (1996). CO2 emissions from passenger transport: a comparison of international trends from 1973 to 1992. Energy Policy 24, 17-30.
Schwartz, R.A. (2010). Micro Markets: A Market Structure Approach to Microeconomic Analysis. Chichester: Wiley
SGH2 Energy (2022). Economics. SGH2 Energy. https://www.sgh2energy.com/top-coverage
Sinha, P. & Brothy, B. (2021, March 27). Life cycle assessment of renewable hydrogen for fuel cell passenger vehicles in California. Sustainable Energy Technologies and Assessments 45, 1-8. https://doi.org./10.1016/j.seta.2021.101188
Source (2020, March 12). New catalyst resolves hydrogen fuel cell cost and longevity issues. The Washington University in St. Lewis. https:// engineering.wustl.edu/news/2020/New-catalyst-resolves-hydrogen-fuel-cell-cost-longevity-issues.html
UCLA (2016, November 17). Changing fuel cell catalyst shape would dramatically increase efficiency and lower costs. UCLA Samueli School of Engineering. https://samueli.ucla.edu/changing-fuel-cell-catalyst-shape-would-dramatically-increase-efficiency-lower-cost/#
Yang, C., McCollum, D., McCarthy, R., Leighty, W. (2008). Identifying options for deep reductions in greenhouse gas emissions from California transportation: Meeting an 80% reduction goal in 2050. Institute of Transportation Studies, University of California, Davis. https://escholarship.org/uc/item/4408q7cs
Yang, C., McCollum, D., McCarthy, R., Leighty, W. (2009). Meeting an 80% reduction in greenhouse gas emissions from transportation by 2050: a case study in California, USA. Transportation Research Part D: Transport and Environment 14, 147-156. doi: 10.1016/j.trd.2008.11.010