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There is growing interest in the use of hydrogen as a transportation fuel but the environmental benefits of using hydrogen depend critically on how it is produced and distributed. Leading alternatives to using fossil natural gas to make hydrogen through the conventional method of steam methane reforming include using electrolyzers to split water into hydrogen and oxygen, and the use of biogas as an alternative feedstock to fossil natural gas. This report examines the latest carbon intensity (CI) estimates for these and various other hydrogen production processes, adding important nuances to the general “colors of hydrogen” scheme that has been used in recent years. CI values for hydrogen production can vary widely both within and across hydrogen production pathways. The lowest CI pathways use biomass or biogas as a feedstock, and solar or wind power. The report also analyses jobs creation from new hydrogen production facilities and shows that these benefits can be significant for large-scale facilities based on either future biomass/biogas-to-hydrogen or solar-hydrogen production technologies. Recommendations include setting stricter goals for the state’s Low Carbon Fuel Standard (LCFS) program to continue to reduce the carbon footprint of California’s transportation fuels.

To achieve California’s ambitious climate goals, a shift to hydrogen fuel for some transportation sectors may be essential.In this report, we explore the build-out of a hydrogen fuel distribution system including uptake of light-, medium-, and heavy-duty fuel cell electric vehicles. Our analysis of Base and High Case scenarios includes costs of building and operating a hydrogen vehicle and fuel system and estimates workforce impacts. We consider scenarios with about 125,000 vehicles by 2030 in the Base Case and 250,000 in the high case. This increases by an order of magnitude to 2045. Vehicle and station investment costs associated with the Base Case reach anywhere from $4 to 12 billion USD by 2030 and increase by a factor of eight by 2045. Costs per kg of hydrogen, including fuel transmission to stations and station costs delivered to vehicles, could be in the range of $4 to 8 per kg. This becomes $6 to 10/kg as a final delivered cost, if production of hydrogen were to cost $2/kg. Workforce impacts in the Base Case include 600 to 2,200 jobs created by 2030, rising rapidly thereafter. This report was prepared by the ITS-UC Davis Energy Futures Hydrogen Program in partnership with the UCLA Luskin Center for Innovation.

This study proposes a new dense membrane for selectively separating CO2 and O2 at high temperatures and simultaneously producing syngas. The membrane consists of a cermet-type material infiltrated with a ternary carbonate phase. Initially, the co-doped ceria of composition Ce0.9Zr0.05Y0.05O2−δ (CZY) was synthesized by using the conventional solid-state reaction method. Then, the ceramic was mixed with commercial silver powders using a ball milling process and subsequently uniaxially pressed and sintered to form the disk-shaped cermet. The dense membrane was finally formed via the infiltration of molten salts into the porous cermet supports. At high temperatures (700–850 °C), the membranes exhibit CO2/N2 and O2/N2 permselectivity and a high permeation flux under different CO2 concentrations in the feed and sweeping gas flow rates. The observed permeation properties make its use viable for CO2 valorization via the oxy-CO2 reforming of methane, wherein both CO2 and O2 permeated gases were effectively utilized to produce hydrogen-rich syngas (H2 + CO) through a catalytic membrane reactor arrangement at different temperatures ranging from 700 to 850 °C. The effect of the ceramic filler in the cermet is discussed, and continuous permeation testing, up to 115 h, demonstrated the membrane's superior chemical and thermal stability by confirming the absence of any chemical interaction between the material and the carbonates as well as the absence of significant sintering concerns with the pure silver. [ABSTRACT FROM AUTHOR]

California has set a goal of reaching 100% zero emission vehicle (ZEV) sales by 2035. Most ZEV sales to date have been battery electric vehicles (BEVs) or plug-in hybrid electric vehicles (PHEVs), while fuel cell electric vehicles (FCEVs) make up only a small portion of ZEV sales. The market for FCEVs may be partially constrained because, unlike BEVs and PHEVs, they cannot use any existing infrastructure. This research investigates FCEV drivers use of hydrogen stations in California (of which there are 47 in operation) with the goal of informing the development of hydrogen infrastructure. Hydrogen station use was studied using results from a 2017 survey of 395 fuel cell electric vehicle (FCEV) owners and a 2018 survey of 328 FCEV owners. The results show FCEV drivers use on average 2.4 hydrogen stations. The average shortest distance FCEV owners would need to travel from home, work, or their commute to a hydrogen refueling station was 10 miles. Those whose most-used station was not the closest station available were more likely than those whose most-used station was the closest to use renewable hydrogen, suggesting that some drivers may prefer renewable hydrogen. Currently the percentage of California census block groups with one, two, and three hydrogen stations within 10 miles of households are 52.4%, 25.6%, and 22.5%; these census block groups are concentrated primarily in large metropolitan areas. Finally, 70% of FCEV owners said they would not have purchased the vehicle if their primary station had not been available, pointing the importance of station availability to FCEV adoption.

This study proposes a new dense membrane for selectively separating CO2 and O2 at high temperatures and simultaneously producing syngas. The membrane consists of a cermet-type material infiltrated with a ternary carbonate phase. Initially, the co-doped ceria of composition Ce0.9Zr0.05Y0.05O2−δ (CZY) was synthesized by using the conventional solid-state reaction method. Then, the ceramic was mixed with commercial silver powders using a ball milling process and subsequently uniaxially pressed and sintered to form the disk-shaped cermet. The dense membrane was finally formed via the infiltration of molten salts into the porous cermet supports. At high temperatures (700–850 °C), the membranes exhibit CO2/N2 and O2/N2 permselectivity and a high permeation flux under different CO2 concentrations in the feed and sweeping gas flow rates. The observed permeation properties make its use viable for CO2 valorization via the oxy-CO2 reforming of methane, wherein both CO2 and O2 permeated gases were effectively utilized to produce hydrogen-rich syngas (H2 + CO) through a catalytic membrane reactor arrangement at different temperatures ranging from 700 to 850 °C. The effect of the ceramic filler in the cermet is discussed, and continuous permeation testing, up to 115 h, demonstrated the membrane’s superior chemical and thermal stability by confirming the absence of any chemical interaction between the material and the carbonates as well as the absence of significant sintering concerns with the pure silver.

Mixing in the combustion chamber is influenced by the velocity distribution of the inlet airflow. Numerical simulations are carried out by using the 3D coupled implicit Reynolds-averaged Navier-Stokes (RANS) equations and the SST k-ω turbulence model. This article compares the flow field characteristics of non-uniform flows with uniform flows. The results show that the penetration depth increases by 22% in the case of a decreasing velocity distribution along the longitudinal direction compared to the increasing velocity condition. The difference in total pressure loss compared to uniform flow is greater than 4%. The mixing coefficient in the cavity is only 81% of uniform flow. The two-hole jet flow approach is able to rapidly reach 90%. The study shows that the non-uniform inlet has a considerable impact on fuel mixing. The high velocity region near the jet hole contributes to the mixing performance of the engine combustion chamber. • A numerical study of the mixing mechanism in supersonic non-uniform flow. • The effects of different flow on the mixing characteristics. • The high-speed region is distributed near the jet is helpful for mixing. • The high velocity flow close to the jet causes the local flow to lift much higher. [ABSTRACT FROM AUTHOR]

A spatial optimization model was developed for deploying, over the next two decades, hydrogen refueling stations for heavy-duty zero-emission hydrogen vehicles. The model assigns trips to vehicles by applying a routing algorithm to travel demand data derived from another model—the California Statewide Travel Demand Model (developed by the California Department of Transportation). Across a range of adoption levels of hydrogen fuel-cell truck technology, from 2020 through 2030, the results suggest that heterogeneity of travel demand may necessitate an extensive distribution of refueling stations, which may lead to low utilization of stations in the short term. To efficiently employ the capacity of stations, a certain volume of vehicle adoption must be met, and/or truck routes must be planned and committed to specific roadways. Once the number of stations reaches a threshold to meet the principal demand in affected transportation area zones, a small set of smaller “top-off” stations can be built to meet marginal excess demand. The best location of a hydrogen refueling station within a transportation area zone also depends on the criteria such as land cover, slope, and distance from gas stations, truck hubs, and the truck network.

Zero-emission vehicles are seen as key technologies for reducing freight- related air pollution and greenhouse gas emissions. California’s 2016 Sustainable Freight Action Plan established a target of 100,000 zero-emission freight vehicles utilizing renewable fuels by 2030. Hydrogen fuel cell vehicles are a promising zero-emission technology, especially for applications where batteries might be difficult to implement, such as heavy-duty trucks, rail, shipping and aviation. However, California’s current hydrogen infrastructure is sparse, with about 25 stations, primarily sited to serve fuel cell passenger vehicles and buses. New infrastructure strategies will be critical for implementing hydrogen freight applications. The researchers analyzed hydrogen infrastructure requirements, focusing on hydrogen fuel cells in freight applications, using a California-specific EXCEL-based scenario model developed under the Sustainable Transportation Energy Pathways program (STEPS) at the Institute of Transportation Studies at UC Davis (Miller et al, 2017). Hydrogen vehicle adoption and demand was estimated for trucks, rail, shipping, and aviation, for a range of scenarios out to 2050.

This study considers the aircraft configuration impacts of a liquid-hydrogen fuel-cell electric propulsion system when integrated into a single-aisle, transport-class aircraft having comparable performance capability of a Boeing 737-800. This study demonstrates that, given estimated developments in future components and subsystem technologies for a 2050 entry into service date, the design of an aircraft with a liquid-hydrogen fuel-cell-based propulsion system can be feasibly achieved while still meeting mission-level performance characteristics consistent with modern commercial aircraft throughout the anticipated lifetime of the aircraft. Key technologies that enable this are the purposeful integration of fuel cell thermal management, independent inlet compression to pressurize the air input to the fuel cells, and leveraging distributed electric propulsion advantages. Exploration into the impact of fuel cell power loss due to degradation is also presented. The results show a promising configuration of a liquid-hydrogen fuel-cell-based commercial aircraft to serve as a feasible replacement of narrow-body transport aircraft to help meet climate goals set for the aviation industry. [ABSTRACT FROM AUTHOR]

California’s low carbon fuel standard (LCFS) specifies that the state’s transportation fuel supply achieve a 20% reduction in carbon intensity (CI) below 2011 levels by 2030. Reaching the standard will require substantive changes in the fuel mix, but the specifics and the cost of these changes are uncertain. We assess if and how California is likely to achieve the standard, and the likely impact of infrastructure credits on this compliance outlook. We begin by projecting a distribution of fuel and vehicle miles demand under business-as-usual economic and policy variation and transform those projections into a distribution of LCFS net deficits for the entire period from 2019 through 2030. We then construct a variety of scenarios characterizing LCFS credit supply that consider different assumptions regarding input markets, technological adoption over the compliance period, and the efficacy of complementary policies. In our baseline scenario for credit generation, LCFS compliance would require that between 60% and 80% of the diesel pool be produced from biomass. Our baseline projections have the number of electric vehicles reaching 1.3 million by 2030, but if the number of electric vehicles reaches Governor Jerry Brown’s goal of 5 million by 2030, then LCFS compliance would require substantially less biomass-based diesel. Outside of rapid zero emission vehicle penetration, compliance in 2030 with the $200 credit price may be much more difficult. New mechanisms to allow firms to generate credits by building electric vehicle charging stations or hydrogen fueling stations have minor implications for overall compliance because the total quantity of infrastructure credits is restricted to be relatively small.

Recently, the theme of the "green transition", in which the economic and commercial prospects of the hydrogen industry play a leading role, in the global energy industry has attracted special attention from business, government and scientific circles in many countries, which is associated with its predicted impact, incl. due to the climate agenda, to the economic, technological and geopolitical redistribution of the energy map of the world at the global and regional levels. Some slowdown in the "green transition" is expected due to the need to overcome the global energy crisis in the next two or three years, which may turn out to be more serious than the crisis of the 1970s of the last century which will require eliminating the shortage of traditional non-renewable energy resources in the near future. Nevertheless, the "green transition", in which hydrogen accents are intensifying, continues to be implemented, which will have a serious impact on the system of international and international economic relations in the world. Thanks to the financial support of the state and business, modern technologies of the entire hydrogen energy chain are actively developing, hydrogen markets are being formed in the conditions of inter-fuel competition, as well as hydrogen energy command centers at the global, regional, country and corporate levels. [ABSTRACT FROM AUTHOR]

Understanding boundary-layer flashback is critical to the design of safe and efficient gas turbines, especially as the addition of highly reactive hydrogen to these devices becomes a prevailing trend for reduction of carbon dioxide emissions. In this work, the boundary-layer flashback of lean hydrogen-air mixtures is studied using large-eddy simulations based on a generic turbulent swirl burner previously investigated experimentally. Simulations at increasing equivalence ratios are used to identify the flashback limits, showing reasonable qualitative agreement with experimental measurements. Flame dynamics during flashback are compared to previous experimental studies, indicating that important physics are captured in the simulations even if the exact flashback limits are not. In particular, a change in the swirl vane angle is shown to dramatically change the flame dynamics, with flame propagation occurring in the direction of swirl at high angles and against the direction of swirl at low angles, consistent with experimental observations. The near-wall nonreacting mean velocity field is shown to be controlled by a temporally stationary flow instability, which is directly responsible for the counterswirl flame flashback exhibited at low swirl angles. Finally, the interaction of local axial flow velocity and flame propagation speed of the leading flame point is investigated with varying swirl angles both before and after the onset of flashback, elucidating the differences in flame dynamics in all four of these cases. In particular, the importance of local flame extinction on flashback limits is emphasized. [ABSTRACT FROM AUTHOR]

Artificial fuels have been researched for more than a decade now in an attempt to find alternative sources of energy. With global climatic conditions rapidly approaching the end of their safe line, an emphasis on escalating the change has been seen in recent times. Synthetic fuels are a diverse group of compounds that can be used as replacements for traditional fuels, such as gasoline and diesel. This paper provides a comprehensive review of synthetic fuels, with a focus on their classification and production processes. The article begins with an in-depth introduction, followed by virtually classifying the major synthetic fuels that are currently produced on an industrial scale. The article further discusses their feedstocks and production processes, along with detailed equations and diagrams to help readers understand the basic science behind synthetic fuels. The environmental impact of these fuels is also explored, along with their respective key players in the industry. By highlighting the benefits and drawbacks of synthetic fuels, this study also aims to facilitate an informed discussion about the future of energy and the role that synthetic fuels may play in reducing our reliance on fossil fuels. [ABSTRACT FROM AUTHOR]

The emergence of natural gas (NG) as an abundant, inexpensive fuel in the United States has highlighted the possibility that it could play a significant role in the transition to low carbon fuels. It is often cited as a “bridge” to low carbon fuels in the transportation sector. Major corporations are already investing billions of dollars to build NG fueling infrastructure to expand its use in U.S. trucking fleets.In California, NG fueling infrastructure is expanding, especially in and around the ports of Los Angeles and Long Beach, and the use of NG-fueled medium- and heavy-duty fleets is currently on an upswing. The state is relying in part on the development and use of alternative fuels such as renewable natural gas (RNG) and hydrogen, which have low greenhouse gas and criteria pollutant emissions, to meet its climate change and air quality goals.This policy brief summarizes findings from the research project which examines how NG infrastructure can be economically and technologically synergistic for both NG and RNG in the near term, and for RNG and other renewables such as hydrogen in the long term. In particular, it examines optimum paths for developing infrastructure in the near term that will accommodate alternative fuels once they become available at the commercial scale. The original design of California’s Low Carbon Fuel Standard (LCFS) provides time for the development of advanced, near-zero technologies. The research considers the use of LCFS credits in its analysis.View the NCST Project Webpage

It is becoming increasingly important to develop effective combustion technologies for low calorific industrial gases (LCIG) because of the rising energy demand and environmental issues caused by the extensive use of fossil fuels. In this review, the prospect of these opportunity fuels in China is discussed. Then, the recent fundamental and engineering studies of LCIG combustion are summarized. Specifically, the differences between LCIG and traditional fuels in the composition and fundamental combustion characteristics are described. The state-of-the-art combustion strategies for burning LCIG are reviewed, including porous media combustion, flameless combustion, oxy-fuel combustion, and dual-fuel combustion. The technical challenges and further development needs for efficient LCIG combustion are also discussed. [ABSTRACT FROM AUTHOR]

An evaluation of renewable hydrogen production technologies anticipated to be available in the short, mid- and long-term timeframes was conducted. Renewable conversion pathways often rely on a combination of renewable and fossil energy sources, with the primary conversion step relying on a completely renewable source and the auxiliary steps using a more readily available energy mix such as grid electricity. The conversion technologies can be broadly classified into four categories based on the primary conversion mechanism: thermal processes, electrolytic processes, photolytic processes, and biochemical processes. Based on anticipated technology readiness, water electrolysis and biogas reforming pathways will be available in the near term whereas biomass gasification and bio-derived liquids reforming pathways are expected to be available in the mid-term. Photolytic and dark fermentation approaches are still in the research stage and must go through significant development and demonstration.View the NCST Project Webpage

The emergence of natural gas as an abundant, inexpensive fuel in the United States has highlighted the possibility that natural gas could play a significant role in the transition to low carbon fuels. Natural gas is often cited as a “bridge” to low carbon fuels in the transportation sector. Major corporations are already investing billions of dollars to build infrastructure to feed natural gas into the U.S. trucking industry and expand the use of natural gas in fleets. In the state of California, natural gas fueling infrastructure is expanding, especially in and around the ports of Los Angeles and Long Beach. The use of natural gas fueled medium and heavy duty fleets is currently on an upswing. The authors examine the precise natural gas infrastructure that is economically and technologically synergistic for both natural gas and renewable natural gas in the near-term, and alternative fuels like renewable natural gas (RNG) and hydrogen in the long term. In particular, the authors examine optimum paths for developing infrastructure in the near-term that will accommodate alternative fuels once they become available at the commercial scale. The original design of the Low Carbon Fuel Standard (LCFS) provides time for the development of advanced, near zero technologies. The authors consider the credits from the LCFS in our analysis.View the NCST Project Webpage

The transportation and electricity sectors are major sources of U.S. greenhouse gas (GHG) emissions because fossil fuels are the dominant energy source for the transportation sector and for electricity generation. Both sectors are facing the challenge of shifting to a more sustainable future. In the transportation sector, plug-in electric vehicles (PEV) and hydrogen fuel cell electric vehicles (FCEV) will play a key role in meeting California’s 2050 GHG goals. This research studied the feasibility of the deployment of renewable hydrogen fueling for FCEVs and DC fast charging stations for PEVs at Highway Safety Roadside Rest Areas (SRRAs) and the integration of the stations with the electricity grid, including solar electric generation, to lower the infrastructure cost and to accelerate the usage of renewable energy in the California transportation sector. Three hydrogen fueling/DC fast charging system configurations were studied: two integrated stations with energy storage using compressed hydrogen or batteries as the energy storage medium located on a single site, and a distributed system configuration deployed on different sites. In this analysis, we assessed the sustainable integrated fueling/charging stations based on 100% of utilization of the local PV electricity for hydrogen fueling/DC fast charging. The hydrogen fuelings and EV chargings were evenly divided based on their energy consumption. However, in the early stage of FCEV and PEV adoption, a relatively low utilization of fueling/charging stations is likely. In that case, the integrated stations could function as distributed power generation and energy storage for the grid. As the market for FCEVs and EVs develops, the integrated stations have the potential to serve the larger numbers of FCEVs and PEVs by using grid electricity during off-peak hours.View the NCST Project Webpage

During the 1990s, a high temperature lubricant called Triboglide was developed as a derivative of the NASA 200 series coating system. The new lubricant was the result of a collaboration [...]

Solar thermochemical water‐splitting cycle models for hydrogen production with single and multiple receivers working between 1773 and 1173 K are developed. The receiver pressures and aperture sizes are optimized for maximum cycle efficiency. The efficiency of the cycle increases with the number of receivers because of the decrease in vacuum pump work. The solar‐to‐fuel efficiency is increased by 14% going from a one receiver system to a four‐receiver system. The performance analyses of the cycles with varying direct normal irradiance (DNI) shows that the advantage of multiple receivers vanishes as DNI decreases because of the constant radiation losses from the receiver apertures. These radiation losses from the aperture can be lowered when a receiver with a variable aperture size is used. The efficiency of a two‐receiver system increases by 48% at DNI 300 W m−2% and 15% at DNI 900 W m−2 using a variable aperture size. The performance of the multireceiver systems with variable aperture size is discussed using a linear regression model. In addition, the option of cogeneration of hydrogen and electricity in a multireceiver system is analyzed. The efficiencies of single‐, two‐, three‐, and four‐receiver systems for cogeneration are 19.6%, 20.0%, 20.57%, and 21.1%, respectively. [ABSTRACT FROM AUTHOR]

This white paper reviews previous studies on prospects for reducing CO2 emissions from trucks. It provides a new investigation into the feasibility of achieving an 80% reduction in CO2-equivalent (CO2e) greenhouse gas (GHG) emissions in the United States and California from trucks by 2050. The authors assess the technological and economic potential of achieving deep market penetrations of low-carbon vehicles and fuels, including vehicles operating on electricity, hydrogen, and biofuels. Achieving such a target for trucks will be very challenging and, if focused on hydrogen and electric zero emission vehicle (ZEV) technologies, will require strong sales growth beginning no later than 2025.View the NCST Project Webpage

The United States and California have made commitments to reduce energy-related greenhouse gas (GHG) emissions, with California aiming to cut GHG emissions by 80% below 1990 levels by 2050. Individual sectors and transportation modes are not necessarily required to meet this “80-in-50” goal, but if any one mode (such as trucks) fails to, it puts more pressure on other modes to achieve deeper cuts. Trucking is the dominant domestic freight mode in the country, and is also the fastest growing sector and consumes more energy than any other freight mode. This policy brief summarizes research that suggests that the combination of significantly improved vehicle efficiency coupled with very low-carbon fuels (electricity, hydrogen, or biofuels) can help the trucking sector reach the GHG target.View the NCST Project Webpage

It is becoming increasingly important to develop effective combustion technologies for low calorific industrial gases (LCIG) because of the rising energy demand and environmental issues caused by the extensive use of fossil fuels. In this review, the prospect of these opportunity fuels in China is discussed. Then, the recent fundamental and engineering studies of LCIG combustion are summarized. Specifically, the differences between LCIG and traditional fuels in the composition and fundamental combustion characteristics are described. The state-of-the-art combustion strategies for burning LCIG are reviewed, including porous media combustion, flameless combustion, oxy-fuel combustion, and dual-fuel combustion. The technical challenges and further development needs for efficient LCIG combustion are also discussed.