Natural Gas Vehicle Technology Forum 2023 Meeting Summary
The 2023 Natural Gas Vehicle Technology Forum (NGVTF) was held on Jan. 31 and Feb. 1, 2023, at the SoCalGas Energy Resource Center in Downey, California. Following is a summary of the meeting.
Day One: January 31, 2023
Welcome and Agenda Review
Margo Melendez, NREL
Margo welcomed forum participants and introduced the National Renewable Energy Laboratory (NREL). She provided an overview of the meeting structure and agenda.
Southern California Gas Program Overview
Don Widjaja, Southern California Gas Company
Don Widjaja welcomed forum participants to the SoCalGas Energy Resource Center. He then presented an overview of SoCalGas, highlighting that it is the largest natural gas distribution utility in the United States, serving 22 million customers over 20,000 square miles of territory, and annually delivering 1 trillion cubic feet of natural gas (5% of U.S. natural gas deliveries). He then talked about SoCalGas’ programs addressing future customer needs, including renewable natural gas (RNG), hydrogen, and hydrogen blends in natural gas. He discussed SoCalGas' goal of achieving net-zero greenhouse gas (GHG) emissions in its operations and delivery of energy by 2045. Having already met a goal of delivering 5% volume RNG to customers, SoCalGas plans to deliver 20% volume RNG by the end of 2030. Don was particularly excited about SoCalGas’ H2 Innovation Experience hydrogen home demonstration, located at the Energy Resource Center. Unveiled earlier that week, the H2 Innovation Experience hydrogen home includes a co-located scaled hydrogen generation and storage infrastructure that is capable of powering 100 homes for a week. The H2 Hydrogen Home includes currently available production natural gas appliances that can handle up to 20% volume hydrogen blend without issues. Don also discussed SoCalGas’ fleet that includes Toyota Mirai hydrogen fuel cell vehicles, which was on display outside the SoCalGas Energy Resource Center.
NGVTF – U.S. Department of Energy (DOE) Update
Michael Laughlin, DOE
Michael Laughlin provided an update on DOE activities related to natural gas for transportation. His overview included ongoing work with a natural gas emphasis, including funding opportunity announcements (FOAs) and research at DOE national laboratories which is primarily funded by the Technology Integration Program in the DOE Vehicle Technologies Office (VTO). Technology Integration Program highlights included: deployment of a natural gas refuse trucks with the City of Kansas City; collection of maintenance costs for natural gas freight trucks versus diesel (with over 1,600 vehicles currently in the database); demonstration of a smart compressed natural gas (CNG) fueling system for more complete vehicle fills; development of a next generation natural gas vehicle (NGV) driver information system to accurately predict miles-to-empty; helping rural communities transition to cleaner fuels and vehicles; development of a natural gas locomotive concept using multiple on-road natural gas engines; and deploying natural gas trucks in a tribal community in the north slope of Alaska using locally-sourced natural gas. DOE national laboratory natural gas work highlights included safety modeling of CNG/liquefied natural gas (LNG)/propane release behavior (Sandia National Laboratories); MotorWeek television segments on alternative fuels (Oak Ridge National Laboratory); and Alternative Fuel Data Center (AFDC) information for Clean Cities stakeholders, fleets, transportation decisions makers, and the public (NREL).
Laughlin also reviewed related research and development from other VTO programs and discussed what is on the horizon. He summarized FOA awards over the last several years including natural gas fuel storage technologies, waste to energy/RNG production, and natural gas engine enabling technologies. He further explained that these award projects are being managed by the VTO Decarbonization Team (formerly the Advanced Combustion & Fuels Team). He pointed to the future reminding NGVTF participants that the fiscal year (FY) 2022 FOA included two natural topics for which a selection announcement would be coming. Those topics were natural gas engines for off-road, rail, and marine ($5 million), and low GHG concepts for off-road vehicles and equipment ($5 million). He explained that FY 2023 appropriations for VTO included language on addressing technical barriers to increased use of NGVs, focusing on non-fossil based RNG (up to $10 million). Further, he explained that the U.S. Department of Transportation (DOT) Community and Fueling Infrastructure Grant Program under the Bipartisan Infrastructure Law includes provisions for natural gas fueling.
California Energy Commission (CEC) Technology Program Overview
Peter Chen, CEC
Peter Chen provided a review of CEC’s mission to strategically invest funds to catalyze change and accelerate achievement of energy policy goals, and how that ties to CEC’s Energy Research and Development Division funding programs, under which the Gas Research and Development (R&D) Program operates. The Gas R&D Program supports the transition to clean energy, greater reliability, lower costs, and increased safety for Californians. The current annual budget is $24 million, funded by a surcharge on gas consumption, supports state energy policy, and focuses on energy efficiency, renewables, conservation, environmental issues, and transportation. He explained California policy drivers including Executive Orders to achieve carbon neutrality as soon as possible—no later than 2045—and related goals to transition light-, medium-, and heavy-duty vehicles and off-road equipment to zero-emission wherever possible.
Chen also reviewed the Transportation Gas R&D Portfolio. These projects include in-use emissions and fuel use assessment (South Coast Air Quality Management District’s 200 vehicle study). Hydrogen fuel cell demonstrations include hydrogen fuel cells for switcher locomotives (led by GTI Energy with Sierra Northern Railway), tugboats at the Port of Los Angeles (led by CALSTART), and small fast harbor craft (led by Zero Emission Industries). Hydrogen fuel cell truck demonstrations for challenging duty cycles include long-haul—aiming for 500-mile range with 700 bar storage (with Cummins Electrified Power)—and heavy payloads with long routes and limited fueling opportunities (with GTI Energy and Symbio). He explained the Transportation Gas R&D Portfolio also included the Natural Gas Vehicle Research Consortium coordinated by NREL, with CEC funding supporting four projects: Cummins, Transient Plasma Systems, US Hybrid, and GTI Energy. Chen concluded by highlighting future gas R&D initiatives and concepts, spanning topics such as hydrogen leakage, air pollutant exposure assessment in CA residences, advancing innovative onboard hydrogen storage for transportation, gas system safety, renewable power generation, low carbon entrepreneur development, and supporting equitable, safe, and cost-effective decarbonization of California’s gas system.
RD&D Within the Clean Transportation Program
Jeffrey Chase, Southern California Gas Company (SoCalGas)
Jeffrey Chase provided an overview of SoCalGas’ research, development, and demonstration (RD&D) plan, incorporating SoCalGas’ values around science, synergy, and equity. The RD&D research plan supports hundreds of projects while considering ratepayer needs, regulatory and policy drivers, and industry input. The project portfolio benefits customers with projects focused on: reliability (203 projects), reduced GHG emissions (211), improved air quality (167), safety (177), improved affordability (107), and operational efficiency (144). The RD&D structure is based around low-carbon resources, gas operations, clean transportation, clean generation, and customer end-use applications. He explained how SoCalGas’ efforts involved synergistic collaboration with universities, public agencies, national laboratories, research consortia, and other businesses.
Chase then dived deeper into SoCalGas’ Clean Transportation Program, encompassing off-road, on-road, onboard storage, and refueling stations. He highlighted projects including a hydrogen fuel cell switcher locomotive demonstration (led by GTI Energy), fuel cell electric paratransit shuttle demonstration (led by A-1 Alternative Fuels), metal hydride hydrogen storage for heavy-duty vehicles (led by Sandia National Laboratories), and development of a new high-flow hydrogen refueling protocol for medium- and heavy-duty vehicles (led by NREL). He also displayed a Doosan hydrogen fuel cell drone, capable of up to 2-hours flight time with 300 g hydrogen capacity.
South Coast Air Quality Management District (SCAQMD) Technology Program Overview
Sam Cao, SCAQMD
Sam Cao provided an overview of SCAQMD’s Clean Fuels Program in addition to an update on the 200-vehicle emissions study. He began with a review of SCAQMD’s 2022 air quality management plan to reduce NOx emission by 83% from 2018 to 2037. While reductions from already adopted regulations and programs are projected to reduce NOx emissions from 350 tons per day in 2018 to ~180 tons per day in 2037, additional reductions are needed to attain 70 parts per billion which relates to a carrying capacity of approximately 60 tons per day. Cao explained how the Clean Fuels Program Fund uses a $1 fee on Department of Motor Vehicle registrations to generate ~$12 million/year in addition to a stationary source fee which generates ~$400,000/year. The Clean Fuels Program Fund leverages these funds with grants and other project partners to research, develop, demonstrate, and deploy clean technologies. The main incentive programs SCAQMD leverages are the Carl Moyer program, the Proposition 1B goods movement program, the Lower E School Bus program, and Replace Your Ride. He then reviewed highlights of SCAQMD’s journey to 0.02 grams per brake horsepower-hour (g/bhp-hr) engines since the year 2000. He reviewed SCAQMD’s draft 2023 Clean Fuel Plan Update that proves a new focus on technology development for zero-emission. The key technical areas of the draft 2023 Clean Fuel Plan Update include: zero-emission medium- and heavy-duty trucks and equipment, challenges and solutions to zero-emission infrastructure, zero-emission microgrids, ultra-low NOx and heavy-duty zero-emission engine technologies, emissions studies on renewable fuels and other sources, and maintaining other areas of emphasis.
Cao then gave an update on the 200 Vehicle Program emissions study, that included 236 vehicles, 5 vocations, and 10 technologies. Testing elements of the study included portable activity measurement systems (PAMS), portable emissions measurement systems (PEMS), a new chassis dynamometer test cycle, and road grade data. The resulting data and analysis feed emission inventory models. Cao explained key findings, including PAMS data where idle, low-speed, and low power operation dominated the activity data. As a result, 162 PAMS datasets were used as inputs to the U.S. Environmental Protection Agency (EPA) California EMFAC (short for EMission FACtor) model for 2021. In addition, three new chassis dynamometer cycles and four new real-world test routes were developed from PAMS data. He also discussed how understanding of duty-cycle and averaging methods impacted results. For example, a 0.2 g/bhp-hr NOx goods movement truck could vary from 0.07 to 0.33 g/bhp-hr in the study, highlighting how real-world variability (other than the test article) impacted results. The PEMS daily averaged NOx emissions showed high variability, with duty cycle variation masking any trends. However, chassis cycle averaged data show real NOx reductions for alternative fuel vehicles. On-road route-averaged NOx trends were as expected. The study provided valuable lessons learned regarding systemic, rare/random, and duty-cycle related data outliers, as well as measurement system effects (with constant volume sampling) creating system errors for measuring natural gas engine emissions. The 200 Vehicle Program study final report was under review at the time of NGVTF.
Natural Gas Consortia Projects Update
Matt Panec and Brad Zigler, 44 Energy
Brad Zigler began the presentation introducing 44 Energy to the audience and explaining how they were assisting NREL under subcontract to provide technical assistance and support for NREL’s management of projects under the Natural Gas R&D Consortium. He explained NREL had a successful history of collaboratively working with DOE, CEC, and SCAQMD to encourage innovation in medium- and heavy-duty NGVs, working to improve NGV total cost of ownership, emissions, and efficiency. The current Natural Gas R&D Consortium was formed in 2018 by NREL with DOE VTO, CEC, and SCAQMD funding, focusing on three key objectives: achieving total cost of ownership and efficiency improvements approaching conventional vehicles, realizing low NOx and low emissions benefits, and increasing partnering with key stakeholders in the NGV industry. NREL coordinated a Request for Proposals that resulted in awarded projects to Cummins, GTI Energy, Michigan Technological University (MTU), Southwest Research Institute (SwRI), Transient Plasma Systems (TPS), US Hybrid, University of Alabama, and University at Buffalo.
Matt Panec then provided an overview of Natural Gas R&D Consortium projects, most of which were covered in detail with their own NGVTF presentations. Panec provided more detailed presentations for the University of Alabama and MTU projects. University of Alabama’s project involves improving dual-fuel natural gas engine emissions and efficiency by optimizing fuel combustion strategies and investigating alternative pilot combustion fuels. This project included studies on replacing use of diesel fuel for traditional pilot ignition with polyoxymethylene dimethyl ether (POMEDME), which has a high cetane number to prevent misfire and high oxygenation to produce sootless emissions. The research also includes spray targeted stratification with multiple pilot injection events and will consider temperature-controlled exhaust gas recirculation. Successes to date include demonstration of 57.5% indicated thermal efficiency with diesel-NG and 54.2% with POMDME-natural gas, with near zero soot and NOx approaching 0.02 g/bhp-hr. The MTU project, conducted in collaboration with Westport Fuel Systems, focuses on feasibility demonstration of compression ignition of directly injected natural gas to enable the commercialization of mono-fuel natural gas compression ignition combustion engine technology. The project incorporates Westport’s high-pressure direct-injection (HPDI) technology operated as a mono-fuel injector capable of supplying multiple gaseous injection events per combustion cycle. Testing is also currently underway to measure the effects of thermal barrier coating on the piston to increase efficiency and optimize emissions. Successes to date include demonstration of 24 bar mean effective pressure load and 48% indicated thermal efficiency. Future work planned includes natural gas/hydrogen blends.
Hydrogen HPDI – Hydrogen IC Engine Development
David Mumford, Westport Fuel Systems
David Mumford discussed Westport’s alternative fuel capabilities, covering a range of alternative fuels, including liquified petroleum gas, CNG, LNG, and hydrogen (including hydrogen/CNG blends). He discussed the overlay of mobile applications, fuel choice, and engine technologies. The applications range from high-horsepower (mining, rail, and marine) to heavy-duty on-highway to medium- and light-duty vehicles. Westport’s HPDI uses a unique injector with a diesel pilot, allowing LNG or CNG fueling. HPDI engine performance matches diesel power and torque with comparable efficiency (within 1%), with full engine drivability and engine braking performance. Significantly, HPDI with natural gas allows a 20% GHG benefit over a diesel engine, reaching over 85% on RNG with suitable blends. Demonstrations in Europe this year will reach close to 800 HPDI LNG trucks at 18 locations.
Mumford also discussed Westport’s promising preliminary work with hydrogen engine combustion using HPDI. Computational fluid dynamics modeling and engine test data indicate a full load hydrogen HPDI brake thermal efficiency of 46%–47% versus 41%–43% with natural gas, with the relative efficiency gain of hydrogen versus natural gas being larger at high load points. Residual CO2 emissions from the hydrogen HPDI engine could be further lowered with reductions in the pilot fuel quantity or by shifting to a low- or zero-carbon content pilot fuel. Tradeoffs for hydrogen HPDI include increased engine-out NOx due to higher flame temperature and excess air. Development in adjusting fuel injection pressure, timing, and exhaust gas recirculation (EGR) are bringing down engine-out NOx down to natural gas HPDI levels while maintaining significant indicated mean effective pressure and indicated specific fuel consumption advantages. He explained that a joint Westport Fuel Systems/AVL total cost of ownership study showed hydrogen HPDI trucks can provide a lower total cost of ownership and much more cost-effective CO2 reduction than fuel cell electric vehicles due to lower cost of hydrogen HPDI with similar operational costs.
Cummins Heavy Duty Hydrogen Engine Update
Jay Shah, Cummins Engine Company
Jay Shah provided an update on Cummins’ hydrogen internal combustion engine development program. He began with Cummins’ initiative to reach destination zero for CO2 emissions, with many solutions competing segment by segment to reach broadly available zero emissions solutions by 2050. He then described Cummins’ new fuel-agnostic internal combustion engine platform, derived from a common base engine with a high degree of parts commonality. Each engine version will have different components above the head gasket for different fuel types but maintain largely similar components below the head gasket. Heavy-duty versions use clean diesel, natural gas, and hydrogen. Medium-duty versions use gasoline, propane, clean diesel, natural gas, and hydrogen. As part of this fuel agnostic approach, Shah described the new X15 global platform which will launch in natural gas for 2024, add diesel in 2026, followed by hydrogen in 2027.
Cummins’ hydrogen engine lineup includes a 6.7L (B6.7H) at 170–215 kW, a 9.9L (X10H) at 230–280 kW, and a 14.5L (X15H at 300–400 kW). The “X” series engines use the new global fuel agnostic platform described earlier. All feature a pent roof cylinder head with tumble combustion, spark ignition, direct injection, lean burn, with selective catalytic reduction aftertreatment, and are planned to meet EPA 2027 emissions levels. The B6.7H and X15H are planned for field trials starting in 2025 with series production in 2027. Both hydrogen engines have completed several hours of multicylinder engine testing, and have demonstrated target peak torque, power, and brake thermal efficiency. Cummins recently announced hydrogen internal combustion engine partnerships with Werner Enterprises, Transport Enterprise Leasing, Tata, Versatile (off-road tractor), and Daimler Truck. During the question-and-answer period, Shah was asked if Cummins was also pursuing hydrogen internal combustion engines for locomotive. He replied, yes, but under a different business unit. Cummins has interest in hydrogen engines for off-road, marine, and rail, in addition to on-road.
Hydrogen Compression and Fueling Advancements
Graham Barker, ANGI Energy
Graham Barker gave an overview of hydrogen vehicle fueling equipment development, highlighting opportunities and challenges. He began with an overview of ANGI Energy, which is a division of Gilbarco Veeder-Root (GVR) and supplies refueling solutions to 22 countries and over 260,000 retail fueling customer sites. Barker discussed ANGI/GVR’s decision to enter the hydrogen refueling market based on market surveys in North America and Europe. He discussed voice of the customer feedback that for the past 20 years, hydrogen equipment has primarily been supplied by companies whose expertise is outside of retail fueling and have been designed without focus on redundancy and serviceability, causing station downtime. Other challenges include length of time for permitting, approvals, and certifications and that the hydrogen market is currently too reliant on government funding. ANGI/GVR plans to leverage experience from other successful fueling business like gasoline, diesel, and CNG to develop a reliable retail experience feature integrated payment systems, remote communication, and monitoring, along with configurability and modularity. Barker explained that the lack of redundancy is due to two main reasons. First, component costs are extremely high due to hydrogen fueling pressures, with an exponential increase from 350 bar to 700 bar. Second, inexperience in compressed gas fueling strategies results in inefficient designs and low consideration for redundancy. ANGI/GVR believes component prices will drop significantly as the market increases and permitting and approval times can be approved with training for permitting/approval bodies by providing standardized requirements. He cautioned that if government funding were removed too early, the market ramp-up curve would stall. However, government funding would not be needed after increased expansion of hydrogen stations led to reduced costs and return on investment for businesses. Barker pointed out that the CNG market was once in a similar situation to the current hydrogen market, facing “growing pains” with non-standard equipment, long permitting times, lack of original equipment manufacturer (OEM) vehicles, and concerns about funding and return on investment. He then provided an overview of ANGI/GVR’s hydrogen retail dispensing equipment and compressing solutions features.
DOE Natural Gas Listening Sessions Review
Ted Barnes, GTI Energy
Ted Barnes opened with a brief overview of GTI Energy and explained how DOE VTO contracted with GTI to get a pulse of the industry by conducting a series of natural gas listening sessions. The mission was to “organize and facilitate fuel and technology-specific listening session with fleets and other stakeholders to identify technology gaps and critical research needs to improve vehicle/infrastructure performance and usability.” GTI coordinated this effort with Clean Cities coalition directors, holding around 60 listening sessions with stakeholders over five years (2018–2022). Over 1,000 comments were received and analyzed by GTI, resulting in identification of around 50 distinct barriers to adoption. Six key barrier categories were identified: technology (33% of comments), outreach and education (29%), industry support (20%), cost (9%), policy and incentives (5%), and other (4%). Barnes noted that while the focus on technology and outreach encompasses two things that DOE and Clean Cities are very good at, listening to Clean Cities stakeholders was important.
Under technology barriers, range anxiety was the single most mentioned topic. Technology barriers included groupings related to engine problems (largest group), vehicle fuel system, and fuel station issues. Barnes presented deeper dives into key technology barriers. Range anxiety issues include confusion over temperature compensation and how a “full” fuel system changes based on temperature, that fuel gauges based on pressure only are unreliable due to gas thermodynamics, and oversized (or additional) tanks add cost and weight. Potential solutions include smart fuel gauge/full-fill technologies with operator training enabling tanks sized for the job. Engine issues included lingering complaints from early engine models (with piston failures and valvetrain issues), maintenance intervals and life being shorter than diesel, and inadequate power with overheating. Potential solutions include OEM engine design improvements, training technicians and operators to follow OEM guidelines, and correct specification of engines for the job (recognizing a CNG engine is not a direct diesel drop-in). CNG fuel system issues include limited range with fuel storage too small for the job, component failures and leaks, and cargo penalty with fuel system weight. Potential solutions include a thorough application review for specifying equipment, component improvements (i.e., filters, regulators, and receptacles), and avoiding applications that will not work (i.e., 100,000 lb. gross vehicle weight rating with a 12 L engine or a 600-mile range for school buses). CNG fueling station issues include low station reliability with frequent, complex, and costly maintenance, poor user experience with dispensers and nozzles, inconsistent fills (i.e., slow or low pressure), high electricity demand charges, and fuel quality issues (impurities in natural gas). Potential solutions include additional technology development for compressors, filters, dispensers, and fueling algorithms, as well as exchange of best practices and success stories.
Under outreach and education, Barnes emphasized ensuring fleet managers get the right truck for the job and avoiding blindsiding drivers and technicians with technology differences. He also added that sharing success stories and best practices is needed to not let the “bad news be the only news.” Barnes highlighted a shortage of qualified technicians and the need to educate first responders, inspectors, and authorities having jurisdiction who may be unfamiliar with the technology. Key feedback regarding industry support barriers focused on dealers not having parts in stock and that not having enough stations makes fleets nervous about fueling and range. The shortage of qualified technicians and lack of vehicle/engine options is challenging, as is not having a single point of contact for ownership of the full system. Cost issues include high vehicle purchase, operation, and maintenance, as well as the prohibitive cost of CNG stations, forcing reliance on public infrastructure. Lastly, other issues exist such as inadequate incentives and policy support (i.e., weight exemptions, “Buy America” for federal incentives, and more incentives for zero emission vehicles), the impermanent status of tax credits, and frequency of CNG tank inspections (although the recent change to DOT regulation should help).
Vehicle Incidents and Lessons Learned
Paul Sandsted, NGVAmerica
Paul Sandsted opened with a background overview of NGVAmerica and how they represent over 200 companies, fleets, OEMs, and environmental and government organizations. He highlighted NGVAmerica’s Technology and Development Committee’s work for technology, safety, codes and standards, and best practices. Sandsted also discussed the sustainability of RNG with bio-CNG’s highly negative (beneficial) carbon intensity score under the California Low Carbon Fuel Standard, and how 64% of all on-road fuel used in NGVs in 2021 was RNG. He then detailed recent incident investigations. RNG is in production in 276 operating facilities, with 114 under construction and another 150 in development.
Sandsted presented some natural gas properties related to safety, with favorable dissipation, high ignition temperature, and a limited range of combustion in air. NGVs have CNG tanks with relief valves to vent gas in the event of catastrophic impact or fire, but regular tank inspections are required. Five fatalities have occurred in the United States caused by breach of a CNG fuel system in 60 years. The NGVAmerica working group meets bimonthly to discuss NGV incidents and works with the U.S. DOT, DOE, and standard development organizations. He explained how NGVAmerica tracks NGV incidents using data collection forms developed by John Jordan (Hexagon Agility) and others within the NGVAmerica Incident Investigation and Root Cause Analysis Working Group. Incident investigation data are analyzed, reviewed against compliance with codes/standards/regulations, and operation of NGV fuel system safeguards are reviewed. Investigations are closed when root cause is identified, NGV system reaction is confirmed, and any required industry response is determined.
Sandsted reviewed recent incidents. In 2017, an explosion with burn injuries occurred in a McNeilus manufacturing facility paint booth with a refuse vehicle inside. A CNG leak was identified as the root cause, and the importance of adhering to existing NGV codes and standards for maintenance facilities and personnel was communicated. In 2018, a CNG truck being serviced inside a fleet maintenance shop developed a CNG leak resulting in a fire. Frozen moisture damage to a pressure relief device (PRD) was found, highlighting the importance of PRD inspection with an annual cold weather advisory to the NGV industry. In 2020, three parked Los Angeles Metro buses were burned after a third-party contractor used a heat gun on a PRD to release CNG. PRDs on the other buses operated as intended to mitigate damage. This highlighted an outreach need to communicate that only trained and qualified personnel service NGVs. In 2023, a fire occurred at a parking lot for old NGV school buses and Class 8 trucks in various states of disrepair. Firefighters doused the vehicles with water either without awareness of the CNG fuel systems or without proper training. And in 2016, a CNG cylinder rupture on a pickup truck resulted in four fatalities. In that case, well gas was used as fuel source, uncertified personnel without proper training performed vehicle modifications, and proper refueling protocols were not followed. Sandsted closed by highlighting NGVAmerica resources developed in association with the Incident Investigation and Root Cause Working Group.
Day Two: February 1, 2023
Natural Gas Codes and Standards Updates
John Jordan, Agility
John Jordan provided a review of recently published codes and standards related to natural gas. These include: CSA LNG 3 series of standards, NGV 4.3 temperature compensation for NGV refueling, NGV 4.2 hose and hose assemblies for CNG dispensing, NGV 1 CNG vehicle fueling connections devices, NGV 6.1:21 Amendment 1 for CNG storage and delivery standards, and NFPA 52 vehicular natural gas fuel systems code. Two more NGV standards are soon to be published, related to residential fueling appliances and vehicle fueling appliances, and one more NGV standard related to CNG vehicle fuel container is ready to go to ballot. Jordan discussed how development of many new or revised NGV standards is scheduled to start in early 2023. He also discussed ISO activity from the TC22/SC41 September plenary, in addition to other items of interest. During the question-and-answer period, Jordan explained that ISO is working on documents for blended natural gas fuels. While there hadn’t been interest in the past, recent interest in hydrogen blends with natural gas resulted in this being an agenda item for the next CSA technical committee.
Final Project Presentation – Multi-Cylinder Transient Plasma Ignition System for Increased Efficiency and Reduced Emissions in Natural Gas Engines
Dan Singleton, Transient Plasma Systems (TPS)
Dan Singleton provided a final project presentation for this project, conducted under subcontract to NREL as part of the Natural Gas R&D Consortium with funding from DOE and CEC. TPS was founded in 2009 as a new venture spin-out from Singleton’s Ph.D. research at the University of Southern California and is developing a technology platform based on nanosecond pulsed power for emissions reduction and efficiency improvement. The key to TPS technology is the ability to make very short pulses, allowing them to drive higher power loads, turning megawatts of power on and off in 1 billionth of a second. The primary goal of this project was to advance previously demonstrated transient plasma low-energy ignition technology toward a production system, allowing an increase in natural gas engine efficiency with minimal additional capital or operational costs. The challenge for making this advanced ignition system market-ready for mass adoption includes extending current dilution limits, making a compact size with cost that matches benefit, increased transient performance, drawing a nominal load on battery power, seamlessly fitting with engine architecture, and bettering spark plug lifetime. Singleton explained TPS’ solution checked all these boxes, except for spark plug lifetime, where positive data are encouraging but long-term studies are still needed. Singleton outlined TPS’ development with funding under a prior CEC agreement to demonstrate multicylinder transient plasma ignition with solid-state hardware and the currently funded NREL agreement to confirm an approach that has the potential to meet commercial package size and cost. Next steps toward commercialization include partnering with an engine technology manufacturer.
Singleton discussed the project approach to determine nanosecond pulse parameters based on six-cylinder testing conducted at Argonne National Laboratory under the previous CEC-funded effort and designing a pulse tracking sense and control method to enable “smart pulse train” operation that can adjust pulse parameters in real time based on discharge mode. After this effort to find the most efficient way to deliver energy and design a closed-loop control system, the project focused on miniaturization of the system and testing at Argonne to validate system performance. Singleton explained how TPS’ approach differs from other plasma systems, with nanosecond pulsed discharge. An advantage of this approach includes plasma electrons colliding with gas producing chemically reactive species, enhancing ignition and stabilizing lean burn combustion. Other advantages include spatial distribution of the plasma enabling a single streamer to impact a large volume and controlled energy density. TPS has demonstrated stable operation at lean (lambda >2), dilute (exhaust gas recirculation, EGR, >40%), and high pressure (>100 bar) conditions. The project resulted in successful development of a closed-loop, automated control system and plasma plug optimization that have the potential to extend spark plug lifetime, reduce prime power consumption, and improve performance in dilute conditions. Multiple miniaturized versions of the TPS nanosecond ignition systems were designed, built, and vetted, with a new system with closed loop control and a new plug design demonstrated on a multicylinder engine at Argonne. The TPS system is now ready for design validation and project testing to support commercialization.
Development of a Zeolite-Based Catalysts for Improved Low Temperature HC4 Conversion
Tala Mon, University at Buffalo
Tala Mon presented this project, also conducted under subcontract to NREL as part of the Natural Gas R&D Consortium in collaboration with DOE, CEC, and SCAQMD. Professor Eleni Kyriakidou is the principal investigator, and she is a Ph.D. graduate student in her group. She explained how this project addresses methane slip in NGV exhaust, which is both challenging to address but necessary as methane has a 23x global warming potential (100-year) than CO2 on a molecular basis. Methane is challenging for engine aftertreatment because methane is so difficult to oxidize compared to other hydrocarbons due to methane’s stable C-H bonds. Palladium (Pd) is the most active methane oxidation metal compared to other platinum group metals. Unfortunately, water present in engine exhaust inhibits low-temperature methane oxidation over the conventional palladium-alumina catalyst, Pd/Al2O3. Promising alternatives to the alumina support for palladium are zeolites. Zeolites are microporous aluminosilicates with unique 3-dimensional frameworks and size-limiting pores. Of particular benefit to exhaust catalysts, zeolites have high surface area, hydrothermal stability, ion-exchange ability, and tunable hydrophobicity through Si/Al molar ratio.
Mon discussed how palladium-zeolite catalysts can achieve higher methane conversions compared to Pd/Al2O3 and how a particular zeolite structure, Chabazite (CHA) with palladium outperforms other studied Pd/zeolites in methane oxidation stability testing. Low temperature methane oxidation has improved by increasing Si/Al molar ratios of Pd/CHA. Limited information on the effect of Pd/CHA with Si/Al > 50% for methane oxidation performance presents a research challenge. Synthesis of Pd/zeolites with dealumination to increase Si/Al ratio leads to deconstruction of the zeolite framework. And direct synthesis of high silica CAH can lead to the formation of undesired phases. One of the research goals of this project is to modify direct synthesis of Pd/CHA (Si/Al >50) to prevent the formation of undesired phases. A related goal is to optimize the Si/Al ratio to achieve 90% methane conversion below 400C over fresh, hydrothermally aging, and sulfur poisoned catalysts. They are using a microreactor with simulated industrially relevant hydrothermal conditions to test trial catalyst samples. University at Buffalo is also collaborating with Prof. Dimitris Assanis at Stony Brook University to study catalyst samples with a single cylinder research engine providing a stream of exhaust under targeted engine operating conditions. Mon summarized with details describing Si/Al molar ratios and Pd loading optimization they have achieved for low temperature methane oxidation in realistic exhaust compositions, including with hydrothermal aging and sulfur poisoning. This is an ongoing project showing promising results to date.
CNG Full Fill with a Complete Smart Fueling System
Ted Barnes, GTI Energy
Ted Barnes provided an overview of CNG research at GTI Energy, including a smart CNG fueling station project conducted under subcontract to NREL as part of the Natural Gas R&D Consortium in collaboration with DOE, CEC, and SCAQMD. He began with a summary of GTI Energy’s mobility research capabilities, including R&D focus areas related to innovation, design, fabrication, deployments, data collection, analysis, codes & standards, hazard reviews, advanced vehicles, fueling stations, and fuel production.
Barnes then focused on the smart CNG fueling station project. The project aims to develop CNG full fills using smart vehicles and dispensers, an advanced full fill algorithm, and cost-effective pre-cooling. They intend to build and test a smart dispenser and vehicle, program a dispenser with the full fill algorithm, build an isentropic CNG reciprocating piston expander/compressor, and demonstrate full fills using the expander/compressor to supply cold gas to the smart dispenser and vehicle. Preliminary testing of the smart dispenser has achieved 95%+ full fills in a GTI Energy test cell and GTI Energy is working with ANGI to adapt the system to a commercial dispenser for real-world demonstration. GTI Energy has also been developing a free-piston expander for pre-cooling, where pressure differential is used to do work, removing energy from the gas and converting the energy to electricity, which can be used to help with compression. Initial testing with nitrogen is at 2,000 psig, ramping up to 12,500 psig.
Barnes presented another GTI Energy project for a next-generation NGV driver information system, with an improved fuel gauge with 98% accuracy for calculating remaining fuel. The gauge displays upper and lower bounds for distance-to-empty based on remaining fuel and recent driving patterns. The gauge has been installed for field testing on an Ozinga natural gas concrete mixer truck. The distance-to-empty calculation uses a smart phone app to predict fuel economy and mapping with connection to fleet dispatch. The concrete mixer is a challenging duty cycle, with > 50% idle time and fuel also used to spin the mixer. After a validation period, the system will be installed on nine additional Ozinga trucks.
Barnes also reviewed a project for a free piston linear motor compressor for methane leak recovery. This will help midstream compressor stations that have concentrated methane leaks that are currently manifolded and vented. GTI Energy is developing a unique, linear motor driven compressor to put this methane back into the pipeline, starting with inlet conditions near atmosphere (0–0.25 psig) and outlet conditions at 1,500 psig, with a target flow of 60 standard cubic feet per minute. He also reported on a collaboration with GTI Energy, UC Riverside, US Hybrid, FEV, Cummins Westport, and SoCalGas under CEC sponsorship to optimize and demonstrate a near-zero NOx, heavy-duty, hybrid-electric CNG truck.
Lastly, he discussed the FY 2023 DOE Office of Energy Efficiency and Renewable Energy funding for NGVs and NGVAmerica’s request to appropriations committees regarding requests for FY 2024. He solicited input for NGV R&D needs and how to leverage RNG and hydrogen interest.
Cummins High Efficiency, Ultra Low Emissions Heavy-Duty Natural Gas Engine R&D
Jay Shah, Cummins Engine Company
Jay Shah provided an update on Cummins’ high-efficiency, ultra-low emissions natural gas engine R&D program conducted under subcontract to NREL as part of the Natural Gas R&D Consortium in collaboration with DOE, CEC, and SCAQMD. He again summarized Cummins’ initiative to reach destination zero for CO2 emissions, with many solutions competing segment by segment to reach broadly available zero emissions solutions by 2050. He described Cummins’ new fuel-agnostic X15 global engine platform, derived from a base engine with a high degree of parts commonality. Heavy-duty versions use clean diesel, natural gas, and hydrogen. The natural gas variant of the X15 platform will be the lead engine, launching in 2024.
Shah discussed natural gas value drivers, including environmental and sustainability benefits (with potential to reach sub-zero well-to-wheel emissions with RNG), economic benefits, and operational benefits. He provided some background on Cummins and natural gas power, stating that Cummins has been building natural gas engines since 1986 and is the only manufacturer in the United States developing and producing heavy- and medium-duty commercial RNG engines. He stated that most fleets operating natural gas engines do so for 8–12 years of service and that 98% of all Class 8 tractors with the ISX12N engine are day cabs. He explained that the majority of private fleets switching to RNG power are advancing corporate environmental sustainability plans to reduce corporate carbon or GHG liabilities.
Cummins’ current lineup of natural gas engines are all certified to the near-zero optional low NOx standard of 0.02 g/bhp-hr, including the B6.7N, L9N, and ISX12N. The upcoming X15N will be the industry’s first big-bore natural gas engine, designed for linehaul heavy-duty applications. It will be capable of meeting CARB24/27 and future EPA NOx regulations while providing up to 500 hp and 1,850 lb.-ft of torque. The engine is a compact size, targeting ISX12N and 13 L chassis installations, and is about 500 lbs. lighter than the current 15 L diesel engine. It can use RNG for carbon-negative well-to-wheel emissions, offers up to a 10% fuel economy/GHG improvement over the ISX12N, and uses a passive single unit aftertreatment three-way-catalyst (TWC) system.
Shah then explained that, specifically, the Natural Gas R&D Consortium program has funded improvement beyond planned 2024 X15N base engine with advanced combustion, air-handling, and fuel system development to improve efficiency while maintaining low NOx capability on a diesel-like torque curve. A prototype multicylinder 15 L engine has been built, validated over 300 hours of runtime, with steady-state calibrations developed for stable engine operation. Program efficiency targets have been met while demonstrating target torque curve capability. The final reporting will come in late 2023. Separately, Cummins has also worked on dynamic skip fire technology for the heavy-duty natural gas engine in partnership with Tula Technologies, funded by DOE. That project is about 30% complete and focuses on the design and development of advanced air-handling technology for heavy-duty natural gas engines to demonstrate improvement in brake specific CO2 emissions on low load cycles while maintain capability to meet low NOx emissions. Lastly, Shah discussed hydrogen blending in natural gas engines, in response to interest in hydrogen injection into natural gas pipelines by industry to reduce carbon footprint. Blends up to 20 vol% are being considered, with challenges for knock, spark plug life, and pre-ignition. Cummins has been performing boundary condition analysis and computational fluid dynamics simulations to estimate impacts to combustion. They are testing 5% blends on a production L9N at UC Riverside with plans to also study a 15 L.
Development of a Pent-Roof Medium-Duty Spark-Ignited Natural Gas Engine in an Optimized Hybrid Vehicle System
Chris Chadwell, Southwest Research Institute
Chris Chadwell presented an overview of Southwest Research Institute’s (SwRI’s) development, in partnership with Isuzu, of a pent-roof medium-duty spark ignition natural gas engine and its integration in an optimized hybrid vehicle system. This project is also being conducted under subcontract to NREL as part of the Natural Gas R&D Consortium with funding from SCAQMD. The project objective is to “reach an efficiency level similar to that of conventionally fueled vehicles and reduce emission to near-zero levels with improvements to the natural gas engine as part of a hybrid powertrain, capable of being commercially salable into a medium- or heavy-duty vehicle.” Chadwell highlighted key program deliverables included a medium-duty natural gas hybrid demonstration vehicle, with a 24% reduction in GHG compared to the diesel baseline, with 0.02 g/bhp-hr NOx. The project began with single cylinder engine research based on the Isuzu 4HK diesel platform with a bespoke high-tumble, pent-roof cylinder head operating on natural gas. The single cylinder engine featured variable valve timing, both fumigated and port injection, and cooled EGR. The project progressed to multi-cylinder development, with updates to 12:1 compression ratio and custom connecting rods and a new high-tumble, pent-roof four valve cylinder head. The target engine torque curve was achieved, along with a peak brake thermal efficiency of 40%. Due to time and cost constraints, the aftertreatment system incorporated a production BMW X7 xDrive 40i production TWC system that included close coupled catalyst and under-floor catalyst blocks. An additional custom under-floor catalyst was used downstream of the BMW catalyst to obtain the capacity needed for this application, but the end result is still based on a relatively inexpensive gasoline TWC system. A Woodward EGR module was used with steady state calibration development, then transients were calibrated to meet 0.02 g/bhp-hr NOx emission targets. CO2 emissions meet targets out to 2027, including methane trading. Ammonia and particulate matter were not measured, but are expected to meet regulations.
Drive cycle performance was modeled in GT-DRIVE using an Isuzu 4H F-series VF76 Class 6 medium-duty truck. The best plug-in hybrid electric vehicle architecture was determined to be a P2 hybrid with a 100-kW motor and 40 kWh battery. The resulting simulated plug-in hybrid fuel economy improvements over diesel baseline were 24%–48% over standard cycles, with a 10% improvement over Isuzu’s own city cycle and less than 1% improvement over Isuzu’s own highway cycle. SwRI continued with hybrid control development, converting and refining control strategies converted from GT-DRIVE to Simulink and co-simulated with software-in-loop. The natural gas fuel system, natural gas engine, hybrid hardware, and ancillary systems integration to the Isuzu F-series Class 6 truck chassis has been completed. Remaining steps include hybrid control and powertrain system calibration and testing on SwRI’s chassis dyno, along with on-road drivability testing and emissions performance validation.
Plug-In Hybrid CNG Drayage Truck
Macy Neshati, US Hybrid
Macy Neshati provided a brief summary of US Hybrid’s plug-in hybrid CNG drayage truck project, which is being conducted under subcontract to NREL as part of the Natural Gas R&D Consortium in collaboration with DOE, CEC, and SCAQMD, with additional funding support from SoCalGas. The project involves developing a plug-in hybrid powertrain integrating a natural gas Cummins 9 L engine into two Freightliner M2-112 day cab Class 8 tractors for drayage operations. After performing simulations, the hybrid powertrain designs were completed and integrated into the trucks. Chassis dynamometer testing was performed and the trucks are currently in fleet demonstrations. Macy explained that while the trucks can operate on battery-only power, they are not recognized in California as zero emission vehicles.
Hydrogen Plus other Alternative Fuels Risk Assessment Models (HyRAM+)
Myra Blaylock, Sandia National Laboratories
Myra Blaylock presented an overview of Sandia National Laboratories’ Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HyRAM+) software toolkit. HyRAM+ integrates public data and models to assess safety related to the use, delivery, and storage infrastructure of hydrogen and other alternative fuels (i.e., methane and propane). It addresses the challenge that safety regulatory requirements for the production, distribution, and use of alternative fuels (i.e., hydrogen, natural gas, and propane) should be based on a sound technical basis, including validated software for risk and consequence modeling. In this latest update, Blaylock discussed how HyRAM’s hydrogen physics and risk assessment were modified for methane, blends, and propane.
She provided an overview of risk calculations in HyRAM+, including leaks (component leaks or dispenser failures), outcomes (detection/isolation and ignition probabilities), consequences (physical harm and fatality probability), and risk metrics (potential loss of life, fatal accident rate, and average individual risk). She reviewed fault tree analysis for leak frequencies and event tree analysis for leak outcomes. HyRAM+ uses a 1-dimensional reduced order model for a jet flame at the leak to calculate heat flux for every occupant point to assess thermal harm. The model also calculates overpressure harm based on various unconfined overpressure models. Reduced order 1-dimensional physics models are used to calculate jet plume dispersion based on leak size, local conditions, and the surrounding environment.
Blaylock summarized that reduced-order engineering models for hydrogen release behavior and risk assessment have been modified to enable the use of other alternative fuels, leveraging efforts from prior development of hydrogen base models. HyRAM+ currently has physics models for hydrogen, liquid hydrogen, CNG, LNG, propane, and blends. The model is free and open source, available for download from Sandia. The development of HyRAM+ was supported by the U.S. DOE Hydrogen and Fuel Cell Technologies Office and VTO, in addition to the U.S. DOT Pipeline and Hazardous Materials Safety Administration.
Southern California Hydrogen House Tour (On site)
Southern California Gas Company
SoCalGas hosted a tour of their H2 Innovation Experience hydrogen home demonstration, located at the Energy Resource Center. The H2 Innovation Experience includes a 2,000 square foot hydrogen home with a co-located scaled hydrogen generation (from renewable electricity) and storage microgrid infrastructure that is capable of powering 100 homes for a week. The hydrogen is then blended with natural gas to feed currently available production natural gas appliances that can handle up to a 20 vol % hydrogen blend without issues.
Issues, Key Points, Next Steps, and Priorities for Next Meeting
John Gonzales, NREL
Michael Laughlin, DOE
John Gonzales and Mike Laughlin thanked NGVTF attendees for their participation and informative exchange. They also recognized support from CEC and SoCalGas for hosting. They sought feedback on what topics were missed, future priorities, and how needs could be better served in future events.