Gaseous Fuels in Transportation -- Prospects and Promise Dr. James J. Eberhardt, Director U.S. Department of Energy Presented at the Gas Storage Workshop Kingston, Ontario, Canada July 11-12, 2001 OHVT Mission To conduct, in collaboration with our heavy vehicle industry partners and their suppliers, a customer-focused national program to research and develop technologies that will enable trucks and other heavy vehicles to be more energy efficient and able to use alternative fuels while simultaneously reducing emissions.
Gaseous Fuels in Transportation -- Prospects and Promise Outline The Transportation Energy Situation Transportation Options for the 21 st Century Future of Combustion Engines in Transportation Natural Gas As Alternative Fuel Two-Pronged Fuels Strategy Hydrogen As Alternative Fuel Summary
Rationale for a Heavy Vehicle Technologies R&D Program Since the 1973 Oil Embargo All of the Increase in U.S. Surface Transportation Fuel Consumption has been due to Heavy Vehicles Energy Use - Million Barrels per Day 16 14 12 10 8 6 4 2 0 Actual Railroad Projected Marine Off-Highway Class 3-8 Trucks Class 1-2 Trucks (Pickups, Vans, SUVs) Automobiles 1970 1980 1990 2000 2010 2020 Sources: EIA Annual Energy Outlook 2000, DOE/EIA-0383(2000), December 1999 Transportation Energy Data Book: Edition 20, DOE/ORNL-6959, October 2000
The Transportation Sector Is Almost Totally Dependent on Liquid Carbon-Based Fuels Transportation Energy Consumption, 1997 Natural Gas Electricity 2.8% 0.2% 97% Petroleum Source: DOE/EIA Monthly Energy Review; July 1998
Creating Transportation Options for the 21st Century
Transportation Energy Conversion Technology R&D History of Promising Alternatives 1960s Steam (Rankine cycle) engines 1970s Gas turbines Stirling engines 1980s Adiabatic engines Alternative fuels 1990s Hybrids Fuel cells
Transportation Energy Conversion Technology R&D Rankine Cycle Engine ($24M) Automotive Stirling ($142M) Automotive Gas Turbine ($393M) EV Battery (>$410M) Fuel Cell (>$150M) Hybrid (>$220M) 1970 1975 1980 1985 1990 1995 2000 Less than $5M in a given year Greater than $5M in a given year Program Terminated
Alternatives to Carbon-based Fuels As a chemical storage system, we have no practical substitute for the C-C bond. Gas Room Temp Transition Liquid 0-500 -1000-1500 -2000-2500 -3000 Hydrogen Methane Ethane Propane Butane Pentane Hexane Octane Nonane Cetane Enthalpy of Combustion (kcal/mol)
Energy Density of Fuels 1,200 1,000 1058 990 922 Thousand Btu per ft 3 800 600 400 683 635 594 488 270 266 200 0 Diesel Diesel Fuel F-T Gasoline Propane LNG Ethanol Methanol Liquid CompressedHydrogen H 2 CNG Compressed Diesel (@ 3626 psi) 68 Hydrogen (@ 3626 psi) 14 NiMH Battery
Comparison of Energy Conversion Efficiencies Fuel Cell-Stored Hydrogen Fuel Cell-Stored Hydrogen Fuel Cell-Methanol Reformer Compression-Igniton, Heavy Duty Diesel Engine Compression-Ignition Direct-Injection ICE Gas Turbine Gasoline Direct Injection Conventional Conventional Spark ICE Ignition ICE Today's Capability Projected Capability (2004) 0% 10% 20% 30% 40% 50% 60% 70% Peak Thermal Efficiency (%)
Vehicle Range Limitation - Challenge To Be Overcome By Alternatives Diesel Engine- Conv. Diesel Fuel Diesel Engine- F-T Diesel Fuel Cell - Gasoline Direct Injection Engine- Gasoline Adv. NG Engine- CNG (3,600 psi) Fuel Cell- Hydrogen (3,600 psi) 0 20 40 60 80 100 Comparison of Miles Driven (Same Volume of On-Board Fuel)
Creating Transportation Options for the 21st Century Combustion Engines Are Still the Most Viable for Future Heavy Vehicles
Diesel Engines Continue To Be The Most Viable Option for Heavy Vehicles Heavy-Duty Diesel Engine Progress THERMAL EFFICIENCY (%) 55 50 45 40 35 30 RESEARCH Efficiency objective reached with DOE assisted R&D Consent Decree PRODUCTION 0.25 0.3 0.35 0.4 0.45 BSFC (LB / HP - HR) Increasing Efficiency 1930 1940 1950 1960 1970 1980 1990 2000 Source: Caterpillar YEAR Decreasing Emissions Source: Cummins, modified by DOE NOx (gm/hp-hr) 16 1.5 14 12 10 8 6 4 2 0 NOx 1987 Models 1988 Models Particulates 1991 Models 1994 Models EPA 2007 Consent Decree 1980 1990 2000 YEAR EPA/CARB 2004 (SOP) 1.0 0.5 Particulates (gm/hp-hr)
Progress in Reducing Diesel Emissions Integrated systems approach Progress made in all 3 areas Partnerships with leading industry suppliers, truck/auto manufacturing, energy companies, and national labs Cross-cutting applications Fuels Emission Controls Engine Combustion Auto Light Truck Heavy Truck
Laboratory Demonstrated Diesel Emissions Tier 2 Results 0.6 0.4 Laboratory Setup: Stationary engine control system Stationary aftertreatment system Urban Dyno Drive Schedule (UDDS) First 1,392 secs. of FTP Sulfur < 4 ppm, 48 Cetane NOx accuracy +/- 0.025 g/mi PM accuracy +/- 0.005 g/mi NOx (g/mi) 0.2 5,500 lb vehicle NOx Adsorber then Soot filter Diesel fuel reductant (< 5%) 10.4 km per liter (24.4 mpg) city 0.0 0.00 0.02 0.04 0.06 0.08 Particulates (g/mi) Source: Cummins
Natural Gas Vehicles Pros and Cons Current natural gas engines can have very low engine-out emissions compared to current model diesels. Customers are seeking better fuel economy, higher power ratings, and lower capital expenditures. Ultra-low NOx emissions (<0.2 g/bhp-hr) will be needed to meet future regulations and to compete with emerging clean diesel technology. Efficiency may continue to be a barrier along with on vehicle storage. Recent price increases for natural gas create uncertainty for vehicle operators. Use of natural gas for power generation competes with use for vehicles.
Natural Gas as Fuel for Heavy Vehicles Technology Barriers Current natural gas engines operate at lower efficiency than conventional engines. On-board fuel storage for natural gas too expensive, too heavy and inconvenient for operators to refill. Natural gas transportation fuel facilities not widely available. Fueling facilities for natural gas are too expensive.
EPA Emissions Standards February 10, 2000 EPA adopted Tier 2 Emissions Standards which became effective April 10, 2000. (Includes reducing sulfur levels in gasoline to 30 ppm.) December 2000 EPA adopted heavy-duty diesel engine emissions standards to be phased in 2007-2010. January 18, 2001 EPA issued rule requiring 80 percent of all on-road diesel fuel to have less than 15 ppm sulfur starting in 2006.
EPA Emissions Standards Tier 2 Regulations for Light-Duty Vehicles (LDVs): 0.07 g/mi NOx and 0.01 g/mi PM; represent 77 to 95% reduction from Tier 1 levels Includes all LDVs under 10,000 lbs Phased in 2004-2008 Heavy-Duty Diesel Engine Regulations: 0.2 g/bhp-hr NOx and 0.01 g/bhp-hr PM; represents about 90% reduction from 2004 regs Phased in 2007-2010 Heavy-duty regulations include ultra-low sulfur diesel fuel
New Emissions Standards Introduce New Challenges Impact of EPA 2007 emissions standards 0.2 g/bhp-hr NOx will be difficult to achieve with natural gas as well as diesel Other regulated emissions also tough Progress in emissions control technologies R&D indicates diesel engines are likely to meet standards Emissions advantage of natural gas is diminishing.
Homogeneous Charge Compression Ignition (HCCI) Engines Potential of HCCI Engines High efficiency Very low NO x Lower cost (possibly no need for high pressure injection system, 1/3 rd of diesel engine cost) Low cycle-to-cycle variation Fuel flexibility Unthrottled operation Technical challenges of HCCI Difficult to control Difficult to start High peak heat release and peak pressure High hydrocarbon and CO emissions Natural gas may be a good fuel choice for HCCI. -6 + 4 + 10 Spark ignition HCCI Recent HCCI experiments by Honda
On-Board Gas Storage The Subject of This Workshop
On-Board Natural Gas Storage Challenges Current and projected pressures (3,600 psi to 10,000 psi) are inconvenient and potentially very hazardous. Heavy and strong tanks are required. Multistage compression is required and very expensive.
Breakthrough Enables Two-Pronged Fuels Strategy Liquid Fuels for All Heavy Vehicles Gaseous Fuels for Light and Medium Trucks Clean, High Efficiency Compression Ignition Engines (Diesel or Homogeneous Charge)
Hydrogen As Alternative Fuel Strategy for Fuel Cell Vehicles HYDROGEN FUEL CELL Hydrocarbon Fuel FUEL FLEXIBLE FUEL PROCESSOR H 2 - Rich Gas Hydrogen can be stored on board and supplied directly to the fuel cell: Storage (volume, pressure, weight) and Infrastructure Issues Hydrogen can be derived on-board from fuels such as ethanol, methanol, natural gas, gasoline or FT fuels: Complexity, Cost, & Start-up Issues
Hydrogen Production Hydrogen Infrastructure Las Vegas, NV Station - autothermal reformer/steam methane reformer Palm Desert Station, CA - autothermal reformer advanced cyclic reformer electrolyzers Chula Vista, CA Station steam methane reformer Storage Pressurized Tanks 5,000 to 10,000psi Cryogas Tank - private auto company vehicle Vehicles 30% Hydrogen/70% Natural Gas Mixture
Hydrogen Storage Today Tomorrow Compressed Storage Tanks Cryogenic Liquid Hydrogen Metal Hydrides and Carbon-nanotubes?
Summary The transportation sector is almost totally dependent on liquid carbon-based fuels. Combustion engines are still the most viable transportation energy conversion technologies for the near future despite a history of R&D on promising alternatives. Vehicle range limitation is one challenge that needs to be overcome by alternatives, especially gaseous fuels. EPA enacted emissions regulations that include ultra-low sulfur fuel requirements have diminished the emissions advantage of gaseous fuels burned in internal combustion engines. Research results show that ultra-low sulfur fuel will enable diesel engines to meet stringent emissions standards. Breakthroughs are needed in on-board storage and engine efficiency (e.g., HCCI) to improve prospects for gaseous fuels as alternatives to liquid carbon-based fuels for transportation.