Compressed Natural Gas
“It gets easier after the first billion miles”
Los Angeles Metro’s Experience with Alternative Fuels, Compressed
Natural Gas (CNG), and Zero Emission Buses
John DraytonDirector of Vehicle Technology
Los Angeles Metro June 2016
Alternative Fuel Basics – What are Hydrocarbons?
More Carbon = More Energy + More Emissions
Hydrogen: H2 High Fuel Cost, lowest emissionsMethane (CNG): CH4 Lower Fuel Cost, lower emissionsGasoline: C6H14 Higher Fuel Cost, higher emissionsDiesel: C15H32; Higher Fuel Cost, higher emissionsCoal: C240H90O4NS Lowest Fuel Cost, highest EmissionsElectricity: NA Note - Primarily sourced from hydrocarbons.
H C C C
H H
H H H
H
C C C C C C C C C C C C H
H H H H H
H H H H H H H H H H H H
H H H H H H HC HH
H
H
Methane Gas(CNG) CH4
Diesel Fuel C15H32
History of Metro Alternative Fuel and CNG Buses
Metro’s Alternative Fuel Fleet• First 10 CNG buses purchased in 1988• Purchased fleet of 333 Methanol
buses 1989-1992• AFI Policy Adopted - Purchased only
CNG buses since 1992• First fleet purchase of 294 CNG buses
in 1995• CNG Fueling Public/Private
Partnerships in 1998• 100% CNG Operation since 2011• ~ 1.5 billion miles on CNG buses 1973 “Steam Bus”
• GMC New Look bus with custom built Leer Steam Engine
• Unreliable, inefficient, high emissions• “Not every idea is a good one”
Current Outlook for CNG at Metro
• We foresee continued refinement of CNG engines, exhaust systems.
• CNG fuel prices expected to be stable – diesel fuel prices are expected to be more volatile in our region
– Diesel currently $1.80/gallon – fuel cost ~$0.60/mile (price currently rising).
– CNG cost $0.465/therm – total fuel cost of ~$0.40/mile (price stable ~ last 48 months)
– Since 2002, average diesel fuel price for Metro is $2.80/gallon, which equates to $0.85 per mile in our service
– Since 2002, average CNG fuel price for Metro is $0.51/therm , which, including compression, equates to $0.38/mile in our service.
Comparison of CNG and Diesel Fuel Prices 2002-2016 (cost/mile)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1/7/
2002
4/7/
2002
7/7/
2002
10/7
/200
21/
7/20
034/
7/20
037/
7/20
0310
/7/2
003
1/7/
2004
4/7/
2004
7/7/
2004
10/7
/200
41/
7/20
054/
7/20
057/
7/20
0510
/7/2
005
1/7/
2006
4/7/
2006
7/7/
2006
10/7
/200
61/
7/20
074/
7/20
077/
7/20
0710
/7/2
007
1/7/
2008
4/7/
2008
7/7/
2008
10/7
/200
81/
7/20
094/
7/20
097/
7/20
0910
/7/2
009
1/7/
2010
4/7/
2010
7/7/
2010
10/7
/201
01/
7/20
114/
7/20
117/
7/20
1110
/7/2
011
1/7/
2012
4/7/
2012
7/7/
2012
10/7
/201
21/
7/20
134/
7/20
137/
7/20
1310
/7/2
013
1/7/
2014
4/7/
2014
7/7/
2014
10/7
/201
41/
7/20
154/
7/20
157/
7/20
1510
/7/2
015
1/7/
2016
Dol
lars
Average Fuel Cost Per MileDiesel Fuel Cost/Mile CNG Fuel Cost/Mile
Resolved CNG Engine Issues
Over the last 5 years, Cummins-Westport has provided a number of engine and calibration upgrades that have improved CNG engine performance and reliability:
• EGR Cooler Coolant Leaks - Cummins campaigned 100% of Metro’s ISL-G engines and provided upgraded “Tube Style” EGR coolers. This has gone a long way toward mitigating turbo, sensor, piston and other failures from internal coolant contamination.
• ICM (ignition control module) failures– Cummins has retrofitted engines up to a Gen IV “bulletproof” ICM, to remedy ignition system misfires/check engine lights.
• Cracked/Warped/Leaking 2-piece exhaust manifolds have now been upgraded to a more robust 3-piece manifold.
Ongoing CNG Engine Issues
• Piston Failures – Cummins has made improvements in piston design, yet there is still ongoing, yet reduced, cracking issues. We expect to see more work here from Cummins in the future.
• More frequent PM schedule—Valve adjustments at 2000 hrs vs. 5000 hrs. on diesel ISL9 engine. Also, spark plug changes at 18,000 miles (none on diesel).
• Cylinder head/valve recession– Caused by high combustion temps, cylinder heads may need to be replaced more often than diesel engines.
Next Generation CNG?
Can “Near Zero” CNG engines reduce fleet emissions? • Low NOx Engines with Renewable Natural Gas
– New Low NOx engine certified at 0.02g/bhp– 90% NOx and PM reduction possible.– 80% reduction in CO and GHG with RCNG– 0.02g/bhp NOx; PM <0.01g/bhp– Nearly equivalent to battery electric ZE in Los Angeles
• Post 2020 – Smaller engines? Next generation of smaller displacement CNG engines optimized for HD applications– Metro expects CNG to be a core part of our operation for the
foreseeable future and a transitional step to economical, proven ZE technologies
1985 1990 1991 2000 2010 2016
NOx (g/hp-hr) 10.8 6 5 4 0.2 0.02
PM (g/hp-hr)
0.59 0.59 0.25 0.05 0.01 0.01
10
=
108054054
0.01
Emission Reductions Since 1980’s
One 1980 RTS-II 1000+ Low NOx CNG Engines
Next Generation CNG Engines
• Next generation diesel-derived spark ignited engine architecture
• Designed to provide:– Improved power and torque over state-of-
the-art diesel engines– 15% product cost reduction compared to
diesel engine plus after-treatment– Much higher fuel economy through
engine downsizing– Near Zero NOx capability
• Stoichiometric operation and simple three-way catalyst after-treatment
• Using 100% natural gas; RNG, CNG or LNG
Source: Westport Innovations
Next Generation CNG Engines
Optimized in-cylinder air motion &
variable valve timing Packaged within
base diesel engine
architecture
Improved thermal mgt.
Lower peak cylinder
pressure than diesel
Simpler piston bowl with better heat dissipation
Improved airflow
distribution cyl-to-cyl
Carryover diesel bottom end for robust product
EGR for knock mitigation &
improved efficiency
Multi – point fuel injection &
high energy ignition
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