1. Impacts of hydrogen pathways vs
Impacts of hydrogen pathways vs. gasoline/diesel pathways on urban air quality: a Sacramento case study
Guihua Wang
Joan M. Ogden
Presented at the
NHA Annual Hydrogen Conference 2008
Sacramento, CA, March 30-April 3, 2008

2. Overview of Talk
Using the Sacramento metropolitan area as the setting, 3 natural gas-based hydrogen pathways and 4 gasoline fleet operation scenarios are compared in terms of resulting changes in urban air quality.
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3. Motivation of Research
H2 as a transportation fuel is becoming increasingly compelling.
High efficiency (together with FCVs)
No air pollutant tailpipe emissions (with FCVs)
Energy security (can be made from many sources)
We focus on Air Quality Implications of H2
Examine changes in ambient air quality due to various H2 pathways compared to current and advanced gasoline/diesel pathways
On a lifecycle analysis (LCA) basis
In a particular region (Sacramento Metro.)
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4. The Sacramento metropolitan area includes six counties: Sacramento, Yolo, Sutter, Yuba, Placer, and El Dorado.
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5. Centralized H2 production with pipeline delivery
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6. Distributed H2 production (onsite)
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7. Centralized H2 production with liquid truck delivery
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8. Gasoline/diesel pathways
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9. Emissions and Air Pollution
Criteria air pollutants (4 APs)
Emissions from H2 fuel pathways (WTW)
Gasoline/diesel vehicle emissions
Pollutant
Vehicle emission processes and sources CO
Running exhaust, idle exhaust, starting exhaust
NOx
TOG or VOC
Running exhaust, idle exhaust, starting exhaust,
diurnal, hot soak, running loss, resting loss
PM10
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10. Method for H2 Pathway Scenarios
Specify spatial location, characteristics of all emissions sources for H2 pathways
Use atmospheric dispersion model to calculate impact on ambient pollutant concentrations for Sacramento area
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11. Hydrogen pathway scenarios and demand/supply assumptions
Sacramento city population (2000)1
1.393 million
Light Duty vehicle ownership (2000)
0.8 vehicles/person
Light Duty vehicles (2000)
1.114 million
H2 FCV Fraction of the 2000 LD
fleet in urbanized Sacramento
10%
25%
Number of H2 FCVs
111,400
278,600
Hydrogen fuel demand
78,000 kg/day
195,000 kg/day
Number of hydrogen stations (assuming 3000 kg/d stations) 27 66
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12. Method for Gasoline fleet scenarios
Light duty (LD) fleet, including passenger cars and light trucks of 8500 lbs or less.
Vehicle operation stage only
Upstream (refinery) emissions not included
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13. Transportation networks in the Sacramento area (6-counties)
The modeling domain is divided into (=220×220) grid cells at a 1×1 km resolution.
Transportation network links (i.e., roadways or roadway segments, including centroid connectors).
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14. Fleet fraction =10% H2 station siting H2 central plant
27 stations located for consumer accessibility
H2 central plant
sited outside city near existing power plants
Air quality monitors
9 sites (existing network)
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15. Fleet fraction =25% H2 station siting H2 central plant
66 stations located for consumer accessibility
H2 central plant
sited outside city near existing power plants
Air quality monitors
9 sites (existing network)
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16. Incremental pollution due to hydrogen pathways (CO)
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17. Incremental pollution due to hydrogen pathways (VOC)
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18. Incremental pollution due to hydrogen pathways (NOx)
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19. Incremental pollution due to hydrogen pathways (PM10)
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20. Four gasoline fleet scenarios
Composite 2025 LD fleet: calendar year 2025, model years spanning , projected in-use LD fleet in 2025
New 2025 LD fleet: calendar year 2025, model year 2025, advanced LD vehicle fleet on the road in 2025
Composite 2005 LD Fleet: calendar year 2005, model years spanning , in-use fleet in 2005
New 2005 LD Fleet: calendar year 2005, model year 2005, current LD vehicle fleet on the road in 2005
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21. Comparison of concentration ratios relative to the hydrogen pipeline pathway
Reference H2 scenario
Advanced gas. vehicle
Current gas. vehicle
For reference: On-road mobile sources (including LD vehicles) contribute % of VOC, % of NOx, and % of PM10 to annual ambient concentrations in Sacramento for 2005 (Wang et al., 2008).
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22. Conclusions (1)
The onsite pathway and the pipeline pathway result in very similar pollution levels.
The truck pathway results in higher pollution levels than the other two hydrogen pathways.
All the three pathways have a low impact compared to ambient measurement.
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23. Conclusions (2)
The composite 2025 LD fleet results in much less pollution, with the exception of PM10, than the composite 2005 LD fleet.
For a scenario year, the new LD vehicle fleet would lead to much lower concentrations than the composite fleet.
For the new vehicle fleet scenarios, the 2025 model vehicles would be dramatically more advanced than the 2005 model vehicles in terms of environmental impacts (with the exception of slight improvement for PM10).
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24. Conclusions (3)
As the least polluting representative of LD gasoline/diesel fleet operations, the future evolved gasoline vehicle with a model year 2025 would lead to
164 times greater CO,
52 times greater VOC,
4.7 times greater PM10, and
1.9 times greater NOx, concentrations than
those caused by the centralized/pipeline hydrogen pathway
In summary, hydrogen pathways (including truck delivery pathways) are less polluting than gasoline fleet operations examined in the study.
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25. Acknowledgements
We are grateful for research support from the sponsors of the
Hydrogen Pathways program at UC Davis
Sustainable Transportation Energy Pathways (STEPS) program at UC Davis
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26. Q & A
Thanks!