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

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. 3/31/2008

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.) 3/31/2008

The Sacramento metropolitan area includes six counties: Sacramento, Yolo, Sutter, Yuba, Placer, and El Dorado. 3/31/2008

Centralized H2 production with pipeline delivery 3/31/2008

Distributed H2 production (onsite) 3/31/2008

Centralized H2 production with liquid truck delivery 3/31/2008

Gasoline/diesel pathways 3/31/2008

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 3/31/2008

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 3/31/2008

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 3/31/2008

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 3/31/2008

Transportation networks in the Sacramento area (6-counties) The modeling domain is divided into 48400 (=220×220) grid cells at a 1×1 km resolution. Transportation network links (i.e., roadways or roadway segments, including centroid connectors). 3/31/2008

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) 3/31/2008

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) 3/31/2008

Incremental pollution due to hydrogen pathways (CO) 3/31/2008

Incremental pollution due to hydrogen pathways (VOC) 3/31/2008

Incremental pollution due to hydrogen pathways (NOx) 3/31/2008

Incremental pollution due to hydrogen pathways (PM10) 3/31/2008

Four gasoline fleet scenarios Composite 2025 LD fleet: calendar year 2025, model years spanning 1981-2025, 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 1965-2005, in-use fleet in 2005 New 2005 LD Fleet: calendar year 2005, model year 2005, current LD vehicle fleet on the road in 2005 3/31/2008

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 30.6-38.5% of VOC, 34.3-62.2% of NOx, and 4.4-5.7% of PM10 to annual ambient concentrations in Sacramento for 2005 (Wang et al., 2008). 3/31/2008

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. 3/31/2008

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). 3/31/2008

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. 3/31/2008

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 3/31/2008

Q & A Thanks!