摘要 :
Ambient concentrations of pollutants are correlated with emissions, but the contribution to ambient air quality of on-road mobile sources is not necessarily equal to their contribution to regional emissions. This is true for sever...
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Ambient concentrations of pollutants are correlated with emissions, but the contribution to ambient air quality of on-road mobile sources is not necessarily equal to their contribution to regional emissions. This is true for several reasons such as the distribution of other pollution sources and regional topology, as well as meteorology. In this paper, using a data-set from a travel demand model for the Sacramento metropolitan area for 2005, regional vehicle emissions are disaggregated into hourly, gridded emission inventories, and transportation-related concentrations are estimated using an atmospheric dispersion model. Contributions of on-road motor vehicles to urban air pollution are then identified at a regional scale. The contributions to ambient concentrations are slightly higher than emission fractions that transportation accounts for in the region, reflecting that relative to other major pollution sources, mobile sources tend to have a close proximity to air quality monitors in urban areas. The contribution results indicate that the impact of mobile sources on PM_10 is not negligible, and mobile sources have a significant influence on both NO_x and VOC pollution that subsequently results in secondary particulate matter and ozone formation.
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摘要 :
In this paper we examine the potential air quality impacts of hydrogen transportation fuel from a lifecycle analysis perspective, including impacts from fuel production, delivery, and vehicle use. We assume that hydrogen fuel cell...
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In this paper we examine the potential air quality impacts of hydrogen transportation fuel from a lifecycle analysis perspective, including impacts from fuel production, delivery, and vehicle use. We assume that hydrogen fuel cell vehicles are introduced in a specific region, Sacramento County, California. We consider two levels of market penetration where 9% or 20% of the light duty fleet are hydrogen fuel cell vehicles. The following three natural gas to hydrogen supply pathways are assessed in detail and compared in terms of emissions and the resulting changes in ambient air quality: (1) onsite hydrogen production; (2) centralized hydrogen production with gaseous hydrogen pipeline delivery systems; and (3) centralized hydrogen production with liquid hydrogen truck delivery systems. All the pathways examined use steam methane reforming (SMR) of natural gas to produce hydrogen. The source contributions to incremental air pollution are estimated and compared among hydrogen pathways. All of the hydrogen pathways result in extremely low contributions to ambient air concentrations of NO_x, CO, particulates, and SO_x, typically less than 0.1% of the current ambient pollution for both levels of market penetration. Among the hydrogen supply options, it is found that the central SMR with pipeline delivery systems is the lowest pollution option available provided the plant is located to avoid transport of pollutants into the city via prevailing winds. The onsite hydrogen pathway is comparable to the central hydrogen pathway with pipeline systems in terms of the resulting air pollution. The pathway with liquid hydrogen trucks has a greater impact on air quality relative to the other pathways due to emissions associated with diesel trucks and electricity consumption to liquefy hydrogen. However, all three hydrogen pathways result in negligible air pollution in the region.
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摘要 :
Interest in hydrogen as a transportation fuel is growing in Shanghai. Shell Hydrogen, Tongji University, and the City of Shanghai plan to construct a network of refueling stations throughout the city to stimulate fuel cell vehicle...
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Interest in hydrogen as a transportation fuel is growing in Shanghai. Shell Hydrogen, Tongji University, and the City of Shanghai plan to construct a network of refueling stations throughout the city to stimulate fuel cell vehicle and bus deployment. The purpose of this paper is to (1) examine the near-term costs of building hydrogen stations of various types and sizes in Shanghai and (2) present a flexible cost analysis methodology that can be applied to other metropolitan regions.
The costs for four different station types are analyzed with respect to size and hydrogen production method. These costs are compared with cost estimates of similar stations built in California. Based on the hydrogen station cost analysis conducted here, we have found that hydrogen costs ($/kg) vary considerably based on station type and size. On-site hydrogen production from methane or methanol results in the lowest cost per kg. The higher cost of truck-delivered hydrogen from industrial sites in Shanghai vs. California is mainly due to feedstock costs differences. Electrolyzer stations yield the highest hydrogen cost.
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