July 29, 2007

A scientific assessment of plug-in hybrids

Clean Edge News published a story on a new report that analyzes the benefits of PHEVs (Plug-in Hybrid Energy Vehicles).

The EPRI-NRDC study represents the most comprehensive analysis of the potential reductions of global warming and other emissions from wide-scale introduction of PHEVs over time. The study addresses the impact that lower-emitting electricity generation can have for increasing these benefits.

How would air quality and greenhouse gas emissions be affected if significant numbers of Americans drove cars that were fueled by the power grid?

A recently completed assessment conducted by the Electric Power Research Institute and the Natural Resources Defense Council made a detailed study of the question – looking at a variety of scenarios involving the U.S. fleet of power generation and its fleet of light-duty and medium-duty cars and trucks.

The objectives of this study are the following:
• Understand the impact of widespread PHEV adoption on full fuel-cycle greenhouse gas
emissions from the nationwide vehicle fleet.
• Model the impact of a high level of PHEV adoption on nationwide air quality.
• Develop a consistent analysis methodology for scientific determination of the
environmental impact of future vehicle technology and electric sector scenarios.

The study focused on plug-in hybrid electric vehicles (PHEVs) and projected changes in power generation technology from 2010 through 2050.

The EPRI Perspective
Policymakers, technology developers, and utility and environmental planners need objective and accurate information to make sound decisions about developing and deploying PHEVs in support of national energy and environmental policy. PHEVs offer the potential for reducing both emissions and fuel consumption, simultaneously addressing the issues of global warming and the nation’s dependence on imported oil. Quantifying these benefits has proved challenging, however, and misinformation has circulated about the environmental performance of PHEVs.

Summary of Results
Because of the significant reduction in emissions from gasoline and diesel fuel use and because caps are in place for some conventional pollutants for the electric power sector, the study finds that in many regions deployment of PHEVs would reduce exposures to ozone and particulate matter, and reduce deposition rates for acids, nutrients, and mercury.

On the other hand, because of assuming no further controls beyond existing regulations for the power sector, ozone levels would increase locally in some areas. Similarly, the direct emissions of particulate matter and mercury would increase somewhat and some regions and populations would experience marginal increases in exposures to those pollutants. However, as explained in the key findings, PHEVs do not increase the U.S. contribution to the global mercury budget over the long term.

Overall, the air quality benefits from PHEVs are due to a reduction of vehicle emissions below levels required by current regulation (due to their non-emitting operation in all-electric mode), and because most electricity generation emissions are constrained by existing regulatory caps. Any additional increase in the amount of all-electric vehicle miles traveled or further emissions constraints on the electric sector would tend to magnify these benefits.

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