By Paul Lucas | 28 February 2011, 19:01 BST
According to the team at Carnegie Mellon University the net emissions from the use of plug-in vehicles depends primarily on the efficiency of the entire vehicle fleet, charging strategy, battery pack capacity and driving patterns. They modelled the net emissions in two regional transmission operators under different scenarios for future power generation.
The study suggests that if a 2020 conventional vehicle fleet efficiency target of 35mpg is compared to the 2020 charge depleting efficiency then net CO2 emissions will drop by switching from petrol to electricity but less in PJM because of differences in generation.
In a paper published in the ACS journal Environmental Science & Technology, they offer results for a 10 per cent plug-in hybrid electric vehicle market. They estimate that plug-in hybrid electric vehicles will have lower net CO2 and NOx emissions than a conventional vehicle fleet but SO2 will increase unless a cap binds.
Among the results of the study are that the differences in timing will result in changes in the generator mix and emissions. Battery size has few qualitative changes while home charging does not decrease CO2 emissions as much as smart or work charging.
They conclude that there are strong arguments for electrification and if plug-in hybrid electric vehicle cars replace light trucks and SUVs, as well as vans from the fleet, emissions will be further reduced.
Source: The Green Car Website