(Source: Carnegie Mellon University Design Decisions Laboratory)

PITTSBURGH— Carnegie Mellon University professor Jeremy J. Michalek and researchers Dr. Constantine Samaras and C.-S. Norman Shiau report in a new study that plug-in hybrid electric vehicles with small battery packs may be the best bet for saving drivers money while addressing U.S. dependency on foreign oil and global warming.

            In an article to appear in the journal Energy Policy, the authors find that urban drivers who can charge their vehicles frequently (every 20 miles or less) can simultaneously reduce petroleum consumption, greenhouse gas emissions, and expenses with a plug-in hybrid vehicle whose battery pack is sized for about 7 miles of electric travel per charge. In contrast, plug-in hybrid vehicles with large battery packs – sized for 40 or more miles of electric travel – are too expensive for fuel savings to compensate, even in optimistic scenarios.

            Plug-in hybrid vehicles use charged batteries to propel the vehicle partly using electricity instead of gasoline, which gives them potential to reduce petroleum consumption and greenhouse gas emissions. “Larger battery packs allow drivers to go longer distances on electric power. But batteries are heavy and expensive,” says Michalek. “We accounted for the effects of additional batteries on vehicle cost, weight and efficiency in order to understand the net implications on petroleum consumption, cost, and greenhouse gas emissions. Over a range of scenarios — including fluctuating gas prices, new battery technologies or high taxes on carbon dioxide emissions — plug-ins with small battery packs are economically competitive with ordinary hybrid and conventional vehicles for drivers who charge frequently.”

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