Cars must change. Our detailed vehicle computer simulations have shown that business-as-usual with incremental improvements in the venerable gasoline-powered internal combustion engine (ICE) will not be adequate to avoid the triple threats of greenhouse gas emissions, oil dependence and urban air pollution. We conclude that, to avoid massive environmental and energy security disruptions, society must accelerate the process of electrifying the transportation system. In one sense, we will be turning back the clock over 100 years: in 1900 approximately 25% of cars on the road were electric vehicles powered by batteries (most were powered by steam engines, and another 25% or so by gasoline internal combustion engines).
Hybrids. The process of partial re-electrification of the car fleet has already begun with the introduction of hybrid electric vehicles (HEVs) that rely on both a small gasoline-powered ICE and an electric motor to drive the wheels.
Plug-in Hybrids. The next step in the electrification evolution is the introduction of plug-in hybrid electric vehicles (PHEVs), now introduced by several automobile companies, beginning with the Chevy Volt. As the name suggests, plug-in hybrids are connected to the electrical grid while parked to recharge onboard batteries, thereby reducing the amount of gasoline consumed.
Biofuel Plug-in Hybrids. To further reduce oil consumption and GHGs, we analyzed PHEVs running on biofuels such as biodiesel or cellulosic ethanol instead of gasoline.
All electric Vehicles. In our judgment, society must eventually move back to the complete electrification of the automobile. There are two practical choices: battery-powered electric vehicles (BEVs) or hydrogen-powered fuel cell electric vehicles (FCEVs). Our computer simulations show that unless we eventually eliminate nearly all internal combustion engines, we cannot meet our societal objectives of cutting greenhouse gas emissions to 80% below 1990 levels while simultaneously curtailing dependence on imported oil and eliminating most urban air pollution.