What If Plug-In Hybrids Work?

July 23, 2007

Plug-in hybrids seem like a fantastic technology that could make a serious impact in the amount of petroleum fuel needed for transportation. GM executives have been using the phrase "displacing petroleum" when talking about the long term strategy for powering vehicles in the future. Biofuels, rather than fossil fuels, are drawing a lot of attention, and hydrogen is being explored both as a combustion fuel and for use in fuel cells. And many of these systems are being considered in conjunction with vehicles with some battery-powered component.

What happens to the air we breathe when plug-in hybrids become commonplace in a few years? Are we going to suddenly need hundreds of additional electrical plants to make all that extra electricity for the power that is no longer being supplied by gasoline? Would wide-scale switching from gasoline vehicles to plug-in electric vehicles be jumping out of the frying pan and into the fire?

A report jointly issued by the National Resources defense Council (NRDC) and the Electric Power Research Institute (EPRI) addresses some of these questions in greater detail. It is worthwhile to think about these questions as these technologies get closer to widespread implementation. Unintended consequences of increasing numbers of electric cars already include concerns about the very quiet operation of electric hybrids when their gas engines are not running, and the potential hazard these vehicles now pose for blind pedestrians, who have much more difficulty detecting the approach of these vehicles than ordinary internal combustion vehicles.

"Among study’s key findings:

  • Widespread adoption of PHEVs can reduce GHG emissions from vehicles by more than 450 million metric tons annually in 2050 — the equivalent to removing 82.5 million passenger cars from the road
  • There is an abundant supply of electricity for transportation; a 60 percent U.S. market share for PHEVs would use 7 percent to 8 percent of grid-supplied electricity in 2050
  • PHEVs can improve nationwide air quality and reduce petroleum consumption by 3 million to 4 million barrels per day in 2050"

Keeping a few dozen coal-burning power plants clean, and adding extra equipment to further clean their exhaust output is far easier and more cost-effective than carrying out the changes necessary to clean the exhaust systems for millions of vehicles. Greater efficiency is possible for a fixed installation, like a coal plant scrubber, than is practical for any on-board equipment that a car has to carry around.


Generate more juice to power cars, and greenhouse gas emissions from power plants will rise, even as the carbon dioxide pouring out of tailpipes declines. However, it’s not an equal tradeoff, because even dirty electricity produced on a grand scale is cleaner than running millions of internal-combustion engines. According to the 2006 DOE study, switching to PHEVs would yield an average net reduction in greenhouse gas emissions of 27 percent per car. In California, which has the country’s cleanest electric-generation system, the figure would be 40 percent. (Popular Mechanics)


Some additional electricity will neeed to be generated to offset transmission losses from electricity traveling through wires, but that is balanced somewhat by the reduction of tanker trucks needed to deliver gasoline from refineries to fueling stations across the country (a transmission loss in petroleum fuel, as it were). Recharging of plug-in vehicles will most likely take place in the evening, when electrical demand is already off-peak. With very little extra equipment, intelligent recharging can be timed to take place when demand on the grid is lowest.

Rewiring existing garages with adequate electrical service to be able to supply the vehicles without causing a household fire hazard may be one of the biggest hurdles to overcome for many plug-in hybrid owners. Existing wiring may be only marginal for vehicle recharging in many cases.

The likely outcome of increasing numbers of plug-in hybrids (and other electric vehicles) seems likely to be a net environmental positive.

Cross-posted at EcoGeek.org

Link: NRDC press release
via: Popular Mechanics