by Drew Kodjak
Technology Review
August/September 1996
The debate about electric vehicles (EVs) often revolves around whether increased smokestack emissions-from the power plants generating the electricity needed to recharge all those EV batteries-will offset the reduction in pollution from tailpipes. Such analyses usually overlook a critical factor, however: gasoline cars tend to get dirtier and dirtier over time, while electric power plants do not.
According to the US. Environmental Protection Agency, pollution from tailpipes grows by an average of 25 percent every 10,000 miles, culminating in vehicles that are 2 to 5 and sometimes 10 times dirtier than when they left the assembly line. Indeed, because of this steadily deteriorating efficiency, a gasoline car will over the course of its working life emit twice as much nitrogen oxides (NOx) as will a generating facility producing the power to charge a comparable electric vehicle. The conventional car will also spew out 60 times more carbon monoxide, 30 times more volatile organic compounds, and twice the carbon dioxide emissions as the electric power plant. This comparison assumes that electric vehicles will be recharged with power drawn mainly from oil- and natural gas-fired generators.
Maintaining the emissions control systems in millions of individually-owned vehicles has proved extremely difficult. Indeed, in the northeastern United States, the single largest source of air pollution is aging gasoline-powered vehicles. Recognizing this fact, several Northeast states announced plans in 1993 to upgrade their automobile inspection and maintenance systems. In some states, these programs are expected to eventually achieve up to 40 percent of the reduction in volatile organic compound emissions necessary to comply with new clean air standards. Unfortunately, most of these programs have been delayed, on large part due to concern about public response to the cost of repairing catalytic converters and other such components. Utilities, by contrast, employ teams of professional engineers to keep the power plants well maintained and operating at peak efficiency.
Another benefit unique to electric vehicles is the immediate reduction in air pollution over the entire EV fleet once new power-plant emission controls are installed. Under pressure from regulators, for example, electric utilities in the Northeast have committed to reducing power plant emissions of NOx by 55 to 75 percent over the next seven years. The entire fleet of EVs will reap the environmental advantage of this upgrade at a few hundred facilities. With gasoline vehicles, by contrast, the benefits from more stringent new emission standards are realized only incrementally as older vehicles are junked and replaced. Since 95 percent of the fleet turns over only after 12-15 years, more than a decade can elapse before the desired emissions reductions are achieved.
Because of the rising popularity of gas-guzzling sport utility vehicles, which now account for more than 40 percent of new vehicle sales, the overall efficiency of passenger cars has dropped in the last several years. EVs, on the other hand, are entering the market as highly fuel-efficient machines. The General Motors EV1, for example, gets the equivalent of 100 miles per gallon.
Moreover, gasoline vehicles of all kinds are often restarted several times a day, once running, the engine must frequently change speeds as the vehicles accelerates, decelerates, and traverses hills. Such sporadic and variable operation works against fuel efficiency. EVs are charged by electric generators that reap the efficiency benefit of running continuously at a constant speed.
Not all automobile pollution comes from the tailpipe. About a third of the volatile organic compounds that gasoline automobiles introduce into the atmosphere evaporate during refueling and from the gas tank, engine, and fuel line. Significant additional emissions come for the operation of refineries and from ships and trucks that transport the liquid fuel. Electric vehicles reduce these emissions as well as exposure at the gas station to the toxic chemicals present in gasoline, such as benzene and 1,3-butadiene.
Over the next fifteen years, EV batteries in the Northeast will increasingly be recharged by modern natural gas-fired power plants. These plants are much cleaner and more efficient than today's coal or oil-fired plants. For example, facilities in Southern California already emit 40 times less NOx than Northeast power plants.
And unlike conventional vehicles, which run almost exclusively on petroleum-based fuels, electric vehicles are able to tap into a large number of power sources, including renewable s such as hydro, wind, geothermal, and biomass, In a demonstration project run by the Massachusetts energy office, solar cells provide the electricity to recharge EVs parked at two commuter rail train stations in the Boston area. Solar panels on the roof of houses could collect solar energy by day and use it to charge a spare EV battery. Once home, the motorist would simply exchange today's spent battery pack with the newly charged one.
The move to EVs must be understood as a long-range air-quality strategy. It will take many years from the time EVs are introduced until even half the cars on the road are electric. Ultimately, EVs can make a difference only if people buy them. In the near term, consumers will have to choose between internal-combustion vehicles that offer the romantic roar of a V8 and 500-mile road trips, and electric vehicles that zoom silently from 0 to 60 and can be recharged overnight in their garage. Over the long term the clean-air payback will become apparent as gracefully aging EVs supplant the elderly, atmospherically incontinent fleet of gasoline cars.
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Drew Kodjak is attorney for mobile sources at Northeast States for Coordinated Air Use Management (NESCAUM) in Boston, an interstate association of air quality control agencies.