Q: Would a large SUV that is 50 percent electric, 50 percent gas powered use more resources (both from electricity if it's generated by a non-renewable resource, and from the gas itself) than a small station wagon (such as a Volvo)?
Asked by Amanda Schlott Lietman, ’88, Chagrin Falls, Ohio
We're here at SAGE live in the heart of Palo Alto's Tesla country, and we've been hungrily gawking as many of those all-electric roadsters go zipping around the area. But would completely electric or electric hybrid technology really work for the mainstream? Could it make an SUV pollute less than a typical gasoline-powered car? Can new, efficient transport technologies really allay the eco-concerns of those who want to do right by the environment but still need a big SUV to traverse the Sierras or look really cool pulling up to little league games?
The short answer: forget the humongoloid hybrids and get the Volvo. It is safer for the environment, safer for you, safer for your budget, and much safer for everyone else you will meet on the road—especially on the narrow two lane ones!
The Volvo is a better choice primarily because of its lighter weight. When we press down on the gas pedal to accelerate, only a small fraction of the energy produced by the engine actually transports the mass of our bodies. If we weigh 150 pounds and the car weighs 3,000 pounds, then only 5 percent of the car's energy (and pollution) is actually getting us to where we want to go. The rest is taking a lifeless piece of metal along for the ride. The smaller the car, the more the engine output is put to useful work. A Volvo powered solely by gasoline will produce about two-thirds the CO2 of a large, partly electric SUV.
(Don't think this is an argument in favor of gasoline engines though— 80 percent of the energy in the gasoline is lost to heat and exhaust straight from the get go. That means less than 1 percent of the energy and pollution generated by burning gasoline actually does something useful. Small will always be better than large, but a giant hybrid is better than a giant conventional vehicle, just as a small hybrid is better than a small conventional car.)
Plotting average U.S. vehicle fuel efficiency against average U.S. vehicle weight over time, we see that huge gains in mileage were realized while vehicle weight dropped, but as vehicle weight ceased to decline in the mid 1980s, improvements in fuel efficiency also stagnated. (Data Source: U.S. EPA)
You might want to keep in mind that Volvos aren't even particularly light. They may not be your typical vision of an urban assault vehicle, but they are still built like tanks, which is how they get their good safety rating. Most other small cars would be more energy efficient—but travel weight is not the end of the road here.
It takes a lot of energy to make a car—and big vehicles will have larger amounts of this "embodied" energy than small ones. It takes energy to produce those larger tires, and the second sunroof, and the eight extra cup holders. In addition, hybrid vehicles will also tend to have larger amounts of embedded energy than a similarly sized gasoline car because of the energy-intensive battery production. The metals used in the batteries are often hard to extract and hard to process, and the end result is a very heavy battery that must also be taken along for the ride. In a Tesla, batteries alone account for about 1,000 pounds—almost half the total weight of the car! As Einstein almost said, Energy = mass times cruising speed squared (or something like that). So, large vehicles with lots of heavy batteries will have a massive environmental footprint before they even spin their wheels—and the faster they go (over 55 mph), the worse it gets.
Okay, everyone, here comes the moral of the story (engineers, look away—this may be blasphemy): Technology alone isn't going to save the environment, and driving sexier engines will not substitute for driving smaller cars—or taking the bus, or riding a bike. But if we begin to value efficiency over excess, we might have a chance. If we choose to simplify our lives instead of further synthesizing them, we might have a chance. And if we buy only what we need instead of just what is new . . . we might have a chance there, too. When you're thinking of a new car, embrace the gifts of efficient technologies. But remember also that the best things often come in small packages.
Chris Fedor, ’10, is an earth systems major.
