Getting to 54.5 MPG
If your very next car purchase had to meet the new mileage standards announced today, you’d be buying something roughly the size of a thimble. It would certainly be smaller than the petite Ford Fiesta, which gets a comparatively gluttonous 38 miles per gallon, highway.
Or, you could do away with any MPG concerns and get a new all-electric Nissan Leaf, though the range can dip down to around 62 miles. Forget the comfy hybrid Toyota Prius – that one only gets 50 MPG overall.
Luckily for car buyers, automakers have until 2025 to get their fleet average up to 54.5 MPG. By then, the choices will be much different than today.
Today’s New York Times story on the increase focuses on plans for hybrid and electric cars. But other technologies will have to come into play. According to Sujit Das of the Center for Transportation Analysis at Oak Ridge National Laboratory, drive train changes will not be enough to meet the new standards.
There will be more electric and hybrid cars, but overall, Das says, passenger cars will also have to be made smaller and lighter. Part of the problem is that it is too expensive to make larger trucks and SUVs high mileage, and automakers still want to sell a lot of those. So, regular cars will have to be designed for REALLY high gas mileage to make the averages work out.
Oak Ridge scientists estimate that for every 10% of weight reduction in a vehicle, the gas mileage improves by 6.5%. To make that happen, they are studying how automakers can use lightweighting materials including advanced high-strength steels, aluminum, magnesium, titanium, and composites including metal-matrix materials and glass- and carbon-fiber reinforced thermosets and thermoplastics.
Automakers have been using lighter weight materials for years, but not in a quest to increase mileage. According to a report [PDF] by the Pew Center on Global Climate Change, “Although technology to improve vehicle efficiency is available and is being used in vehicles now, vehicle manufacturers have directed much of the potential of the technology to purposes other than fuel economy, such as making vehicles larger and more powerful.” That’s a strategy that they’ll have to re-think.
Still, carbon fiber is not the first choice for automakers. Not too long ago I priced a carbon-fiber bicycle, and decided it was way too expensive. A carbon fiber car would be like George Jetson’s flying car that folds into a suitcase. It doesn’t exist, and if it did, very few people could afford it. Though parking would be a snap. The cost problem is a real barrier, which is why Oak Ridge scientists are also studying ways to make lightweighting materials more affordable.
Meanwhile, an organization called the Diesel Technology Forum says more people are choosing “clean diesel” cars, and that the new standards will bring more diesel models for consumers. The new diesel cars perform well on the highway – the Volkswagon Jetta TDI gets 42 MPG highway. A fiberglass and aluminum version would likely get even more.
The new mileage standards will also likely force automakers to experiment with more efficient designs for combustion engines. New approaches get more mechanical power from the same amount of gas, bypassing steps where energy is lost as heat.
A start-up called Transonic Combustion builds a system that heats and pressurizes gasoline into a supercritical state before directly injecting it into the combustion chamber. There, like in diesel engines, no spark is needed to ignite the fuel and move the piston. It is an efficiency improvement that the company says can increase mileage by 50%.