Micro-Hybrids Hold the Key to Future Auto Fuel Efficiency

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Photo: David Malan/Getty Image

Electric cars and hydrogen fuel cells alone won’t allow automakers to meet aggressive new fuel efficiency standards over the next decade. Instead, the biggest efficiency boost may come from micro-hybrid car technology capable of automatically stopping and restarting engines when they would otherwise be idle during a stop at a red light or in traffic jams. 

Micro-hybrid technology uses an improved or additional battery to help quickly restart combustion car engines. Such “start-stop” technology sometimes also includes regenerative braking to capture and store energy for later use. Better versions of today’s micro-hybrid technology could contribute 48 percent of the improvements needed for future cars to meet United States and European fuel efficiency standards of 2025, according to a recent Lux Research report.

“The automotive industry is under intense pressure to lower emissions and increase fuel efficiency," said Anthony Schiavo, Lux Research Associate and the lead author of the report, in a press release. “Improved energy storage options will help make micro-hybrids the most cost-effective way to respond, along with ongoing improvements to lightweight materials.”

Such predictions don’t mean automakers will necessarily go down this path. But Lux Research calculates that such a route would represent the most economical choice for making cars capable of meeting the new standards. Future U.S. fuel economy standards will require cars to have a fleet-wide average fuel efficiency of 54.5 miles per gallon by 2025. European Union standards will limit new vehicles to emitting an average of 95 grams of carbon dioxide per kilometer by 2021.

The improvements in micro-hybrid technology will rely greatly upon lighter and better-performance versions of 12-volt and 48-volt mild hybrid batteries. They would also require better supercapacitors to help store and release energy quickly within future vehicles. Last but not least, falling prices for lithium-ion batteries could play a role.

But other technologies could also help meet the targets of the new fuel efficiency standards over the next decade. Lighter materials that reduce the weight of car components could lead to a 39 percent improvement in overall vehicle fuel efficiency.

Alternative fuels could also provide a smaller contribution in meeting the new fuel efficiency standards. A 13 percent improvement may come from increases in biofuel blending requirements that also boost the Research Octane Number—the measure of a fuel’s resistance to the “knocking” mini-explosions that occur when fuel fails to burn smoothly.

More fuel-efficient vehicles won’t come cheap. Lux Research estimates that vehicle prices will increase by an average of $1,700 in response to the newer technologies required for improving fuel economy. Ideally, the fuel efficiency savings would pay off in the long run.

Drivers who don’t want to buy a new car to get such “start-stop” technology can already buy plug-and-play services that upgrade their existing cars. For example, start-up Voyomotive will offer an “aftermarket connected car system” starting in March that will include an optional EcoStart feature capable of partly emulating micro-hybrid car technology to stop and start the engine.

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