Micro-Hybrids Hold the Key to Future Auto Fuel Efficiency

Start-stop car technology may contribute more to auto efficiency than all-electric vehicles or fuel cells

2 min read
Micro-Hybrids Hold the Key to Future Auto Fuel Efficiency
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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We Need More Than Just Electric Vehicles

To decarbonize road transport we need to complement EVs with bikes, rail, city planning, and alternative energy

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A worker works on the frame of a car on an assembly line.

China has more EVs than any other country—but it also gets most of its electricity from coal.

VCG/Getty Images

EVs have finally come of age. The total cost of purchasing and driving one—the cost of ownership—has fallen nearly to parity with a typical gasoline-fueled car. Scientists and engineers have extended the range of EVs by cramming ever more energy into their batteries, and vehicle-charging networks have expanded in many countries. In the United States, for example, there are more than 49,000 public charging stations, and it is now possible to drive an EV from New York to California using public charging networks.

With all this, consumers and policymakers alike are hopeful that society will soon greatly reduce its carbon emissions by replacing today’s cars with electric vehicles. Indeed, adopting electric vehicles will go a long way in helping to improve environmental outcomes. But EVs come with important weaknesses, and so people shouldn’t count on them alone to do the job, even for the transportation sector.

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