If your car is idling for as little as 10 seconds, you would save gasoline by turning it off. Americans waste 1.4 billion gallons of gasoline per year from voluntary idling (idling that doesn’t result from traffic congestion), emitting over 12,000,000 metric tons of CO2. Utilizing what is called start-stop technology, already common in Europe and costing as little as a few hundred dollars to include with a new car, would eliminate this and other gasoline consumption at no inconvenience to the driver.
In a car with start-stop technology, sometimes referred to as a mild hybrid or micro-hybrid, the engine turns off when the car comes to a stop instead of simply idling. When the accelerator pedal is pressed or, in a manual car, the clutch engaged, the engine turns back on automatically. While the engine is off, stored energy in the battery keeps the car’s auxiliary functions—lighting, heating and air conditioning, and the radio, for example—running normally. Estimates (by automakers, start-stop system manufacturers, and industry analysts) of the fuel economy improvement from this technology range from 5 to 15 percent.
Most start-stop systems include an enhanced 12-volt battery, a starter-generator, and a gasoline engine. As the car slows, regenerative braking turns the starter-generator and creates electricity, which is stored in the battery. This stored electricity is used to power the auxiliary systems and also gets sent back to the starter-generator when the driver reengages the clutch or accelerator, restarting the engine.
Some start-stop system developers have begun to experiment with using ultracapacitors alongside batteries. Ultracapacitors can store and discharge electricity quickly, and would allow manufacturers to use up to 30 percent smaller batteries. Maxwell technologies, an ultracapacitor supplier, claims that equipping start-stop systems with ultracapacitors could provide a 15 percent fuel economy increase by 2013.
What does it bring to the table?
Convenient fuel efficiency and cost savings.
The fuel economy gains of the start-stop system come at very little cost or inconvenience to the consumer. Installing a system in a new car increases the cost to the manufacturer by $300 to $1,500, according to Jacob Grose of Lux Research. The Energy Information Administration (EIA) recently estimated that the average household would spend $3,235 on motor fuel in 2011. If this represents two cars (according to the EIA the actual average number of cars per household was 1.9, as of 2001), replacing one with a car with start-stop technology that offered a 10 percent fuel economy improvement would save a household $162, meaning the start-stop system could pay for itself in as little as two years. Furthermore, consumers would not have to sacrifice convenience, as none of the creature comforts cars provide would be affected by having the engine off. In fact, the only difference the driver would notice is that the car would be quieter when stopped.
Preventing idling has other benefits as well. Idling can damage engines over time by forcing them to operate in an inefficient manner. It also produces an outsized amount of local air pollutants in areas where passers-by are most affected, because most idling is done close to the curb.
How scalable is it?
As scalable as the automobile industry.
Start-stop systems have long been standard in hybrid cars in the United States and elsewhere, but they are soon to be included in conventional models as well. Though it is not easy to retrofit a car to use a start-stop system, they are compatible with standard car designs when incorporated from the time of production. Such systems were included in 8 percent of new cars in 2010 according to Johnson Controls, a leading manufacturer. Johnson Controls expects that number to top 50 percent by 2016, representing 25 million vehicles. Pike Research predicts 37 million start-stop vehicles will be sold in 2020.
How close is it to commercialization?
Closer in Europe than the U.S.
Start-stop technology has been used in Europe since the 1980s, when it was first introduced in Volkswagen and Fiat cars. As of 2009, a large number of European models included start-stop systems, with Volvo, Alfa Romeo, and others introducing new models since then. The first internal combustion engine cars with start-stop systems will arrive in the U.S. in the 2012 model year, including the Chevrolet Malibu, Buick LaCrosse and Regal, Kia Rio, BMW 5 series, and many Ford models. Many analysts believe that the technology is now spreading in the U.S. as automakers look for inexpensive ways to comply with increasing fuel economy standards.
What is the biggest obstacle to success?
In the U.S., its differences in both driving behavior and regulation
Start-stop systems are most useful for city driving, as is any technology based on regenerative braking. Suburban driving, on the other hand, rarely involves full stops. Even in heavy highway traffic, the engine of a start-stop vehicle would need to stay on, negating any possible fuel economy benefit. With much of the driving in the U.S. done on highways and outside urban centers, the benefits of start-stop are reduced compared to those in more densely populated countries in Europe.
Furthermore, the Environmental Protection Agency’s (EPA) methodology for measuring fuel economy does not fully account for the benefits of start-stop technology, leaving consumers with incomplete information when making purchasing decisions and thus providing less incentive for automakers to utilize it. The EPA measures fuel economy based on tailpipe emissions that result from driving the car through a simulated laboratory course. This course does not emphasize full stops, and therefore fuel economy statistics may underestimate the impact of start-stop technology.
The final word(s):
Full speed ahead.
Start-stop technology seems like the kind of innovation that should win broad approval. Some worry that it will slow adoption of true hybrids or electric vehicles, but the introduction of start-stop technology would also reach a large segment of the population not ready to switch away from internal combustion vehicles. With the clear value it provides consumers in terms of reduced fuel costs, start-stop technology should quickly become commonplace in the U.S. and around the world.