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Heard At The Show: Snippets from SAE 2009 World Congress

Where does all of the energy go? In a session on total vehicle energy consumption, several people shared similar pie charts showing the flow of energy within an automobile.

For every kJ of chemical energy in the fuel for a spark ignition internal combustion engine, 73 % is sacrificed to chemical and thermal losses. Braking losses add another 6%. Only 22% remains to power the vehicle. Breaking out the 22%, aerodynamic losses account for 39%, tire resistance is 25%, transmission and drivetrain 20%, accessories 12% and bearings 3%.

Major factors contributing to Li-ion battery aging. Michael Crane, Managing Director, HEV N.A., and Continental Corp. shared their data on lithium-ion battery aging. While the numbers will vary depending upon the lithium-ion sub-chemistry, here’s what they have found:

CategoryContribution to Aging
Storage Temperature 40%
Driving Temperature 20%
State of Charge 20%
Cycling 10%
Other 10%

Crane also mentioned that one-quarter to one-third of the cost of a battery system is the packaging, integration and electronics. The cells make up the remainder.

How did the high fuel prices impact customer behavior in 2008? Paul Taylor, Chief Economist for the National Automotive Dealers Association, had the following observations:

At $4/gallon gas people looked at more economical versions of the same vehicle rather than going down in vehicle size—they continue to buy cars that meet their needs. They may take a 4 cylinder version rather than a 6 cylinder version rather than cram themselves into smaller cars. A $1 change in gas prices can lead to a 4-6% shift in take rates (i.e. the 4 cylinder engine may go from a 20% take rate to a 25% take rate). Customers do not make dramatic changes unless it is traumatic times.

Alexander Edwards, President, Automotive Strategic Vision believes the exodus from full size SUVs was caused by economic caution as much as higher gas prices. “People were concerned about spending $35,000 for an SUV that seats five, they were saying for $21,000 I can get a sedan that seats five. It doesn’t do everything I want it to do emotionally” regarding freedom and esteem but it is the more secure choice.

Cash for Clunkers. There are two bills in the US House of Representatives to give people cash for replacing an old, fuel inefficient vehicle with a new, more efficient, one. Similar programs have been successful in Western Europe. Dr. Taylor of the NADA:

At a time when there is $5,000 on the hood of a car, another $2,000 is going to help. But you won’t see the dramatic changes you see in Germany and Japan because they have their inspection regimes that drive them towards newer cars. In this country a lot of the new cars are purchased by higher income households and a typical modest income household is driving a used car...The typical American that is buying a new car, which costs on average $28,000, likely isn’t driving a car worth only $2,000.

How much does it cost to save weight? As the industry grapples with reducing weight without reducing attributes like size, safety or performance they are going to need to increase the use of lightweight materials. Randall Scheps of Alcoa shared research from The Aluminum Association.

The association expects the amount of aluminum per vehicle to increase from 8.6% to 10.4% by 2020 and in one case study they were able to save between 70 and 75 lbs (32 to 34 kg) of vehicle mass for a cost penalty of $280-$350 ($4-$5/lb).

On a “mine to wheels” level, aluminum reduces greenhouse gases vs. steel. Aluminum takes more energy to produce but this is more than offset by improved vehicle performance. The association estimates a net savings of 22 lbs (10 kg) of CO2 per pound (0.45 kg) of aluminum used.

More detail can be found at

Personal mobility redefined. Honda demonstrated their “Walking Assist Device” at the Congress. The systems are designed to maintain mobility for the elderly and those with weakened leg muscles. The devices were found to increase muscle exertion but decrease heart usage in test subjects. Honda is still interpreting the data but they believe the user’s externally powered legs are acted like a second heart, helping pump blood.

Honda also found that the devices improved the users posture and lengthened their stride and these improvements were maintained even after the user was disconnected from the device.

They also demonstrated a similar device called “Walking Assist Device with Bodyweight Support” which provides a little saddle for the user to sit on. A portion of the user’s bodyweight is transferred directly to the floor via special legs and shoes. Honda believes it will be a help in climbing stairs or industrial operations that require a lot of squatting.

Department of Defense and Fuel Economy. Paul F. Skalny, Director, US Army TARDEC shared the following insights on fuel usage within the Department of Defense (DOD):

  • Every $10/barrel increase in oil prices adds $1.3 billion/year to the DOD’s fuel bill.

  • 70% of the bulk tonnage in a war effort is fuel and that fuel can be very expensive financially and in terms of human casualties.

  • The operations in Kuwait and Iraq use approximately 431 million gallons of fuel per year. It takes more than 9,000 convoys to distribute this fuel and each convoy involves approximately 120 soldiers. These convoys are prime targets for improvised explosive devices. If the US could reduce its fuel consumption by 1%, it would save more than 6,000 soldier-trips/year.

  • Fuel becomes very expensive by the time it reaches the front line, ranging from $20/gallon up to $600/gallon when it is delivered by helicopter in Afghanistan.

Skalny and TARDEC are leveraging synergies between the auto industry, the commercial truck business and the federal government to improve the DOD’s fleet fuel economy without sacrificing soldier safety.

—Bill Cooke



Storage Temperature contributes 40% to the aging of cells....

I had no idea. I would have guessed load profile and cycling. Cycling contributes only 10% to the aging.

It is good to see the loses, like tires and wind resistance, gears and the like. Weight is still right up there as a factor in energy usage. You can see that every time you launch a 4000 car from dead stop.


You can find videos on all of these subjects at SAE's new website. You can essentially watch the whole of the World Congress 2009 at

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