INSIGHT: Lighter auto parts don’t always raise fuel efficiencies

06 January 2012 16:31  [Source: ICIS news]

By Nigel Davis

California freeway as snow clearsLONDON (ICIS)--Plastics and other types of chemicals find increasing use in the auto industry, largely replacing metal and glass and helping to reduce weight and the environmental impact of light vehicles.

Automobiles and vans benefit from increased fuel efficiency and should be delivering more miles per gallon (whether US or imperial) or kilometres per litre of precious fuel. But new research has shown that this is not always the case.

“The major automakers have produced large increases in fuel efficiency through better technology in recent decades,” the Massachusetts Institute of Technology (MIT) said this week. “There’s just one catch. All those advances have barely increased the mileage per gallon that autos actually achieve on the road.”

Since 1980, the US consumer has opted for larger, sportier vehicles. And while auto makers have worked hard at improving gasoline fuel efficiency, the actual gain in miles per gallon has been has been just 15%.

Between 1980 and 2006 fuel economy increased by 60%, MIT economist Christopher Knittel shows in a new research paper, ‘Automobiles on Steroids’, published in the December 2011 issue of the American Economic Review. But over the same period the average curb weight of US autos increased by 26% and their horsepower by 107%.

“Most of that technological progress has gone into [compensating for] weight and horsepower,” Knittel says.

Engine and transmission improvements over the 25-year period were significant and continue to deliver efficiency improvements, as do the weight savings made by introducing new materials.

The American Chemistry Council (ACC) noted last month that plastics and composites now account for 9.4% by weight of the average light vehicle in the US. That’s 32% higher than in 2000 and a 95% improvement on 1990.

An estimated average of 378lbs (171kg) of plastics and composites were used in automobiles, light duty trucks, SUVs and minivans in 2010 with polypropylene (PP), polyurethane and nylon accounting for more than 50% of the materials used.

Each pound of plastics and composite supplants two to three pounds of other materials, helping to reduce weight, improve fuel efficiency and reduce greenhouse gas (GHG) emissions.

“ACC econometric analysis indicates that for each 10lb increase in plastics substitution for other materials, a vehicle’s fuel efficiency increases by 0.11% to 0.14%. The light vehicle market presents significant opportunities for further diffusion of plastics and composites in the future,” the chemicals trade group says.

This can be achieved simply by substituting more metal parts with plastics and composites or by cleverly reducing the weight of existing plastic parts by using low-density additives, nanoparticles and alternative fibres.

Even more plastics will be used in the hybrid and electric vehicles that are expected to make further inroads into the US light vehicle markets in future.

As far as the chemical industry in the US is concerned, light vehicles account for more than 30% of demand each for PP, polyurethane, nylon, other engineering polymers and thermoplastic polyesters.

But if lower hydrocarbon fuel consumption per mile travelled is the goal, then simply reducing the weight of vehicle components is not of itself likely to produce results.

The transportation sector produces more than 30% of US greenhouse gas emissions, MIT notes. Turning innovation into increased overall vehicle mileage would produce considerable environmental benefits.

But Knittel can’t see consumers turning away from their useful SUVs and powerful trucks.

“When it comes to climate change, leaving the market alone isn’t going to lead to the efficient outcome,” he says. “The right starting point is a gas tax.”

A gasoline tax, he says, would create demand for fuel-efficient vehicles, while meeting greater fuel efficiency targets under new Corporate Average Fuel Economy (CAFE) standards may simply make motorists drive more.

CAFE targets, announced by President Barack Obama in July, are for an average fuel efficiency of 35.5 miles per gallon by 2016 and 54.5 miles per gallon in 2025. The current average for the country’s fleet of vehicles is 27 miles per gallon.

Knittel calculates, MIT says, that “automakers could meet the new CAFE standards by simply maintaining the rate of technological innovation experienced since 1980 while reducing the weight and horsepower of the average vehicle sold by 25%.

The MIT commentary adds: “Alternately, Knittel notes, a shift back to the average weight and power seen in 1980, along with a continuation of the trend toward greater fuel efficiency, would lead to a fleet-wide average of 52 miles per gallon by 2020.”

By: Nigel Davis
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