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Low-Hanging Fruit in Transportation Efficiency January 14, 2009

Posted by federalist in Energy, Transportation.
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No, it’s not electric hybrids, which depending on the longevity and cost of their battery packs may never break even.  It’s incremental improvements to internal-combustion engines.  Ford is rolling out “EcoBoost direct-injection gasoline engines, which should boost fuel economy by about 20%.

The company argues the premium for EcoBoost … is a better value than a hybrid or diesel. [A]ssuming a gallon of gas is $3 or less, it would take 12 to 18 months to see the cost savings of owning an EcoBoost vehicle. The equivalent for a hybrid … is five to seven years and as long as a decade for diesel at current prices.

Further down the road are homogenous-charge compression-ignition (HCCI) engines that should offer another 10% boost in efficiency.

Granted, no matter how efficient engines become they will always lose useful energy through braking.  But I still think hydraulic hybrids are the answer for maximizing fuel efficiency in vehicles that make frequent stops (like delivery trucks and inner-city cars), since the hydraulic motor can potentially recover practically all of the energy currently lost as heat through braking.  Electric hybrids will always be limited in how much they can recapture by the size of their motors and the charge rate of their batteries.  And even if battery lifespans are improved there is the problem that battery packs do not scale as gracefully (in size, weight, or cost) as hydraulic cylinders.  [Addendum: Dave Vanderwerp has a great column detailing the state of the art in hydraulic hybrids, including prototype hybrid UPS delivery trucks.]

One other piece of low-hanging fruit is materials: Most of the transportation fuel we burn is spent moving the frames and bodies of our vehicles, not their passengerss.  Mass-produced vehicles contain tons of frame metal that in principle could be replaced with vastly lighter and stronger carbon fiber or other composites.  Someday soon we will look back on the era of steel and aluminum vehicle bodies as archaic.

[Update: Gordon Murray provides a technical history of Structural Composites in Cars.]

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1. federalist - February 2, 2011

WSJ reports:

[R]esearchers hope to make automotive-grade carbon fiber using a process similar to how knitting yarn is created. The development could lower the price of carbon fiber by as much as 25%.

Meanwhile, Callaway has come up with “forged composites” which press smaller carbon fiber threads in molds instead of weaving them. The results aren’t as strong as woven carbon fiber, but the pieces are still very light and string and vastly easier to produce. Lamborghini is prototyping forged composites in its Sesto Elemento car.


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