Prototype Natural-Gas Vehicles Use Gasoline As Range Extender

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To date, natural-gas vehicles have come with significant compromises.

The high-pressure tanks that hold enough compressed natural gas to run 200 miles or more take up many cubic feet of space in the trunk, load bay, or pickup bed.

But what if you could design a vehicle that had just enough natural gas to run 50 to 75 miles--without any change to its cargo space?

That's just what vehicle-development consultant Carlab designed--four of them, in fact--and we drove the prototypes last month.

The concept is identical to that of a Chevrolet Volt range-extended electric car: Run the vehicle's first miles on a cheaper energy source that can be provided at home, then switch to gasoline for those occasions where longer continuous range is needed.

Overnight home fueling

In this case, though, the primary fuel is natural gas rather than electricity, and it powers the combustion engine--meaning no electric motors, battery packs, or electronics are needed.

These cars are best suited, Carlab said, to those regions where natural gas is plentiful, cheap, and already installed in a large numbers of homes for heating or hot water.

For home fueling, the vision is that a small compressor fills the natural-gas tank to its maximum pressure of 3600 psi overnight.

Major appliance makers, including some who attended the drive event, view such a compressor as an opportunity to launch a new category of home appliance sales.

Whirlpool concept for home natural-gas refueling appliance

Whirlpool concept for home natural-gas refueling appliance

No gasoline for weeks?

Almost four-fifths of U.S. vehicles travel 40 miles or less each day--as Chevy Volt advocates repeatedly note--so conceivably a driver could run for weeks by filling up on natural gas at home each night.

Visits to gas stations might stretch to weeks apart, a popular selling point.

But the biggest incentives are cost--natural gas costs less than $2 per gallon-equivalent in most markets--and the opportunity to drive using a domestically-produced fuel, rather than on gasoline refined from imported oil.

Mainstream vehicles

The four prototype vehicles--we're tempted to call them Range-Extended Natural Gas Vehicles, or RENG-Vs--are being unveiled today at the Alternative Clean Transportation (ACT) Expo in Washington, D.C.

On one level, they're simply traditional bi-fuel conversions--but with much smaller CNG tanks, and no requirement that the driver select which fuel is used.

But on another level, they're the first vehicle aside from the low-volume Honda Civic Natural Gas to show how natural gas can be used for everyday passenger vehicles--and they're designed to avoid that car's drawbacks of limited range and minimal trunk space.

At a preview drive event, held May 21 in Los Angeles, journalists drove four vehicles that covered popular market segments, from four different automakers.

Natural-gas vehicle prototypes, Los Angeles, May 2013 - BMW X3 added instrumentation

Natural-gas vehicle prototypes, Los Angeles, May 2013 - BMW X3 added instrumentation

They were a BMW X3 compact crossover utility vehicle, a Ford Mustang GT sports coupe, a GMC Acadia large crossover, and a Hyundai Sonata mid-size sedan.

Their engines varied from a 2.4-liter four-cylinder in the Sonata to sixes in the BMW X3 and GMC Acadia and a 5.0-liter V-8 in the Mustang GT, to show that natural gas could be used in vehicles with a variety of engines and power ratings.

All were engineered to start up and run on their CNG supplies, giving them rated ranges of 55 to 77 miles on natural gas.

Ranges of 375 to 574 miles

When the natural gas supply was exhausted, each vehicle switched seamlessly to its gasoline for the remainder of its range--an additional 320 to 518 miles.

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