Now that the 2011 Chevy Volt is on sale, car buyers can experience electric vehicles with range-extending engines in everyday driving. And the Volt is just the start.

In the future, range extenders to generate electric power will move beyond the Volt's standard car engine to purpose-built designs. One could be the tiny Lotus 1.2-liter three-cylinder engine-and-generator set, and another might be small diesel or gas turbine engines.

Jaguar was the first major automaker to pioneer this concept, with the striking C-X75 concept coupe it debuted last fall. The design study was praised for its sleek, futuristic lines, made possible by the compact size of its tiny twin microturbine generators, each just 21 inches long.

Jay Leno drives the Jaguar C-X75 Concept

Jay Leno drives the Jaguar C-X75 Concept

At the other end of the scale, a North Carolina company called DesignLine has proposed to build transit buses propelled by electric motors that draw current from a large lithium-ion battery pack, which in turn is recharged by a diesel turbine generator. The design was originally developed in New Zealand.

The diesel turbine was provided by Capstone, a company that itself had built a prototype range-extended electric supercar based around its 30-kilowatt microturbine. A year ago this month, a Los Angeles firm called Velozzi announced plans to build both a supercar and a crossover using the technology

For New York City, the hope was that the turbine generator in the DesignLine buses would return 7 miles per gallon of diesel fuel in regular duty. That's almost double the fuel efficiency of New York City's fleet of hybrid diesel-electric buses today.

Capstone Turbine CMT-380 concept car

Capstone Turbine CMT-380 concept car

Sadly, the DesignLine buses have proven no match for the grueling conditions of daily bus service in New York City.

After a test of five DesignLine buses that lasted 18 months, the New York City Transit Authority has concluded the prototype buses simply weren't capable of providing reliable service.

While bus drivers gave them high marks for responsive acceleration, and riders loved the smooth, quiet operation, the TA said that the 30-kilowatt (40-horsepower) turbine generators didn't "provide enough power to operate in regular passenger service in a multitude of conditions."

DesignLine subsequently fitted a much larger 65-kW (87-hp) turbine to one of the test buses, but the TA said it wasn't sufficiently reliable. It has now ended the test, returned the test buses to DesignLine, and is getting a refund on the money it spent on the tests.

[Second Avenue Sagas]