The rotary engine may have a future after all.

Once thought to be the next big thing in automotive powertrains, the rotary, or Wankel, engine largely was shelved by developers in the late 1970s, a victim of toughening emissions standards and rising fuel-economy demands.

Nearly every major auto maker seemed to have a rotary in the works during the decade, but Mazda Motor Corp. was alone in putting one into volume production during that era and is the sole producer of a Wankel-powered car at present, the RX-8.

But the rotary may have new life, ironically as a result of the industry's push into vehicle electrification.

Gary Hunter, chief technologist-diesel engines for AVL Powertrain Engineering Inc., says the rotary may find a home in future extended-range electric vehicles, similar to General Motors Co.'s upcoming Chevrolet Volt.

EREVs run on electricity but use a small internal-combustion engine as a generator once battery power begins to run low.

Speaking at a University of Michigan Transportation Research Institute conference in Ann Arbor, MI, on future powertrain technology, Hunter says the rotary offers a packaging advantage over a conventional piston engine in such applications.

A 0.57L 2-cyl. piston engine producing the same amount of power as a 0.25L rotary will be bulkier and weigh 24 lbs. (11 kg) more, he says. To prove its point, AVL has cobbled together an EREV based on BMW AG's Mini Cooper, using a rotary engine to keep the 10 kWh lithium-ion battery charged.

AVL built the rotary, Hunter tells Ward's, though it is seeking to license production, not actually manufacture the engine itself.

The single-piston rotary engine displaces 0.254L and weighs 64 lbs. (29 kg), including the starter/generator. Combined with the power electronics, cooling circuit for the electronics and core unit to connect to the vehicle's cooling system, the setup weighs 143 lbs. (65 kg) and measures 19.2 ins. (49.0 cm) long.

The unit generates 15 kW of electric power at 5,000 rpm, but can be scaled up to 25 kW at 7,000 rpm. A slightly bigger version of the rotary engine, displacing 0.357L, can produce 36 kW at 7,000 rpm, while a double-rotor engine could deliver 50 kW.

The test vehicle can travel 19 miles (30 km) on a single charge.