Extended-Range PHEV Pool Deepens as AVL Says It Has Rotary Engine-Generator

By John O'Dell July 20, 2010

There are those who doubt the marketability of extended-range plug-in hybrids like the Chevrolet Volt (several of our readers among them), but there certainly seems to be a lot of interest in the powertrain industry - an indication that those who make a living handicapping automotive trends see profit potential in the technology.

Several companies, including Lotus Engineering, are betting that range extenders for plug-in  hybrids will, indeed, take off and that demand will swell for engine-generators to supply electrical power after a hybrid's rechargeable battery pack is depleted.AVL15kWRangeExtender1.jpg

Microsoft's Bill Gates made headlines last week when he invested some of his pocket change in EcoMotor, a company developing a lightweight opposed-piston, opposed-cylinder engine (the Opoc) that is intended solely for the extend-range PHEV market. Now comes word that Austria's AVL Powertrain Engineering Inc., a biggie in the alternative power systems development industry, has come up with a model of its own.

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AVL Powertrain has designed a rotary-engine based range extender for plug-in hybrids.

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In a presentation this week at a University of Michigan technology program, AVL said it has designed a system - built around a Wankel rotary engine - that would supply loads of electrical power from a fairly small and lightweight package.

We spoke this morning with Jerry Klarr, director of AVL's Michigan-based North American hybrid programs unit, and he said that the company already is talking to a number of automakers and others abut potential manufacturing partnerships (AVL would license the technology to the engine maker).

He wouldn't identify any, but we can't help recalling that jut a few weeks ago General Motors Corp.'s global vehicle engineering chief, Karl Stracke, told us the company already is testing a rotary-engine system for the next-generation Volt.

The AVL concept - shown in a converted Mini hybrid - used a 250 cubic-centimeter, single-piston rotary that weighed-in at just 64 pounds and was capable of generating 15 kilowatts of energy at a steady 5,000 rpm.

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In a paper presented in Austria late last year, AVL engineers said that the system, using a 10 kilowatt-hour lithium-ion battery and a 10 liter (2.6 gallons) fuel tank would deliver a total range of at least 200 kilometers (125 miles) before the tank would need refilling - that's about 48 mpg overall fuel economy. In a Mini-sized car, the system would deliver up to 30 kilometers, or 19 miles, of all-electric range before the gas engine-generator would kick in, according to the company.

AVL also has designed a variant of the 250 cc model that would operate at 7,000 rpm and deliver 25 kilowatts of power. A slightly larger single-piston rotary engine that would deliver 36 kilowatts at 7,000 rpm and a double-piston model capable of 50 kilowatts at 7,000 rpm also are on the drawing boards.

Weight and mass of course, are critical issue in EVs and PHEVs, because the less of there is, the more range can be squeezed from batteries that won't have to haul it around.

Including power electronics, battery cooling system and electric motor, the entire 15 kilowatt, extended-range PHEV system for the Mini concept tipped the scales at just 143 pounds.

The smallest rotary engine measures just 9.84 inches (250 mm) by 9.45 inches (240 mm) and the largest is just 15.75 inches (400mm) by 9.45 inches.

Klarr said the system, which still must undergo substantial validation and verification testing, is scalable and could be used in anything from small city cars to large transit buses. The engine could even be used on its own or as part of a conventional (non rechargeable) hybrid system for a small car, he said.

John O'Dell, Senior Editor

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