I’m a big fan of electric vehicles but there are plenty of limiting factors in their use and deployment, not the least of which is the ability to go from nearly “empty” to full range capacity in something less than an overnight stay. With a high-capacity charger and 240-volt service you can get some high-performance vehicle battery packs to recharge in under an hour but if you’re using regular household, 110-volt systems, you’re looking at 6-8 hours. Either way, that doesn’t begin to compete with the kind of zero-to-maximum-range ability that exists with regular gasoline engines. You pull in to the gas pumps running on fumes and you’re leaving with your full 400-mile range in less than 5 minutes.
The Chevy Volt offered a promising story in that regard. While the car was electric (which was an exaggeration, we now know) it had a range-extender motor built into it that you could fill up with gas. That motor was effectively an on-board generator that would allow you to have the “recharge” time of a regular car but be an electric vehicle at the same time. The idea is sound, even if Chevy’s approach wasn’t all it was cracked up to be. The key is in finding an engine type that’s very, very efficient that can serve as a generator to power the electric motor.
Toyota has come up with a fascinating design for just such an engine, the Free Piston Engine Linear Generator:
Instead of connecting a separate generator to the crankcase of an internal combustion engine, the linear generator turns the piston itself into a generator, reducing the overall size and mechanical complexity of the machine.
Opposite the combustion end is a sealed chamber that acts as a gas spring to cycle the piston in lieu of the rotational action of a crank. In this case, a section of the piston is constructed of a magnetic material that interacts with coils in the walls of the chamber to generate electricity
The real advantage of this engine is that it’s not actually doing the work of pushing the car. All it’s doing is pushing the magnet pack back and forth in the wire coils, a job that requires far less kinetic energy. This lighted load means less fuel consumed which lets the engine be calibrated for maximum fuel burn. Multiple Linear Generators would be installed in a single vehicle, increasing the power generated and, positioned properly, would provide vibration cancellation. The gas spring can also be tuned to allow for different fuel densities and timings so the same engine could burn fuels ranging from gasoline to propane to hydrogen. There’s some real promise in this one.
I also see application for this technology in the home as a backup generator for home use. Who knows, it might even be able to power electric aircraft as well.
I look forward to seeing more about this. If you’d like to see the animation about how this works, have a look here.