Quite a few years ago, we wrote about a free piston engine design being tested in research labs. It's a pretty interesting concept where a piston is used to generate electricity by moving a magnet past a coil. The piston isn't attached to a crankshaft, it just connects to a magnet and the linear motion does all the work. Now it looks like Toyota is working to make this engine a reality.
It looks a little different than the design we showed you earlier, but it's the same principle, it doesn't do any mechanical work to drive the wheels, it charges the batteries or could be used as a range extender when the batteries are discharged. It's fairly compact, too.
This could have a lot of uses if they get the kinks out, but with six years already gone since we last wrote about this, there's obviously some tricky engineering involved.