Those are amazing engines. It's a pity that in the future we'll just be using magnets and coils, there something about these designs that moves me in a way that nothing electrical ever will. And I'm a great fan of renewable energy, and realize that the pollution that has been created (and is still being created) is absolutely unsustainable.

There are people working on internal combustion engines with a very similar design currently, for many applications (military, trucking, etc) diesel or diesel electric is the only realistic option for the foreseeable future: https://achatespower.com/