Hüttlin Spherical Engine

How it Works: This one is so far away from normal engine design it's almost hard to comprehend. To start, imagine a very stout pin in the center of a sphere. Attached to this pin are two pairs of pistons, arranged in a pseudo-triangular configuration. The two sets of pistons face each other and create two semi-toroidal opposed piston combustion chambers. Attached to the back side of the pistons at the top of the triangle are two very large ball bearings which lie in a track on the stationary outer housing. As the piston and combustion chamber assembly rotates, the bearings guide the pistons to create a back-and-forth rocking motion that's recognizable as a four-stroke combustion engine cycle. Output is taken from a gearset machined into the piston housing or it can act as a generator. The incredible part is that this wildly complex engine has already gone through several generations of refinement and simplification.

Claimed Benefits: The Hüttlin spherical engine is a mind-bending design, and it can run on almost any fuel, but its specialty is flexibility. Within the same spherical envelope, the basic architecture has been adapted to operate as a standard internal combustion engine, a fully integrated hybrid system, a range-extender, and as a wind turbine's electrical generator that also outputs compressed air. It can be air-cooled or liquid-cooled depending on the application.

Status: A little hard to gauge at the moment, but when we first saw it at the 2011 Geneva Motor Show it attracted quite a lot of attention from renewable energy providers and automakers alike.