Cyclone waste heat engine scavenges power from any heat source

Novel technologies to improve the efficiency of existing vehicles and combustion processes are the quickest route to improved fuel mileage. Hybrid cars are great examples of the approach. Another way to recover some of the energy converted into heat in the average engine is the Waste Heat Engine, or WHE. Though applications for the system have not yet been worked out, the returns are promising so far.

Using heat from nearly any source, including the sun, fire or excess exhaust gas heat, the WHE can capture the energy in the heat and turn it into mechanical energy. Radially arranged pistons drive a ring attached to an eccentric output shaft.

It may sound like science fiction, but the idea itself is actually very old. The basic principles of the WHE are the same as those found in the steam engine. Rankine cycle engines, which rely on the same principles, are already in development by Honda and in a modified, split-cycle form by Scuderi. Another name of the Cyclone WHE is the Schoell Cycle engine, named for inventor and Cyclone principle, Harry Schoell. The Schoell cycle is a modified version of the Rankine cycle. It uses a closed-loop water system that vaporizes and condenses water via the application of an outside heat source. The water vaporization is used to drive the pistons, which turn the output shaft to recapture the energy in the waste heat.

Schoell has working prototypes of the engine built, but as yet there have been no automotive applications. The 155 cubic inch (2.5L), 12-cylinder engine turns out a mere 20hp, and its size isn't particularly well-suited to being placed inside an engine bay. Nonetheless, the technology could be ideal for fixed installations that don't have space constraints. Several other implementations have been envisioned by Cyclone, including a prototype weed trimmer, lawn mower and portable generator.

For a visual presentation of the device by its inventor on Engineering TV, see below.