Across the Pacific over in Japan Honda has been putting in extra effort on the hybrid initiative as they push to knock the Prius off its pedestal by 2010. Along with an improved hybrid image in their designs, Honda is also looking to provide their hybrids with something the Prius and no other hybrid on the market today has achieved: improved highway mileage. While the Prius and other hybrids are great around town and under 40 mph, their highway miles, when the car is running solely on its gasoline motor, are not as compelling. Honda is exploring the use of the Rankine System as a means of harnessing the heat that is typically lost via the cars exhaust and turning it into electricity, and thus electric motor horsepower.
The Rankine System is rather complex and would easier be explained by a Science Professor than a car junky, but here is the nutshell version. The heat produced by the internal combustion engine passes through a cylinder that recaptures that heat and uses it to create steam by passing it through water. The steam is then captured and rotates a turbine that generates electricity. The electricity is then harnessed to produce horsepower for the electric hybrid motors of the car (very nutshell version).
The horsepower generated by the Rankine System is designed to assist the gasoline engine on the highway, just as the batteries and regenerative braking supply power to the electric motors for city driving. In tests performed by installing the system in their Honda Stream (only available in Japan) the thermal efficiency of the test resulted in 3-times the energy produced by regenerative braking. However, the resulting horsepower and highway fuel efficiency are not high enough yet to warrant a production version of the system… yet. It is also conceivable that the cost of the heat recapture system is rather inhibitive as well. The transfer of those costs currently would result in a good bit of sticker-shock for perspective buyers.
Honda’s hybrid squad is certainly working on improving upon the Rankine System in conjunction with their motors and will continue to look for ways to topple the Prius. Other auto related companies that are doing their own research with the Rankine System are BMW and Cummins with their diesels. It will make for a rather complex hybrid system over-all and will not ease the pain of an elder looking under the hood and chassis and shaking his head over how complex things have become compared to his 1955 Chevy.