The exhaust gases shooting out the tailpipes of internal-combustion cars aren't just a form of pollution, they also represent wasted energy.
One way to use some of that energy has been turbocharging: An exhaust-driven turbine runs a compressor that packs more air into the combustion chambers, allowing more gasoline to be injected, thus producing more power.
Now, though, exhaust gases are also being used to generate electricity.
Japanese firm YGK recently unveiled a hybrid powertrain that uses an exhaust-driven turbine to generate electricity. According to Technologic Vehicles, YGK first received a patent for the system in 2012.
Jaguar XJR-15 equipped with YGK EER-Hybrid system
That electricity is stored in a supercapacitor until it's needed. The "EER-Hybrid" (Exhaust Energy Recovery) system reportedly provides a 10-percent boost in efficiency.
Every bit of improvement will likely go a long way, because the car YGK chose to demonstrate this technology isn't a Prius or other typical hybrid, but rather a Jaguar XJR-15.
This low-slung two-seat coupe was Jaguar's first attempt at a modern supercar, and is based on the 24 Hours of Le Mans-winning XJR-9 racer.
The XJR-15 entered production in 1990, and just 50 were made. Today, the sleek coupe lets YGK's engineers draw attention as a sexy demonstrator of green technology.
The car originally boasted a 6.0-liter V-12, but that's been replaced by a 4.5-liter unit of indeterminate cylinder count, along with the exhaust-energy recovering turbine.
Mercedes AMG's 2014 Formula One power unit
While a similar setup likely won't be widely adapted for road cars for some time, exhaust energy is already being harnessed in racing.
Exhaust-driven turbines are among the energy-recovery systems used in the new crop of hybrid Formula One powertrains that debuted as the result of a major rule change for the 2014 season.