Certain parts of a car’s engine can reach temperatures in excess of 1,500°F. With this in mind, the engineers at BMW developed a way to boost efficiency: Transform that otherwise wasted heat into energy the engine can use. The resulting Turbo- steamer reclaims more than 80 percent of the heat lost from the engine’s exhaust and cooling systems.
It uses this surplus heat to generate steam that helps drive the engine. It boosts power and torque by 10 percent and cuts fuel consumption by 15 percent without using a single additional drop of gasoline.
At around 220 pounds, the Turbosteamer will have to shed some weight before it meets BMW’s weight-distribution standards, but expect to see a version on the road within the next decade. The TurboSteamer has two separate components: a high-temperature loop [red] heated by the exhaust system and a low-temperature loop [blue] heated by engine coolant. The circuits follow different paths but feed power into the same place. In the high-temperature loop, an electric pump circulates distilled water. First stop: a steam generator that vaporizes the water. A superheater further heats the steam to above 1,000°F. From there, steam spins a piston-driven expander, which powers a belt drive that helps turn the crankshaft. Then, the steam hits a condenser, which cools it back down to a liquid state.
The low-temperature loop-which assists the high-temperature loop-works similarly but uses ethanol because it turns into steam at just 173°. Its pump drives the ethanol through a steam generator heated by engine coolant (the ethanol actually helps cool the engine) and then into a second steam generator that it shares with the primary circuit. Steam exits at about 300° and flows into its own expander, which adds power via a belt drive to that of the high-temperature expander. On exiting, the ethanol flows through the car’s radiator, which cools it back down to liquid.