BMW wants to exploit engine heat waste

Internal combustion engines are terribly inefficient machines.   About 60 percent of the energy generated by an internal combustion engine is lost – half from exhaust heat.

The other half is lost from heat energy absorbed by the engine’s internal cooling mechanisms.   

BMW engineers say that they are making progress on a number of innovations that will recapture some of this heat and make the internal combustion engine more efficient. 

The Turbosteamer employs a heat exchanger to recover heat from engine exhaust. This energy is used to heat a fluid which is under high pressure. This heated fluid then turns into steam, which powers an expansion turbine that generates electrical energy from the recovered heat.   

When completed, this system will weigh only 10-15 kilograms and will be capable of supplying all of the electrical energy required by an automobile. Under these conditions BMW engineers say the average driver will be able to reduce fuel consumption by up to ten percent on long-distance journeys.

BMW engineers are also at work on thermoelectric generation technology (TEG), which converts heat directly into energy. Using technology gleaned from NASA, TEG makes use of the Seebeck Effect which demonstrates how electrical voltage can be generated between two thermoelectric semiconductors if they have different temperatures.   

BMW is deploying TEG technology as part of an automobile’s exhaust gas recirculation system. In this configuration, testing has shown that 250 watts can be generated while CO2 emissions and fuel consumption are reduced by two percent at the same time.   By the time the TEG system is perfected, BMW engineers predict a five percent savings in fuel consumption.

BMW is looking to integrate these two technologies into a comprehensive “heat management” system that they say will reduce fuel consumption and reduce CO2 emissions.

Steve Duda, EarthTechling