At the moment car engines are very inefficient, with only 14% - 26% of the fuel that goes into a car actually being used to move the car along the road. Around 60% of all energy loss in a car is due to thermal energy being wasted in the engine. 5% -6% more energy is lost to sources such as the alternator, which charges the car's battery. The goal of my project was to experiment with using a Peltier chip to generate electricity from exhaust heat, thus removing the energy consuming alternator and using otherwise wasted exhaust heat to charge the battery.

Method/Materials: I began experimenting with just a Peltier chip and a candle to try to determine what kind of electricity output I was getting. This proved to be mostly ineffective, with voltage reaching a peak of 0.7V, nowhere near enough to charge a car battery. The candle was causing far too much inconsistencies in data, so I decided to move on to a heat gun with which I could select different temperatures. The flowing air out of a heat gun mimicked the flow of exhaust gas very well, so I set about getting readings for voltages at different temperatures. Since car exhausts can produce in excess of 750 degrees Fahrenheit, I experimented with temperatures from 450 degrees to 850 degrees to check how much voltage I could get. I had to use higher temperatures on my heat gun than those that were indicated, because the actual output of the gun was lower than the indicated value.

Results: At it's peak with exhaust gas running perpendicular to the Peltier chip. my 0.4cm by 0.4cm Peltier chip produced 1.3 volts with the temperature set at around 800 degrees Fahrenheit. As the temperature decreased, so did the voltage of the Peltier chip, with 450 degrees only giving an output of around 0.8 volts. I experimented with angling the peltier chip so that the gas was targeted more at the Peltier chip than perpendicular to it, but the resulting lack of airflow would have been detrimental to the performance of a car. Conclusions/Discussion My results suggest that with enough Peltier chips, it would be possible to generate enough electricity to charge the battery. It would take at least 12 to charge the battery with each chip at maximum efficiency, and even then the electricity would not be high enough current to power many of the electrical devices within the car. For now at least it would seem that the alternator is a better solution than Peltier devices in the exhaust system.

Summary: I tried to make a Peltier device that would charge a car's battery in place of an alternator to improve the car's fuel efficiency.