Where does the energy go?

This week the departments of  Transportation and  Environmental Protection announced a new goal of a combined fleet efficiency of 54.5 MPG by 2025. To attain this goal,  automakers will have to develop lighter, smaller, and more efficient cars. In order to see the inefficiencies of today’s internal combustion car, it would make sense to step back and see how energy is lost from the second we switch on our cars, to the moment they propel forward.

In a recent Nature article published in Nature magazine Secretary of Energy Steven Chu discusses the challenges for creating more sustainable transportation. According to the Department of Energy, out of each gallon of gas combusted in our cars only 21% is used to move the car. Assuming each gallon costs $3.77 (national average) a meager 79 cents is actually powering the wheels. Boradly, 33% of energy is lost through the exhaust, 29% is used for cooling, and the other 38% is lost due to mechanical power inefficiencies  The image below shows the leading sources of inefficiencies.

Where does the energy go? (click to enlarge)

Presently, electric motors are already showing higher conversion rates of stored energy into kinetic energy. Moreover, they allow engineers to experiment with lighter materials, and technologies such as regenerative breaking  that can later be used for all modes of transportation.