Venkat Viswanathan, Carnegie Mellon University; Shashank Sripad, Carnegie Mellon University, and William Leif Fredericks, Carnegie Mellon University

(THE CONVERSATION) As electric cars and trucks appear increasingly on U.S. highways, it raises the question: When will commercially viable electric vehicles take to the skies? There are a number of ambitious efforts to build electric-powered airplanes, including regional jets and planes that can cover longer distances. Electrification is starting to enable a type of air travel that many have been hoping for, but haven’t seen yet – a flying car.

A key challenge in building electric aircraft involves how much energy can be stored in a given amount of weight of the on-board energy source. Although the best batteries store about 40 times less energy per unit of weight than jet fuel, a greater share of their energy is available to drive motion. Ultimately, for a given weight, jet fuel contains about 14 times more usable energy than a state-of-the-art lithium-ion battery.
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