Batteries Improve But Need To Improve More
Michael Dudley of the NASA Ames Research Center provided a presentation of electric aircraft power system requirements. He said NASA is actively investigating electric propulsion as a viable option for some aerial applications but it has a long way to go before it can match the energy storage efficiency of fossil fuels. The internal combustion engine has three times the energy density of even the most sophisticated battery-electric system currently available. He said that situation is unlikely to change in the short term because an "improvement factor" of 20 is required to make lithium ion battery systems even come close to conventional engines. Motor technology seems to be advancing more quickly.
Various speakers at the symposium described advances in motor power-to-weight ratios and there are some truly impressive developments. There are motors that are actually small and powerful enough to be housed with the propeller and Steve Neu has developed a motor four inches long and two inches in diameter capable of a peak output of 10 Kw or 13.4 horsepower. Vans aircraft is developing a hybrid system using a gasoline engine in combination with an electric motor.