A Study on the Future of Battery Based Electric Aircraft Propulsion

Today the aircraft industry is witnessing a paradigm shift in the propulsion technology which has been unseen since the 1930s, when the gas turbine took over from the more established piston engines. For electric propulsion to survive and flourish, it must demonstrate clear superiority over the mature baseline technology of the gas turbine. It is a fact that the current battery technology is a limiting factor as it is not competitive compared to a gas turbine that is 30-50 times more energy dense. Naturally, the present electric propulsion developments concentrate on smaller aircraft designs and use on a large aircraft is possibly decades away. Apart from the energy density, from thermal perspective the architectures are vastly different from each other. A conventional aircraft fitted with a gas turbine has readily available heat sinks in fuel and air that aids in heat transfer. Compressed air bleeds from the engine manage the thermal demands of the engine itself plus the aircraft systems. On the other hand, a battery-based aircraft does not have this advantage and therefore must deploy dedicated thermal management systems for cooling and heating demands, and that drains energy from the battery. This paper summarizes a thermodynamic evaluation of gas turbine and electric propulsion to compare their benefits and shortcomings. It concludes that the battery based electric propulsion, with its currently limited energy density, needs efficient thermal management systems to mature as a technology. In the long run, with emerging battery technologies it has potential to come closer to a gas turbine of similar capacity. A TRIZ analysis was carried out to predict the trend of technology to address the current limitations. It identifies structural composite batteries, thermally conductive airframe, distributed electric propulsion and advanced hybrid-electric architecture among potential trends of electric propulsion. The regulatory authorities are adapting the airworthiness regulations to the ongoing changes, and more regulatory evolution is likely to keep up with these technological trends.