In 2016, Solar Impulse 2 was the first solar-powered electrified aircraft to make a trip around the world. But that aircraft wasn’t the first to partake in electric flight, nor will it be the last.
Since the development of the battery-powered Militky MB-E1 in the early 1970s, there has been excitement surrounding the promise of an electric aircraft. However, many of the concepts being floated around by aerospace companies assume huge improvements in current battery technology.
The problem? According to a recently published article in Wired, current battery technology does not offer the power-to-weight ratio needed to make battery-powered planes feasible.
But battery technology has taken leaps over the past few years. Energy storage devices are become more efficient and lighter simultaneously. But how long will it take to be able to pack enough energy into a device while remaining light enough to glide through the sky?
“There’s already been a lot of progress,” Venkat Srinivasan, battery expert with Argonne National Lab, told Wired. “It’s not the same ballpark as Moore’s law progress because it’s chemistry, not electronics, but it’s still very good.”
(MORE: Read papers published by Srinivasan in the ECS Digital Library.)
Following the prediction of Moore’s law, transistors per square inch have doubled approximately every 18 months. This has enabled the quick development of smaller, faster, better electronics. While battery technology does not follow that prediction, there has been exponential growth in the field over the years. However, Wired notes that the specific energy of batteries is roughly two percent of liquid fuels – which equates to 1,000 pounds of jet fuel yielding 14 times more energy than a 1,000 pound battery.
While battery energy density doesn’t double every 18 months, it has increased by two to three percent per year. But according to experts, batteries do not need to match liquid fuel pound for pound to catch up on efficiency. Because of this, experts estimate that electric airplanes could arrive as soon as 2045.
“Electric propulsion permits new design architectures,” says Venkat Viswanathan, past winner of the ECS San Francisco Section Daniel Cubicciotti Student Award. “Future electric aircraft will look nothing like the aircraft of today, and they will be able to fly with much less energy—as little as 400 watt-hours/kg—thanks to distributed motors and reduced drag. We’ll redesign aircraft around electric motors.”