Drones would be amazing if they weren't so terrible. That is, they're great at putting cameras and sensors in the sky, but they're awful at keeping them there. The flight-time for high-end consumer drones generally tops out at 25 minutes, and commercial drones don't fare much better.
For drone hobbyists, the limited flight-time is an annoyance. But for companies that want to put their drones to hard use, constantly replacing and recharging batteries is more than frustrating. "It's a brick wall," said Matt McRoberts, one of the co-founders of Pegasus Aeronautics, a hardware startup based in Waterloo, Ontario. We were chatting in one of boardrooms at the University of Waterloo's Velocity Garage, the largest free startup incubator in North America, where the company has been working to take the cap off drone flight-times.
The problem is batteries. Even high-end lithium-polymer (Li-Po) batteries—the kind most commonly used in drones—have low energy density. Which is to say, they are big and heavy relative to the amount of juice they contain. You can't simply pile batteries on a drone to make it stay in the air longer, because it wouldn't be able to lift itself off the ground.
Pegasus has developed a solution: skip the batteries, and use gasoline instead. The company is currently beta-testing its GE-30 Range Extender system, a hybrid gas-electric engine that plugs into the battery terminal of most commercial drones and promises to extend flight-time on existing models of drones by two hours, with the possibility of going much further on bigger models in the future.
In terms of energy density, gasoline beats the hell out of batteries. According to the American Physical Society, "the gasoline in a fully fuelled car has the same energy content as a thousand sticks of dynamite." For the purposes of drone operators, gasoline also has more than fifty times the energy density of the best batteries you can buy, said McRoberts.
Essentially, the Range Extender is a two-stroke internal combustion engine that fits on your drone, though it's not as simple as it sounds. You can't put rotors on a lawnmower and make it fly, or someone would have done that already. (You can, of course, make a drone that looks like a lawnmower, but that's another story.)
Pegasus's Range Extender is a hybrid gas-electric system, but unlike a hybrid car, which has both an electric and a gas engine that each transfer power directly to the wheels to varying degrees, the Range Extender doesn't integrate mechanically with the drone at all, McRoberts said.
Instead, it's a miniaturized version of the powertrains used on big ships, in which energy from a diesel engine is converted into electricity to power an electric motor that turns the propellor. (McRoberts was inspired by his brother, a mechanical engineer who works in shipbuilding.)
Amateur drone enthusiasts should hold off rejoicing. The Range Extender, which should be available for purchase by end of summer, is built to fit on large commercial drones—not the small consumer ones at Best Buy. Pegasus won't say how much the system costs, but McRoberts pointed out that most commercial drone operators spend around $12,000 a year on batteries, which can only be charged so many times before they degrade. The Range Extender will priced well below that.
Pegasus isn't the first company to try to solve the battery problem in drones. Top Flight Technologies in Massachusetts uses a gas engine to power a generator that recharges the drone's battery while it flies. Intelligent Energy in the UK offers a hydrogen fuel cell that attaches to the battery and, like Pegasus, extends its life by two hours.
Of course, apart from commercial drone operators that want to inspect oil pipelines or survey mine sites, no one is all that excited about gasoline as a power source. According to the US Energy Information Administration, a single gallon of gasoline produces nearly 20 pounds of carbon dioxide.
If the researchers developing the lithium-air (Li-Air) battery are successful, that technology could equal the energy density of gasoline. But if the Li-Ion battery used in smartphones and laptops is any indication, a good candidate might take decades to reach mass production.
Until then, at least we'll have drones that can stay in the sky.